Tropical Reforestation Aided By Bats

Tropical forests are of global ecological importance. They are a key contributor to the global carbon balance and are host to a major part of the world’s biodiversity. Between 2000 and 2005, worldwide net losses of tropical forest cover averaged 0.18 % annually and regionally even exceeded 1.5 % annually in some Latin American countries. Forest is usually replaced by agriculture. Often soils become rapidly infertile and land is abandoned. Because deforested areas rarely offer much food or protection for seed dispersers such as birds or small mammals, natural forest regeneration is hampered by a lack of natural seed inputs. The alternative, replanting tropical forests, is too expensive and rarely a feasible option, and, in general, knowledge on how best to rapidly restore natural vegetation is lacking.

“We believe that bats could help in reforestation. They are able to cover large distances during their nightly foraging flights and are willing to enter deforested areas”, says Detlev Kelm from the IZW. Many bats eat fruits or nectar, and thus are key species for seed dispersal and flower pollination. Kelm and colleagues showed that the principal barrier to reforestation - the lack of seed inputs - could be overcome by the deployment of artificial day roosts for bats in deforested areas. These roosts were designed to approximate characteristics of large, hollow tree trunks, the main type of natural bat roost. “Within a few days to weeks the first bats will move in. So far we have found ten bat species using the roosts, and several of these are common and important seed dispersers”, Kelm reports. “We measured the effect of the roosts on seed dispersal and found seeds of more than 60 plant species being transported by the bats”. Of these plants, most were pioneer species, which represent the initial stages of natural forest succession.

This cost and labour efficient method can thus support and speed up natural forest regeneration. Artificial roosts are simply built boxes, which require little maintenance and can be used by bats for many years. “We hope that this cheap and easy to use method will be applied in many parts of the tropics in the near future, and that bats will be “employed” as efficient agents of reforestation”, says Kelm. They may provide an effective contribution to the amelioration of deforestation and climate change.

Detlev H. Kelm, Kerstin R. Wiesner, Otto Von Helversen. Effects of Artificial Roosts for Frugivorous Bats on Seed Dispersal in a Neotropical Forest Pasture Mosaic. Conservation Biology. Published article online: 25-Apr-2008.