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============ PLANET OF WEEDS by David Quammen, part 1 of 2 =============

                           PLANET OF WEEDS
         Tallying the losses of Earth's animals and plants
                          by David Quammen

Hope is a duty from which paleontologists are exempt. Their job is to
take the long view, the cold and stony view, of triumphs and
catastrophes in the history of life. They study teeth, tree trunks,
leaves, pollen, and other biological relics, and from it they attempt to
discern the lost secrets of time, the big patterns of stasis and change,
the trends of innovation and adaptation and refinement and decline that
have blown like sea winds among ancient creatures in ancient ecosystems.
Although life is their subject, death and burial supply all their data.
They're the coroners of biology. This gives to paleontologists a certain
distance, a hyperopic perspective beyond the reach of anxiety over
outcomes of the struggles they chronicle. If hope is the thing with
feathers, as Emily Dickinson said, then it's good to remember that
feathers don't generally fossilize well. In lieu of hope and despair,
paleontologists have a highly developed sense of cyclicity. That's why I
recently went to Chicago, with a handful of urgently grim questions, and
called on a paleontologist named David Jablonski. I wanted answers
unvarnished with obligatory hope.

Jablonski is a big-pattern man, a macroevolutionist, who works
fastidiously from the particular to the very broad. He's an expert on
the morphology and distribution of marine bivalves and gastropods--or
clams and snails, as he calls them when speaking casually. He sifts
through the record of those mollusk lineages, preserved in rock and
later harvested into museum drawers, to extract ideas about the origin
of novelty. His attention roams back through 600 million years of time.
His special skill involves framing large, resonant questions that can be
answered with small, lithified clamshells. For instance: By what
combinations of causal factor and sheer chance have the great
evolutionary innovations arisen? How quickly have those innovations
taken hold? How long have they abided? He's also interested in
extinction, the converse of abidance, the yang to evolution's yin. Why
do some species survive for a long time, he wonders, whereas others die
out much sooner? And why has the rate of extinction--low throughout most
of Earth's history--spiked upward cataclysmically on just a few
occasions? How do those cataclysmic episodes, known in the trade as mass
extinctions, differ in kind as well as degree from the gradual process
of species extinction during the millions of years between? Can what
struck in the past strike again?

The concept of mass extinction implies a biological crisis that spanned
large parts of the planet and, in a relatively short time, eradicated a
sizable number of species from a variety of groups. There's no absolute
threshold of magnitude, and dozens of different episodes in geologic
history might qualify, but five big ones stand out: Ordovician,
Devonian, Permian, Triassic, Cretaceous. The Ordovician extinction, 439
million years ago, entailed the disappearance of roughly 85 percent of
marine animal species--and that was before there were any animals *on
land*. The Devonian extinction, 367 million years ago, seems to have
been almost as severe. About 245 million years ago came the Permian
extinction, the worst ever, claiming 95 percent of all known animal
species and therefore almost wiping out the animal kingdom altogether.
The Triassic, 208 million years ago, was bad again, though not nearly so
bad as the Permian. The most recent was the Cretaceous extinction
(sometimes called the K-T event because it defines the boundary between
two geologic periods, with K for Cretaceous, never mind why, and T for
Tertiary), familiar even to schoolchildren because it ended the age of
dinosaurs. Less familiarly, the K-T event also brought extinction of the
marine reptiles and the ammonites, as well as major losses of species
among fish, mammals, amphibians, sea urchins, and other groups, totaling
76 percent of all species. In between these five episodes occurred some
lesser mass extinctions, and throughout the intervening lulls extinction
continued, too--but at a much slower pace, known as the background rate,
claiming only about one species in any major group every million years.
At the background rate, extinction is infrequent enough to be
counterbalanced by the evolution of new species. Each of the five major
episodes, in contrast, represents a drastic net loss of species
diversity, a deep trough of biological impoverishment from which Earth
only slowly recovered. How slowly? How long is the lag between a nadir
of impoverishment and a recovery to ecological fullness? That's another
of Jablonski's research interests. His rough estimates run to 5 or 10
million years. What drew me to this man's work, and then to his
doorstep, were his special competence on mass extinctions and his
willingness to discuss the notion that a sixth one is in progress now.

