We don’t know exactly how many bats will die this year, but we are increasingly confident that we will see a population crash in bats in the northeast. As a biologist working on bats, I have academic and scientific reasons to worry about such a population crash, but many of the researchers involved with studying this die-off (including me) have been asked why the public should be concerned. The sheer complexity of the ecosystems involved and the understudied role of bats in the ecosystem make it difficult to know exactly what to expect, but I will try my best to summarize some of the possibilities below. I do want to emphasize that we have never seen a population decline of the magnitude we expect to see this year, so even those of us studying bats can only guess what will happen.

All of the bats in the Northeast are insectivorous (they eat only insects). They consume huge numbers of insects each night during the summer including crop and agriculture pests, various swarming insects, moths, and even the occasional mosquito (but mosquitoes are not a large part of their diet as is sometimes claimed). What exactly will happen when all of these insect populations are released from their main predator is unknown. The standard answer that we bat biologists give the media is that we should expect an increase in all of these insects—especially, it often seems, the ones that cause the most harm to humans. Unfortunately, this “sound bite” type answer doesn’t really do justice to the scope of the problem.

The latest and greatest ecological theory would predict that some species of insects, but probably not all, will experience population increases. Some species will do better than others, either because they reproduce more quickly or because they are better competitors for food. This will lead to a change in the composition of the insect communities in addition to an increase in their overall numbers. Changes in the insect communities may trickle down and lead to changes in the plant communities; changes in the plant communities may affect herbivore communities; changes in herbivores may affect carnivore communities; and so on throughout the entire food web (ecologists call this a trophic cascade). The possibilities are endless (and almost completely unpredictable) and the direct effect of this ecological change on humans is unknown, but should concern environmentally-conscious people nonetheless.

If an ecological catastrophe doesn’t concern you, it is almost assured that some economic impacts will result from the population decline of bats and the subsequent increase in insects. If an agricultural pest increases, there are the obvious costs associated with decreased crop production. The affected area is relatively minor in terms of agriculture, but if this spreads to the Midwest in the future, the economic costs may skyrocket. If forest pests increase, there will be costs (and they can be substantial) related to controlling the pest, whether through application of pesticides or more extreme measures. If an insect species that is a vector for a human disease increases, there will be medical costs.

As I mentioned before, we really don’t know what the ecological and economic outcome of WNS and the decline in bat numbers will be. As Scott Darling of the Vermont Fish and Wildlife Department said, “We may be living in an ecological experiment that will demonstrate the role of bats”

This entry was posted on Friday, April 4th, 2008 at 12:10 pm and is filed under Justin Boyles. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.