Environmental Engineering Reference
In-Depth Information
Noticing this ecosystem decline, officials decided to reintroduce gray wolves to Yellowstone National Park. In
1995, gray wolves were relocated to the park from Canada and the reintroduction began. Populations increased
over time, and the ecosystem of the park started to rebalance back to its previous state. Having fewer large
herbivores increased vegetation along streams, leading to an increase in beaver populations. More kills by the
wolves meant more food for scavengers. And more wolves also meant more coyotes killed by the larger wolf,
leading to an increase in smaller animal populations such as foxes and rodents.
Because of the success of the reintroduction, gray wolves were downgraded to threatened status in 2003.
California Condor
California condor numbers declined dramatically in the 20th century as result of habitat destruction, lead pois-
oning from consuming lead shot while scavenging hunting remains, poaching, and the inability of the birds to
adapt to the changing environment caused by humans. In 1987, there were 22 remaining wild condors—7 in
the wild and 15 in captive breeding programs. The last remaining condors in the wild were captured to expand
the breeding programs at the San Diego and Los Angeles zoos. The San Diego Zoo's population was moved to
the San Diego Wild Animal Park. The birds' DNA was tested so that the most unrelated birds could be mated
to avoid over-similarity in the gene pool.
As the population in the two zoos grew, additional breeding programs were established, including in the Ore-
gon Zoo and at the World Center for Birds of Prey in Boise, Idaho. Beginning in 1991, condors were released
in California; in 1996, they were released in Arizona. Currently, wild condors can be seen in three sites in Cali-
fornia; at Zion National Park in Utah; in the Grand Canyon area in Arizona; and in Baja California, Mexico.
As of August 2010, there are 384 birds, including 188 in the wild. However, the birds continue to struggle to
reproduce in the wild.
The California Condor recovery project is the most expensive species conservation project in U.S. history,
costing over $35 million including $20 million in federal and state funding. Several milestones have been
reached in the wild. In early 2007, a condor laid an egg in Mexico for the first time since the 1930s, with a
second egg being laid in 2009. Special note: Several sources suggest that DDT has played a role in the decline
of the California condor. On the 2003 APES, the use of DDT as an explanation for the decline of the California
condor
was not allowed.
Water
Lake Erie Waste Dumping
By 1969, Lake Erie was generally regarded as dead due to a low amount of dissolved oxygen, high pollution
concentrations, and large amounts of algae. The lake is surrounded by a large number of major cities, each con-
tributing sewage and industrial wastes. Detroit was the capital of the automotive industry, Cleveland had petro-
chemical and steel industries, Toledo had steel works, Erie had paper mills, and chemical manufacturing took
place in Buffalo. By the 1960s, the area was home to 9 million people on the U.S. side of Lake Erie. Partially
treated waste was commonly discharged into the lake, and another 2 million people had septic-tank waste sys-
tems with waste that also frequently reached the Lake. By the 1960s, fish die-outs in the lake were common.
Changes were made in local and federal laws that reduced the waste dumped into Lake Erie. High-phosphate
detergents were banned in several surrounding states, industrial waste dumping was put under strict controls,
and municipal sewage was extensively treated before being discharged into the lake. As a result, it is making a
