Species endangered by
unsustainable hunting.
Overhunting and overfishing have threatened animal species
since aboriginal Europeans, Australians, and Americans developed effective
hunting technology thousands of years ago. The dodo, passenger pigeon, great
auk, and Steller's sea cow were hunted to extinction. Unstainable hunting and
fishing continue to endanger numerous animals worldwide. In the United States,
many of the animals considered national symbols—bald eagle, grizzly bear,
timber wolf, American Bison, bighorn sheep, Gulf of Mexico sea turtles—have
been threatened by overhunting. (American bison, incidentally, are no longer
considered threatened, but they exist mainly in managed herds, and have never
repopulated their wide range across the American and Canadian west.)
The eskimo curlew is a large sandpiper that was abundant in
North America in the nineteenth century. The birds were relentlessly hunted by
market gunners during their migration from the prairies and coasts of Canada
and the United States to their wintering grounds on the pampas and coasts of
South America. The eskimo curlew became very rare by the end of the nineteenth
century. The last observation of a curlew nest was in 1866, and the last
"collection" of birds was in 1922. There have been a few reliable
sightings of individuals in the Canadian Artic and small migrating flocks in
Texas since then, but sightings are so rare that the species' classification
changes to extinct between each one.
The Guadalupe fur seal was abundant along the coast of
western Mexico in the nineteenth century, numbering as many as 200,000
individuals. This marine mammal was hunted for its valuable fur and almost
became extinct in the 1920s. Fortunately, a colony of 14 seals, including pups,
was discovered off Baja California on Guadalupe Island in 1950. Guadalupe
Island was declared a pinnaped sanctuary in 1975; the species now numbers more
than 1,000 animals, and has begun to spread throughout its former range. The
Juan Fernandez fur seal of Chile had a similar history. More than three million
individuals were killed for their pelts between 1797 and 1804, when the species
was declared extinct. The Juan Fernandez seal was rediscovered in 1965; and its
population presently numbers several thousand individuals.
Commercial whaling for meat and oil since the eighteenth
century has threatened most of the world's baleen whale species, and several
toothed whales, with extinction. (Baleen whales feed by straining
microorganisms from seawater.) Faced with severe depletion of whale stock, 14
whaling nations formed the International Whaling Commission (IWC) in 1946.
While the IWC was somewhat successful in restoring whale populations, it lacks
authority to enforce hunting bans, and non-member
The endangered golden frog, Panama. JLM Visuals. Reproduced
by permission.
Nations often threaten to disregard IWC directives. The
Marine Mammal Protection Act of 1972 banned all whaling in United States
waters, the CITES treaty protects all whale species, and many whales have been
protected by the ESA. In spite of these measures, only a few whale species have
recovered to their pre-whaling populations, and a number of species remain on
the brink of extinction. Seven baleen whales, and four toothed whales, remain
on the ESA list and the IUCN Red List today: northern and southern right
whales, bowhead whale, blue whale, fin whale, sei whale, humpback whale, sperm
whale, vaquita, baiji, and Indus susu. The California gray whale is a rare
success story. This species was twice hunted near extinction, but it has
recovered its pre-whaling population of about 21,000 individuals. The gray
whale was removed from the endangered species list in 1993.
Large predators and
trophies.
Many large predators are killed because they compete with
human hunters for wild game like deer and elk, because they prey on domestic
animals like sheep, or sometimes because they threaten humans. Consequently,
almost all large predators whose former range has been developed by humans have
become extirpated or endangered. The list of endangered large predators in the
United States includes most of the species that formerly occupied the top of
the food chain, and that regulated populations of smaller animals and fishes:
grizzly bear, black bear, gray wolf, red wolf, San Joaquin kit fox, jaguar,
lynx, cougar, mountain lion, Florida panther, bald eagle, northern falcon,
American alligator, and American crocodile.
A number of generally harmless species are, sadly,
endangered because of their threatening appearance or reputation, including
several types of bats, condors, non-poisonous snakes, amphibians, and lizards.
Internationally, many endangered species face extinction because of their very
scarcity. Though CITES agreements attempt to halt trade of rare animals and
animal products, trophy hunters, collectors of rare pets, and traders of luxury
animal products continue to threaten numerous species. International demand for
products like elephant tusk ivory, rhino horn, aquarium fish, bear and cat
skins, pet tropical birds, reptile leather, and tortoise shells have taken a
toll on many of the earth's most extraordinary animals.
Endangerment caused
by introduced species.
In many places, vulnerable native species have been
decimated by non-native species imported by humans. Predators like domestic
cats and dogs, herbivores like cattle and sheep, diseases, and broadly-feeding
omnivores like pigs have killed, starved, and generally outcompeted native
species after introduction. Some destructive species introductions, like the
importation of mongooses to the Pacific islands to control snakes, are
intentional, but most of the damage caused by exotic species and diseases is
unintended.
For example, the native birds of the Hawaiian archipelago
are dominated by a family of about 25 species known as honeycreepers. Thirteen
species of honeycreepers have been rendered extinct by introduced predators and
habitat loss since Polynesians discovered the islands, and especially since
European colonization. The surviving 12 species of honeycreepers are all
endangered; they continue to face serious threats from introduced diseases,
like avian malaria, to which they have no immunity.
