Bats are declining worldwide due to a combination of threats, with some species losing over 90% of their populations in less than a decade. Of the 1,336 bat species assessed by the IUCN, 25 are critically endangered, 87 are endangered, and 110 are vulnerable. No single cause explains these losses. Instead, a web of pressures is pushing bat populations toward collapse.
White-Nose Syndrome Has Been Devastating
The most dramatic bat die-off in recent history has been caused by white-nose syndrome, a fungal disease first documented in a New York cave in 2006. The fungus grows on bats’ skin during hibernation, waking them repeatedly and causing dehydration, starvation, and death. In fewer than 10 years, it wiped out over 90% of northern long-eared, little brown, and tri-colored bat populations across North America. As Winifred Frick, chief scientist of Bat Conservation International, put it: “Nine out of 10 bats of the most vulnerable species are now gone.”
The disease has since spread to 35 U.S. states and seven Canadian provinces, confirmed in 12 North American bat species. Indiana bats and big brown bats have also declined. The speed and scale of this single disease makes it one of the worst wildlife epidemics ever recorded on the continent.
Wind Turbines Kill Hundreds of Thousands Annually
Hundreds of thousands of bats die each year from collisions with wind turbines in the United States alone. Bats are drawn to turbines for reasons that aren’t fully understood, possibly mistaking them for tall trees or following insect swarms near the structures. The spinning blades can kill bats on contact, and the rapid pressure changes near the blades can cause fatal internal injuries even without direct contact. As wind energy expands globally, this threat is growing alongside it.
Habitat Loss Shrinks Their World
Deforestation strips bats of both food and shelter. Many species depend on structurally complex forests that provide roosting sites in hollow trunks, under bark, and in dense canopy foliage. When forests are cleared, these microclimates and refuges disappear. Smaller bat species are hit especially hard because they can’t fly long distances across open, deforested landscapes to reach remaining patches of habitat. Larger bats may cross these gaps, but smaller species like short-tailed fruit bats become effectively trapped or absent from cleared areas.
This isn’t just a tropical problem. Urbanization, agricultural expansion, and logging reduce bat habitat on every continent. Even partial forest thinning can eliminate the structural complexity bats need, reducing the variety of species an area can support.
Pesticides Weaken Bat Immune Systems
Bats eat enormous quantities of insects, which means they also absorb whatever chemicals those insects carry. Recent research has revealed that pesticide exposure doesn’t just poison bats directly. It quietly dismantles their immune defenses. Within three days of exposure to a common pesticide, bats showed reduced levels of proteins involved in inflammation and cell death, early signs of immune suppression. By seven days, the damage deepened, impairing a key defense system the body uses to fight off pathogens.
One particularly striking finding: pesticide exposure reduced levels of a protein called tetherin, which bats use to prevent viruses like Ebola and Nipah from spreading between cells. This may compromise the remarkable viral resistance that bats are known for. Pesticides also disrupted proteins involved in immune signaling and white blood cell function. For a group of animals already battling fungal disease and other stressors, weakened immunity can turn a manageable infection into a fatal one.
Hunting Affects More Species Than Most People Realize
At least 167 bat species, roughly 13% of all known bats, are hunted for food or traditional medicine. The practice is most common in Africa, Asia, and the Pacific Islands, with smaller-scale hunting in Central and South America. Large fruit bats bear the heaviest burden: half of all species in the Old World fruit bat family are hunted. Those that are hunted are six times more likely to be classified as threatened on the IUCN Red List compared to unhunted species.
Most bat hunting happens at local markets on a relatively small scale, but even modest harvests can devastate populations. Bats reproduce slowly, typically raising just one pup per year, so they can’t bounce back quickly from losses the way rodents or insects can.
Extreme Heat Is Causing Mass Die-Offs
Climate change is adding a newer, more unpredictable threat. In eastern Australia in 2014, temperatures exceeded 48°C (118°F) at multiple locations, killing many thousands of flying foxes. In one well-studied colony, up to 13% of black flying foxes died from overheating, with dependent young making up the majority of deaths. Similar mass die-offs were recorded in India during heat waves in 2010 and 2015. Researchers have concluded that climate change drove the extreme temperatures in Australia in 2013 and 2014 that killed hundreds of thousands of flying foxes.
These mass mortality events will likely increase as heat waves become more frequent and intense. Bats that roost in exposed tree canopies, particularly the large fruit bats of the tropics and subtropics, are most vulnerable.
Why Losing Bats Matters
Bats provide ecosystem services that are difficult to replace. Over 400 bat species contribute as seed dispersers, pollinators, insect controllers, or nutrient recyclers. At least 549 plant species depend on bats for pollination or seed dispersal, including economically important crops like durian, which relies on pollination by island flying foxes. In the tropics, fruit bats are among the most effective seed dispersers for reforesting cleared land.
The economic value is staggering. Insect-eating bats save U.S. agriculture an estimated $22.9 billion per year through natural pest control, with estimates ranging from $3.7 billion to $53 billion. In Texas cotton fields, bat predation on pests saves farmers between $30 and $427 per hectare, representing 12% to 29% of the crop’s value. Chilean vineyards see about 7% less grape damage thanks to bat activity, worth roughly $188 to $248 per hectare annually.
These numbers only capture agriculture. Bats also suppress mosquito and other pest populations in cities and suburbs, pollinate wild plants that hold ecosystems together, and deposit nutrient-rich guano that fertilizes cave and forest ecosystems. Losing bats means losing services that no technology or human effort can efficiently replicate at scale.