SPECIES DISAPPEARING
Chapter 3. Signs of Stress: The Biological Base
Lester R. Brown, Eco-Economy: Building an Economy for the Earth
(W.W. Norton & Co., NY: 2001).
The archeological record shows five great
extinctions since life began, each representing an evolutionary
setback, a wholesale impoverishment of life on the earth. The last
of these mass extinctions occurred some 65 million years ago, most
likely when an asteroid collided with the earth, spewing vast amounts
of dust and debris into the atmosphere. The resultant abrupt cooling
obliterated the dinosaurs and at least one fifth of all other extant
life forms.71
We are now in the early stage of the sixth great extinction. Unlike
previous ones, which were caused by natural phenomena, this one
is of human origin. For the first time in the earth's long history,
one species has reached the point where it can eradicate much of
life.
As various life forms disappear, they alter the earth's ecosystem,
diminishing the services provided by nature, such as pollination,
seed dispersal, insect control, and nutrient cycling. This loss
of species is weakening the web of life, and if it continues it
could tear huge gaps in its fabric, leading to irreversible and
potentially unpredictable changes in the earth's ecosystem. Species
of all kinds are threatened by habitat destruction, principally
through the loss of tropical rainforests. As we burn off the Amazon
rainforest, we are burning one of the great genetic storehouses,
in effect one of the great libraries of genetic information. Our
descendents may one day view the wholesale burning of this repository
of genetic information much as we view the burning of the library
in Alexandria in 48 BC.
Habitat alteration from rising temperatures, chemical pollution,
or the introduction of exotic species can also decimate both plant
and animal species. As human population grows, the number of species
with which we share the planet shrinks. We cannot separate our fate
from that of all life on the earth. If the rich diversity of life
that we inherited is continually impoverished, eventually we will
be as well.72
The share of birds, mammals, and fish that are vulnerable or in
immediate danger of extinction is now measured in double digits:
12 percent of the world's nearly 10,000 bird species; 24 percent
of the world's 4,763 mammal species; and an estimated 30 percent
of all 25,000 fish species.73
When the World Conservation Union-IUCN released its newest Red
List of Threatened Species in 2000, it showed an increase in
the "critically endangered" in all categories. For example, the
number of critically endangered primates rose from 13 in 1996 to
19 in 2000. The number of freshwater species of turtles in this
category, many of them in strong demand in Asia for food and for
medicinal uses, increased from 10 to 24. For birds overall, the
number in the critically endangered category went from 168 in 1996
to 182 in 2000. Like many other trends of environmental decline,
this one, too, is accelerating.74
Among mammals, the 600 known species of primates other than humans
are most at risk. IUCN reports that nearly half of these species
are threatened with extinction. Some 79 of the world's primate species
live in Brazil, where habitat destruction poses a particular threat.
Hunting, too, endangers many primate species. It is a threat principally
in West and Central Africa, where the deteriorating food situation
is creating a lively market for "bushmeat."75
The bonobos of West Africa, a smaller version of the chimpanzees
of East Africa, may be our closest living relative both genetically
and in terms of social behavior. But this is not saving them from
the bushmeat trade or the destruction of their habitat by loggers.
Concentrated in the dense forest of the Democratic Republic of the
Congo, their numbers fell from an estimated 100,000 in 1980 to fewer
than 10,000 by 1990. Today there are only 3,000 left. In less than
one generation, 97 percent of the bonobos have disappeared.76
Birds, because of their visibility, are a useful indicator of the
diversity of life. Of the 9,946 known bird species, roughly 70 percent
are declining in number. Of these, an estimated 1,183 species are
in imminent danger of extinction. Habitat loss and degradation affect
85 percent of all threatened bird species. For example, 61 bird
species have become locally extinct with the extensive loss of lowland
rainforest in Singapore. Some once-abundant species may have already
dwindled to the point of no return. The great bustard, once widespread
in Pakistan and surrounding countries, is being hunted to extinction.
Ten of the world's 17 species of penguins are threatened or endangered,
potential victims of global warming.77
The threat to fish may be the greatest of all, with nearly one third
of all speciesfreshwater
and saltwaternow
facing possible extinction. Worldwide, the principal causes of this
loss are habitat degradation in the form of pollution and the excessive
extraction of water from rivers and other freshwater ecosystems.
An estimated 37 percent of the fish species that inhabit the lakes
and streams of North America are either extinct or in jeopardy.
Ten North American freshwater fish species have disappeared during
the last decade. In semiarid regions of Mexico, 68 percent of native
and endemic fish species have disappeared. The situation may be
even worse in Europe, where some 80 species of freshwater fish out
of a total of 193 are threatened, endangered, or of special concern.
