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6Agriculture, water, andecosystems: avoiding thecosts o going too ar
Fuelwood
Recreation
Pestcontrol
Soilformation
Regulationof waterbalance
Nutrientcycling
Cropproduction
Climateregulation
Provisioning services Regulating services
Supporting services Cultural services
Natural ecosystem
Coordinating lead authors: Malin Falkenmark, C. Max Finlayson, and Line J. Gordon
Contributing authors: Elena M. Bennett, Tabeth Matiza Chiuta, David Coates,Nilanjan Ghosh, M. Gopalakrishnan, Rudol S. de Groot, Gunnar Jacks, Eloise Kendy,Lekan Oyebande, Michael Moore, Garry D. Peterson, Jorge Mora Portuguez,Kemi Seesink, Rebecca Tharme, and Robert Wasson
Overview
Agricultural systems depend undamentally on ecological processes and on the services provided
by many ecosystems. Tese ecological processes and services are crucial or supporting and
enhancing human well-being. Ecosystems support agriculture, produce ber and uel,
regulate reshwater, puriy wastewater and detoxiy wastes, regulate climate, provide pro-
tection rom storms, mitigate erosion, and oer cultural benets, including signicant
aesthetic, educational, and spiritual benets.
Agricultural management during the last century has caused widescale changes in land
cover, watercourses, and aquiers, contributing to ecosystem degradation and undermining the
processes that support ecosystems and the provision o a wide range o ecosystem services. Many
agroecosystems have been managed as though they were disconnected rom the widerlandscape, with scant regard or maintaining the ecological components and processes that
underpinned their sustainability. Irrigation, drainage, extensive clearing o vegetation, and
addition o agrochemicals (ertilizers and pesticides) have oten altered the quantity and
quality o water in the agricultural landscape. Te resultant modications o water ows
and water quality have had major ecological, economic, and social consequences, includ-
ing eects on human health [well established]. Among them are the loss o provisioning
services such as sheries, loss o regulating services such as storm protection and nutrient
retention, and loss o cultural services such as biodiversity and recreational values. Adverse
ecological change, including land degradation through pollution, erosion, and saliniza-
tion, and the loss o pollinators and animals that prey on pest species, can have negative
Natural ecosystem services
Artist: Peter Grundy, United Kingdom
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eedback eects on ood and ber production [well established]. In extreme cases human
health can also suer, or example, through insect-borne disease or through changes in diet
and nutrition. All too oten the consequences o modiying agroecosystems have not been
ully considered nor adequately monitored.
It has been increasingly recognized that agricultural management has caused some ecosystems
to pass ecological thresholds (tipping points), leading to a regime change in the ecosystem and loss
o ecosystem services. Ecosystem rehabilitation is likely to be costly, i possible at all. Some
changes can be nearly irreversible (or example, the establishment o anoxic areas in marine
water bodies). Tese changes can occur suddenly, although they oten represent the cumula-
tive outcome o a slow decline in biodiversity and reduced ecological resilience (the ability
to undergo change and retain the same unction, structure, identity, and eedbacks).Te poor people in rural areas who use a variety o ecosystem services directly or their
livelihoods are likely to be the most vulnerable to changes in ecosystems. Tereore, ailure to
tackle the loss and degradation o ecosystems, such as that caused by the development and
management o agriculture-related water resources, will ultimately undermine progress
toward achieving the Millennium Development Goals o reducing poverty, combating
hunger, and increasing environmental sustainability.
An integrated approach is needed or managing land and water resources and ecosystems
that acknowledges the multiunctionality o agroecosystems in supporting ood production and
ecosystem resilience. Tat requires a better understanding o how agroecosystems generate
multiple ecosystem services and o the value o maintaining biodiversity, habitat hetero-
geneity, and landscape connectivity in agricultural landscapes. Social issues, such as theimportance o the role o gender in management decisions, also require more emphasis.
Attention should be directed toward minimizing the loss o ecosystem resilience and build-
ing awareness o the importance o cumulative changes and o extreme events or generat-
ing ecosystem change. It is also necessary to meet the water requirements or sustaining
ecosystem health and biodiversity in rivers and other aquatic ecosystems (marshes, lakes,
estuaries) and to demonstrate the benets o these services to society as a whole.
It has been estimated that by 2050 ood demand will roughly double. As populations and
incomes increase, demand or water allocations or agriculture will rise. Simplied, there are
three main ways in which this increased water requirement can be met: through increased
water use on current agricultural lands, through expansion o agricultural lands, and through
increased water productivity. While all are plausible and a mix o solutions is likely, each hasvastly dierent implications or nonagricultural ecosystems and the services they generate.
With the current high levels o land conversion and river regulation globally, greater con-
sideration should be given to improving management o water demand within existing agri-
cultural systems, rather than seeking urther expansion o agriculture. Dependent on local
conditions, technologies and management practices need to be substantially improved,
and ecologically sound techniques implemented more widely to reduce the impacts rom
agriculture, whether extensive or intensive. Further intensication will require careul
management to prevent urther degradation and loss o ecosystem services through in-
creased external eects and downstream water pollution. With the basis o many essen-
tial ecosystem services already seriously undermined, there is an urgent need not only to
An integrated
approach isneeded or
managing land,
water, and eco-
systems thatacknowledges
the multi-
unctionality o
agroecosystems
in supportingood production
and ecosystem
resilience
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6Agriculture, water, and
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minimize uture impacts, but also to reverse loss and degradation through rehabilitation
and, in some cases, ull restoration.
An integrated approach to land, water, and ecosystems at basin or catchment scale is urgently
needed to increase multiple benefts and to mitigate detrimental impacts among ecosystem services.
Tis involves assessing the costs and benets as well as all known risks to society as a whole
and to individual stakeholders. Societally accepted tradeos are unlikely without wide stake-
holder discussion o consequences, distribution o costs and benets, and possible compensa-
tion. It is also important that the results eed into processes o social learning about ecosystem
behavior and management. A ew tools are available to assist in striking tradeos (including
economic valuation and desktop procedures or establishing environmental ows), but more
ecient and less sectorally specic tools are needed. Most o the tools were developed toenable better decisionmaking on well known problems and benets. Needed are tools to ad-
dress the lesser known problems and benets and to prepare or surprises.
Decisions on tradeos under uncertain conditions should be based on a set o alternative
scientifcally inormed arguments, with an understanding o the uncertainties that exist when
dealing with ecological orecasting. o minimize the sometimes very high uture costs o
unexpected social and ecological impacts, it will be necessary to conceptualize uncertainty
in decisionmaking. Adaptive management and scenario planning that improve assessment,
monitoring, and learning are two components o this conceptualization.
Ongoing attention is required to communicate ecological messages across disciplinary and
sectoral boundaries and to relevant policy and decisionmaking levels. Te challenge is to pro-
duce simple messages about the multiple benets o an ecosystem and about how eco-systems generate serviceswithout oversimpliying the complexity o ecosystems.
In view o the huge scale o uture demands on agriculture to eed humanity and eradicate
hunger, and the past undermining o the ecological unctions on which agriculture depends, it is
essential that we change the way we have been doing business. o do this, we need to:
Address social and environmental inequities and ailures in governance and policy as
well as on-ground management.
Rehabilitate degraded ecosystems and, where possible, restore lost ecosystems.
Develop institutional and economic measures to prevent urther loss and to encour-
age urther changes in the way we do business.
Increase transparency in decisionmaking about agriculture-related water management
and increase the exchange o knowledge about the consequences o these decisions. Inthe past many changes in ecosystem services have been unintended consequences o
decisions taken or other purposes, oten because the tradeos implicit in the decision-
making were not transparent or were not known [well established].
Water and agriculturea challengeor ecosystem management
Changes in agriculture over the last century have led to substantial increases in ood security
through higher and more stable ood production. However, the way that water has been man-
aged in agriculture has caused widescale changes in land cover and watercourses, contributed
There is a need
not only to
minimize uture
ecosystemimpacts, but
also to reverse
loss and
degradationthrough
rehabilitation
and, in some
cases, ull
restoration
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to ecosystem degradation, and undermined the processes that support ecosystems and the
provision o a wide range o ecosystem services essential or human well-being.
