[Marxism] The extinction debt
lnp3 at panix.com
Tue Jun 15 14:22:54 MDT 2004
Boston Review, April/May 2004
End of the Wild
The extinction crisis is over. We lost.
Stephen M. Meyer
For the past several billion years evolution on Earth has been driven by
small-scale incremental forces such as sexual selection, punctuated by
cosmic-scale disruptions—plate tectonics, planetary geochemistry, global
climate shifts, and even extraterrestrial asteroids. Sometime in the
last century that changed. Today the guiding hand of evolution is
unmistakably human, with earth-shattering consequences.
The fossil record and statistical studies suggest that the average rate
of extinction over the past hundred million years has hovered at several
species per year. Today the extinction rate surpasses 3,000 species per
year and is accelerating rapidly—it may soon reach the tens of thousands
annually. In contrast, new species are evolving at a rate of less than
one per year.
Over the next 100 years or so as many as half of the Earth's species,
representing a quarter of the planet's genetic stock, will either
completely or functionally disappear. The land and the oceans will
continue to teem with life, but it will be a peculiarly homogenized
assemblage of organisms naturally and unnaturally selected for their
compatibility with one fundamental force: us. Nothing—not national or
international laws, global bioreserves, local sustainability schemes,
nor even "wildlands" fantasies—can change the current course. The path
for biological evolution is now set for the next million years. And in
this sense "the extinction crisis"—the race to save the composition,
structure, and organization of biodiversity as it exists today—is over,
and we have lost.
This is not the wide-eyed prophecy of radical Earth First! activists or
the doom-and-gloom tale of corporate environmentalists trying to boost
fundraising. It is the story that is emerging from the growing mountain
of scientific papers that have been published in prestigious scientific
journals such as Nature, Science, and the Proceedings of the National
Academy of Sciences over the past decade.
The Real Impact
Through our extraordinary capacity to modify the world around us, we
human beings are creating a three-tiered hierarchy of life built around
human selection. The great irony here is that this anthropogenic
transformation of the biosphere springs as much from our deliberate
efforts to protect and manage the life around us as it does from our
wanton disregard for the natural environment.
At one extreme we are making the planet especially hospitable for the
weedy species: plants, animals and other organisms that thrive in
continually disturbed, human-dominated environments. (I borrow this term
from David Quammen's seminal A Planet of Weeds.) Many of these organisms
are adaptive generalists—species that flourish in a variety of
ecological settings, easily switch among food types, and breed
prolificly. And some have their needs met more completely and
efficiently by humans than by Mother Nature. In the United States, for
example, there are five times as many raccoons (Procyon lotor) per
square mile in suburban settings than in corresponding natural
populations in "the wild."
From dandelions to coyotes, weedy species will enjoy expanding
populations, spatial distribution, ecological dominance, and
opportunities for further speciation into the far future. Many of these
species have become so comfortable living with us that they have been
labeled pests, requiring stringent control measures: the common (Norway)
rat (Rattus norvegicus) and white-tailed deer (Odocoileus virginianus)
come immediately to mind.
Living on the margins in ever-decreasing numbers and limited spatial
distribution are relic species. Relic species cannot thrive in
human-dominated environments—which now nearly cover the planet. Facing
the continual threat of extinction, relic species will linger in either
ecologically marginalized populations (e.g., prairie dogs and elephants)
or carefully managed boutique populations (e.g., pandas). Most,
including the Sumatran rhinoceros (Dicerorhinus sumatrensis), the
California condor (Gymnogyps californianus), and virtually all of
Hawaii's endemic plants, will require for survival our permanent,
direct, and heavy-handed management, including captive breeding and
Other relics, such as rare alpine plants, may survive in isolated
patches through benign neglect. Over time they will experience
progressive genetic erosion and declining numbers, and will rapidly lose
their ecological value. In essence, they will be environmental ornaments.
But a large fraction of the non-weedy species will not be fortunate
enough to have special programs to extend their survival or will be
incapable of responding to such efforts. These are the ghost
species—organisms that cannot or will not be allowed to survive on a
planet with billions of people. Although they may continue to exist for
decades, their extinction is certain, apart from a few specimens in zoos
or a laboratory-archived DNA sample.
Some, such as the East Asian giant soft-shell turtle (extirpated except
for one left in the wild) and the dusky seaside sparrow (extinct), are
incapable of adapting their highly specialized needs rapidly enough to
keep up with human-induced pressures. Others we intentionally try to
eradicate. Although they are now protected, wolves and black-tailed
prairie dogs in North America were once hunted for extermination as part
of federal and state animal-control programs (and unofficially, they
still are). In Africa, the lion population has plunged from over 200,000
in 1980 to under 20,000 today due to preemptive eradication by livestock
Still other prospective ghosts we simply consume beyond their capacity
to successfully reproduce—for food, for commercial products, or as pets.
Recent reports suggest that we have consumed 90 percent of the stocks of
large predatory fish, such as tuna and swordfish, in the world's oceans.
And while 10,000 tigers live as private pets in the United States, fewer
than 7,000 live in the wild throughout the world!
A great many of the plants and animals we perceive as healthy and
plentiful today are in fact relics and ghosts. This seeming
contradiction is explained by the fact that species loss is not a simple
linear process. Many decades can pass between the start of a decline and
the collapse of a population structure, especially where
moderate-to-long-lived life forms are involved.
Conservation biologists use the term "extinction debt" to describe this
gap between appearance and reality. In the past century we have
accumulated a vast extinction debt that will be paid, with interest, in
the century ahead. The number of plants and animals we "discover" to be
threatened will expand out of control as the extinction debt comes due.
Thus, over the next hundred years, upwards of half of the earth's
species are destined to become relics or ghosts, while weedy species
will constitute an ever-growing proportion of the plants and animals
around us. By virtue of their compatibility with us, weedy species can
follow us around the planet, homogenizing (in both plausible
interpretations of the word) the biosphere by filling in the spaces
vacated by relics and ghosts. More and more we will encounter on every
continent remarkably similar, if not the very same, species of plants,
insects, mammals, birds, and other organisms.
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