title: The future distribution of the savannah biome: model-based and biogeographic contingency.
abstract: The extent of the savannah biome is expected to be profoundly altered by climatic change and increasing atmospheric CO2 concentrations. Contrasting projections are given when using different modelling approaches to estimate future distributions. Furthermore, biogeographic variation within savannahs in plant function and structure is expected to lead to divergent responses to global change. Hence the use of a single model with a single savannah tree type will likely lead to biased projections. Here we compare and contrast projections of South American, African and Australian savannah distributions from the physiologically based Thornley transport resistance statistical distribution model (TTR-SDM)-and three versions of a dynamic vegetation model (DVM) designed and parametrized separately for specific continents. We show that attempting to extrapolate any continent-specific model globally biases projections. By 2070, all DVMs generally project a decrease in the extent of savannahs at their boundary with forests, whereas the TTR-SDM projects a decrease in savannahs at their boundary with aridlands and grasslands. This difference is driven by forest and woodland expansion in response to rising atmospheric CO2 concentrations in DVMs, unaccounted for by the TTR-SDM. We suggest that the most suitable models of the savannah biome for future development are individual-based dynamic vegetation models designed for specific biogeographic regions.This article is part of the themed issue 'Tropical grassy biomes: linking ecology, human use and conservation'.
authors: Fynbos Node, South African Environmental Observation Network (SAEON), Centre for Biodiversity Conservation, Kirstenbosch Gardens, Private Bag X7, Rhodes Drive, Claremont 7735, Cape Town, South Africa Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, Stellenbosch, South Africa glennwithtwons@gmail.com.
authors: Glenn R
authors: 0000-0002-0066-4371
authors: GR
authors: Moncrieff
authors: Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, 60325 Frankfurt am Main, Germany.
authors: Simon
authors: S
authors: Scheiter
authors: Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, 60325 Frankfurt am Main, Germany.
authors: Liam
authors: L
authors: Langan
authors: Impacts on Agriculture, Forests and Ecosystem Services (IAFES) Division, Euro-Mediterranean Center on Climate Change, via De Nicola 9, 07100, Sassari, Italy.
authors: Antonio
authors: A
authors: Trabucco
authors: Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, 60325 Frankfurt am Main, Germany Department of Botany, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
authors: Steven I
authors: SI
authors: Higgins
mesh_terms: D000349:Africa; D001315:Australia; D002245:Carbon Dioxide / Q000032:analysis*; D057231:Climate Change; D062305:Geographic Mapping; D065948:Grassland; D008954:Models, Biological; D013020:South America
chemical_list: D002245:Carbon Dioxide
keywords: CO2 fertilization; dynamic global vegetation model; global change; savannah; statistical distribution model; tropics