Some people will tell you that we as a species, *Homo sapiens*, the
savvy ape, all 5.9 billion of us in our collective impact, are
destroying the world. Me, I won't tell you that, because "the world" is
so vague, whereas what we are or aren't destroying is quite specific.
Some people will tell you that we are rampaging suicidally toward a
degree of global wreckage that will result in our own extinction. I
won't tell you that either. Some people say that the environment will be
the paramount political and social concern of the twenty-first century,
but what they mean by "the environment" is anyone's guess. Polluted air?
Polluted water? Acid rain? A frayed skein of ozone over Antarctica?
Greenhouse gases emitted by smokestacks and cars? Toxic wastes? None of
these concerns is the big one, paleontological in scope, though some are
more closely entangled with it than others. If the world's air is clean
for humans to breathe but supports no birds or butterflies, if the
world's waters are pure for humans to drink but contain no fish or
crustaceans or diatoms, have we solved our environmental problems? Well,
I suppose so, at least as environmentalism is commonly construed. That
clumsy, confused, and presumptuous formulation "the environment" implies
viewing air, water, soil, forests, rivers, swamps, deserts, and oceans
as merely a milieu within which something important is set: human life,
human history. But what's at issue in fact is not an environment; it's a
living world.

Here instead is what I'd like to tell you: The consensus among
conscientious biologists is that we're headed into another mass
extinction, a vale of biological impoverishment commensurate with the
big five. Many experts remain hopeful that we can brake that descent,
but my own view is that we're likely to go all the way down. I visited
David Jablonski to ask what we might see at the bottom.

On a hot summer morning, Jablonski is busy in his office on the second
floor of the Hinds Geophysical Laboratory at the University of Chicago.
It's a large open room furnished in tall bookshelves, tables piled high
with books, stacks of paper standing knee-high off the floor. The walls
are mostly bare, aside from a chart of the geologic time scale, a
clipped cartoon of dancing tyrannosaurs in red sneakers, and a poster
from a Rodin exhibition, quietly appropriate to the overall theme of
eloquent stone. Jablonski is a lean forty-five-year-old man with a dark
full beard. Educated at Columbia and Yale, he came to Chicago in 1985
and has helped make its paleontology program perhaps the country's best.
Although in not many hours he'll be leaving on a trip to Alaska, he has
been cordial about agreeing to this chat. Stepping carefully, we move
among the piled journals, reprints, and photocopies. Every pile
represents a different research question, he tells me. "I juggle a lot
of these things all at once because they feed into one another." That's
exactly why I've come: for a little rigorous intellectual synergy.

Let's talk about mass extinctions, I say. When did someone first realize
that the concept might apply to current events, not just to the Permian
or the Cretaceous?

He begins sorting through memory, back to the early 1970s, when the full
scope of the current extinction problem was barely recognized. Before
then, some writers warned about "vanishing wildlife" and "endangered
species," but generally the warnings were framed around individual
species with popular appeal, such as the whooping crane, the tiger, the
blue whale, the peregrine falcon. During the 1970s a new form of concern
broke forth--call it wholesale concern--from the awareness that
unnumbered millions of narrowly endemic (that is, unique and localized)
species inhabit the tropical forests and that those forests were quickly
being cut. In 1976, a Nairobi-based biologist named Norman Myers
published a paper in *Science* on that subject; in passing, he also
compared current extinctions with the rate during what he loosely called
"the 'great dying' of the dinosaurs." David Jablonski, then a graduate
student, read Myers's paper and tucked a copy into his files. This was
the first time, as Jablonski recalls, that anyone tried to quantify the
rate of present-day extinctions. "Norman was a pretty lonely guy, for a
long time, on that," he says. In 1979, Myers published *The Sinking
Ark*, explaining the problem and offering some rough projections.
Between the years 1600 and 1900, by his tally, humanity had caused the
extinction of about 75 known species, almost all of them mammals and
birds. Between 1900 and 1979, humans had extinguished about another 75
known species, representing a rate well above the rate of known losses
during the Cretaceous extinction. But even more worrisome was the
inferable rate of unrecorded extinctions, recent and now impending,
among plants and animals still unidentified by science. Myers guessed
that 25,000 plant species presently stood jeopardized, and maybe
hundreds of thousands of insects. "By the time human communities
establish ecologically sound life-styles, the fallout of species could
total several million." Rereading that sentence now, I'm struck by the
reckless optimism of his assumption that human communities eventually
will establish "ecologically sound life-styles."

