IPCC ‘Climate Change 2007’• Frequency of heavy precipitation events has increasedover most land areas - consistent with warming andincreases of atmospheric water vapour• Drying in the Sahel, the Mediterranean, southern Africaand parts of southern Asia• More intense and longer droughts observed since the1970s, particularly in the tropics and subtropics
highlowModelled present day Africanplant species richnessAssuming species occur at allclimatically suitable placesSommer et al. Nees Institute forBiodiversity of Plants, BonnEffect of Climate ChangeAfrica
Patterns of African plantspecies richness in 2100Assuming species move into newhabitats and occur at allclimatically suitable placesSommer et al. Nees Institute forBiodiversity of Plants, BonnEffect of ClimateChangeAfrica
Shea presence localitiesDistribution data fromJohn Hall (University ofWales, Bangor); plotlocations from BurkinaFaso, Mali and Ghana;one record fromTROPICOS– 241 points in total (216paradoxa, 25 nilotica)– 216 locations to nearestminute, remainder tonearest degreeINNOVKAR WP2: Shea distribution under climate change Platts, Poudyal, McClean (February 2011)
Analysing present daydistribution• Using generalised additive models (GAMs), the presentday shea distribution was correlated with climate,topography, agro-ecological zone data and fire radiativepower• Predictor variables were chosen using two contrastingstepwise selection procedures: beginning with a null/fullmodel, variables were added/removed according toAkaike/Bayesian Information Criterion, respectively• Platts, Poudyal, McClean INNOVKAR WP2INNOVKAR WP2: Shea distribution under climate change Platts, Poudyal, McClean (February 2011)
INNOVKAR WP2: Shea distribution under climate change Platts, Poudyal, McClean (February 2011)Shea distribution (present) predicted by a GAM usingclimate, topography, soil constraints and fireintensityShea distribution (present) predicted by a GAM usingclimate variables only (mean temperature, moistureindex and driest month rainfall)
Climate scenariosINNOVKAR WP2: Shea distribution under climate change Platts, Poudyal, McClean (February 2011)Summary of temperature changes forecast according to various IPCC SRES emissions scenarios (IPCC,2007). A1: maximum energy requirements, with emissions differentiated according to fuel sources (A1Fl,fossil intensive; A1T, technological development of non-fossil sources; A1B, balance across sources). B1:minimum energy requirements and low emissions. A2: high energy requirements; emissions less than A1Fl.B2: low energy requirements, but emission greater than B1. Considered here are SRES scenarios A2 and B2.
INNOVKAR WP2: Shea distribution under climate change Platts, Poudyal, McClean (February 2011)Maps showing modelled climatic suitability for shea under current and future climatescenarios (extrapolating the GAM predictions)
INNOVKAR WP2: Shea distribution under climate change Platts, Poudyal, McClean (February 2011)Plots showing forecast changes in the number of10 arc-minute grid cells providing climaticallysuitable conditions for shea. Viable conditions aredefined by model predictions of at least 0.5The two SRES scenarios (A2 and B2) returnedsimilar results for the first half of the 21st century,but thereafter the A2 scenario (higher emissions)resulted in a more rapid increase in the amount ofclimate-space suitable for shea, particularly withinits current latitudinal range (0°-15°N).
Satellite data and highresolution modellingstudies show thatstorms needheterogeneous soil toinitiateIn particular, afternoonconvection over drySahel regions needsthis variation in groundsurface to initiate.Convection forms overgradients in soilmoisture.
Air passage overforested regionsenhances seasonalrainfall by up to 10 mmper day
Carbon Estimates• Shea parkland 20-50 MgC/ ha• 3.7 million km2 Sahel-Savannah woodedparkland zone• = 74,000,000,000 tonnes C (@20 MgC/ ha)• = 271,000,000,000 tonnes CO2• World CO2 emissions: 33,376,327,000 tonnesCO2• Shea parkland C stock equivalent to more than 8times global CO2 emissions
Conclusion• Sahelian climate unpredictable• Climate change models predict a drierSahel• Bioclimatic envelope modelling showsmajor shifts in vegetation; with Shea rangeexpanding• Vegetation affects Sahel rainfall; andcarbon storage/ sequestration can mitigateclimate change
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