session 3.6 synergies & trade offs amngst multiple fxns of trees
TRANSCRIPT
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.