Climate Change Impacts on the Congo Basin Region

This report presents analyses of climate change impacts in the Congo Basin on water for agriculture and hydropower, forest ecosystem functioning and carbon storage and impacts of climate variability and change on future economic development. To quantify the impacts of future climate we developed a modelling framework which links climate models with different impact models. Bias corrected climate model output was used to force the macro-hydrological model VIC and therefore it is necessary to use numerical models. For this project a modelling framework was developed which made it possible to link climate models with hydrological, agricultural and ecosystem models. In general, our analyses shows that more water will be available for hydropower in the future. So on average, climate change will have a positive impact on potential electricity production. However the river discharge will also become more variable which will increase the flood risks and could make the power production less reliable. The increased flow variability however will make dam management more complicated because the balance between flood prevention and optimal power production will be more difficult to manage. Climate change will have a range of different impacts of forest ecosystems. The higher atmospheric CO2 concentrations will probably increase forest growth and carbon capture. Higher temperatures however will have negative impacts on forest growth and reduce the amount of carbon in the forests. The impact analyses show that as a result of climate change, the Congo basin is unlikely to see a decline in forest growth such as is sometimes predicted for the Amazon basin. Instead there could be a moderate increase in ecosystem carbon. Depending on how the climate will change there could be a shift in land cover of the different ecosystems. Based on the analyses a moderate expansion to the North and South of Evergreen forests into savannas and grasslands is the most likely future scenario. In general, climatic conditions are currently not limiting agricultural production in the Congo basin region. Only on the (drier) edges of the region water limitation is sometimes reducing the potential agricultural productions. In the tropical climates too much rainfall and high humidity limits agricultural production through nutrient leaching and fungal growth. The impact of future climate on agricultural production will therefore be limited in the region. In most of the area the water stress will increase slightly in the future. However the agriculture will not suffer from structural water shortages. Only the agriculture in the savanna regions surrounding the Congo basin could potentially face water shortages in the future. In the southern savanna region analyses indicate that more frequent droughts will affect agriculture production and water stress. In several of the COMIFAC countries there is a clear correlation between annual rainfall and GDP growth. GDP and Agricultural GDP growth rates tend to be higher in years with above-average rainfall than in the dry years. The impact of climate variability on GDP growth is most pronounced during dry years. During below-average rainfall years growth is sometimes severely reduced and generally the dryer the lower the GDP growth rate. All above-average rainfall years tend to have relatively similar economic growth rates. The correlation between rainfall and GDP growth rates is stronger in countries with lower and more variable rainfall. In most countries, agricultural GDP growth rates are affected stronger by climate variability than the total GDP growth rates. In terms of future climate change impacts on economic development our analysis shows that COMIFAC countries are especially vulnerable to a reduction in rainfall and a significant increase in interannual rainfall variability. Our results show that at a continental scale, climate change is likely to have a negative impact on development in Africa. However the economies of central African countries are likely to be less affected by climate change compared to countries in West, East and Southern Africa. Also at macro scale the climate scenarios seem to be more favourable in the central African part compared to the rest of Africa. However some climate change scenarios show large increases in climate variability and this could have a negative impact on development. In conclusion the climate change impacts on the different sectors shows that the main impacts will come from a more variable climate. No major impacts are expected in terms of water availability for agriculture and future carbon storage in the tropical forests. Also the average potential energy production from hydropower will not reduce. The most severe impacts will result from a more variable hydrological regime. This will result is higher flood frequency and will complicate future dam management. Keywords: Climate change; water resources; agriculture; forestry; carbon stocks; GDP