Te Millennium Ecosystem Assessment, an international assessment by more than
1,300 scientists o the state o the worlds ecosystems and their capacity to support hu-
man well-being, identied agricultural expansion and management as major drivers o eco-
system loss and degradation and the consequent decline in many ecosystem services and
human well-being (www.maweb.org). Analyses illustrated that by 2000 almost a quarter o
the global land cover had been converted or cultivation (map 6.1), with cropland cover-
ing more than 50% o the land area in many river basins in Europe and India and more
than 30% in the Americas, Europe, and Asia. Te Millennium Ecosystem Assessment also
showed that the development o water inrastructure and the regulation o rivers or manypurposes, including agricultural production, oten resulted in the ragmentation o rivers
(map 6.2) and the impoundment o large amounts o water (gure 6.1; Revenga and oth-
ers 2000; Vrsmarty, Lvque, and Revenga 2005).
Many scientists argue that as a society we are becoming more vulnerable to environ-
mental change (Steen and others 2004; Holling 1986), reducing our natural capital and
degrading options or our current and uture well-being (Jansson and others 1994; Arrow
and others 1995; MEA 2005c). Natural and human-induced disasters, such as droughts
and amine, are also likely to increase the pressure on vulnerable people, such as the rural
poor, who depend most directly on their surrounding ecosystems (Silvius, Oneka, and
Verhagen 2000; WRI and others 2005; Zwarts and others 2006).
Furthermore, as populations and incomes grow, it has been estimated that ood de-mand will roughly double by 2050 and shit toward more varied and water-demanding
diets, increasing water requirements or ood production (see chapter 3 on scenarios).
map6.1 Extent o cultivated systems in 2000
Note: Cultivated systems are defned as areas where at least 30% o the landscape is in croplands, shiting cultivation, confnedlivestock production, or reshwater aquaculture.
Source: MEA 2005c.
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6Agriculture, water, and
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map6.2 River channel ragmentation and ow regulation o global rivers
Source: Revenga and others 2000.
Unragmented Moderately ragmented Highly ragmented No data Unassessed
Sumo
fdischarge(cubickilometersperyear)
Sumo
fcapacity(cubickilometers)
16,000 5,000
4,000
3,000
2,000
1,000
0
14,000
12,000
10,000
8,000
6,000
4,000
2,000
019201900 1940 1960 1980 2000 19201900 1940 1960 1980 2000
Intercepted continental runoff Reservoir storage
Note: The time series data are taken from a subset of large reservoirs (0.5 cubic kilometers maximum storage each),
geographically referenced to global river networks and discharge.
Source: Millennium Ecosystem Assessment.
fgure6.1 Development o water inrastructure and regulation o riversresulted in the impoundment o large amounts o water
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Simplied, there are three main ways to meet this water requirement: increasing water
use on current agricultural lands through intensication o production (see chapters 8 on
rained agriculture and 9 on irrigation), expanding agricultural lands, and increasing water
productivity (see chapters 7 on water productivity and 15 on land).
Tese options have vastly dierent implications or ecosystems and the services they
generate. Increased water use on agricultural lands through irrigation will reduce the avail-
ability o blue water resources (surace water and groundwater), especially or downstream
aquatic systems, and can contribute to waterscape alterations, or example, through the
introduction o dams or irrigation. Increased green water ows (soil moisture generated
rom rainall that inltrates the soil) through higher consumptive water use in rained
agriculture (as a result o increased crop productivity) will also reduce the availability owater downstream, although the extent to which this could occur varies [established but
incomplete]. Expanding agricultural land can alter the water ow in the landscape, with
impacts on terrestrial and aquatic ecosystems. Finally, while increased water productivity is
intended to produce more ood without using more water, it can lead to deterioration in
water quality through increased use o agrochemicals.
Humanity is acing an enormous challenge in managing water to secure adequate ood
production without undermining the lie support systems on which society dependsand
in some instances while simultaneously rehabilitating or restoring those systems. Research on
ecosystems has generally been separate rom research on water in agriculture, leading to a seg-
regated view o humans and ood security on one side and nature conservation on the other. In
this chapter we challenge this view by describing recent understanding o how all ecosystemssupport human well-being, including ensuring ood security and redressing social inequities.
We ocus on the links between ecosystems and management o water in agriculture.
Water unctions as the bloodstream o the biosphere (Falkenmark 2003). It is vital or
the generation o many ecosystem services in both terrestrial and aquatic ecosystems and
provides a link between ecosystems, including agroecosystems. As or agricultural produc-
tion, we consider the importance o both blue and green water (see chapter 1 on setting the
scene) or ecosystems, both those characterized by the presence o blue water, such as marsh-
es, rivers, and lakes, and terrestrial ecosystems that depend on and modiy green water.
We rst assess the ecosystem eects o past water-related management in agriculture,
highlighting some o the oten unintentional tradeos between water or ood production
and water or other ecosystem services. We then outline response options or improvingwater management. We emphasize the need to intentionally deal with the unavoidable and
oten surprising tradeos that arise when making decisions to increase ood production,
noting that these are oten embedded within complex social situations where dierent
stakeholders have highly diverse interests, skills, and inuence (see, or example, chapters
5 on policies and institutions, 15 on land, and 17 on river basins).
Agriculture and ecosystems
While agricultural production is driven by human management (soil tillage, irrigation, nu-
trient additions), it is still inuenced by the same ecological processes that shape and drive
nonagricultural ecosystems, particularly those that support biomass production and others
Humanity
is acing anenormous
challenge in
managing
water to secure
adequate oodproduction
without
undermining
the lie supportsystems on
which society
depends
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6Agriculture, water, and
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such as nitrogen uptake rom the atmosphere and pollination o crops. Agricultural systems
are thus viewed as ecosystems that are modied, at times highly, by activities designed to en-
sure or increase ood production (box 6.1). Tese ecosystems are oten reerred to as agroeco-
systems; the dierence between an agroecosystem and other ecosystems is considered to be
largely conceptual, related to the extent o human intervention or management.
Disruption o the processes that maintain the structure and unctioning o an eco-
system, such as water ow, energy transer, and growth and production, can have dire con-
sequences, including soil erosion and loss o soil structure and ertility. Severe disruption
can result in the degradation or loss o the agroecosystem itsel or other linked ecosystems
and the ecosystem services that it supplies (see chapter 15 on land). Te degradation o the
Aral Sea is a dramatic example o human intervention having gone too ar (box 6.2).
There are many land and water manipulations that can increase the productivity o agricultural land
in order to meet increasing demands or more ood. All have consequences or ecosystems. The key
message is that agriculture makes landscape modifcation unavoidable, although smarter application
o technology and more emphasis on ecosystemwide sustainability could reduce adverse impacts.
These land and water manipulations include:
Shifting the distribution of plants and animals. Most apparent are the clearing o native vegetation
and its replacement with seasonally or annually sown crops, and the replacement o wild animals
with domestic livestock.Coping with climate variability to secure water for crops. As water is a key material or photo-
synthesis, crop productivity depends intimately on securing water to ensure growth. Three dier-
ent time scales need to be taken into account when considering water security: seasonal shortalls
in water availability that can be met by irrigation so that the growing season is extended and extra
crops can be added; dry spells during the wet season that can be met by specifc watering that can
be secured, even in small-scale arming, i based on locally harvested rain; and recurrent drought
that has traditionally been met by saving grain rom good years to rely on during dry years.
Maintaining soil fertility. The conventional way to secure enough air in the root zone is by drainage
and ditching through plowing to ensure that rain water can infltrate. However, this also leads to
erosion and the removal o ertile soil by strong winds and heavy rain. These side eects can be
limited by ocusing on soil conservation actions, such as minimum tillage practices.
Coping with crop nutrient needs. The nutrient supply o agricultural soils is oten replenished
through the application o manure or chemical ertilizers. Ideally, the amount added should bal-
ance the amount consumed by the crop, to limit the water-soluble surplus in the ground that may
be carried to rivers and lakes.
Maintaining landscape-scale interactions. When natural ecosystems are converted to agricultural
systems, some ecological processes (such as species mobility and subsurace water ows) that
connect parts o the landscape can be interrupted. This can have implications or agricultural
systems as it can aect pest cycles, pollination, nutrient cycling, and water logging and saliniza-
tion. Managing landscapes across larger scales thus becomes important; an increasing number
o studies illustrate how to design landscapes to increase the productivity o agriculture while
also generating other ecosystem services (Lansing 1991; Cumming and Spiesman 2006; Anderies
2005; McNeely and Scherr 2003).
box 6.1 Agriculture makes landscape modifcations unavoidable
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It is thus important to adapt agricultural management (including crop types) to the
ecological conditions. Growing crops unsuited to the climate conditions, or example,
could have harmul consequences. When agricultural techniques that had been developed
in the temperate climate o Europe were introduced in late 18th century Australia, the
result was vast areas o salinized lands (Folke and others 2002). rying to grow lucrative
oil palms on saline soils in the Indus Delta and Pakistan and the acid sulphate soils o
Southeast Asia is another example o a severe mismatch between agricultural activity and
ecological conditions. In the 1970s it was argued that there was a climate biaswater
blindnessthat led to eorts to transer inappropriate agricultural technology rom de-
veloped to developing countries (Falkenmark 1979).
Human well-being and ecosystem services
Te Millennium Ecosystem Assessment (MEA 2005c) showed that the well-being o hu-
man society was intimately linked to the capacity o ecosystems to provide ecosystem
services and that securing multiple ecosystem services depended on healthy ecosystems.
The Aral Sea is probably the most prominent example o how unsustainable water management or
agriculture has led to a large-scale and possibly irreversible ecological and human disaster. Reduced
water ow in the rivers supplying the sea has resulted in outcomes that have impaired human liveli-hoods and health, aected the local climate, and reduced biodiversity. Since 1960 the volume o wa-
ter in the Aral Sea Basin has been reduced by 75%, due mainly to reduced inows as a consequence
o irrigation o close to 7 million hectares o land (UNESCO 2000; Postel 1999). This has led to the
loss o 20 o 24 fsh species and collapse o the fshing industry; the fsh catch ell rom 44,000 tons
annually in the 1950s to zero, with the loss o 60,000 jobs (Postel 1996). Species diversity and wildlie
habitat have also declined, particularly in the wetlands associated with the sea (Postel 1999). The
water diversions together with polluted runo rom agricultural land have had serious human health
eects, including an increase in pulmonary diseases as winds whipped up dust and toxins rom the
exposed sea bed (WMO 1997).
Wind storms pick up some 100 million tons o dust containing a mix o toxic chemicals and salt
rom the dry sea bed and dump them on the surrounding armland, harming and killing crops as well
as people (Postel 1996). The low ows into the sea have concentrated salts and toxic chemicals,
making water supplies hazardous to drink (Postel 1996). In the Amu Darya River Basin chemicals
such as dichlorodiphenyl-trichloroethane (DDT), lindane, and dioxin have been carried by agricultural
runo and spread through the aquatic ecosystems and into the human ood chain. Secondary salini-
zation is also occurring (Williams 2002).
Attempts to rehabilitate the Northern Sea are under way through the Syr Darya and Northern Aral
Sea Project (www.worldbank.org.kz); initial results are seen as positive (Pala 2006). A dam has been
constructed between the two parts o the sea to allow the accumulation o water and to help reha-
bilitate parts o the delta. While the project aims to reestablish and sustain fshery and agricultural
activities and to reduce the harmul eects on the drinking water, the extent o past changes makes
restoration highly unlikely. The ecological and social changes in the Aral Sea ecosystem are consid-
ered largely irreversible.
box 6.2 The Aral Seaan ecological catastrophe
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6Agriculture, water, and
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Whether an ecosystem is managed primarily or ood production, water regulation, or or
other services (gure 6.2), it is possible to secure these or the long term only i basic eco-system unctioning is maintained. In many agroecosystems considerable eort goes into
ensuring crop production, but oten at the expense o other important services, such as
sheries (Kura and others 2004), reshwater supply (Vrsmarty, Lvque, and Revenga
2005), and regulation o oods (Daily and others 1997; Bravo de Guenni 2005).
Biodiversityvariability and diversity within and among species, habitats, and eco-
system servicesis important or supporting ecosystem services and has value in its own
right. Further, biodiversity can act as an insurance mechanism by increasing ecosystem
resilience (box 6.3). Some species that do not seem to have an important role in ecosystems
under stable conditions may be crucial in the recovery o an ecosystem ater a disturbance.
Similarly, i one species is lost, another with similar characteristics may be able to replace it.
While the concept o biodiversity comprises ecosystems, species, and genetic components,most o the discussion in this chapter ocuses on the unctional role o ecosystems and spe-
cies (or taxa) in terms o the ecosystem services that they provide.
Tere is increasing evidence that ecosystems play an important role in poverty reduction
(Silvius, Onela, and Verhagen 2000; WRI and others 2005). Many rural poor people rely on
a variety o sources o income and subsistence activities that are based on ecosystems and are
thus most directly vulnerable to the loss o ecosystem services [established]. Tese sources o
income, oten generated by women and children, include small-scale arming and livestock
rearing, shing, hunting, and collecting rewood and other ecosystem products that may be
sold or cash or used directly by households. Floodplain wetlands, or example, support many
human activities, including sheries, cropping, and gardening (photos 6.16.3).
Provisioning services
Goods produced or providedby ecosystems
Food Fuel wood
Fiber Timber
Regulating services
Benefits from regulation ofecosystem processes
Water partitioning Pest regulation
Climate regulation Pollination
Cultural services
Nonmaterial benefits fromecosystems
Spiritual Recreational
Aesthetic Educational
Support services
Factors necessary forproducing ecosystem services
Hydrological cycle Soil formation
Nutrient cycling Primary production
Source: Adapted from MEA 2003.
fgure6.2 Types o ecosystem services
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The decline o biodiversity globally, most severely maniested in reshwater systems (MEA 2005b),
has renewed interest in ecosystem conservation and management and in the links between bio-
diversity and ecosystem unctioning (Holling and others 1995; Tilman and others 1997), including
the role in human well-being (MEA 2005c) and the links to poverty (Adams and others 2004; WRI
and others 2005). Many people highlight the ethical argument or conserving biodiversity or its own
intrinsic value, and projects aimed at conserving endangered species (establishment o protected
areas, changed land-use practices) have been common investment strategies, with dierent social
outcomes (Adams and others 2004).
Research in recent decades has illustrated the importance o species diversity or ecosystemunctioning (see photos o wetland biodiversity). The general theory is that a more diverse system
contributes to more stable productivity by providing a means o coping with variation.
However, it has recently been argued that it is not the richness o species that contributes to eco-
system unctioning, but rather the existence o unctional groups (predators, pollinators, herbivores,
decomposers) with dierent and sometimes overlapping unctions in relation to ecosystem process-
es (Holling and others 1995). To understand the role o diversity or ecosystem unctioning, it is
necessary to analyze the identities, densities, biomasses, and interactions o populations o species
in the ecosystem, as well as their temporal and spatial variations (Kremen 2005). Diversity o organ-
isms within and between unctional groups can be critical or maintaining resistance to change.
Species that may seem redundant during some stages o ecosystem development may be criti-
cal or ecosystem reorganization ater disturbance (Folke and others 2004). Response diversity (the
dierential responses o species to disturbance) helps to stabilize ecosystem services in the ace o
shocks (Elmqvist and others 2003).
box 6.3 Biodiversity and ecosystem resilience
PhotobyC.
MaxFinlayson
PhotobyKarenConnif
PhotobyC.
MaxFinlayson
PhotobyC.
MaxFinlayson
Pelicans Dragony
ElephantsCrocodile
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6Agriculture, water, and
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Te Millennium Ecosystem Assessment concluded that a ailure to tackle the decline in
ecosystem services will seriously erode eorts to reduce rural poverty and social inequity and
eradicate hunger; this is a critical issue in many regions, particularly in Sub-Saharan Arica
(WRI and others 2005). It is also true that continued and increasing poverty can intensiy
pressure on ecosystems as many o the rural poor and other vulnerable people are let with no
options but to overexploit the remaining natural resource base. Te result is oten a vicious
cycle in which environmental degradation and increased poverty are mutually reinorcing
orces (Silvius and others 2003). Te Millennium Ecosystem Assessment (MEA 2005c) con-
cluded that interventions that led to the loss and degradation o wetlands and water resources
would ultimately undermine progress toward achieving the Millennium Development Goals
o reducing poverty and hunger and ensuring environmental sustainability.
Consequences and ecosystem impacts
Modications o the landscape to increase global ood production have resulted in in-
creased provisioning services, but also in adverse ecological changes in many ecosystems,
with concomitant loss and degradation o services (MEA 2005c). Water management has
caused changes in the physical and chemical characteristics o inland and coastal aquatic
ecosystems and in the quality and quantity o water, as well as direct and indirect biological
changes (Finlayson and DCruz 2005; Agardy and Alder 2005; Vrsmarty, Lvque, and
Revenga 2005). It has also caused changes in terrestrial ecosystems through the expansion
o agricultural lands and changes in water balances (Foley and others 2005).Tese changes have had negative eedback on the ood and ber production activities o
agroecosystems, or example through reductions in pollinators (Kremen, Williams, and Torp
2002) and degradation o land (see chapter 15 on land) [established but incomplete]. Adverse
changes have varied in intensity, and some are seemingly irreversible, or at least dicult or
expensive to reverse, such as the extensive dead zones in the Gul o Mexico and the Baltic
Sea (Dybas 2005). Te catastrophic collapse o coastal sheries as a consequence o environ-
mental change is another example (see chapter 12 on inland sheries). Tis chapter ocuses
on the consequences or ecosystems o green and blue water management in agriculture while
acknowledging that many other human activities also play a role. Synergistic and cumulative
eects can make it extremely dicult to attribute change to a single cause (box 6.4).
PhotosbyC.
MaxFinlayson
Fisheries, cropping, and gardening are among the many human activities supported by oodplain wetlands.Photo
6.1
Photo
6.2
Photo
6.3
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Aquatic ecosystems
Water-related agricultural modications have had major ecological, economic, and social
consequences, including eects on human health, through changes in the key ecological
components and processes o rivers, lakes, oodplains, and groundwater-ed wetlands [well
established]. Tese changes include alterations to the quantity, timing, and natural vari-ability o ow regimes; alterations to the waterscape through the drainage o wetlands and
the construction o irrigation storages; and increased concentrations o nutrients, trace
elements, sediments, and agrochemicals.
Aquatic ecosystems provide a wide array o ecosystem services [well established].
Teir nature and value are not consistent, however, and our understanding o how eco-
system processes support many o these services is inadequate (Finlayson and DCruz
2005; Baron and others 2002; Postel and Carpenter 1997). In several areas around the
world changes have contributed to a loss o provisioning services such as sheries, regu-
lating services such as storm protection and nutrient retention, and cultural services
such as recreational and aesthetic uses. In some cases ecosystems have passed thresholds
New challenges are emerging or water managers in agriculture as a consequence o the cumulative
and sometimes synergistic eects o multiple drivers, including climate change and invasive spe-
cies.
Global climate change is expected to directly and indirectly alter and degrade many ecosystems
(Gitay and others 2002). For example, it will exacerbate problems associated with already expanding
demand or water where it leads to decreased precipitation, while in limited cases, where precipita-
tion increases, it could lessen pressure on available water. There are also major expected conse-
quences or wetland ecosystems and species, although the extent o change is not well established
(Gitay and others 2002; van Dam and others 2002; Finlayson and others orthcoming).There is growing recognition o the important role that invasive species can play in degradation o
ecosystems and ecosystem services (MEA 2005c). Invasive species, spread through water regula-
tion or transport and water transer and through trade, have altered the character o many aquatic
ecosystems (see photo). Once established, invasive plants can block channels and irrigation canals
and decrease connectivity within and between rivers and wetlands, replace valuable species, and
damage inrastructure (Finlayson and DCruz 2005).
Invasive species rom orest plantations are also
threatening water supply or downstream users, as
shown in South Arica where cities such as Cape
Town and Port Elisabeth depend on runo rom the
natural low biomass vegetation in the catchment
(Le Maitre and others 1996). Invasive species in ri-parian areas are a problem or water resources in
several other parts o the world. The annual losses
due to the invasive woody species tamarisk in the
semiarid western United States reach $280$450
a hectare, with restoration costs o approximately
$7,400 a hectare (Zavaleta 2000).
box 6.4Cumulative changesnew challenges or
water management in agriculture
PhotobyC.
MaxFinlayson
Water hyacinth, a rapidly growing, ree-oatinginvasive plant, has degraded many ecosystems
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6Agriculture, water, and
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or gone through regime shits leading to a collapse o ecosystem services, making the
costs o restoration (i possible at all) very high. Tese losses have adverse eects on
livelihoods and economic production [well established]. Tere is ongoing debate whether
the positive outcomes in terms o increased upstream production o ood outweigh the
negative consequences or people dependent on downstream ecosystem services. While
most cost-benet studies show that the costs o the losses have been higher than the
gains, other scientists argue that these studies have many weaknesses (Balmord and
others 2002).
Although agriculture, especially water management in agriculture, is a major driver
behind the loss o downstream ecosystem services [well established], there are competing
explanations or the manner and importance o individual processes and events and theultimate role o agriculture as a triggering orce or degradation is in many situations un-
known. Dams, overshing, urban water withdrawals, and natural and anthropogenic cli-
mate variation can contribute to cumulative and synergistic eects, reduced resilience, and
increased degradation o downstream ecosystems (photo 6.4). Uncertainty is oten high
when it comes to the exact location or timing o the response o downstream ecosystems to
upstream water alterations. Tis does not mean that we can ignore the role o agriculture.
But we need to address the problems as complex and interacting, and to consider a systems
perspective or analyzing multiple drivers o change.
Te next two sections oer examples o how water-related management in agriculture
has changed the capacity o downstream ecosystems to generate ecosystem services and a
brie discussion o the consequences o some o these changes.
Water quantity and waterscape alterations. Increased cultivation in recent decades has
resulted in increased diversion o reshwater, with some 70% o water now being used or
agriculture and reaching as high as 85%90% in parts o Arica, Asia, and the Middle
PhotobyC.
MaxFinlayson
Photo 6.4 Dams provide many benefts or people, but also aect ecosystems by changing thehydrology and ragmenting rivers
Long-term trend
analysis o 145major world
rivers indicates
that discharge
has declinedin one-th o
cases
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East (Shiklomanov and Rodda 2003) [well established]. Regulation o the worlds rivers
has altered water regimes, with substantial declines in discharges to the ocean (Meybeck
and Ragu 1997). Long-term trend analysis (more than 25 years) o 145 major world riv-
ers indicates that discharge has declined in one-th o cases (Walling and Fang 2003).
Worldwide, large articial impoundments hold vast quantities o water and cause signi-
cant distortion o ow regimes (Vrsmarty and others 2003), oten with harmul eects
on human health (box 6.5).
Water diversion and the construction o hydraulic inrastructure (reservoirs, physical
barriers) have altered downstream ecosystems through changes in the quantity and pattern
o water ows and the seasonal inows o reshwater (see global summaries in Vrsmarty,
Lvque, and Revenga 2005 and Finlayson and DCruz 2005). Negative eects includethe loss o local livelihood options, ragmentation and destruction o aquatic habitats,
changes in the composition o aquatic communities, loss o species, and health problems
resulting rom stagnant water. Less ooding means less sedimentation and deposition o
nutrients on oodplains and reduced ows and nutrient deposition in parts o the coastal
zone (Finlayson and DCruz 2005).
Many water-related diseases have been successully controlled through water management (or ex-
ample, malaria in some places), but others have been exacerbated by the degradation o inlandwaters through water pollution and changes in ow regimes (the spread o schistosomiasis). Where
diseases have spread, the adverse eects on human health are due to a complex mix o environmen-
tal and social causes. The Millennium Ecosystem Assessment reported many instances where water
management practices contributed to a decline in well-being and health (MEA 2005a; Finlayson and
DCruz 2005). This includes diseases caused by the ingestion o water contaminated by human or
animal eces; diseases caused by contact with contaminated water, such as scabies, trachoma, and
typhus; diseases passed on by intermediate hosts such as aquatic snails or insects that breed in
aquatic ecosystems, such as dracunculiasis and schistosomiasis, as well as dengue ever, flariasis,
malaria, onchocerciasis, trypanosomiasis, and yellow ever; and diseases that occur when there is
insufcient clean water or basic hygiene.
In addition to disease rom inland waters, waterborne pollutants have a major eect on human
health, oten through their accumulation in the ood chain. Many countries now experience problems
with elevated levels o nitrates in groundwater rom the large-scale use o organic and inorganic ertil-
izers. Excess nitrate in drinking water has been linked to methemoglobin anemia in inants.
