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Modelling biome shifts and tree cover change for 2050 in West Africa

Authors

  • Jonathan Heubes,

    Corresponding author
    1. Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, D-60325 Frankfurt/Main, Germany
      Jonathan Heubes, Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, D-60325 Frankfurt/Main, Germany.
      E-mail: jonathan.heubes@senckenberg.de
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  • Ingolf Kühn,

    1. UFZ, Helmholtz Centre for Environmental Research – UFZ, Theodor-Lieser-Str. 4, D-06120 Halle, Germany
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  • Konstantin König,

    1. Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, D-60325 Frankfurt/Main, Germany
    2. World Agroforestry Center – ICRAF, Amazon Initiative Consortium, EMBRAPA Amazônia Oriental, Travessa Enéas Pinheiro, 66095-100 Belém, Pará, Brazil
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  • Rüdiger Wittig,

    1. Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, D-60325 Frankfurt/Main, Germany
    2. Institute of Ecology, Evolution and Diversity, J.W. Goethe-University, Siesmayerstraße 70, D-60323 Frankfurt/Main, Germany
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  • Georg Zizka,

    1. Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, D-60325 Frankfurt/Main, Germany
    2. Institute of Ecology, Evolution and Diversity, J.W. Goethe-University, Siesmayerstraße 70, D-60323 Frankfurt/Main, Germany
    3. Senckenberg Research Institute and Natural History Museum, Senckenberganlage 25, D-60325 Frankfurt/Main, Germany
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  • Karen Hahn

    1. Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, D-60325 Frankfurt/Main, Germany
    2. Institute of Ecology, Evolution and Diversity, J.W. Goethe-University, Siesmayerstraße 70, D-60323 Frankfurt/Main, Germany
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Jonathan Heubes, Biodiversity and Climate Research Centre (LOEWE BiK-F), Senckenberganlage 25, D-60325 Frankfurt/Main, Germany.
E-mail: jonathan.heubes@senckenberg.de

Abstract

Aim  Africa is expected to face severe changes in climatic conditions. Our objectives are: (1) to model trends and the extent of future biome shifts that may occur by 2050, (2) to model a trend in tree cover change, while accounting for human impact, and (3) to evaluate uncertainty in future climate projections.

Location  West Africa.

Methods  We modelled the potential future spatial distribution of desert, grassland, savanna, deciduous and evergreen forest in West Africa using six bioclimatic models. Future tree cover change was analysed with generalized additive models (GAMs). We used climate data from 17 general circulation models (GCMs) and included human population density and fire intensity to model tree cover. Consensus projections were derived via weighted averages to: (1) reduce inter-model variability, and (2) describe trends extracted from different GCM projections.

Results  The strongest predicted effect of climate change was on desert and grasslands, where the bioclimatic envelope of grassland is projected to expand into the desert by an area of 2 million km2. While savannas are predicted to contract in the south (by 54 ± 22 × 104 km2), deciduous and evergreen forest biomes are expected to expand (64 ± 13 × 104 km2 and 77 ± 26 × 104 km2). However, uncertainty due to different GCMs was particularly high for the grassland and the evergreen biome shift. Increasing tree cover (1–10%) was projected for large parts of Benin, Burkina Faso, Côte d’Ivoire, Ghana and Togo, but a decrease was projected for coastal areas (1–20%). Furthermore, human impact negatively affected tree cover and partly changed the direction of the projected change from increase to decrease.

Main conclusions  Considering climate change alone, the model results of potential vegetation (biomes) show a ‘greening’ trend by 2050. However, the modelled effects of human impact suggest future forest degradation. Thus, it is essential to consider both climate change and human impact in order to generate realistic future tree cover projections.

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