Post on 27-Jun-2020
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Agroecology Ecological understanding of farming systems
Ben-Gurion University of the Negev
Prof. Bertrand Boeken The Wyler Dept. of Dryland Agriculture Jacob Blaustein Institute for Desert Research Ben-Gurion University of the Negev Sede Boqer Campus 84990 Israel Office 08-659 6893 Mobile 052-3847603
1. Introduction • Definitions
• Contexts
• Perspectives
• History of agriculture
bboeken@bgu.ac.ilhttp://www.bgu.ac.il/desert_agriculture/Agroecology/© BBoeken 2005-18
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Agroecology - definitions
Gliessman 2000: “The application of ecological
concepts and principles to the design and management of sustainable farming systems”
Understanding (Science)
Practice (Technology)
Object
Goal and Motivation Limited to a subset of farming systems (i.e., not the unsustainable ones) What is sustainability?
How does sustainability vary?
What makes a farming system sustainable?
Is sustainability always attainable?
→ Agroecology as agricultural practice
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Agroecology - definitions B. Boeken, this course: The application of ecological concepts
and principles to farming systems
All agro-systems Ecological processes associated with farming
• Trophic structure
• Flows of energy and materials (water, nutrients, carbon)
• Landscape and scale
• Population dynamics of organisms
• Natural selection and co-evolution
• Biodiversity of biotic communities
• Conventional, traditional and alternative agriculture
• Crop and animal production
• Development through time
Understanding (Science)
→ Agroecology as a scientific discipline Wezel A. et al. 2009. Agron. Sustain. Dev. 29 (2009)
503–515 (www.agronomy-journal.org) Bensin B.M.1930. Int. Rev. Agr. Mo. Bull. Agr. Sci.
Pract. (Rome) 21, 277–284.
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Agroecosystems - context
Human activities for food production • Hunting • Gathering • Fishing • Grazing • Farming • Bio-industry
Human land-use • Cropland • Rangeland • Woodland • Urban/industrial • Nature
Material human requirements • Water, air • Food • Fiber • Fodder • Fuel • Shelter • Space • Goods
www.worldfuturefund.org
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www.worldfuturefund.org
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Agroecosystems: perspectives
• Social
• Ecological
• Biological
• Technical
• Historical http://www.worldisround.com
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Social perspectives
• Sociology • Economy • Politics • Culture • Religion • Heritage • Education
www.whitehouse.gov
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Ecological perspectives • Energy and resource flows • Trophic structure • Biodiversity • Population dynamics • Natural selection • Animal behaviour • Landscape dynamics • Spatial relationships:
Relationships with surrounding ecosystems
• Resource flows from outside • Predators, pests and weed invasion • Export of plant and animal products • Leakage of water, nutrients, agro-chemicals
Processes within agro-ecosystems • Energy, resource flows • Crop plant performance • Biotic community dynamics • Soil processes
Natural ecosystems
Agro-ecosystems
Relationships between agro-ecosystems and the ‘rest of the world’
• Resource subsidies • Introduction of invasive species • Export of plant and animal products • Pollution • Global climate change
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Biological perspectives
• Physiology and biochemistry • Genetics, genomics • Phytopathology • Soil microbiology
www.soils.agri.umn.edu
www.ncgbc.org
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Technical perspectives • Irrigation • Soil preparation • Planting and sowing
www.opico.com
www.rec.udel.edu
• Fertilizer application • Pest control • Harvesting
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Historical perspectives
Increasing trends • Global and local human population size • Control over food production
• Dependence on technology, transport
Time-line (yrs) Archaic Homo sapiens -250,000 hunting-gathering, nomadic
Prehistoric -15,000 domesticated plants and grazers
Ancient -5,000 soil cultivation, irrigation
Medieval -1,500 deep plowing, manure, selection, profit
Modern -200 scientific approach
Contemporary -60 industrialization, alternative approaches, ecological sustainability (?)
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Early human foraging
250,000 years ago • Nomadic hunter-gatherers
• Small communities in open landscapes
• Human evolution and early cultural development
http://www.archaeologyinfo.com/homosapiens.htm
Social structure: clan/family groups Food: grains, nuts, berries, tubers, vertebrates, insects Problems: predators, resource depletion, adverse selection, rival clans Innovations: clothing, domestication of dogs
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Adverse selection Gathering of wild cereal grain
• Normal retention frequency distribution
• People collect seeds remaining on the plants • Moves population mean to genotypes with
lower retention
• In short time local populations become costlier to collect
Seed retention
Freq
uenc
y
Seed retention
Freq
uenc
y
Harvested
www.flickr.com
Assumptions • Essential or important food source • Abundant population • No overharvesting by reducing
abundance (no seed limitation of recruitment)
Consequences (Based on optimal foraging decisions by humans) • Diversity of food sources (“prey switching”) • Migration (nomadism)
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Prehistoric agriculture
www.sanford-artedventures.com
Social structure: larger clan/family groups Food: wild animals and plants, local produce Problems: predators, resource depletion, rival clans Innovations: tools, domestication of grains, herbivores
Started 15,000 years ago • Small semi-sedentary
communities
• Stone tools
• Early agriculture
• Early art
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Domestication Cultivation of cereal grain
• Wild populations have normal retention frequency distribution
• Planting of grains remaining in ears • Crop population mean with higher retention
• Crop populations become more profitable to collect www.geog.ucsb.edu
Seed retention Fr
eque
ncy
Consequences • More control over food supply and quality • Larger, sedentary human populations • Reliance on resources, technology and knowledge • Danger of resource depletion (and over-harvesting in non-seed crops)
Seed retention
Freq
uenc
y
Harvested
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Ancient agriculture
Started 5,000 years ago • Larger villages, cities
• Large-scale agriculture
• Metal tools
• Soil cultivation, irrigation
• Food storage
• Burocracy www.touregypt.net
Social structure: large non-family groups Food: local produce, storage Problems: predators, resource depletion, rival clans Innovations: domestication of vegetables, fruit trees, cats
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Medieval agriculture
http://medieval.ucdavis.edu
Started 1,500 years ago • Feudal relations
• Large cities, manors
• Large-scale agriculture
• Sustenance and profit
• Plowing, fertilization
Social structure: feudal (serfdom) Food: local produce, storage, import Problems: food shortage, desease Innovations: selection, work
differentiation
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Modern agriculture
www.stolaf.edu
Started 200 years ago • Population increase
• Land development
• Production maximization
• Mechanization
• Profit
Social structure: family business Food: local produce, storage, import, industrial processing Problems: pests, pollution, subsidies, capital investment, scale enlargement, uniformity Innovations: science-based, hybrid crops
Crop trait selection
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http://www.doctortee.com/
Genotype-environment interactions (G×E)
• Reaction norms for 2 phenotypic traits (a,b)
• Trade-off between the traits (c) • Physical/physiological trade-offs:
Limitation of selection (d)
Selection for desired phenotypic traits • Crop diversity • Market value • Genotypes adapted to different
conditions (temperature, resource availability, seasonality, etc.)
Soil moisture
Gro
wth
Gen
otyp
es
Wet Dry
(d)
A
B
1 2
A
B
Environment
Trai
t 1
Trai
t 2
Trai
t 2
1 2 Environment
A
B
Trait 1
A
B
(a) (b) (c)
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Contemporary agriculture Started ca. 60 years ago • Population increase
• Reduced natural area
• Production maximization
• Globalization
• Profit, monopoly
Social structure: private and corporate business Food: import/export, industrial processing Problems: pests, pollution, subsidies, capital investment,
encroachment on nature, global warming Innovations: bio-industry, precision agriculture, genetic engineering,
alternative life-styles
encarta.msn.com