Environmental news and talk regarding conservation is often one tragic story after another. Headlines like “Scope of Yellowstone River oil spill may grow,” “Scientists warn of a mass extinction of marine species,”and “Megafires may change the Southwest forever,” are just a few recent examples of the tone of the media when discussing future of our planet. If you aren’t careful, it can get quite depressing and discouraging.
Let’s revisit a very familiar story– that of DDT. Rachel Carson shared with the world the dangers of DDT in her 1962 book Silent Spring, which many have attributed the birth of modern environmentalism. Here is the gist of the story: DDT (dichloro-diphenyl-trichloroethane) is an extremely effective pesticide used to control insects that may be vectors of disease, protect crops against pests, and control invasive insects that may pose a threat to native environments. However, it was discovered to be the cause of declines in several bird populations. DDT is very persistent and will move through the food web accumulating at each step.
For example, once DDT is sprayed on crops rain runoff will carry it into streams that lead to rivers that lead to larger lakes and even oceans. As the DDT is consumed by smaller organisms and those organisms are consumed by larger fish, the chemical DDT becomes more and more concentrated. Animals at the top of the food chain like Ospreys and Pelicans accumulate large amounts of chemicals like DDT in their bodies for a few reasons. First, they consume more in prey than their own body weight, so the toxins that were in all the prey’s tissues are concentrated into the one predator’s body. Also, birds of prey tend to have long lifespans. Ospreys can live from 20-25 years, and Pelicans can live up to 30 years. Overtime, more and more toxins build up in the animal.
Heavy use of DDT across the country during the 1950s and 1960s coincided with Brown Pelican populations dwindling almost to extinction along with birds of prey like the Osprey, Bald Eagle, and Peregrine Falcon declines. The DDT didn’t kill the birds directly, but altered their calcium metabolism preventing them from creating eggshells thick enough to hatch successfully.
OK, so far this story sounds like it belongs with all the other depressing headlines listed above, but the most important part is what happened next. Scientists were able to connect the decline in bird populations to DDT, and with the help of public awareness raised in part by Silent Spring, we made a change. In 1972, the EPA banned the use of DDT on crops in the United States. As a result, Ospreys and Brown Pelicans, both listed as endangered species in the 1970s, are now a common sight in most coastal ecosystems, especially here on Sanibel and Captiva!
Don’t get discouraged by the “end-of-the-world” tone taken by much of the media regarding environmental issues. Yes, it is true that we are facing some huge environmental challenges right now, but that doesn’t mean we can’t fix them.
If your morale needs a boost, read some other success stories: