Synergies and trade-offs amongst multiple functions of trees in agricultural

landscapes in Sub-Saharan Africa

S Kuyah, I Öborn, A Malmer, E Barrios,A S Dahlin, M Jonsson, C Muthuri, S Namirembe,

J Nyaga, Y Nyberg, F L. Sinclair

Outline

• Introduction and research question• Literature review and synthesis• Assessing ecosystem services

provided by trees• Benefits and tradeoffs between

ecosystem services• Lessons learned and knowledge gaps

Trees in agricultural landscapes provide ecosystem servicesEcosystem service categories (MA, 2005);• provisioning (e.g. food, fodder),• regulating (e.g. microclimate), • supporting (e.g. nutrient cycling),• cultural (e.g. shade, aesthetic).

jackfruit

Shaded tea Calliandra hedges

Multi-functional landscapes in sub-Saharan Africa • Sub-Saharan Africa (SSA) is home to ≈910 million

people (The World Bank, 2012) • About 63% of this population dwell in rural, and rely

on ecosystem services• Multifunctional landscapes offer a range of multiple

ecosystem services relevant to SSA

Overall question• What is the present scientific evidence base that

integration of trees on farms and in agricultural landscapes will contribute to enhanced agricultural productivity, resource utilization and livelihoods for smallholder farmers?

• Are all these benefits indeed co-benefits or are there trade-offs, and are there empirical studies available for relevant scales and contexts?

Methodology

Structured literature searchRelevant studies • Peer reviewed journals• Agricultural landscapes within

sub-Saharan AfricaInformation sources• Web of science, Scopus, Science

directSearch strings combining variants of ecosystem services produced by treesBias minimised by multiple reviewers

Synthesis

Number of studies determined by vote-count

Positive (+) or negative (-) impact of trees captured where significant

Stratification based on• Ecosystem categories• Agro-ecological zones • Field, farm and landscape

Ecosystem services provided by treesResults

• A total of 409 studies at 202 sites in 23 countries

• Relevant to 4 agro-ecological zones.

• The ecosystem services are grouped into four major classes

• The ecosystem services are produced, utilized and assessed at different scales

Ecosystem services provided by trees1%

46%

27%

25%

Arid Semi-aridSub-humid Humid

Results

• A total of 409 studies at 202 sites in 23 countries

• Relevant to 4 agro-ecological zones.

• The ecosystem services are grouped into four major classes

• The ecosystem services are produced, utilized and assessed at different scales

Ecosystem services provided by trees

33.3

28.4

38.1

0.2

Provisioning RegulatingSupporting Cultural

Results

• A total of 409 studies at 202 sites in 23 countries

• Relevant to 4 agro-ecological zones.

• The ecosystem services are grouped into four major classes

• The ecosystem services are produced, utilized and assessed at different scales

Ecosystem services provided by treesResults

• A total of 409 studies at 202 sites in 23 countries

• Relevant to 4 agro-ecological zones.

• The ecosystem services are grouped into four major classes

• The ecosystem services are produced, utilized and assessed at different scales

63

23

14

Field FarmLandscape

Benefits and Tradeoffs

• Ecosystem services are interlinked, and they interact• Management practices alter a range of ecosystem

services positively, yielding benefits or negatively resulting in tradeoffs

Results

Enclosures in grazing areas Guava tree planted at river bank

Benefits and Tradeoffs

• Ecosystem services are interlinked, and they interact• Management practices alter a range of ecosystem

services positively, yielding benefits or negatively, resulting in tradeoffs

Results

Benefits and Tradeoffs

More value is placed in provisioning services

Results

Food

Fodder

Nutrient cycling

Soil fertility

Carbon storage

Microclimate

0

20

40

Benefits

Benefits and Tradeoffs

More value is placed in provisioning services

Results

Food

Fodder

Nutrient cycling

Soil fertility

Carbon storage

Microclimate

0

50

100

TradeoffsFood

Fodder

Nutrient cycling

Soil fertility

Carbon storage

Microclimate

0

20

40

Benefits

Conclusion• Trees play a crucial role in sustaining productivity of

agricultural systems, but there are also tradeoffs, in particular with food crops

• Ecosystem services are often studied at lower (field) scale than where they are produced and utilized

• Many ecosystem services from trees are known to be produced in forest areas, but few studies on farms

Acknowledgement

The study was supported by funds allocated to the Swedish University of Agricultural Sciences by the Swedish

Ministry of Foreign Affairs as part of its special effort on global food security.