Potential Vegetation in West Africa
Miriam Machwitz, Martin Wegmann, Kim Knauer, Tobias Landmann, Heiko Paeth, Michael Schmidt and Stefan Dech (GLOWA Volta Project), University of Wuerzburg, Remote Sensing Department, Am Hubland, 97074 Wuerzburg
Introduction
Magnitudes and factors associated with land cover change are essential data feeds for political reporting mechanisms
and for the improvement of models that predict determinants and impacts of climate change scenarios. Especially
because of the impact of deforestation on climate change, this issue demands new attention. But what is the amount of
land cover change? What would be the natural vegetation without human impact?
In land cover and deforestation studies it is becoming increasingly critical to correctly quantify and entangle the natural
vegetation and/or climate variability from the human induced change. To contribute to the above challenges we created
a new and functional dataset with the potential vegetation in West Africa, covering largely the countries Benin, Burkina
Faso, Ghana, Ivory Coast and parts of Mali.
Method
The land cover, based on the FAO LCCS standard, inside protected areas (IUCN nature reserves and national parks),
was deemed to represent the natural vegetation cover. Based on these findings, we predicted the potential vegetation
land cover on the sites outside the protected areas that exhibit the same climate, elevation and soil conditions.
Interpolated climate date with 1-km spatial resolution from WORLDCLIM (Hijmans et al. 2005), were used for the
determination of the climate conditions. The climate elements considered were mean, minimum and maximum
temperature and monthly precipitation from 19502000. Moreover, the soil information is represented
by the FAO’s map of world soil resources.
Additionally we created a data layer with wetland
occurrences and rivers, based on the 90-meter
digital
elevation
model
SRTM
which
was
incorporated in this model.
The distribution of the different vegetation classes
was determined with the MAXENT model (Maximum
Entropy Approach to Species Distribution Modeling).
This algorithm showed very good results for
modeling the spatial distribution of species in other
studies (Stevens et al. 2004).
Results and Conclusions
The results of the modeled distribution of the
potential vegetation in the Volta basin in West Africa
are shown in Figure 1. The latitudinal gradient is well
visible. The modeled land cover classes are
evergreen forest in the south, followed by closed
and open woodland and open grassland with sparse
shrubs in the northern parts (Sahel).
This dataset can be used to analyze the deviation
from actual land cover. In detail, this map has high
potential for the determination of the degree of
degradation due to human impact or for the analysis
of potential carbon stocks.
Figure 1: Potential vegetation in the Volta basin in West Africa