Although this early stab at quantification helped to galvanize public
concern, it also became a target for a handful of critics, who used the
inexactitude of the numbers to cast doubt on the reality of the problem.
Most conspicuous of the naysayers was Julian Simon, an economist at the
University of Maryland, who argued bullishly that human resourcefulness
would solve all problems worth solving, of which a decline in diversity
of tropical insects wasn't one.

In a 1986 issue of *New Scientist*, Simon rebutted Norman Myers, arguing
from his own construal of select data that there was "no obvious recent
downward trend in world forests--no obvious 'losses' at all, and
certainly no 'near catastrophic' loss." He later co-authored an op-ed
piece in the *New York Times* under the headline "Facts, Not Species,
Are Periled." Again he went after Myers, asserting a complete absence of
evidence for the claim that the extinction of species is going up
rapidly--or even going up at all." Simon's worst disservice to logic in
that statement and others was the denial that *inferential* evidence of
wholesale extinction counts for anything. Of inferential evidence there
was an abundance--for example, from the Centinela Ridge in a
cloud-forest zone of western Ecuador, where in 1978 the botanist Alwyn
Gentry and a colleague found thirty-eight species of narrowly endemic
plants, including several with mysteriously black leaves. Before Gentry
could get back, Centinela Ridge had been completely deforested, the
native plants replaced by cacao and other crops. As for inferential
evidence generally, we might do well to remember what it contributes to
our conviction that approximately 105,000 Japanese civilians died in the
atomic bombing of Hiroshima. The city's population fell abruptly on
August 6, 1945, but there was no one-by-one identification of 105,000
bodies.

Nowadays a few younger writers have taken Simon's line, pooh-poohing the
concern over extinction. As for Simon himself, who died earlier this
year, perhaps the truest sentence he left behind was, "We must also try
to get more reliable information about the number of species that might
be lost with various changes in the forests." No one could argue.

But it isn't easy to get such information. Field biologists tend to
avoid investing their precious research time in doomed tracts of forest.
Beyond that, our culture offers little institutional support for the
study of narrowly endemic species in order to register their existence
*before* their habitats are destroyed. Despite these obstacles, recent
efforts to quantify rates of extinction have supplanted the old
warnings. These new estimates use satellite imaging and improved
on-the-ground data about deforestation, records of the many human-caused
extinctions on islands, and a branch of ecological theory called island
biogeography, which connects documented island cases with the mainland
problem of forest fragmentation. These efforts differ in particulars,
reflecting how much uncertainty is still involved, but their varied
tones form a chorus of consensus. I'll mention three of the most
credible.

W.V. Reid, of the World Resources Institute, in 1992 gathered numbers on
the average annual deforestation in each of sixty-three tropical
countries during the 1980s and from them charted three different
scenarios (low, middle, high) of presumable forest loss by the year
2040. He chose a standard mathematical model of the relationship between
decreasing habitat area and decreasing species diversity, made
conservative assumptions about the crucial constant, and ran his various
deforestation estimates through the model. Reid's calculations suggest
that by the year 2040, between 17 and 35 percent of tropical forest
species will be extinct or doomed to be. Either at the high or the low
end of this range, it would amount to a bad loss, though not as bad as
the K-T event. Then again, 2040 won't mark the end of human pressures on
biological diversity or landscape.

Robert M. May, an ecologist at Oxford, co-authored a similar effort in
1995. May and his colleagues noted the five causal factors that account
for most extinctions: habitat destruction, habitat fragmentation,
overkill, invasive species, and secondary effects cascading through an
ecosystem from other extinctions. Each of those five is more intricate
than it sounds. For instance, habitat fragmentation dooms species by
consigning them to small, island-like parcels of habitat surrounded by
an ocean of human impact and by then subjecting them to the same
jeopardies (small population size, acted upon by environmental
fluctuation, catastrophe, inbreeding, bad luck, and cascading effects)
that make island species especially vulnerable to extinction. May's team
concluded that most extant bird and mammal species can expect average
life spans of between 200 and 400 years. That's equivalent to saying
that about a third of one percent will go extinct each year until some
unimaginable end point is reached. "Much of the diversity we inherited,"
May and his co-authors wrote, "will be gone before humanity sorts itself
out."

The most recent estimate comes from Stuart L. Pimm and Thomas M. Brooks,
ecologists at the University of Tennessee. Using a combination of
published data on bird species lost from forest fragments and field data
gathered themselves, Pimm and Brooks concluded that 50 percent of the
world's forest-bird species will be doomed to extinction by
deforestation occurring over the next half century. And birds won't be
the sole victims. "How many species will be lost if current trends
continue?" the two scientists asked. "Somewhere between one third and
two thirds of all species--easily making this event as large as the
previous five mass extinctions the planet has experienced."

Jablonski, who started down this line of thought in 1978, offers me  a
reminder about the conceptual machinery behind such estimates. "All
mathematical models," he says cheerily, "are wrong. They are
approximations. And the question is: Are they usefully wrong, or are
they meaninglessly wrong?" Models projecting present and future species
loss are useful, he suggests, if they help people realize that *Homo
sapiens* is perturbing Earth's biosphere to a degree it hasn't often
been perturbed before. In other words, that this is a drastic experiment
in biological drawdown we're engaged in, not a continuation of routine.

Behind the projections of species loss lurk a number of crucial but
hard-to-plot variables, among which two are especially weighty:
continuing landscape conversion and the growth curve of human
population.

Landscape conversion can mean many things: draining wetlands to build
roads and airports, turning tallgrass prairies under the plow, fencing
savanna and overgrazing it with domestic stock, cutting second-growth
forest in Vermont and consigning the land to ski resorts or vacation
suburbs, slash-and-burn clearing of Madagascar's rain forest to grow
rice on wet hillsides, industrial logging in Borneo to meet Japanese
plywood demands. The ecologist John Terborgh and a colleague, Carel P.
van Schaik, have described a four-stage process of landscape conversion
that they call the land-use cascade. The successive stages are: 1)
*wildlands*, encompassing native floral and faunal communities altered
little or not at all by human impact; 2) *extensively used areas*, such
as natural grasslands lightly grazed, savanna kept open for prey animals
by infrequent human-set fires, or forests sparsely worked by
slash-and-burn farmers at low density; 3) *intensively used areas*,
meaning crop fields, plantations, village commons, travel corridors,
urban and industrial zones; and finally 4) *degraded land*, formerly
useful but now abused beyond value to anybody. Madagascar, again, would
be a good place to see all four stages, especially the terminal one.
Along a thin road that leads inland from a town called Mahajanga, on the
west coast, you can gaze out over a vista of degraded land--chalky red
hills and gullies, bare of forest, burned too often by grazers wanting a
short-term burst of pasturage, sparsely covered in dry grass and scrubby
fan palms, eroded starkly, draining red mud into the Betsiboka River,
supporting almost no human presence. Another showcase of degraded
land--attributable to fuelwood gathering, overgrazing, population
density, and decades of apartheid--is the Ciskei homeland in South
Africa. Or you might look at overirrigated crop fields left ruinously
salinized in the Central Valley of California.

Among all forms of landscape conversion, pushing tropical forest from
the *wildlands* category to the *intensively used* category has the
greatest impact on biological diversity. You can see it in western
India, where a spectacular deciduous ecosystem known as the Gir forest
(home to the last surviving population of the Asiatic lion, *Panthera
leo persica*) is yielding along its ragged edges to new mango orchards,
peanut fields, and lime quarries for cement. You can see it in the
central Amazon, where big tracts of rain forest have been felled and
burned, in a largely futile attempt (encouraged by misguided government
incentives, now revoked) to pasture cattle on sun-hardened clay.
According to the United Nations Food and Agriculture Organization, the
rate of deforestation in tropical countries has increased (contrary to
Julian Simon's claim) since the 1970s, when Myers made his estimates.
During the 1980s, as the FAO reported in 1993, that rate reached 15.4
million hectares (a hectare being the metric equivalent of 2.5 acres)
annually. South America was losing 6.2 million hectares a year.
Southeast Asia was losing less in area but more proportionally: 1.6
percent of its forests yearly. In terms of cumulative loss, as reported
by other observers, the Atlantic coastal forest of Brazil is at least 95
percent gone. The Philippines, once nearly covered with rain forest, has
lost 92 percent. Costa Rica has continued to lose forest, despite that
country's famous concern for its biological resources. The richest of
old-growth lowland forests in West Africa, India, the Greater Antilles,
Madagascar, and elsewhere have been reduced to less than a tenth of
their original areas. By the middle of the next century, if those trends
continue, tropical forest will exist virtually nowhere outside of
protected areas--that is, national parks, wildlife refuges, and other
official reserves.

How many protected areas will there be? The present worldwide total is
about 9,800, encompassing 6.3 percent of the planet's land area. Will
those parks and reserves retain their full biological diversity? No.
Species with large territorial needs will be unable to maintain viable
population levels within small reserves, and as those species die away
their absence will affect others. The disappearance of big predators,
for instance, can release limits on medium-size predators and
scavengers, whose overabundance can drive still other species (such as
ground-nesting birds) to extinction. This has already happened in some
habitat fragments, such as Panama's Barro Colorado Island, and been well
documented in the literature of island biogeography. The lesson of
fragmented habitats is Yeatsian: Things fall apart.

Human population growth will make a bad situation worse by putting ever
more pressure on all available land.

Population growth rates have declined in many countries within the past
several decades, it's true. But world population is still increasing,
and even if average fertility suddenly, magically, dropped to 2.0
children per female, population would continue to increase (on the
momentum of birth rate exceeding death rate among a generally younger
and healthier populace) for some time. The annual increase is now 80
million people, with most of that increment coming in less developed
countries. The latest long-range projections from the Population
Division of the United Nations, released earlier this year, are slightly
down from previous long-term projections in 1992 but still point toward
a problematic future. According to the U.N's middle estimate (and most
probable? hard to know) among seven fertility scenarios, human
population will rise from the present 5.9 billion to 9.4 billion by the
year 2050, then to 10.8 billion by 2150, before leveling off there at
the end of the twenty-second century. If it happens that way, about 9.7
billion people will inhabit the countries included within Africa, Latin
America, the Caribbean, and Asia. The total population of those
countries--most of which are in the low latitudes, many of which are
less developed, and which together encompass a large portion of Earth's
remaining tropical forest--will be more than twice what it is today.
Those 9.7 billion people, crowded together in hot places, forming the
ocean within which tropical nature reserves are insularized, will
constitute 90 percent of humanity. Anyone interested in the future of
biological diversity needs to think about the pressures these people
will face, and the pressures they will exert in return.

We also need to remember that the impact of *Homo sapiens* on the
biosphere can't be measured simply in population figures. As the
population expert Paul Harrison pointed out in his book *The Third
Revolution*, that impact is a product of three variables: population
size, consumption level, and technology. Although population growth is
highest in less-developed countries, consumption levels are generally
far higher in the developed world (for instance, the average American
consumes about ten times as much energy as the average Chilean, and
about a hundred times as much as the average Angolan), and also higher
among the affluent minority in any country than among the rural poor.
High consumption exacerbates the impact of a given population, whereas
technological developments may either exacerbate it further (think of
the automobile, the air conditioner, the chainsaw) or mitigate it (as
when a technological innovation improves efficiency for an established
function). All three variables play a role in every case, but a
directional change in one form of human impact--upon air pollution from
fossil-fuel burning, say, or fish harvest form the seas--can be mainly
attributable to a change in one variable, with only minor influence from
the other two. Sulfur-dioxide emissions in developed countries fell
dramatically during the 1970s and 80s, due to technological improvements
in papermaking and other industrial processes; those emissions would
have fallen still farther if not for increased population (accounting
for 25 percent of the upward vector) and increased consumption
(accounting for 75 percent). Deforestation, in contrast, is a
directional change that *has* been mostly attributable to population
growth.

According to Harrison's calculations, population growth accounted for 79
percent of the deforestation in less-developed countries between 1973
and 1988. Some experts would argue with those calculations, no doubt,
and insist on redirecting our concern toward the role that distant
consumers, wood-products buyers among slow-growing but affluent
populations of the developed nations, play in driving the destruction of
Borneo's dipterocarp forests or the hardwoods of West Africa. Still,
Harrison's figures point toward an undeniable reality: more total people
will need more total land. By his estimate, the minimum land necessary
for food growing and other human needs (such as water supply and waste
dumping) amounts to one fifth of a hectare per person. Given the U.N.'s
projected increase of 4.9 billion souls before the human population
finally levels off, that comes to another billion hectares of
human-claimed landscape, a billion hectares less forest--even without
allowing for any further deforestation by the current human population,
or for any further loss of agricultural land to degradation. A billion
hectares--in other words, 10 million square kilometers--is, by a
conservative estimate, well more than half the remaining forest area in
Africa, Latin America, and Asia. This raises the vision of a very
exigent human population pressing snugly around whatever patches of
natural landscape remain.

============ PLANET OF WEEDS by David Quammen, part 1 of 2 =============

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