Tropical land savannization: Impact of global warming

Abstract

This study investigates the impact of global warming on the savannization of the tropical land region and also examines the relative roles of the impact of the increase of greenhouse gas concentration and future changes in land cover on the tropical climate. For this purpose, a mechanistic-statistical-dynamical climate model with a bidirectional interaction between vegetation and climate is used. The results showed that climate change due to deforestation is more than that due to greenhouse gases in the tropical region. The warming due to deforestation corresponds to around 60% of the warming in the tropical region when the increase of CO2 concentration is included together. However, the global warming due to deforestation is negligible. On the other hand, with the increase of CO2 concentration projected for 2100, there is a lower decrease of evapotranspiration, precipitation and net surface radiation in the tropical region compared with the case with only deforestation. Differently from the case with only deforestation, the effect of the changes in the net surface radiation overcomes that due to the evapotranspiration, so that the warming in the tropical land region is increased. The impact of the increase of CO2 concentration on a deforestation scenario is to increase the reduction of the areas covered by tropical forest (and a corresponding increase in the areas covered by savanna) which may reach 7. 5% in future compared with the present climate. Compared with the case with only deforestation, drying may increase by 66. 7%. This corroborates with the hypothesis that the process of savannization of the tropical forest can be accelerated in future due to global warming. © 2011 Springer-Verlag.