An attempt to differentiate climatic and human induced changes on vegetation in Botswana

1. An attempt to differentiate climatic and human induced changes on vegetation in Botswana A.C. Chipanshi [Chipanshia@em.agr.ca] S. Ringrose W. Matheson R. Chanda

2. Background/Introduction • Impacts of humans/animals on veg is low at low population densities • Impacts of climate  climax veg (confounded by episodic events) • Natural and human forces are not mutually exclusive

3. Objectives… • Develop an up-to date map of veg cover since first one was made in 1971 • Suggest possible changes to vegetation using climate change scenarios • Indicate adaptive and policy options to resources managers

4. Study area details • Botswana sits astride the Tropic of Capricorn and hence it has an arid-like climate • Low human population (~1.3 million) but has high growth rate (3.5%); area of 582K km2 • Settlement is skewed in favour of the SE • Domesticated animals are estimated at 3 times the human pop (cattle & goats ~ 4.8 million)

5. Location map of the study area

6. Moisture Fields

7. Vegetation types, 30 years ago • Early mapping based on photos and field surveys (Weare and Yalala) • Noticeable trend with moisture gradient • No one species dominates the landscape

8. Map of vegetation types in the 1960s

9. Implications from the early mapping • Degradation due to human activities low • Species diversity quite widespread • Fires and droughts were the main agents controlling vegetation dynamics

10. Current Mapping (1995) • Thematic Mapper: bands 3,4,5 were used • Mapping supplemented by field work for species type and density assessment • Current mapping reveals changes in species type and density

11. Vegetation map in 1995

12. Summary of the satellite mapping 1995) • Arid shrub savanna coincides with 1971 map • Kalahari bush savanna degraded most on eastern side but less so on west • North of Kalahari, dense tree and bush savanna is followed by sparse savanna (reverses 1971) • Floodplain area is now a mixture of shrubs but this was grassland in 1971 • Bushy species are more common in east than elsewhere (Terminalia sericea)

13. Lessons from the map inter-comparison • In the less settled west, climate appears to be the dorminant factor on vegetation • In the east and northern fringes, there appears to be an accelerated rate of vegetation density and species change (humans and climate)

14. Projections into the future • Climate change experiments suggest warming in Botswana (1 to 2o C above present climatology) in next 50yrs • Rainfall shows a decrease by 5 to 20% by most models and composites • What vegetation biomes can we expect?

15. Biome model outputs from GCMs for the 2050s (After Hulme)

16. Summary of changes likely to impact vegetation • In all scenarios, grassland degrades into dry forest or tree and shrub savanna • In dry and ‘core’ scenarios, forests decline and thorn and shrub savanna expands • Over all degradation of present biomes

17. What adaptive options do we take under these conditions? • Informed tree planting programmes (ATHTP vs. ATPP) • Community Based Natural Resources Management strategies (e.g. communal rangelands) are a good adaptive strategy • Include indigenous knowledge • Diversify rural economy

18. Policy Options • Carry out inventories at regular intervals • Reform land tenure to allow open access to forestry resources in less degraded areas (state land and commercial properties) • Involve communities in managing forestry resources

19. CONCLUSIONS • Changes that have taken place in vegetation cover in the past 30 yrs (trees to shrubs) are expected to continue in the near future • Both human and natural forces are contributing to forestry degradation (difficult to separate) • Current adaptive and policy arrangements are not sufficient; community based approaches are the options