climate change in the okavango delta piotr wolski, mike murray-hudson harry oppenheimer okavango...
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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
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
Climate change in the Okavango Delta
Frequency, duration and depth of inundation vary throughout the system
The Okavango Delta
Climate change in the Okavango Delta
Long-term dynamics of the system
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)
Climate change in the Okavango Delta
General approach to assess effects of climate change on OD
Static ecotope model
GCMsCSIRO
Had3CM CGCM2
GFDL
Okavango catchment rainfall-runoff
model
Delta flooding model
Dynamicecotope model
“energy systems”model
P,T
P,T
Q
Q
Inu
nd
atio
n c
har
act
eris
t ic
s
Assumption: CC will affect ecosystem mostly through change in hydrological conditions
Climate change in the Okavango Delta
Static hydrology-ecotope model
Floodplainclass
Sub-class
floodfrequency
flood duration(months/year)
Permanentfloodplain
proper PF1 1 12
fringe PF2 1 8-12Regularlyfloodedseasonalfloodplain
RF1 1 4 - 8
RF2 0.5-1Occasionallyfloodedseasonal
OF 0.1-0.5 1-4
High floodsonly
HFO <0.1 <2
Dryland DL 0 0
After SMEC, 1989
Based on long-term average hydroperiod conditions
Climate change in the Okavango Delta
Static model results (2020-2050, b2)
Baseline
Climate change in the Okavango Delta
Long-term dynamics of the system
Climate change in the Okavango Delta
Vegetation communities
Savanna Grassland
Sedgeland
Aquatics
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
Climate change in the Okavango Delta
Dynamic ecotope model
Climate change in the Okavango Delta
Dynamic ecotope model
Climate change in the Okavango Delta
Dynamic ecotope model
Climate change in the Okavango Delta
Dynamic ecotope model
Climate change in the Okavango Delta
Dynamic ecotope model
Climate change in the Okavango Delta
Results of dynamic model (2020-2050, b2)
Climate change in the Okavango Delta
Dynamic model based on energy systems concept
Sedgeland/grassland floodplain system diagram
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
Climate change in the Okavango Delta
Results of dynamic energy systems model (2020-2050, b2)
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
Climate change in the Okavango Delta
Thank you