Two thirds of the 94 fish species in South Africa need special protection
to avoid extinction.78
Threatened species include both little known ones and those that
are well known and highly valued. The harvest of the Caspian Sea
sturgeon, for example, source of the world's most prized caviar,
has fallen from 22,000 tons per year in the late 1970s to 1,100
tons in the late 1990s. Overfishing, much of it illegal, is responsible.79
Another indicator of the earth's environmental deterioration is
the decline in various types of amphibians-frogs, toads, and salamanders.
Widespread evidence that amphibian populations were disappearing
initially surfaced at the first World Congress of Herpetology in
Canterbury, England, in 1989. It was at this conference that scientists
first realized that the seemingly isolated disappearances of amphibian
populations were actually a worldwide phenomenon. Among the apparent
contributing factors are the clearcutting of forests, the loss of
wetlands, the introduction of alien species, changes in climate,
increased ultraviolet radiation, acid rain, and pollution from both
agriculture and industry. Spending their lives in both aquatic and
terrestrial environments, amphibians are affected by changes in
each, making them an unusually sensitive barometer of the earth's
changing physical condition.80
The leatherback turtle, one of the most ancient animal species,
and one that can reach a weight of 360 kilograms (800 pounds), is
fast disappearing. Its numbers have dropped from 115,000 in 1982
to 34,500 in 1996. At the Playa Grande nesting colony on Costa Rica's
west coast, the number of nesting females dropped from 1,367 in
1989 to 117 in 1999. James Spotila and colleagues, writing in Nature,
warn that "if these turtles are to be saved, immediate action is
needed to minimize mortality through fishing and to maximize hatchling
production."81
One of the newer threats to species, and one that is commonly underestimated,
is the introduction of alien species, which can alter local habitats
and communities, driving native species to extinction. For example,
non-native species are a key reason why 30 percent of the threatened
bird species are on the IUCN Red List. For plants, alien
species are implicated in 15 percent of all the listings. One consequence
of globalization with its expanding international travel and commerce
is that more and more species are being accidentally or intentionally
brought into new areas where they have no natural predators.82
Efforts to save wildlife traditionally have centered on the creation
of parks or wildlife reserves. Unfortunately, this approach may
now be of limited value because of the nature of the principal threats
to biological diversity. If we cannot stabilize population and climate,
there is not an ecosystem on earth that we can save. To optimize
resource use, this would argue for shifting some of the relatively
abundant funds for parkland acquisition into efforts to stabilize
population and climate.
The current species extinction rate is at least 1,000 times higher
than the background rate, yet no one knows how many plant and animal
species there are today, much less how many there were a half-century
ago, when the explosion in human economic activity began. Current
estimates range from 6 million species up to 20 million, with the
best working estimates falling between 13 million and 14 million.
We can measure losses where we have a complete inventory of species,
as with birds, but with insects, where the species number in the
millions, only a fraction of the species have been identified, described,
and cataloged.83
ENDNOTES:
71. David Quammen, "Planet of Weeds," Harper's Magazine, October
1998.
72. Species Survival Commission, 2000 IUCN Red List of Threatened
Species (Gland, Switzerland, and Cambridge, UK: World Conservation
Union-IUCN, 2000).
73. Ibid., p. 8.
74. IUCN, "Confirming the Global Extinction Crisis," press release
(Gland, Switzerland: 28 September 2000).
75. Species Survival Commission, op. cit. note 72; Cat Lazaroff,
"New Primates Discovered in Madagascar and Brazil," Environment
News Service, 26 January 2001; TRAFFIC, Food for Thought: The Utilization
of Wild Meat in Eastern and Southern Africa (Cambridge, UK: 2000).
76. Danna Harman, "Bonobos' Threat to Hungry Humans," Christian
Science Monitor, 7 June 2001.
77. Species Survival Commission, op. cit. note 72, p. 8; Ashley
T. Mattoon, "Bird Species Threatened," in Worldwatch Institute,
Vital Signs 2001 (New York: W.W. Norton & Company, 2001), pp. 98-99;
"Great Indian Bustard Facing Extinction," India Abroad Daily, 12
February 2001; Carol Kaesuk Yoon, "Penguins in Trouble Worldwide,"
New York Times, 26 June 2001.
78. Janet N. Abramovitz, Imperiled Waters, Impoverished Future:
The Decline of Freshwater Ecosystems, Worldwatch Paper 128 (Washington,
DC: Worldwatch Institute, March 1996), p. 159.
79. Cat Lazaroff, "Caviar Export Ban Could Save Caspian Sea Sturgeon,"
Environment News Service, 13 June 2001.
80. Ashley Mattoon, "Deciphering Amphibian Declines," in Lester
R. Brown et al., State of the World 2001 (New York: W.W. Norton
& Company, 2001), pp. 63-82.
81. James R. Spotila et al., "Pacific Leatherback Turtles Face Extinction,"
Nature, 1 June 2000; "Leatherback Turtles Threatened," Washington
Post, 5 June 2000.
82. Species Survival Commission, op. cit. note 72, p. 28.
83. Ibid., p. 1.
Copyright
© 2001 Earth Policy Institute
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