1. Climate change in the Okavango Delta Piotr Wolski, Mike Murray-Hudson Harry Oppenheimer Okavango Research Centre (HOORC) Maun, Botswana Ecohydrological processes and sustainable floodplain management, Lodz, 19-23 May 2008 Linking hydrological variability to ecosystem functionality in the Okavango Delta, Botswana, in the context to adaptation to climate change

2. Climate change in the Okavango Delta Problem statement world largest Ramsar wetland, unspoiled development pressure - source of livelihood! planning and (adaptive) management projects in place lack of or poor climate change adaptation strategy! tools available to work out hydrological effects of climate change limited quantitative data to develop ecological/ecosystem/landscape models Aim: linking hydrology to ecology, in the context of climate change, at a level corresponding to available data

3. Climate change in the Okavango Delta Frequency, duration and depth of inundation vary throughout the system The Okavango Delta

4. Climate change in the Okavango Delta Long-term dynamics of the system

5. Climate change in the Okavango Delta Link between hydrology and ecology Ecological function of various floodplain ecotopes Permanent swamp –anoxic conditions –accumulation of peat, nutrients and C trapping –limited availability of vegetation to herbivores –channels and lagoons support fish Seasonally (regularly, occasionally) inundated floodplains –switching anaerobic-aerobic conditions –intensive nutrient recycling –high biomass and primary productivity –availability of plants to grazers during dry winter Drylands –rain-fed ecosystem –supports browsers (throughout the year) and grazers (during wet summer)

6. Climate change in the Okavango Delta General approach to assess effects of climate change on OD Static ecotope model GCMs CSIRO Had3CMCGCM2 GFDL Okavango catchment rainfall-runoff model Delta flooding model Dynamic ecotope model “energy systems” model P,T Q Q Inundation characteristics Assumption: CC will affect ecosystem mostly through change in hydrological conditions

7. Climate change in the Okavango Delta Static hydrology-ecotope model After SMEC, 1989 Based on long-term average hydroperiod conditions

8. Climate change in the Okavango Delta Static model results (2020-2050, b2) Baseline

9. Climate change in the Okavango Delta Long-term dynamics of the system

10. Climate change in the Okavango Delta Vegetation communities SavannaGrassland Sedgeland Aquatics

11. Climate change in the Okavango Delta Dynamic ecotope model Expert system. Current ecotope depends on: ecotope in previous year inundation duration in previous 5 years

12. Climate change in the Okavango Delta Dynamic ecotope model

13. Climate change in the Okavango Delta Dynamic ecotope model

14. Climate change in the Okavango Delta Dynamic ecotope model

15. Climate change in the Okavango Delta Dynamic ecotope model

16. Climate change in the Okavango Delta Dynamic ecotope model

17. Climate change in the Okavango Delta Results of dynamic model (2020-2050, b2)

18. Climate change in the Okavango Delta Dynamic model based on energy systems concept Sedgeland/grassland floodplain system diagram

19. Climate change in the Okavango Delta Dynamic model based on energy systems concept lumped model no aquatic and dryland ecotopes at this stage grasses/sedges compete for environmental inputs competition moderated by hydroperiod output: –biomass of grasses and sedges (primary producers) –biomass of aquatic (fish) and terrestrial (mammals) consumers. Model diagram

20. Climate change in the Okavango Delta Results of dynamic energy systems model (2020-2050, b2)

21. Climate change in the Okavango Delta Conclusions The empirical models linking transformation in the ecosystem to hydrological change are indicative only. More rigorous approach is needed. However even at this stage they allow for presentation of changes of a complex system in an understandable and meaningful way. Results of global climate models are inconsistent in terms of the magnitude and direction of future change in the Okavango Basin: conditions considerably wetter and drier than those observed in the past are simulated by various models. We are currently looking at convergence of results from muli-model ensembles

22. Climate change in the Okavango Delta Thank you