There is increasing evidence rom wildlie studies that humans are at risk rom a number o chemi-
cals that mimic or block the natural unctioning o hormones, interering with natural bodily processes,
including normal sexual development. Chemicals such as DDT, dioxins, and those in many pesticides
are endocrine disruptors, which may interere with human hormone unctions, undermining disease
resistance and reproductive health.
The draining and burning o orested peat swamps in Southeast Asia have had devastating health
eects (see box 6.6 later in this chapter) that extend across many countries and that may be long-
lasting. The investigation o environment-related health eects linked with the ongoing degradation
o the orested peat swamps is a major issue or health services in the region.
box 6.5 Water management and human health
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6Agriculture, water, and
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Interbasin transers o water, particularly large transers between major river systems
as are being planned in India, or example, are expected to be particularly harmul to
downstream ecosystems (Gupta and Deshpande 2004; Alam and Kabir 2004) and to ex-
acerbate pressures rom hydrological regulation (Snaddon, Davies, and Wishart 1999).
Where these are being considered, scientic and transparent assessments o the benets
and problems are strongly encouraged. Junk (2002) has highlighted the similar adverse
consequences on water regimes expected rom the construction o industrial waterways
(hidrovias) through large wetlands, such as the Pantanal o Maso Grosso, Brazil. Te na-
ture o expected changes depends on the amount and timing o water being transerred
and so needs to be assessed case by case.
Shrinking lakes. Tere are many instances where consumptive water use and waterdiversions have contributed to severe degradation o downstream ecosystem services. Te
degradation o the Aral Sea in Central Asia represents one o the most extreme cases (see
box 6.2).
Te desiccation o Lake Chad in West Arica is another example. It shrank rom
25,000 square kilometers in surace area to one-twentieth that size over a 35-year period.
However, there are competing explanations or this reduction. Natural rainall variability
is an important driver. Te lake is very shallow, and at various times in its history it has
assumed dierent states, with changes triggered by climate variability (Lemoalle 2003). It
is unclear what role human-induced change has played, but dierent drivers include the
withdrawal o irrigation water, land-use changes reducing precipitation through changes
in albedo (the energy that is reected by the earth and that varies with land surace charac-teristics), and reduced moisture recycling (Coe and Foley 2001).
Lake Chapala, the worlds largest shallow lake, situated in the Lerma-Chapala Basin
in central Mexico, is another example o consumptive water use upstream aecting the
size o a lake. During 19792001 water volume in the lake dropped substantially to about
20% o capacity due to excessive water extraction or agricultural and municipal needs.
Average annual rainall rom 1993 to 2003 was only 5% below the historical average and
eorts were made to reduce water use in irrigation, but still the amount o surace and
groundwater used in the basin exceeded supply by 9% on average (Wester, Scott, and
Burton 2005). Above average rains in 2003 and 2004 increased the water volume to about
6,000 million cubic meters. Tere is still intense competition over water allocation, and
environmental water requirements have yet to be determined, leaving the uture o the lakeand the allocation o water or urban and agricultural purposes under threat.
Te high variability in lake volume in both Lake Chad and Lake Chapala means that
the people depending on ecosystem services rom these basins need to have a high adaptive
capacity to cope with the rapidly changing circumstances, whether induced by people or
nature.
Shrinking rivers. Consumptive use and interbasin transers have transormed sev-
eral o the worlds largest rivers into highly stabilized and, in some cases, seasonally non-
discharging, channels (Meybeck and Ragu 1997; Snaddon, Davies, and Wishart 1999;
Cohen 2002). Streamow depletion is a widespread phenomenon in tropical and sub-
tropical regions in rivers with large-scale irrigation, including the Pangani (IUCN 2003),
Worldwide,
large articial
impoundments
hold vastquantities o
water and cause
signicant
distortion o fowregimes, oten
with harmul
eects on
human health
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6Agriculture, water, and
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2003). Indeed, there are instances where the opposite occurs: where wetlands reduce low
ows, increase oods, or act as a barrier to groundwater recharge. Given the wide range o
wetlands, rom entirely groundwater-ed springs and mountain bogs to large inland river
oodplains, such variation should not be surprising.
Changes in water quality. Many actors contribute to changes in water quality. Tis sec-
tion looks at nutrient loads, agrochemicals, and siltation.
Nutrient loading. Te use o ertilizers has brought major benets to agriculture, but
has also led to widespread contamination o surace water and groundwater through run-
o. Over the past our decades excessive nutrient loading has emerged as one o the most
important direct drivers o ecosystem change in inland and coastal wetlands, with the ux
o reactive nitrogen to the oceans having increased by nearly 80% rom 1860 to 1990
(MEA 2005c). Phosphorus applications have also increased, rising threeold since 1960,
with a steady increase until 1990 ollowed by a leveling o at approximately the applica-
tion rates o the 1980s (Bennett, Carpenter, and Caraco 2001). Tese changes are mirrored
Large parts o the tropical peat swamp orests in Southeast Asia have been seriously degraded,
largely due to logging or timber and pulp (Wsten and others 2006; Page and others 2002). The
process has been accelerated over the last two decades by the conversion o orests to agriculture,
particularly oil palm plantations. Drainage and orest clearing threaten the stability o large tracts o
orests in Indonesia and Malaysia and make them susceptible to fre.
Attempts to clear and drain the orests and establish agriculture have high rates o ailure. Under
the Mega Rice Project in Kalimantan, Indonesia, large areas o orest were cleared and some 4,600
kilometers o drainage canals were constructed in an attempt to grow rice on a grand scale using
emigrant workers rom the heavily populated neighboring island o Java. The cleared land was un-suited to rice production, and the scheme was abandoned. In 1997 land clearing and subsequent
uncontrolled fres severely burned about 5 million hectares o orest and agricultural land in Kaliman-
tan, releasing an estimated 0.82.6 billion tons o carbon dioxide into the atmosphere (Glover and
Jessup 1999; Page and others 2002; Wooster and Strub 2002). The fres created a major atmospheric
haze, with severe impacts on the health o 70 million people in six countries. In addition, there have
been economic eects on timber and agricultural activities, with the fres compounding the loss o
peatlands through clearing and ailed attempts to cultivate large areas or rice.
Rehabilitation o some degraded areas is under way, but it is a slow and difcult process trying
to reestablish the hydrology and vegetation (Wsten and others 2006). At a regional level the Asso-
ciation o Southeast Asian Nations (ASEAN) has taken an active interest in the problem through the
ASEAN Peatland Management Initiative, acilitating the sharing o expertise and resources among the
aected countries to prevent peatland fres and manage peatlands wisely. The regional initiatives arelinked with national action plans. Monitoring mechanisms are in place, and a policy o zero burning
or urther land clearing has also been established, in particular or oil palm plantations.
Despite these steps, the problem o peatland degradation continues. The expansion o oil palm
plantations is a major driver. The peat swamps are still being cleared and burned, undermining eorts
to conserve and use the peatlands o Southeast Asia wisely and threatening the health o people lo-
cally and regionally.
box 6.6The widespread impacts o draining and
burning in Southeast Asian peatlands
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by phosphorus accumulation in soils, with high levels o phosphorus runo. In developed
countries annual storage peaked around 1975 and is now at about the same annual rate as
in 1961. In developing countries, however, storage went rom negative values in 1961 to
about 5 teragrams per year in 1996.
Excessive nutrient loading can cause algal blooms, decreased drinking water quality,
eutrophication o reshwater ecosystems and coastal zones, and hypoxia in coastal waters.
In Lake Chivero, Zimbabwe, agricultural runo is seen as responsible or algal blooms,
inestations o water hyacinth, and sh declines as a result o high levels o ammonia and
low oxygen levels (UNEP 2002). In Australia extensive algal blooms in coastal inlets and
estuaries, inland lakes, and rivers have been attributed to increased nutrient runo rom
agricultural elds (Lukatelich and McComb 1986; Falconer 2001). Diuse runo o nu-trients rom agricultural land is held to be largely responsible or increased eutrophication
o coastal waters in the United States as well as or the periodic development, oten varying
rom year to year, o anoxic conditions in coastal water in many parts o the world, such as
the Baltic and Adriatic Seas and the Gul o Mexico (Hall 2002).
