Where have all the insects gone? Last summer, the journal Science published a summary of several long-term studies from America and Western Europe documenting massive declines in insects. The studies have established that even in places where plant diversity and abundance have improved, insect numbers still declined.
My favorite was a Canadian study in which scientists probed into decades of stratified bird droppings in old, abandoned chimneys in which Chimney Swifts have nested for generations. Going through layer upon layer of bird poop, they tracked a striking change in the swifts’ diets in the 1940s, when DDT was introduced and the proportion of beetle remains suddenly dropped. The proportion of beetle remains increased after DDT was banned in the ’70s, but it never reached the level it had been at in the ’40s. Meanwhile, most of the insects the swifts were catching were smaller than the pre-1940s insects, requiring the swifts to work harder for each calorie.
Studies of insect samples collected over several decades in Europe show a horrible crash. Comparing insect samples collected annually, using identical equipment and techniques at more than a dozen sites in Europe from 1989 through 2013, the Krefeld Entomological Society found a shocking 80 percent drop in the mass of insects.
Some insectivorous birds are holding their own, but such species as nightjars, swifts, Purple Martins, and American Kestrels (which eat large numbers of grasshoppers and other large insects) are declining noticeably.
Many factors contribute to insect declines, so reversing the trend will require attacks on many fronts. What can we as individuals do?
Severely limiting our use of lawn and garden pesticides and fertilizers is most important. Many people don’t realize that major lawn-care companies use formulas that don’t take current local conditions into consideration. They use the same amount of the same formulation over every square inch during a drought as during an excessively rainy period, and whether a lawn has never been exposed to weed killers and has a great many dandelions or has been treated for 20 years and has virtually none. Even if cutworms or other lawn pests are not a problem in a given yard, insecticides will be included in the formulation if cutworms have ever been even a minor problem anywhere in that region.
Fertilizers affect insect populations, too. Much of the fertilizer applied in backyards ends up running off into lakes, rivers, and streams. This contributes to thicker algal and plant growth, ultimately leading to reduced light and oxygen depletion, sparking declines in aquatic insects, such as mayfly and dragonfly nymphs, that require clear, well-oxygenated water.
Protecting our backyard insects is a drop in the bucket considering the scope of the problem. But everything we do to foster a culture of conservation makes the world safer for wildlife, including insects, and for us.
This article from Laura Erickson’s column “Attracting Birds” appeared in the March/April 2018 issue of BirdWatching.
Five more columns by Laura Erickson
FEEDING BIRDS JELLY
Feeding it safely involves important caveats.
One of the best ways to see birds up close.
FEEDERS FOR CONSERVATION
In Peru, bird-feeding stations are helping to protect habitat.
MORE THAN BIRD SEED
Four major threats to birds may lurk in your yard.
Unpredictable, surprising, and cherished.
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