Putting a dollar value on nature and the services it provides isn’t easy. Such numbers can show how much our human economy depends on nature’s indiscernible economy. Take bats. A study in Science magazine reveals just how important they are to American agriculture.

Every day, a bat eats much of its body weight in insects, many of them harmful to crops. A group of scientists led by Thomas Kunz at Boston University calculated how much more money cotton farmers in one region of Texas would spend on pesticides if bats weren’t present. Extrapolating from those numbers, they estimated that bats save American farmers somewhere between $3.7 billion and $54 billion a year, most likely about $22.9 billion.

This is a huge savings no one notices as long as bats flourish. But bat populations are severely threatened, especially the commonest species, the little brown bat, which is being decimated by a fungal disease called white-nose syndrome. The disease has spread all across the eastern half of the country and is now moving westward from Oklahoma.

In 2010, Interior Department agencies spent $6.3 million researching and trying to prevent the spread of white-nose syndrome. That money was taken from other programs, and it was barely a start. What’s needed now is financing specifically allocated to staff continuous bat research. The Interior Department should not have to borrow from itself to protect these creatures that are so important to American agriculture. We know all of the talk in Washington these days is about cutting, but spending a little more now could save us a fortune later.