Nutrient management can be undermined by the loss o wetlands that assimilate
nutrients (nitrogen, phosphorous, organic material) and some pollutants. Extensive evi-
dence shows that up to 80% o the global incident nitrogen loading can be retained within
wetlands (Green and others 2004; Galloway and others 2004). However, the ability o
such ecosystems to cleanse nutrient-enriched water varies and is not unlimited (Alexander,
Smith, and Schwarz 2000; Wollheim and others 2001). Verhoeven and others (2006)
point out that many wetlands in agricultural catchments receive excessively high loadingso nutrients, with detrimental eects on biodiversity. Wetlands and lakes risk switching
rom a state in which they retain nutrients to one in which they release nutrients or emit
There are reported cases o regime shits occurring in lakes because o increased nutrient loading,
resulting in the loss o ecosystem services such as fsheries and tourism (Folke and others 2004).
Some temperate lakes have experienced shits between a turbid water and a clear water state, with
the shit oten attributed to an increase in phosphorous loading (Carpenter and others 2001). Some
tropical lakes have shited rom a dominance o ree-oating plants to submerged plants, with nutrient
enrichment seemingly reducing the resilience o the submerged plants, possibly through shading and
changes in underwater light (Scheer and others 2001). Other wetlands and coastal habitats have
also experienced similar shits. In the United States nutrient enrichment caused a shit in emergent
vegetation in the Everglades and a shit rom clear water to murky water with algal blooms in Florida
Bay (Gunderson 2001).
Other evidence comes rom lakes subject to inflling and nutrient enrichment. In Lake Hornborga
in Sweden emergent macrophytic vegetation prolierated ater initial inflling o the lake margins and
increased runo o nutrients. The situation was reversed only ater massive mechanical intervention
and investment (Hertzman and Larsson 1999). In Australia agricultural runo has resulted in shits in
vegetation dominance as a consequence o nutrient enrichment, increased inundation and saliniza-
tion (Davis and others 2003; Strehlow and others 2005).
box 6.7 Regime shits rom excessive nutrient loads
Nutrient
managementcan be
undermined
by the loss
o wetlands
that assimilatenutrients and
some pollutants
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6Agriculture, water, and
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the greenhouse gas nitrous oxide. Regime shits are oten rapid, but they have likely ol-
lowed a slower and dicult to detect change in ecosystem resilience. It is generally dicult
to monitor changes in resilience beore a system hits the threshold and changes rom one
state to another (box 6.7; Carpenter, Westley, and urner 2005).
Agrochemical contamination. Pollution and contamination rom agricultural chemi-
cals have been well documented since the publication o the seminal book Silent Spring
(Carson 1962). Bioaccumulation as a consequence o the wide use o agrochemicals has
had dire outcomes or many species that reside in or eed predominantly in wetlands or
lakes that have accumulated residues rom pesticides [well established]. Te decline in the
breeding success o raptors was a turning point in developing awareness about the dangers
o using pesticides (Carson 1962).An increasing amount o analytical and ecotoxicological data has become available or
aquatic communities, and more recent research has also ocused on risk assessments and
the development o diagnostic tests that can guide management decisions about the use
o such chemicals (van den Brink and others 2003). aylor, Baird, and Soares (2002) have
highlighted the high levels o pesticide use and low levels o environmental risk assessment
in developing countries. Tey have promoted an integrated approach to evaluating envi-
ronmental risks rom pesticides that incorporates stakeholder consultation, chemical risk
assessment, and ecotoxicological testing or ecological eects, also taking into account the
potential eects on human health.
Vrsmarty, Lvque, and Revenga (2005) report that water contamination by pes-
ticides has increased rapidly since the 1970s despite increased regulation o the use oxenobiotic substances, especially in developed countries. However, bans on the use o these
chemicals have generally been imposed only two to three decades ater their rst commer-
cial use, as with DD and atrazine. Many o these substances are highly persistent in the
environment, but because o the generally poor monitoring o their long-term eects the
global and long-term implications o their use cannot be ully assessed. Policy responses
to contamination may lag ar behind the event, as shown in the well documented case o
agricultural pesticide bioaccumulation o DD in the Zambezi Basin (Berg, Kilbus, and
Kautsky 1992).
Siltation o rivers. In many parts o the world extensive sheet wash and gully erosion
due to land management practices have devastated large areas, reduced the productivity o
wide tracts o land, led to rapid siltation o reservoirs and threatened their longevity, andincreased sediment loads in many rivers (see chapter 15 on land). On a regional scale some
reservoirs in Southern Arica are at risk o losing more than a quarter o their storage capac-
ity within 2025 years (Magadza 1995). While many Australian and Southern Arican wa-
ters are naturally silty, many have experienced increased silt loads as a result o agricultural
practices (Davies and Day 1998). Zimbabwes more than 8,000 small to medium-size dams,
or example, are threatened by sedimentation rom soil erosion, while the Save River, an in-
ternational river shared with Mozambique, has been reduced rom a perennial to a seasonal
river system due in large part to increased siltation as a result o soil erosion.
Globally, rivers discharge nearly 38,000 cubic kilometers o reshwater to the oceans
and carry roughly 70% o the sediment input, though rivers draining only 10% o the
Water
contaminationby pesticides
has increased
rapidly since the
1970s despite
increasedregulation,
especially in
developed
countries
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land area contribute 60% o the total sediment discharge (Milliman 1991). Te high sedi-
ment loads carried by Asian rivers are a consequence o land-use practices, particularly
land-clearing practices or agriculture that lead to erosion, a situation likely to continue
as a consequence o the expansion o agriculture in Arica, Asia, and Latin America (Hall
2002). A notable outcome o the supply o sediment and associated nutrients to the oceans
is the increased requency and intensity o anoxic conditions in recent years (Hall 2002).
Tere are also situations where river regulation has caused a decline in silt transport to
downstream habitats, with reduced siltation along oodplains and in deltas and other down-
stream ecosystems. Tis has occurred in the Mesopotamian Marshes, where large-scale drain-
age is a bigger problem than silt-related changes in the downstream ecosystems (box 6.8).
Terrestrial ecosystems
Hydrological changes that occur as a result o agricultural expansion, particularly into
orests, are seldom thought o in terms o water management in agriculture, although such
changes are o at least the same magnitude as those resulting rom irrigation (Gordon and
others 2005). Tis is an area in need o urther research, especially as biouels and tree
The Mesopotamian wetlands, one o the cradles o civilization and a biodiversity center o global
importance, used to cover more than 15,000 square kilometers in the lower Euphrates and TigrisBasins. Agricultural development and other drainage activities over the past 30 years have reduced
them to 14% o their original size, and vast areas have been turned into bare land and salt crusts
(Richardson and others 2005). The ecological implications have been severe, with drastic land deg-
radation and impacts on wildlie, including bird migration and the extinction o endemic species, and
on the ecology o the downstream Shatt el Arab and coastal fsheries in the Persian Gul. The local
population o hal a million Marsh Arabs have become environmental reugees.
The causes o this severe ecological degradation are complex. Some o the causes were inten-
tional, the results o drainage eorts to reclaim marshland, deal with soil salinization, improve agri-
cultural productivity, and strengthen military security in southern Iraq in the 1980s and 1990s. Other
causes were unintentional and included both the large-scale consumptive water use in irrigation
systems and the return o saline drainage, agricultural and industrial chemical pollution, and the loss
o ood ow, with its load o silt and nutrients, linked to recent large-scale streamow regulation inupstream Turkey.
With the extent o existing regulation and degradation, the proposed rehabilitation o 30% o the
Central Marshes upstream o the conuence o the Euphrates and Tigris could generate its own
adverse impacts on aquatic ecosystems urther downstream. The additional evaporation rom just
1,000 square kilometers o restored open-water suraces would consume an average ow o 67 cubic
meters per second, or 25% o the original (pre-regulation) dry season ow, and reduce downstream
streamow even urther. Without an increase in the amount o water available, simply returning the
water to upstream areas may not be enough to restore the marshes and could urther reduce the ow
o water to downstream areas.
Source: Partow 2001; Italy, Ministry or the Environment and Territory, and Free Iraq Foundation 2004.
box 6.8 Desiccation o the Mesopotamian wetlands
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cover and its management (McCulloch and Robinson 1993; Bosch and Hewlett 1982;
Bruijnzeel 1990).
General work on the inuence o vegetation, climate, and land cover on the water
balance o a system has shown that there are vegetation-specic changes (Lvovich 1979;
Calder 2005). Management o plant production that redirects blue water to green water
can reduce the amount o water to downstream systems (Falkenmark 1999). For example,
replacing crop or grasslands with orest plantations can decrease runo and streamow
(Jewitt 2002). Te South Arican Water Act classies orest plantations as a streamow
reduction activity, and orestry companies have to pay or their water use since less o the
precipitation reaches the river.
