The research, with related studies, are part of a package thejournal pulled together in advance of the UN Conference onSustainable Development scheduled for June 20-22 in Rio de Janiero . The meeting marks the 20th anniversary of the "EarthSummit," as the first Rio sustainable-development conferencewas dubbed. Scientists have sounded warnings about the effects of habitatdestruction, global warming, and other changes humans have wroughton their surroundings for years. Moreover, the notion of tippingpoints long has been applied to climate, as well as ecology, atleast on a local or regional scale. But for ecology, "the new twist here is that rather thanthinking about individual parts of the system, we began to thinkabout the biosphere as a whole," says Anthony Barnosky, abiologist at the University of California at Berkeley and the study's lead author. |
While the conclusion is sobering, he adds that, "We are aclever species. We have the solutions to these kinds of problems inour grasp." Among them: Reducing reliance on fossil fuels, make more efficientuse of existing farmland and distribute food more effectively, andbeef up efforts to establish and maintain what the team callsreservoirs of biodiversity broad, relatively pristine ecosystemsrich in species. Key to this, however, is reducing population growth rates, the teamholds. Other researchers have found that good education for womenand enhancing their economic opportunities can play crucial rolesin this effort. The team is frank about the uncertainties involved.
It's unclear ifsuch a shift is inevitable, and if it is, how much time remainsbefore it happens, the researchers say. The team was thinking interms of 50 to 100 years, Dr. Barnosky says, but he adds that thestate of the science and of ecological forecasting isn't up to thetask of answering those questions yet for the globe as a whole. But the globe's biosphere has undergone significant changes before most recently and most rapidly as it emerged from the last iceage, which ended some 12,900 years ago.
Most of the ecologicalchanges took place within the first 1,600 years of deicing, theresearchers say. The team took that event as its benchmark for measuring globalchanges currently underway at the hands of humans. In addition, theresearchers drew on a range of field studies and theoretical workpublished during the past decade but largely over the last fouryears shedding light onto the issue of ecosystems, tippingpoints, and human activities. The short take: "What's going on today is much more dramaticand much more intense" that the changes the landscapeunderwent as the continental glaciers melted, Barnosky says. Globally, the proportion of land humans have farmed, paved, logged,and developed has reached a collective 43 percent of Earth's landsurface.
The retreat of the glaciers affected about 50 percent. Atcurrent rates of landscape alteration, humans will have overhauledroughly 50 percent of the planet's land area by 2025, when theglobal population is expected to reach 8.2 billion, the teamestimates. The 50 percent number could be important if studies ofsmaller-scale ecosystems are any indication. These studies havefound that if 50 to 90 percent of a patch of land is heavilyaltered, the change can trigger wholesale changes in neighboring,relatively pristine patches as well, the team notes.
For most ofthe ecosystems studied so far, though, the figure is closer to 50than 90, Barnosky says. Data are more sparse for oceans, the researchers acknowledge, whichremain a frontier for studying ecological tipping points. Global warming alone is projected to affect roughly 30 percent ofthe Earth in ways that would require species to migrate at rateshigher than those inferred from the fossil record as they spreadduring the end of the last ice age, the researchers note.Meanwhile, from interstate highways to urban sprawl, humans haveerected more barriers to that migration. The researchers call for beefed up efforts to monitor changes anddevelop ecological-forecasting tools that could help societyanticipate what otherwise might be ecological surprises stemmingfrom human-driven changes to the biosphere.
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