Local adaptation to climate change for improved food and energy security in Rural Africa

Transcription

1 Local adaptation to climate change for improved food and energy security in Rural Africa NORAGRIC, UMB, Africa Network, 14 December 2010 Trygve Berg: The use of agrobiodiversity in adaptation to climate change

2 Climate Change Scenarios Most predictions use historic data on relations between climate and crop yields. When expected future climates are imposed on current agriculture there will be change in output, and in the case of sub-saharan Africa the change is mostly negative. Such models fail to take into account that also agriculture will change when the climate becomes different.

3 Potential yield: Defined by CO2, temperature and crop characteristics. Attainable yield: Limited by water and plant nutrients. Actual yield: Reduced by weeds, disseases, pests and pollutants. Yield gap: Difference between attainable and actual yield. In most crop production in SS Africa actual yield is between 10 and 30 percent of atttainable yield. In the most intensive production in the USA and in irrigated rice in Asia, actual yield is very close to attainable yield. Theoretically climate change affects potential yield. In most crop production in SS Africa actual yield is limited mostly by non-climatic factors and there is no obvious direct relation between climate change and actual yield. US climate models are based on a situation where yields are limited primarily by climate because crop management is close to optimal.

4 The low yields in SS Africa

5 Maize Yield (t/ha) Rainfall (mm) ICRISAT: Declining productivity attributed to climate change. Other drivers of change are usually responsible Machakos district in Kenya 1, , , , ,60 Maize Yield Rainfall 300 0, , ,

6 What are the reasons why the yields are so low? Soil degradation: Accumulated loss of soil organic C (60 % in soils of temperate regions and 75 % in cultivated soils in tropical regions) Soil depletion (at an estimated annual rate of 40 kg of NPK/ha of cultivated land in SS Africa)

7 Raising actual yields: Conservation agriculture Water use efficiency Bridging dry spells

8 Factors of adaptation Conservation agriculture: Reversing the soil degradation Water management and supplementary irrigation Crop evolution: Heat stress tolerance Drought stress tolerance CO2 response Resistance to diseases

9 Average Crop Yields Current Climate Yield Gap Low input Practices + Current Climate Yield Gap 1 Yield Gap 2 Low input Practices + Climate Change Improved Practices + Climate Change Improved practices + Adapted germplasm + Climate change Improved practices + Improved germplasm + Current climate Management and Climate Scenarios

10 Crop evolution has untapped potentials. But is should be stressed that genetic change cannot make up for the problems of degraded and depleted soils. Let conservation farming fix the basic problems, then the crops will respond favourably to fertilisers, irrigation and other inputs. That s also when farmers will start demanding crops and varieties that respond with higher yields. Heat stress: In warm tropical environments temperature is already over the optimal and close to maximum temperature for crop growth. Night/day temperatures Is there a threshold? Yes, the highest temperature predictions may exceed possible adaptation in some areas: Mitigation efforts to avoid the worst scenarios are necessary! Change of crop species (C4 species tolerate higher temperatures) Searching for genes in the world collections of crop diversity; opening also the genomes of the wild relatives.

11 Heat and digestibility: Digestibility of fodder is negatively correlated to temperature The negative correlation is stronger for grasses than for legumes Reduced digestibility is associated with lignification and goes faster in stems than in leaves Leaves of legumes and trees have no structural function and is therefore less exposed to lignification

12 Quantitative effects of temperature on digestibility varies from 0,5 to more than 1 percent units per degree C according to different studies. When feed quality is already low, this can have serious consequences.

13 Reduced growing seasons A study on hotspots of vulnerability gave this map where the yellow colour indicates areas with pastoral production systems that are likely to undergo > 20 % reduction in length of growing period by 2050 (Thornton et al. 2006)

14 Adaptation to CO2 Only C3 species respond to higher CO2 Elevated CO2 increases photosynthesis and grain yield and reduces transpiration Genetic variation in CO2 response: There is probably a great potential for breeding CO2 responsive varieties.

15 Conditions for adaptation Agricultural research and services: Availability and access to genetic resources Higher production costs Markets and prices: We must allow the farmers to make profit!