============ 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 ============= ---------------------------------------------------------------------- The Church of Euthanasia churchofeuthanasia.org P.O.Box 261 ftp.etext.org /pub/Zines/Snuffit Somerville, MA 02143 coe@netcom.com