Moisture recycling. Clearing land or agriculture and increasing use o irrigation have modi-
ed green water ows globally, reducing them by 3,000 cubic kilometers through orest clear-
ing and increasing them by 1,0002,600 cubic kilometers in irrigated areas (Dll and Siebert
2002; Gordon and others 2005). Te ability o changes in land cover to inuence climate
through changes in green water ow has been increasingly recognized. It has been suggested
that large-scale deorestation can reduce moisture recycling, aect precipitation (Savenije 1995,
1996; renberth 1999), and alter regional climate, with indications o global impacts (Kabat
and others 2004; Nemani and others 1996; Marland and others 2003; Savenije 1995).
Pielke and others (1998) conclude that the evidence is convincing that land cover
changes can signicantly inuence weather and climate and are as important as other hu-
man-induced changes or the Earths climate. However, the models employed do not dealexplicitly with green water ows, but rather with the compounded eects o changes in al-
bedo, surace wind, lea area index, and other indicators. Nevertheless, regional studies in West
Arica (Savenije 1996; Zheng and Eltathir 1998), the United States (Baron and others 1998;
Pielke and others 1999), and East Asia (Fu 2003) have illustrated that changes in land cover
aect green water ows, with impacts on local and regional climates. Likewise, biome-specic
models o land cover conversions rom rainorest to grasslands have shown a decrease in vapor
ows and precipitation as well as eects on circulation patterns (Salati and Nobre 1991) and
savannahs (Homan and Jackson 2000). Tere are also indications that increased vapor ows
through irrigation can alter local and regional climates (Pielke and others 1997; Chase and
others 1999). Te conversion o steppe to irrigated croplands in Colorado resulted in a 120%
increase in vapor ows (Baron and others 1998), contributing to higher precipitation, lowertemperatures, and an increase in thunderstorm activity (Pielke and others 1997).
Whether these changes can trigger rapid regime shits (box 6.9), which in many cases
may be irreversible, and changes to which armers need to adapt is still speculative. In the Am-
azon the clearing o land has reduced moisture recycling, resulting in prolonged dry seasons
and increased burning, and may have triggered an irreversible regime shit rom rainorest veg-
etation to savannah (Oyama and Nobre 2003). Tere is also increasing concern about changes
in the Arican and Asian monsoons, including weakening o the East Asian summer monsoon
low-pressure system and an increase in irregular northerly ows (Fu 2003). Likewise, modeled
vegetation changes or agricultural expansion in West Arica have shown potentially dramatic
impacts on rainall in the Arican monsoon circulation (Zheng and Eltathir 1998).
There are
indications thatincreased vapor
fows through
irrigation can
alter local
and regionalclimates
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6Agriculture, water, and
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Societal responses and opportunities
Te negative eects o past agricultural management on ecosystem services and the need
to produce more ood or growing populations provide an unparalleled challenge. Meet-
ing this challenge requires large-scale investments to improve agricultural management
practices, increase the availability o techniques to minimize adverse ecological impacts,
enhance our understanding o ecosystem-agriculture interactions, and reduce poverty and
social inequities, including issues o gender, health, and education that aect ecosystem
management decisions.In presenting possible responses or meeting this challenge, we emphasize several
ecological outcomes that we consider to be critical in this eort: maintenance or rehabili-
tation o the ecological connectivity, heterogeneity, and resilience in the landscape, which
in turn implies maintenance or rehabilitation o the biodiversity that characterizes the
landscape. We ocus on integration and awareness o the negative consequences o choices
in terms o the tradeos between ood production and other ecosystem services. We do
not propose specic responses or specic ecosystems or locations, although we aim to
help national and local decisionmaking with a ramework or addressing some o these
issues. Many o the responses outlined are dependent on eective governance measures
and policies that support sustainable development with a balance o ecological and social
Ecosystems change and evolve, with disturbance now seen as an inherent component o ecosystem
processes [well established]. The speed o change in many ecosystems has, however, increased
rapidly, and there is now concern that large-scale changes will increase the vulnerability o some
ecosystems to water-related agricultural activities. Ecosystems are complex adaptive systems (Levin
1999), with nonlinear dynamics and thresholds between dierent stable states. Nonlinear changes
are sometimes abrupt and large, and they may be difcult, expensive, or impossible to reverse. The
increased likelihood o nonlinear changes stems rom drivers o ecosystem change that adversely
aect the resilience o an ecosystem, its capacity to absorb disturbance, undergo change, and still
retain essentially the same unction, structure, identity, and eedbacks (Gunderson and Holling 2002;Carpenter and others 2001) and provide components or renewal and reorganization (Gunderson and
Holling 2002).
Variability and exibility are needed to maintain ecosystem resilience. Attempts to stabilize sys-
tems in some perceived optimal state, whether or conservation or production, have oten reduced
long-term resilience, making the system more vulnerable to change (Holling and Mee 1996). While
todays agricultural systems are able to better deal with local and small-scale variability, the simpli-
fcations o landscapes and reduction o other ecosystem services have decreased the capacity o
agricultural systems and other ecosystems to cope with larger scale and more complex dynamics
through reduced ecosystem resilience locally and across scales (Gunderson and Holling 2002).
Little is yet known about how to estimate resilience and detect thresholds beore regime shits
occur (Fernandez and others 2002). Better mechanisms to monitor regime shits include the iden-
tifcation and monitoring o slowly changing variables (Carpenter and Turner 2000) and measurablesurrogates o resilience (Bennett, Cumming, and Peterson 2005; Cumming and others 2005).
box 6.9Resilience and the increased risk o rapid
regime shits in ecosystems
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outcomes, issues covered in detail in chapters 5 on policies and institutions and 16 on
river basins.
Improving agricultural technology and management practices
Te Millennium Ecosystem Assessment (MEA 2005c) supports the view that intensica-
tion o agricultural systems will create ewer tradeos with ecosystem services than will
expansion. Intensication will require improvements in agricultural productivity, espe-
cially in water productivity (see chapter 7 on water productivity) in water-scarce envi-
ronments. However, because intensication can bring its own ecological problems, or
example, through pollution or the introduction o invasive species, command and control
approaches to management should be avoided (Holling and Mee 1996). Te potentialproblems o intensication could be lessened or avoided through the adoption o a systems
approach to agriculture and integrated approaches to landscape management (see below).
Many o the chapters in this volume address agricultural techniques and improved
management practices. Chapters 14 on rice and 15 on land highlight the need to consider
techniques and practices that may not increase the production o one or a ew specic
crops but that support the provision o multiple benets. Unless responses that restrict
the potential adverse impacts o intensication are applied, intensication will not be any
more environmentally and socially benign than many past agricultural practices.
Applying integrated approaches to water, agriculture, and other
ecosystemsIntegrated policy and management approaches are increasingly seen as crucial in acilitat-
ing decisionmaking and making tradeos between ood and other ecosystem services. In-
tegrated approaches have taken many orms, including integrated river basin management,
PhotobyC.
MaxFinlayson
Photo 6.5 This use o wetlands in Malawi attempts to integrate multiple benefts and costs
The potential
problems ointensication
could be
lessened
through the
adoption oa systems
approach to
agriculture
and integratedapproaches
to landscape
management
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6Agriculture, water, and
ecosystems: avoiding thecosts o going too ar
integrated land and water management, ecosystem approaches, integrated coastal zone
management, and integrated natural resources management. Teir general aim is oten the
same. Tey actively seek to address integration o all the benets and costs associated with
land-use and water decisions, including eects on ecosystem services, ood production,
and social equity, in a transparent manner; to involve key stakeholders and cross-institu-
tional levels; and to cross relevant biophysical scales, addressing interconnectedness across
subbasin, river basin, and landscape scales (photo 6.5).
While integrated approaches or environmental management are seen as an impor-
tant eort and have long been promoted, there are ew successul examples. Te gover-
nance systems required to support the appropriate institutional and managerial arrange-
ments, particularly or the allocation o resources and planning authority concomitantwith responsibility at a local level, seem dicult to achieve (see, or example, chapter 16 on
river basins). One complaint is that most o these approaches are based on a technocratic
view o decisionmaking, whereas real lie is ar messier, with power struggles, lack o trust
between and within stakeholder groups, and complex and evolutionary behavior o eco-
systems that make it dicult to assess total benets and impacts. Folke and others (2005)
see a need or more emphasis on building, managing, and maintaining collaborative social
relationships or river basin governance, which is in line with current thinking about eco-
system management.