Deliberate introduction of the Nile perch caused terrible
damage to the native fish population of Lake Victoria in eastern Africa.
Fisheries managers stocked Lake Victoria, the world's second-largest lake, with
Nile Perch in 1954. In the 1980s the perch became a major fishery resource and
experienced a spectacular population increase that was fueled by predation on
the lake's extremely diverse community of cichlid fishes. The collapse of the
native fish community of Lake Victoria, which originally included more than 400
species, 90% of which only occurred in Lake Victoria, resulted in the
extinction of about one-half of the earth's cichlid species. Today, most of the
remaining cichlids are endangered, and many of those species exist only in
captivity.
Species living on islands are especially vulnerable to
introduced predators. In one case, the accidental introduction of the predatory
brown tree snake to the Pacific island of Guam in the late 1940s caused a
severe decline of native birds. Prior to the introduction of the snake there
were 11 native species of birds on Guam, most of which were abundant. By the
mid-1980s seven of the native species were extinct or extirpated on Guam, and
four more were critically endangered. The Guam rail, a flightless bird, is now
extinct in the wild, although it survives in captivity and will hopefully be
captive-bred and released to a nearby, snake-free island.
Endangerment caused by habitat destruction.
Many species have become extinct or endangered as their
natural habitat has been converted for human land-use purposes. The American
ivory-billed woodpecker, for example, once lived in mature, bottomland hardwood
forests and cypress swamps throughout the southeastern United States. These
habitats were heavily logged and/or converted to agricultural land by the early
1900s. There have been no reliable sightings of the American ivory-billed
woodpecker since the early 1960s, and it is probably extinct in North America.
A related subspecies, the Cuban ivory-billed woodpecker, is also critically
endangered because of habitat loss, as is the closely related imperial
woodpecker of Mexico.
The black-footed ferret was first discovered in the North
American prairie in 1851. This small predator became endangered when the
majority of its grassland habitat was converted to agricultural use. Farming in
the American and Canadian plains also dramatically reduced the population of
prairie dogs, the black-footed ferret's preferred food.
Furbish's lousewort is an example of a botanical species
endangered by habitat destruction. This herbaceous plant only occurs along a
143-mi (230-km) reach of the St. John River in Maine and New Brunswick. It was
considered extinct until a botanist "re-discovered" it in Maine in
1976. At that time, a proposed hydroelectric reservoir threatened the entire
habitat of Furbish's lousewort. In the end, the controversial dam was not
built, but the lousewort remains threatened by any loss of its habitat.
The northern spotted owl lives in the old-growth conifer
forests of North America's Pacific Northwest. These small owls require large
areas of uncut forest to breed, and became endangered when their habitat was
greatly reduced and fragmented by heavy logging. The Environmental Species Act
prescribes, and legally requires, preservation of large areas of extremely
valuable timber land to protect the northern spotted owl. Upon receiving its
status as an endangered species, the otherwise unremarkable owl became a symbol
of the conflict between environmental preservation and commercial enterprise.
For environmentalists, endangered classification of northern spotted owl
brought the possibility of protecting the forests from all exploitation; for
timber industry workers, the decision represented the government's choice to
preserve a small bird instead of their livelihood. Small stores on the back
roads of the Pacific Northwest expressed their resentment for the ESA by
advertising such specialties as "spotted owl barbeque" and activities
as "spotted owl hunts."
Like the northern spotted owl, the endangered redcockaded
woodpecker of the southeastern United States requires old-growth pine forest to
survive. The woodpecker excavates nest cavities in heart-rotted trees, and
younger plantation trees do not meet its needs. Suitable forests have been
greatly diminished by conversion to agriculture, logging, and residential
development. Natural disturbance like hurricanes and wildfires threaten the
remaining diminished and fragmented populations of red-cockaded woodpeckers.
The ESA has attempted to protect the red-cockaded woodpecker by establishing
ecological reserves and non-harvested buffers around known nesting colonies
outside the reserves. Also like the spotted owl, the red-cockaded woodpecker is
maligned by farmers, loggers, and developers for its role in their economic
restriction.
Tropical deforestation presents represents the single
greatest threat to endangered species today, though destruction of coastal and
shallow marine habitats associated with anthropogenic global warming may present
an even larger challenges in the future. While there was little net change
(-2%) in the total forest cover of North America between the 1960s and the
1980s, the global area of forested land decreased by 17% during that period.
Conversion of species-rich tropical forests in Central America, South America,
Africa, and the Pacific islands to unforested agricultural land accounts for
most of the decline. (Ironically, tropical soils have such poor structure and
nutrient content that they generally cannot support profitable agriculture once
the forest biomass has been removed.)
In the mid-1980s, tropical rainforests were being cleared at
a rate of 15–20 million acres (6–8 million hectares) per year, or about 6–8% of
the total equatorial forest area. The causes of tropical deforestation include
conversion to subsistence and market agriculture, logging, and harvesting of
fuelwood. All of these activities represent enormous threats to the multitude
of endangered species native to tropical countries. Recent efforts to slow the
rate of deforestation have included international financial and scientific aid
to help poorer tropical nations protect important ecosystems, and to adopt new,
more sustainable, methods of profitable resource use.
