1006969221 presentation brazil2

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News-Reports

Published on September 21, 2007

Author: Goldye

Source: authorstream.com

An attempt to differentiate climatic and human induced changes on vegetation in Botswana:  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 Background/Introduction:  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 Objectives…:  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 Study area details:  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 andamp; goats ~ 4.8 million) Location map of the study area:  Location map of the study area Moisture Fields:  Moisture Fields Vegetation types, 30 years ago:  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 Map of vegetation types in the 1960s:  Map of vegetation types in the 1960s Implications from the early mapping:  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 Current Mapping (1995):  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 Vegetation map in 1995:  Vegetation map in 1995 Summary of the satellite mapping 1995):  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) Lessons from the map inter-comparison:  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) Projections into the future:  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? Biome model outputs from GCMs for the 2050s (After Hulme):  Biome model outputs from GCMs for the 2050s (After Hulme) Summary of changes likely to impact vegetation:  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 What adaptive options do we take under these conditions?:  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 Policy Options:  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 CONCLUSIONS:  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

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