Where river basin organizations have succeeded, that has oten been because o their
ability to deliver on the common aims o jurisdictions (such as coordinated water man-
agement to supply irrigation). Te situation is more complex when dealing with inter-national transboundary rivers, such as the Nile and the Mekong. An alternative to river
basin processes may be to explore more regional guidance or common policies, as is being
developed in Southern Arica (box 6.10).
Te complexity o the social policy and institutional links that govern ecosystem
management and inuence necessary tradeos is shown or wetlands in gure 6.3. Dier-
ences in local contexts may aect the manner in which relationships between individuals
While integrated
approaches orenvironmental
management
have long been
promoted,
there are ewsuccessul
examples
The South Arican National Water Act o 1998 protects the water requirements or ecosystems and
supports them through an ongoing scientifc eort. This is in line with the principles contained in
the Southern Arican Development Commission (SADC) regional water policy o May 2004, which
recognizes the environment as a legitimate user o water and calls on SADC members to adopt all
necessary strategies and actions to sustain the environment. At the national level water reorms in
South Arica and Zimbabwe have successully mainstreamed environmental water requirements in
water resources policy and legislation. Namibia is similarly considering policy that stresses sectoral
coordination, integrated planning and management, and resource management aimed at coping with
ecological and associated environmental risks.
Mexicos 1992 Law o National Waters is another example o national water reorms that consider
ecosystem needs. It empowers the ederal government to declare as disaster areas watersheds or
hydrological regions that represent or may represent irreversible risks to an ecosystem.
box 6.10 National and regional policy initiatives on water and ecosystems
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6Agriculture, water, and
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and institutions are built and maintained. High levels o knowledge and human capacity
are considered critical to crating the institutions and policies required or successul in-
tegrated water management (see chapter 5 on policies and institutions). Tis chapter em-
phasizes the need to raise awareness o the role o ecosystem services in societal well-being
in both multiunctional agricultural systems and across landscapes and on the importance
o maintaining the ecological and social processes that support these.
Assessing and nurturing multiple benefts
Improving awareness and understanding. Integrated approaches help to deal with the
competing interests in water resources Tey make it possible to share the multiple benetsand costs that are generated across a river basin and that are improved or degraded through
agricultural interventions in the landscape.
Assessment o the multiple ecosystem services and the processes that support them is
a key component o these approaches. Historically, decisions concerning ecosystem man-
agement have tended to avor either conversion o ecosystems or management or a single
ecosystem service, such as water supply or ood production, oten without consideration o
the eects on such groups as the rural poor, women, and children (MEA 2005c). Many eco-
system services do not have a price on the market and are oten neglected in policymaking
and decisionmaking. As we better understand the benets provided by the entire array
o ecosystem services, we also realize that some o the best response options will involve
managing landscapes, including agriculture, or a broader array o services. Tat will entailtaking greater account o social issues, such as gender-based roles and poverty, when mak-
ing decisions about agriculture and water management (WRI and others 2005).
Te Millennium Ecosystem Assessment has provided a major advance in under-
standing the links between the provision o ecosystem services and human well-being
(www.maweb.org). Increased awareness is still needed on several dierent levels. Te
scientic knowledge o how ecosystem services contribute to human well-being within
and between dierent sectors o society, and the role o water in sustaining these ser-
vices, need to be improved. Dissemination o inormation on these issues and dialogue
with stakeholders should be enhanced. Civil society organizations can help to ensure
that appropriate consideration is given to the voices o individuals and social groups and
to nonutilitarian values in decisionmaking. Minority groups and disadvantaged groups,such as indigenous people and women, in particular, need to be heard. Women play a
critical and increasing role in agriculture in many parts o the developing world (Elder
and Schmidt 2004).
Urbanization provides new challenges. For the rst time in human history more
people live in cities than in the rural areas. It has been estimated that the urban areas in
the Baltic Sea region in northern Europe need an area o unctioning ecosystems some 500
times the size o the cities themselves to generate the ecosystem services they depend on
(Folke and others 1997). Te green water needs or ecosystem services that support these
cities are roughly 54 times larger than the blue water needs o households and industry
(Jansson and others 1999). However, people who live in cities oten become mentally
Historically,
decisionsconcerning
ecosystem
management
have tended to
avor conversiono ecosystems
or management
or a single eco-
system service,such as ood
production
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disconnected rom the ecological and hydrological processes that sustain their well-being.
In this perspective armers are the stewards o the landscape in which cities lie. Tis pro-
vides a new challenge or water and ecosystem management.
One o the main gaps in our scientic understanding o ecosystems and ecosystem
services is where the thresholds lie and how ar a system can be changed beore it loses too
many essential unctions and totally changes its behavior (Gunderson and Holling 2002).
Without this knowledge the early warning indicators required to provide advance warn-
ing o anticipated adverse change or o when a threshold is being approached cannot be
developed.
Source: Adapted from Foley and others 2005; chapters 14 and 15 in this volume.
Fuelwood
Recreation
Pestcontrol
Soilformation
Regulation
of waterbalance
Nutrient
cycling
Cropproduction
Climateregulation
Fuelwood
Recreation
Pestcontrol
Soilformation
Regulation
of waterbalance
Nutrient
cycling
Cropproduction
Climateregulation
Provisioning services Regulating services Supporting services Cultural services
Cardamomseed
Fertility transferto other systems
Soil fertilityimprovement
Watershedconservation
Fodder forlivestock
Soilconservation
Commercial timberand fuel wood
Nitrogenxation
Natural ecosystem Intensive cropland
Multifunctionality in rice elds Alder-cardamom system
FishReligious land-scape values
Water storage,lowering ofpeak oods,groundwaterrecharge
Climateair temperature
Ducks,frogs,snails
Biodiversityenhancement
in human-dominatedlandscapes
Riceproduction
Prevention ofsoil erosion
fgure6.4 Comparison o intensive agricultural systemsmanaged or the generation o one ecosystem serviceand multiunctionality in agroecosystems
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6Agriculture, water, and
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Managing agriculture or multiple outputs. Increasing attention to ecosystem services
provides an opportunity to emphasize multiunctionality within agroecosystems and the
connectivity between and within agroecosystems and other ecosystems. It is oten assumed
that agricultural systems are managed only or optimal (or maximum) production o one
ecosystem service, ood, or ber (gure 6.4). But agricultural systems can generate other
ecosystem services, and we need to improve our capacity to assess, quantiy, and value
these as well. Encouraging multiple benets rom these systems can generate synergies
that result in the wider distribution o benets across more people and sectors. Ecosystem-
based approaches to water management need not constrain agricultural development but
can be points o convergence or social equity, poverty reduction, resource conservation,
and international concerns or global ood security, biodiversity conservation, and carbonsequestration (see chapter 15 on land). Ecosystem-based approaches aim to maintain and
where possible enhance diversity and to build the ecological resilience o the agricultural
landscape as well as o ecosystems altered by agriculture (box 6.11).
Te concept o multiunctional agriculture is not new; it has long been practiced in
many orms and combinations. Integrated pest management is one way to manage a whole
landscape in order to sustain an ecosystem service (pest control) that enhances agricultural
production. Tis type o regional management requires integrated approaches based on an
ecological understanding o ragmentation and landscape heterogeneity (Cumming and
Spiesman 2006). Hydrological understanding is also important. Studies have shown that it
is possible to control insect outbreaks by timing irrigation events (Lansing 1991) and that
The resilience perspective shits rom policies that aspire to control change in systems assumed to
be stable to policies to manage the capacity o social-ecological systems to cope with, adapt to, and
shape change (Berkes, Colding, and Folke 2003). Managing or resilience enhances the likelihood o
sustaining development in changing environments where the uture is unpredictable.
Variability, disturbance, and change are important components o an ecosystem. For example,
when variability in river ows is altered, marked changes in ecosystem unctions can be expected
(Richter and others 2003). Wetting and drying o soils can be important or the resilience o ecosystem
unctions, such as pest control and nutrient retention in wetlands. Exactly what level o variability to
maintain and when variability is site specifc are areas o intense research (Richter and others 2003).
Maintaining diversity has been shown to be important or bui
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