Study Claims Light Pollution Impairs Rainforest Regeneration

Bats are known to play a crucial role in pollinating plants and dispersing their seeds. But, a new study discovered that in light-polluted areas bats avoid feeding. The usual behaviour of bats prevents rainforest regeneration.

The study was led by scientists from the German Leibniz Institute for Zoo and Wildlife Research Berlin (IZW).

The study was based on the experiments conducted on Sowell's short-tailed bats (Carollia Sowelli). The researchers divided the flight cage into two different sections. One was naturally dark and the other section was lit with a sodium street lamp. In both the cages the researchers allowed bats to harvest their favourite fruits- mainly pepper plants and figs.

The researchers noticed that the bats flew into the dark compartment twice when compared to the other section that was illuminated. Apart from this, they harvested the fruits twice as often in the dark compartment.

In the second experiment, the researchers lit the pepper plants growing in the wild with a street light. In this case they measured the percentage of ripe fruit the bats harvested from plants in dark sites and those lit with street light.

They noticed that the bats harvested ripe fruits from plants in dark. When compared to 100 percent of ripe fruits in the dark, the bats choose just 78 percent of fruits from lit plants.

Studies earlier have shown how insect-eating bats avoid foraging in areas that are illuminated. But this is the first study that shows how fruit-eating bats also prevent foraging in light-polluted areas.

"In tropical habitats bat-mediated seed dispersal is necessary for the rapid succession of deforested land because few other animals than bats disperse seeds into open habitats," says Daniel Lewanzik, a PhD student at the IZW and first author of the study.

When bats forage under dark conditions, they produce a 'seed rain' or releasing seeds while flying, when they forage in illuminated areas; the light pollution drops the seed rain.

In tropical countries, as human population and economies swell the amount of light pollution also increases.

"The impact of light pollution could be reduced by changes in lighting design and by setting up dark refuges connected by dark corridors for light-sensitive species like bats," Lewanzik said.

The finding has been documented in the journal of Applied Ecology.