Conservation News

Silent Spring Revisited

By Pamela Hunt, Senior Biologist – Bird Conservation

Back in 1962, Rachel Carson gained fame (and a certain degree of notoriety) with the publication of “Silent Spring,” a book which ultimately lead to environmental success stories such as the creation of the Environmental Protection Agency and the banning of the pesticide DDT in the United States. But none of this means that environmental contaminants are no longer an issue, and new threats to birds and wildlife are constantly being discovered and studied.

CARW 3 (Concord 9-Feb-13)

Carolina Wren by Pam Hunt

A decade ago, mercury was a big issue in much of the Northeast. Mercury from coal-burning power plants precipitates into water bodies, where it can eventually be taken up by aquatic organisms and things that eat them. In high enough doses, Mercury can cause physiological problems, and for this reason pregnant women are discouraged from eating too much fish from certain sources. We have long known that fish-eating birds such as loons can accumulate high concentrations of mercury, and more recently, studies of Carolina Wrens and other songbirds in Virginia have shown birds with high mercury levels have trouble learning or singing their songs. The jury is out on the longer term effects of such mercury exposure, but they can’t be good.

Meanwhile, the demands of intensified agriculture required that substitutes be developed for DDT, and other insecticides to which pest insects had developed resistance. And thus were born a new class of chemicals known as neonicitinoids, which affect the central nervous system of insects – causing death. “Neonics” entered widespread use in the 2000s, and it wasn’t long before negative effects (including mortality) on non-target organisms were noticed. They have long been suspected as a factor behind widespread declines in bee and other pollinator populations, and more

Tree Swallow by Pam Hunt

Tree Swallow by Pam Hunt

recently have been linked to bird declines in Europe. While birds may experience lower mortality due to neonic toxicity compared to insects, they may suffer damage to their immune systems and be indirectly affected by the loss of insect prey. In a recent study in Canada, Tree Swallows nesting in heavily agricultural areas tended to weigh less and their young were in poorer condition compared to birds nesting in more natural areas.

Because of concerns about the ecological impacts of neonics, their use has been temporarily suspended in much of Europe until the end of 2015. In the U.S., use remains widespread, and it is actually hard to find even nursery plants that have not been treated with the chemicals. And of course, there are plenty of other chemicals in the environment with potentially negative effects on birds and other wildlife – Rachel Carson’s work is far from done.

For more information on mercury, pesticides, and other contaminants, including some things you can do to help, visit: