How bats help forests grow faster

Hated and unjustly feared, the bats they are actually precious and harmless allies who give us a big hand to keep the number of harmful insects. In fact, several studies have already shown that, hunting for insects every night, help agriculture keeping cultivated fields healthier and more productive.

But what effect does their “insecticidal” role have on natural ecosystems? According to a new study recently published in Ecologybats can even help forests to grow faster and healthier. Without the bats that reduce their density, the insects who eat the leaves of trees they go wild, creating up to nine times more damage for the health and growth of forest ecosystems.

Insect-eating bats are critical to the health of ecosystems
in the picture: Insect-eating bats are critical to the health of ecosystems

They exist in the world over 1400 species of bats, all very precious for the fragile harmony of ecosystems. There are species that they eat nectar contributing to the pollination of flowers, others they prefer the fruita and that help plants disperse seeds and even those that like vampires they drink bloodwe recently told you in ours special episode of Kodami Zoom with a Halloween theme.

But most of the batsthe order of mammals to which bats belong, magic especially insects and therefore occupies a key role within trophic networks. Many of these species, among other things, do not live alone in remote and cold cavesbut they live above all the temperate forest ecosystems of the Northern Hemisphere. Despite this, no one before has ever investigated the impact these mammals can have on forest welfare.

To find out, researchers at the University of Illinois built some gigantic closed networks inside an Indiana forest, preventing so the bats that live there have access to those areas. The jerseys were though sufficiently wide to let in and out freely insects. Also, every morning the fences came leave openthus also allowing the birds to enter and thus be sure to measure exclusively the impact of bats.

For three summers in a row, from 2018 to 2020the researchers therefore counted the number of insects present on the oak and pecan seedlings that grew in the undergrowth of the forest, also measuring the amount of defoliation for each single plant. At the same time, they compared these data with those collected in an equal number of fences but without anti-bat barriersso you can compare the density of insects and the amount of leaves eaten with and without bats in circulation.

In areas where bats could not access there were up to nine times as many insects
in the picture: In areas where bats could not access there were up to nine times as many insects

Overall, the researchers found well three times more insects And five times more seedlings with leaves eaten in the areas where the bats could not access compared to those of control, where instead the bats could fly and eat freely. Furthermore, when analyzed separately, the oaks they have even undergone defoliation nine times greater, while walnut trees three times more. The presence of bats, therefore, greatly reduces the number of insects that eat the leaves (such as caterpillars of moths), thus allowing forests to grow much faster and healthier.

The presence or absence of bats then triggers what naturalists and biologists call trophic cascadebecause by occupying the upper floors of the food chain and eating harmful insects, they generate a positive chain effect also on the lower floorstherefore keeping you healthier and more productive the entire ecosystem. Clearly, more or fewer insects do not cause irreparable damage to a forest, however, according to researchers, the long-term disappearance of bats could prove fatal to the growth of bats. young seedlings which, with a greater number of leaves eaten, would be much more exposed to water loss or ai parasiteslike mushrooms.

Bats are therefore extremely important to the health, structure and composition of our forests
in the picture: Bats are therefore extremely important to the health, structure and composition of our forests

Another equally interesting aspect that emerges from this study is instead relating to birds. In the past, very similar studies have also been carried out on the abilities of birds to check insect densities. However, no one had ever bothered to close the fences at night to exclude bats. This means that in all the studies carried out so far, the birds have also benefited from the precious dark work performed by bats during the night, which they have so “inflated” at least partially the results.

Clearly both birds and bats, alternating day and night, do both a very precious work to keep the number of leaf-eating insects under control, thus playing a fundamental role for forest ecosystems, influencing the health, structure and composition of forests. These results clearly demonstrate the enormous ecological and economic value insectivorous bats and the urgent importance of protecting these animals in danger.

The number of bats around the world stands dropping drastically due to human activities, now carrying numerous species one step away from extinction. The massive use of pesticides that reduces prey, parasitic fungi such as the one responsible for white nose syndrome, habitat loss e collisions with wind turbinesare just some of the main threats to the survival of these precious and often underestimated mammals, which instead deserve quite another consideration from all of us.

How bats help forests grow faster