Land-use changes and agriculture in the tropics: pesticides as an overlooked threat to wildlife

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The growing demand of agricultural products has led to drastic changes in land-use all over the world. Tropical lands are no exception; they are drastically and rapidly changing look and losing their peculiar features. A recent assessment of crop distribution and expansion in 128 tropical countries for the years 1999–2008 showed that soybeans and maize are the crops which expanded most in absolute area (Phalan et al. 2013). Among these crops, it is increasingly recognised that oil palm is one of the main drivers of tropical forest conversion (Carrasco et al. 2014). The growing global demand for oil palm is leading to the expansion of plantations in Asia, Latin America, and West Africa, which are threatening vast tracts of tropical forests with loss of biodiversity and functional diversity (Senior et al. 2013; Edwards et al. 2013). Although expansion of agricultural land has mostly come at the expense of tropical forests, other important biomes of high conservation value (e.g., grasslands, savannas, shrublands) are also shrinking dramatically (Gibbs et al. 2010). The assumption that yield improvement (e.g., ‘‘super palms’’ variety) would spare land for nature has recently been disputed (Carrasco et al. 2014; Giam et al. 2014), leaving little hope for the future of tropical ecosystems. Although habitat loss poses the greatest threat to species, I highlight that there is another important, but overlooked and sneaky threat to tropical wildlife and ecosystems that further reduces any optimism: pesticides. The global use of pesticides (fungicides, herbicides, insecticides, rodenticides) is important for growing oil palms, as well as other crops, by reducing the prevalence of targeted pest species. However, little attention is given in the tropics to the potential unintended effects on non-target species, including