discussing environmental systems (or spheres, or media)—hydrosphere, geosphere,
ID: 232195 • Letter: D
Question
discussing environmental systems (or spheres, or media)—hydrosphere, geosphere, atmosphere, biosphere and anthrosphere. Now, envision beginning a great, new, high-paying environmental job on the West Coast. They’re covering your tuition and textbook, to boot. Your boss walks in and, looking concerned, asks you to brief her on an article she just skimmed: New Hurdle for California Condors May Be DDT From Years Ago. She knows the definition of each sphere, but is not clear on how the environmental systems concept and the issues in the article relate. Also, she thought that DDT went the way of disco and leisure suits in the 1970s. What do you say? What's the story with the condors? Why is DDT still around? Your briefing will appear in yet another sphere: your new employer's blogosphere.
Explanation / Answer
a) The California condor is a majestic icon of the natural world in the southwestern United States. With a wingspan of up to 9.5 feet and a characteristic bald and colorful head, Gmynogyps californianus, is a unique and recognizable character that reigns as North America’s largest flying bird. They can live to be 60 years old in the wild and spend their entire lives in monogamous relationships. Scavengers by nature, condors rely on their impeccable eyesight to spot deceased prey from up to 15,000 feet in the air. They usually prefer to dine on carcasses of sheep, deer, cattle and even marine mammals if they live near the coast. By consuming prey that is already deceased, condors hold an important role by keeping decaying flesh from stinking up the ecosystem.
Sadly, California condor numbers have declined drastically over the last few decades, and their original habitat has shrunk to a nearly unrecognizable size. We cannot be too certain of historical populations of the birds, but we do know that there were only 22 known individuals in the world by 1982, and only nine wild individuals by 1985. And while their natural habitat by the late 1800’s ranged from British Columbia to Baja California, their habitat was downsized to encompass just a small swath of land in southern California. Recovery efforts have placed the birds back into pockets of Baja California, Arizona, Utah as well as a greater range of California.
b) DDT stands for dichloro-diphenyl-trichloroethane. It was developed in the 1940s and become a powerful tool for the United States to control insects in agriculture and insect-born diseases like thyphus and malaria for both the military and civilians. As DDT-use became more widespread, the dangers of the pesticide became more readily apparent. Insects were becoming resistant to DDT, and human and animal exposure to the chemical often resulted in reproductive issues as well as cancer. The perfect pesticide was no longer perfect and the EPA stepped up to ban the substance.
Sadly, the damage of DDT had already been set in place for decades to come. The chemical ended up in marine food chains when it was washed into the ocean. It was absorbed by the smallest micro-organisms like moss and plankton. As you move up the food chain into smaller fish, larger fish, and then top predators like birds, sharks and marine mammals, the concentration of DDT in each organism grows. This phenomenon is called biomagnification and it explains why those on the top of the food chain are most prone to problems from DDT. By continually storing more and more of the pesticide in their fat, larger animals have much higher concentrations of DDT in their bodies than those at the bottom of the food chain.
Unfortunately for condors, the fact that they are scavengers that prefer larger prey means they ingest an awful lot of DDT. Condors that feast on dead seals, sea lions and whales are exposed to the greatest concentration of DDT and DDE (a breakdown of DDE) as their prey is the top of the marine food chain. And this is having a major impact on condor reproduction just as it has had on many other iconic birds of the United States.
Eggshell thinning is a phenomenon noted by scientists when studying birds exposed to DDT. As the birds’ natural ability to metabolize calcium is negatively impacted, the eggs they lay have very thin, weak shells. They cannot support the weight an adult birds sitting on the nest and simply crack before the baby bird inside has had a chance to mature into a viable offspring. Problems with egg shell thinning as the result of DDT is well known in bald eagles and brown pelicans, as well as condors.
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