Transcript agroforestry

Sustainable farming and food security in West
Africa
Jan Gunnarsson
Associate Professor Emeritus
Climate change in West Africa:
Declines in mean annual precipitation over the past
century. Decreases in rainfall are predicted also in the
future.
Warming trend since the 1960s with an increase in the
number of warm spells. This trend is expected to continue
Unusual and unprecedented heat extremes are projected
to occur with greater frequency during summer months
West Africa with the Gambia
The Gambia:
Semi-arid climate:
Total populations 2012:
West Afrika (15 countries): 245.000.000
The Gambia:
1.791.000
South Africa: 52.386.000
Population growth rate (average, annual
2010-2015) (UN statistics)
GDP/capita (current US $) (UN statistics)
Food production index (2004-2006=100)
(UN statistics)
Aims of this lecture:
• Show how biological regulation of ecosystems can be used
to alleviate the negative effects of climate change to
increase the food security.
Illustrated by agroforestry
• Point to cultural and social institutions that prevent or
facilitate biological regulation sufficient for food security.
Supply of essential protein in West Africa:
Protein we cannot produce ourselves of which food from
plants tend to have relatively lower concentration than
food from animals.
• Fish accounts for 50 % of the animal protein consumed
in Ghana, Sierra Leone and in the Gambia even as high
as 59-67 %
• Nuts and legumes (cowpeas, pigeon peas) can replace
meat
• In developing countries meat represents the most
concentrated source of importance for young children
Threats to food security:
•
•
•
•
Potential fish catches off the coast of West Africa is likely
to be reduced by 50 % 2050 as compared with 2000
Senegal ranks among the most vulnerable countries in
Sub-Saharan Africa with regard to climate change driven
impacts
Fresh water fisheries are destroyed as surface water
temperatures are higher, evaporative water loss increases
and summer stratification occurs earlier in the season.
Fresh water fisheries destroyed as water flow and water
levels in the lakes are reduced.
How much does agroforestry add to the
adaptive capacity to climate change?
Framework for assessments that includes:
1) Agroforestry system for sustainable farming
2) Neighboring ecosystems and cross-system flows and
impacts
3) Cultural and social institutions affecting the supply of
essential proteins
Protein limitation hypothesis
• Negative correlation between bush meat hunting
and market fish supply.
• Reductions in the supply of wild animals (fish and
bush animals) can be replaced by increases in
livestock from agricultural production
“Whole system approach” to agroforestry
Kirschenmann suggests a system with three farming
practices:
1. crop-rotation (farmers grow different crops in the
same area in sequential seasons)
2. A regenerative soil-conserving strategy
3. Interactive diversification.
Trees with reported crop yield increases
Tree species
Indigenous
name
Reversed leaf
phenology
Nitrogen
fixing
Faidherbia
albida
Baransango
+
+
Grevillea
robusta
Silver oak
Casuarina
equisetifolia
Filao
+
Leucaena
leucocephala
Leucaena
+
Pterocarpus
erinaceous
Keno
+
Phosphorus
mobilization
[1 [
+
+
Other trees used in agroforestry
Tree species
Indigenous name
Environmental task
Vitellaria paradoxa
Karite´
Regenerate organic matter
Parkia biglobosa
Neto
Regenerate organic matter
[1]
Toth (2007)
Animal Fodder
Potassium mobilization
Gmelina arborea
Gmelina
Animal fodder and shade
Anacardium occidentale
Cashew
Firebreak
Senna siamea
Sinjango
Increases soil pH
Adaptive capacity from agroforestry: acrosssystem flow and impacts
1. Tree planting reduces soil erosion and runoff.
Eutrophication in lakes, rivers, and coastal waters
decreases, which increases the supply of fish
2. Cashew trees as fire belts in agroforests conserve
important habitats both for wild animals and for domestic
livestock.
3. Crop yield increases from agroforestry increase the
perceived economic value of a common pool of trees in the
forest. Increased economic value encourage farmers to
conserve forests and habitats for animals
4. Forests conservation depends on traditional beliefs that
forests generate rainfall on farmland Offspring used in
agroforestry adds economic value to the forest (cf. 3.)
Simple agroforestry: Alley Cropping
Agroforestry and adaptive capacity: role of
social and cultural institutions
•
•
•
Customary rules guide the Tayal people in Taiwan to adopt
environmental friendly farming practices.
in Senegal, farmers comply with a conservation principle
as they believe that dense vegetation has a positive effect
on the rainfall
The supply of essential proteins in the Gambia depends on
customary rules of smallholder farmers, who usually not
keep livestock for meat consumption but as savings,
insurance, for cropping activities (manure, draught) and
for ceremonies