An April 2011 study estimates that insect-eating bats in North America save farmers at least $3.7 billion dollars a year in pest-control costs. The potential loss of these ecological services is one reason concerns are growing over the spread of a deadly disease affecting bats – white-nose syndrome – which has decimated bat populations.
To estimate the value of ecological services provided by bats, these scientists first took a close look at how many insects bats were eating during their flight across the night sky in search of food. They found that a single little brown bat can eat up to 4 to 8 grams (comparable to the weight of a spoonful of sugar) of insects every night. From these data on insect consumption rates, the scientists calculated that bats can save farmers anywhere from $12 to $173 dollars per acre in pesticide costs every year.
Farmers often install bat houses near their crops to help control pests, but until now people were uncertain about how effective bats were in controlling pests. In a press release from the U.S. Geological Survey (USGS), Paul Cryan noted:
This analysis suggests that bats are saving us big bucks by gobbling up insects that eat or damage our crops. It is obviously beneficial that insectivorous bats are patrolling the skies at night above our fields and forests – these bats deserve help.
In North America, bat populations are declining because of an emerging disease called white-nose syndrome, first detected in New York in 2006. White-nose syndrome is thought to be caused by a fungus (Geomyces destructans) that invades the skin of bats causing erratic behavior and death. Over one million bats have died as a result of white-nose syndrome in the northeastern United States. By 2011, white-nose syndrome had spread southward and westward into 16 states and 3 Canadian provinces that contain agriculturally rich landscapes.
Other major threats to bat populations include habitat loss and invasive species. There is some concern for the impact of wind energy turbines on bats and researchers are actively looking for ways to minimize risks.
The authors of the scientific study warn that noticeable economic losses to North American agriculture could occur in the next 4 to 5 years due to losses of bat populations.
In the press release, lead author Justin Boyles from the University of Pretoria, South Africa stated:
Bats eat tremendous quantities of flying pest insects, so the loss of bats is likely to have long-term effects on agricultural and ecological systems. Consequently, not only is the conservation of bats important for the well-being of ecosystems, but it is also in the best interest of national and international economies.
The study titled “Economic importance of bats in agriculture” was published in the April 1, 2011 issue of Science. The scientists hope that their research will increase awareness and appreciation for the economic benefits insectivorous bats provide to agriculture.
Deanna Conners is an Environmental Scientist who holds a Ph.D. in Toxicology and an M.S. in Environmental Studies. Her interest in toxicology stems from having grown up near the Love Canal Superfund Site in New York. Her current work is to provide high-quality scientific information to the public and decision-makers and to help build cross-disciplinary partnerships that help solve environmental problems. She writes about Earth science and nature conservation for EarthSky.