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: