ETIT BYAHAUT, on the lush, frangipani-scented west coast of St. Vincent, has no swimming pools, no televisions, no telephones, no tennis, no minibars and no flags to raise when you want a drink brought to you in your hammock. The guesthouses are corrugated-roofed open-air decks with screened-in areas for bedrooms. Vacationers may share their living space with scurrying little black ants - in a resort where a can of Raid would be about as welcome as Hurricane Ivan, insects happen.

But what's striking about staying in Petit Byahaut, a fiercely determined environmentally sensitive resort, is what you don't have to give up.

Judith Jackson Spa citresse soap and Aromae Botanicals shampoo for the shower, for example. Fresh flowers left on the bed every day by the woman who changes the sheets. Guided snorkeling through a cave. Rum punch made with fresh-squeezed guava juice at sunset. Grilled dorado. Squid stuffed with scallops and shrimp.

Petit Byahaut (pronounced PUH-tee BYE-ah-hah) is one of a generation of so-called eco-resorts that have grown up, offering not only environmental bragging rights but also creature comforts like well-appointed bathrooms and chef-prepared meals.

Virtuous? Yes. Spartan? No.

Even for travelers who haven't much worried about whether their presence on a tropical island might contribute to the paving of paradise, these places can be alluring, presenting an uncrowded, relatively unspoiled face of the islands.

"We get boaters here all the time who don't know we're a hotel," said Brian Durbin, who with his wife, Nicole, manages Petit Byahaut.

No wonder. The place is almost invisible from the sea, its steep green hills meeting the Caribbean at a small black sand beach, its five guesthouses hidden among trees and spread out inland on the resort's 56 acres.

No international standards define an eco-resort, but places that describe themselves as sensitive to nature generally share two characteristics: resource conservation and minimal interference with the natural setting. Solar power, composting, careful waste-handling and projects benefiting indigenous communities are common themes.

Petit Byahaut does not disturb the native forest with roads. Guests are brought in by boat (about a 10-minute ride) to an offshore mooring and transferred to an eight-foot dinghy before landing at the dockless beach and wading to shore. All of Petit Byahaut's supplies arrive in that fashion, as did all of the materials brought in by Charles Meistrell, the Californian who opened Petit Byahaut in 1991, to build it - every nail, bag of cement and propane tank.

The guest dwellings have low-wattage lights powered by photovoltaic cells on their roofs. When it rains, the metal roofs funnel water to discreetly sited tanks, from which it is piped to the guests' solar-heated showers and filtered for drinking.

Toilets are connected to a septic system, and showers and sinks simply drain into planting areas. The tiny black ants venture in from the surrounding woods because pesticides could end up in the coral-studded cove out front.

Other eco-resorts operate in similar fashion. Tiamo Resort, on South Andros Island in the Bahamas, offers beachfront cottages among palms and sea grape trees surrounded by a 125-acre nature preserve accessible only by a three-mile boat ride. A half-acre array of photovoltaic cells provide the electricity for the resort.

Mike and Petagay Hartman, who own Tiamo, are particularly proud that the land for the resort, built in 2000, was cleared by hand, using machetes and chain saws, to limit damage to the vegetation.

Lapa Rios, a full-service resort on the isolated Orsa Peninsula on the Pacific coast of Costa Rica, not only uses solar power and battles bugs with mosquito nets instead of sprays but it has also has refused to heed local law calling for cutting through "monkey bridges" over roads through the rain forest. And 3 Rivers, in the mountains of Dominica, boasts a long list of environmentally sensitive practices, from solar power and composting to running its diesel truck on used vegetable oil.

Yet all of these places also manage to provide enough luxury to attract fairly demanding vacationers.

The island environment itself helps. A solar outdoor shower might not be as reliably hot as one fed from a conventional water heater, but in an open-air setting under a warm sun, amid scents of calabash and guava trees, it's relaxing and exotic. Petit Byahaut's dining room is merely a covered deck, but iridescent hummingbirds feed at flowering bushes next to the tables.

ON a trip to Petit Byahaut last year, my wife and I kayaked along the St. Vincent coast and snorkeled over coral-studded rocks a few feet off the beach, undisturbed by other tourists trying to do the same. We hiked trails to panoramic views and to an ancient Cariban oven carved into a boulder. We also sipped cocktails on a little docklike deck with benches that extended just over the surf - waves would get our legs wet as we watched the sunset.

And we shared dinners prepared by Mr. Durbin, once a chef at Carmine's on Penn in Denver, or by Chuckie Taylor, the main chef, with visiting sailors, some of whom had come across the Atlantic in their boats. Appetizers included callaloo and pumpkin soups, ham and potato cake, and fried calamari; entrees, many of them fresh fish dishes like wahoo wrapped in banana leaves that we had seen Gideon Pompey, Byahaut's boatman, cutting, were all first rate.

Later, there was stargazing or a little reading before sleep. This could get boring, we decided, after a few decades.

At Lapa Rios, the main attraction is the beauty of 1,000 acres of virtually unspoiled rain forest - waterfalls, exotic native animals and extravagant vegetation - its preservation supported by the resort. But guests not fascinated by the hiking can surf, ride horses, fish (catch and release) or indulge in yoga and massage. The resort is proud enough of its food to sell its own cookbook.

In the Bahamas, Tiamo invites guests to leave their private beach bungalows, with their king-size beds and open-air rock-floored showers, to go bonefishing, snorkeling, sailing or kayaking.

Even the relatively rustic 3 Rivers offers Internet access, locally made (and biodegradable) toiletries and soaps that work well with the island's soft water, and Chinese massage - perhaps more a necessity than a luxury for guests who attempt some of the island's spectacular and spectacularly challenging hikes.

While staying at Petit Byahaut, we made a day trip to Bequia (pronounced BECK-way), the largest of the Grenadines, to see Moonhole, an amazing residential community where some houses, with professional cooks and other staff, can be rented by the week. It is a quirky 19-home ecologically oriented development built of native stone, with whalebone accents, on the steep hills of the island's southern tip.

The name comes from a soaring natural arch on the shore through which the moon can be seen at times. The whalebones, remnants of the minimal whaling by the islanders, are big enough to work as elements like stair railings.

The houses, which rely on solar electricity, rainwater and propane tanks, are mostly fanciful open-air affairs with lines blurred between indoors and out. Floors slope so that rainwater can flow to cisterns and the gardens - it can flow in because windows tend to have neither glass nor shutters. Most of the seating is built-in stone benches topped with cushions (remember the "sofa" on "The Flintstones")? Steep stairways link the houses, which appear to have sprouted from the rocky landscape.

"People think they're old ruins," said Jim Johnston, whose father, Tom, a Chicago advertising executive, began developing the site in the 1960's. "But they just look that way."

The community, which evokes Frank Lloyd Wright's Fallingwater as well as Gaudí's Park Guell in Barcelona, fronts a white sand beach with dreamy turquoise water on one side and overlooks a cliff-edged bay popular with divers on the other.

A homeowner at Moonhole needs dedication to the concept of an environmentally sensitive paradise. But visitors at these well-appointed eco-resorts have some choice about how much of their vacation time they want to spend actively supporting the cause. Guests who feel too weary to hike in the forest or to absorb rain-forest ecology lessons are free to spend their time lounging at the beach and sipping something cold, enjoying the pristine landscapes from the comfort of hammocks.

And they can always leave with a souvenir. Tiamo offers one of the most appropriate. Guests are invited to depart carrying packages of used plastic food containers (one of the few products the resort can't figure out how to reuse), suitable for dropping into the municipal recycling boxes back home.

Secluded, Not Spartan
Petit Byahaut, Kingston, St. Vincent, West Indies, (784) 457-7008, www.petitbyahaut.com, four miles north of town, can house 10 guests in four bungalows and a tent on 56 acres. The double-occupancy rates are $140 a night a person in high season, Nov. 1 to May 14, then $112 to Aug. 31; it closes in September and October. All meals, but not bar drinks, are included, as is the use of kayaks and snorkeling gear. Scuba equipment can be rented and hiking or boating excursions arranged. There is a three-night minimum and a 17 percent tax and service charge. Flights go through Barbados, St. Lucia and Grenada.

Tiamo Resort, General Delivery, South Andros Island, Bahamas, (242) 357-2489, fax (305) 768-7707, www.tiamoresorts.com, has 11 bungalows for 22 guests (they urge not taking children under 12). Through Dec. 20, rates are $275 a person a night, including all meals, use of kayaks, sailboats and snorkeling equipment, and many guided activities. Bar drinks and 6 percent tax are extra. Closed August and September. Flights are available to South Andros from Nassau or Fort Lauderdale, Fla.

Lapa Rios, Post Office Box 025216-SJO706, Miami, Fla. 33102; (506) 735-5130, fax (506) 735-5179; www.laparios.com, is south of Puerto Jiménez on the Orsa Peninsula of Costa Rica. It has 16 bungalows for up to four guests each. Rates are $172 to $260 a night a person, double occupancy, including taxes and all meals. The hotel can arrange flights from the capital, San José.

3 Rivers Eco Lodge, Post Office Box 1292, Newfoundland Estate, Rosalie, Dominica; (767) 446-1886, fax (270) 517-4588; and www.3riversdominica.com, has three cottages, sleeping three, for $70 a night; a very secluded thatched house and a bamboo tree house, both for two, for $40 and $50; and a four-bed dormitory-style cabin for $25 a person. Camp sites go for $15 a night, with tents renting for $15 or $20; and a hammock in a shelter is $18 a night. American Airlines (from Puerto Rico) and other regional carriers fly into Dominica.

At www.3riversdominica.com on Bequia, St. Vincent and the Grenadines, a three-bedroom house is offered by Jim and Sheena Johnston, (784)458-3068, www.begos.com/bequiamoonhole, for $1,200 a week for four and $150 each additional person. It comes with a staff of two, including a cook; guests provide groceries.

Another Moonhole owner, (784) 531-7082 , www.burke-house.com, rents two houses. Burke House has two bedrooms with staff for $1,275 a week, and packages with air fare and diving can be added. The second, Tranquility Villa, has four bedrooms, a pool, five terraces and 300-degree water views for $4,999 a week.

Like St. Vincent, Bequia is most easily reached by flights from Barbados. Its harbor at Port Elizabeth, about four miles from the homes but a 25-minute drive, is served by several ferries a day from Kingston on St. Vincent.

STEVE BAILEY is an editor in the Escapes section.

Global warming could help spur severe drought in the Western United States, according to a new study co-authored by a tree-ring researcher at the University of Arizona.

Scientists who examined the width of tree rings over the past 1,200 years found that temperatures were unusually high during "megadroughts" between 900 A.D. and 1300 A.D. The era, known as the "medieval warm period," may be a harbinger of what's to come for the West as the planet keeps getting hotter, the study said.

Were the modern, fast-growing West to suffer a drought like those between 900 and 1300, the results "would be disastrous," the researchers said.

The vast majority of climate experts believe the Earth will keep getting warmer this century, at least partly due to heat-trapping greenhouse gases from tailpipes and smokestacks.

The study, to be published in the next few weeks in the journal Science, was reported earlier this month in the prestigious publication's online edition.

The scientists believe the synchronicity between the warm and dry periods wasn't just a coincidence. They suspect higher temperatures made the eastern Pacific resemble the La Niña pattern that typically makes the West drier than normal.

"It's kind of a cautionary tale," said lead author Edward Cook of Columbia University's Lamont-Doherty Earth Observatory. "Any warming in the future, whether due to greenhouse gases or natural variation, would not be good for the West.

"It certainly ought to be a bit of a worry that we could be looking, long-term, at increasing aridity," he said. "Whether we'll see what happened 1,000 years ago is anyone's guess."

The study's authors are also quick to note there's no proof global warming has caused the West's current dry spell.

"I think it's way too speculative to say that warming is in any way responsible for these last four years of drought," said David Meko, associate research professor at UA's Laboratory of Tree-Ring Research. "A four-year drought is a little blip in the tree-ring record."

But that record also makes it clear the current dry streak is puny by historic standards. Stacked against the megadroughts centered in 936, 1034, 1150 and 1253, "the current drought does not stand out as an extreme event because it has not yet lasted nearly as long," the study said.

"More intense droughts of longer duration have occurred in the past and could occur in the future," it said.

UA scientists have studied tree rings to learn about drought since the 1970s. But back then, only about 65 sites in North America were used to detect climate patterns dating to the 17th century, Meko said. Today, the number of sites is around 600 and scientists can look back to the year 800.

Many of the trees sampled in the West are Douglas firs and ponderosa pines, which reveal the stress of droughts in the width of their rings.

"Their growth is reduced when they get less moisture, so if you look at a cross-section of the tree, you see a narrowing of the rings," Meko said.

The tree-ring findings are also backed up by other indicators of drought, such as fire scars on trees, charcoal deposits and the creation of sand dunes.

Julio Betancourt, a climate expert with the U.S. Geological Survey in Tucson who was not part of the study, praised the paper. He said there's a close match between measurements of rainfall in the 20th century and the reconstruction of climate patterns from tree rings.

"We can map the relative wetness and dryness almost on par with the instrumental record," he said. "There's tremendous reason to trust these mapped views of climate variability over the United States.

"This period from 900 to 1300 was obviously a big notch drier than the period that followed, so it begs the question of exactly what was going on."

Betancourt said he's a bit skeptical of the link between warming and drought because the period from 1976 to 1995 - when the planet was getting hotter - was one of the West's wettest in the past 1,000 years.

"I'm not sure I would have extended that analysis as far as Ed (Cook) did," said Betancourt, who believes warming of the North Atlantic also plays a big role in Western drought.

Scientists aren't sure what caused the medieval warming period, when wine grapes could be planted in Europe 300 miles farther north than they are today. But many have pointed to increased solar activity and a lack of volcanic eruptions that would have shielded the Earth's atmosphere with ash.

The possible link between global warming and Western drought is counterintuitive because it rests on the belief that sea surface temperatures in the eastern, tropical Pacific will fall as the planet heats up.

The researchers think warmer weather will stimulate trade winds, pushing surface water to the west and prompting the "upswelling" of deep, cold water off the coast of South America.

os Angeles — NEW Year's weekend traditionally is a time for us to reflect, and to make resolutions based on our reflections. In this fresh year, with the United States seemingly at the height of its power and at the start of a new presidential term, Americans are increasingly concerned and divided about where we are going. How long can America remain ascendant? Where will we stand 10 years from now, or even next year?

Such questions seem especially appropriate this year. History warns us that when once-powerful societies collapse, they tend to do so quickly and unexpectedly. That shouldn't come as much of a surprise: peak power usually means peak population, peak needs, and hence peak vulnerability. What can be learned from history that could help us avoid joining the ranks of those who declined swiftly? We must expect the answers to be complex, because historical reality is complex: while some societies did indeed collapse spectacularly, others have managed to thrive for thousands of years without major reversal.

When it comes to historical collapses, five groups of interacting factors have been especially important: the damage that people have inflicted on their environment; climate change; enemies; changes in friendly trading partners; and the society's political, economic and social responses to these shifts. That's not to say that all five causes play a role in every case. Instead, think of this as a useful checklist of factors that should be examined, but whose relative importance varies from case to case.

For instance, in the collapse of the Polynesian society on Easter Island three centuries ago, environmental problems were dominant, and climate change, enemies and trade were insignificant; however, the latter three factors played big roles in the disappearance of the medieval Norse colonies on Greenland. Let's consider two examples of declines stemming from different mixes of causes: the falls of classic Maya civilization and of Polynesian settlements on the Pitcairn Islands.

Maya Native Americans of the Yucatan Peninsula and adjacent parts of Central America developed the New World's most advanced civilization before Columbus. They were innovators in writing, astronomy, architecture and art. From local origins around 2,500 years ago, Maya societies rose especially after the year A.D. 250, reaching peaks of population and sophistication in the late 8th century.

Thereafter, societies in the most densely populated areas of the southern Yucatan underwent a steep political and cultural collapse: between 760 and 910, kings were overthrown, large areas were abandoned, and at least 90 percent of the population disappeared, leaving cities to become overgrown by jungle. The last known date recorded on a Maya monument by their so-called Long Count calendar corresponds to the year 909. What happened?

A major factor was environmental degradation by people: deforestation, soil erosion and water management problems, all of which resulted in less food. Those problems were exacerbated by droughts, which may have been partly caused by humans themselves through deforestation. Chronic warfare made matters worse, as more and more people fought over less and less land and resources.

Why weren't these problems obvious to the Maya kings, who could surely see their forests vanishing and their hills becoming eroded? Part of the reason was that the kings were able to insulate themselves from problems afflicting the rest of society. By extracting wealth from commoners, they could remain well fed while everyone else was slowly starving.

What's more, the kings were preoccupied with their own power struggles. They had to concentrate on fighting one another and keeping up their images through ostentatious displays of wealth. By insulating themselves in the short run from the problems of society, the elite merely bought themselves the privilege of being among the last to starve.

Whereas Maya societies were undone by problems of their own making, Polynesian societies on Pitcairn and Henderson Islands in the tropical Pacific Ocean were undone largely by other people's mistakes. Pitcairn, the uninhabited island settled in 1790 by the H.M.S. Bounty mutineers, had actually been populated by Polynesians 800 years earlier. That society, which left behind temple platforms, stone and shell tools and huge garbage piles of fish and bird and turtle bones as evidence of its existence, survived for several centuries and then vanished. Why?

In many respects, Pitcairn and Henderson are tropical paradises, rich in some food sources and essential raw materials. Pitcairn is home to Southeast Polynesia's largest quarry of stone suited for making adzes, while Henderson has the region's largest breeding seabird colony and its only nesting beach for sea turtles. Yet the islanders depended on imports from Mangareva Island, hundreds of miles away, for canoes, crops, livestock and oyster shells for making tools.

Unfortunately for the inhabitants of Pitcairn and Henderson, their Mangarevan trading partner collapsed for reasons similar to those underlying the Maya decline: deforestation, erosion and warfare. Deprived of essential imports in a Polynesian equivalent of the 1973 oil crisis, the Pitcairn and Henderson societies declined until everybody had died or fled.

The Maya and the Henderson and Pitcairn Islanders are not alone, of course. Over the centuries, many other societies have declined, collapsed or died out. Famous victims include the Anasazi in the American Southwest, who abandoned their cities in the 12th century because of environmental problems and climate change, and the Greenland Norse, who disappeared in the 15th century because of all five interacting factors on the checklist. There were also the ancient Fertile Crescent societies, the Khmer at Angkor Wat, the Moche society of Peru - the list goes on.

But before we let ourselves get depressed, we should also remember that there is another long list of cultures that have managed to prosper for lengthy periods of time. Societies in Japan, Tonga, Tikopia, the New Guinea Highlands and Central and Northwest Europe, for example, have all found ways to sustain themselves. What separates the lost cultures from those that survived? Why did the Maya fail and the shogun succeed?

Half of the answer involves environmental differences: geography deals worse cards to some societies than to others. Many of the societies that collapsed had the misfortune to occupy dry, cold or otherwise fragile environments, while many of the long-term survivors enjoyed more robust and fertile surroundings. But it's not the case that a congenial environment guarantees success: some societies (like the Maya) managed to ruin lush environments, while other societies - like the Incas, the Inuit, Icelanders and desert Australian Aborigines - have managed to carry on in some of the earth's most daunting environments.

The other half of the answer involves differences in a society's responses to problems. Ninth-century New Guinea Highland villagers, 16th-century German landowners, and the Tokugawa shoguns of 17th-century Japan all recognized the deforestation spreading around them and solved the problem, either by developing scientific reforestation (Japan and Germany) or by transplanting tree seedlings (New Guinea). Conversely, the Maya, Mangarevans and Easter Islanders failed to address their forestry problems and so collapsed.

Consider Japan. In the 1600's, the country faced its own crisis of deforestation, paradoxically brought on by the peace and prosperity following the Tokugawa shoguns' military triumph that ended 150 years of civil war. The subsequent explosion of Japan's population and economy set off rampant logging for construction of palaces and cities, and for fuel and fertilizer.

The shoguns responded with both negative and positive measures. They reduced wood consumption by turning to light-timbered construction, to fuel-efficient stoves and heaters, and to coal as a source of energy. At the same time, they increased wood production by developing and carefully managing plantation forests. Both the shoguns and the Japanese peasants took a long-term view: the former expected to pass on their power to their children, and the latter expected to pass on their land. In addition, Japan's isolation at the time made it obvious that the country would have to depend on its own resources and couldn't meet its needs by pillaging other countries. Today, despite having the highest human population density of any large developed country, Japan is more than 70 percent forested.

There is a similar story from Iceland. When the island was first settled by the Norse around 870, its light volcanic soils presented colonists with unfamiliar challenges. They proceeded to cut down trees and stock sheep as if they were still in Norway, with its robust soils. Significant erosion ensued, carrying half of Iceland's topsoil into the ocean within a century or two. Icelanders became the poorest people in Europe. But they gradually learned from their mistakes, over time instituting stocking limits on sheep and other strict controls, and establishing an entire government department charged with landscape management. Today, Iceland boasts the sixth-highest per-capita income in the world.

What lessons can we draw from history? The most straightforward: take environmental problems seriously. They destroyed societies in the past, and they are even more likely to do so now. If 6,000 Polynesians with stone tools were able to destroy Mangareva Island, consider what six billion people with metal tools and bulldozers are doing today. Moreover, while the Maya collapse affected just a few neighboring societies in Central America, globalization now means that any society's problems have the potential to affect anyone else. Just think how crises in Somalia, Afghanistan and Iraq have shaped the United States today.

Other lessons involve failures of group decision-making. There are many reasons why past societies made bad decisions, and thereby failed to solve or even to perceive the problems that would eventually destroy them. One reason involves conflicts of interest, whereby one group within a society (for instance, the pig farmers who caused the worst erosion in medieval Greenland and Iceland) can profit by engaging in practices that damage the rest of society. Another is the pursuit of short-term gains at the expense of long-term survival, as when fishermen overfish the stocks on which their livelihoods ultimately depend.

History also teaches us two deeper lessons about what separates successful societies from those heading toward failure. A society contains a built-in blueprint for failure if the elite insulates itself from the consequences of its actions. That's why Maya kings, Norse Greenlanders and Easter Island chiefs made choices that eventually undermined their societies. They themselves did not begin to feel deprived until they had irreversibly destroyed their landscape.

Could this happen in the United States? It's a thought that often occurs to me here in Los Angeles, when I drive by gated communities, guarded by private security patrols, and filled with people who drink bottled water, depend on private pensions, and send their children to private schools. By doing these things, they lose the motivation to support the police force, the municipal water supply, Social Security and public schools. If conditions deteriorate too much for poorer people, gates will not keep the rioters out. Rioters eventually burned the palaces of Maya kings and tore down the statues of Easter Island chiefs; they have also already threatened wealthy districts in Los Angeles twice in recent decades.

In contrast, the elite in 17th-century Japan, as in modern Scandinavia and the Netherlands, could not ignore or insulate themselves from broad societal problems. For instance, the Dutch upper class for hundreds of years has been unable to insulate itself from the Netherlands' water management problems for a simple reason: the rich live in the same drained lands below sea level as the poor. If the dikes and pumps keeping out the sea fail, the well-off Dutch know that they will drown along with everybody else, which is precisely what happened during the floods of 1953.

The other deep lesson involves a willingness to re-examine long-held core values, when conditions change and those values no longer make sense. The medieval Greenland Norse lacked such a willingness: they continued to view themselves as transplanted Norwegian pastoralists, and to despise the Inuit as pagan hunters, even after Norway stopped sending trading ships and the climate had grown too cold for a pastoral existence. They died off as a result, leaving Greenland to the Inuit. On the other hand, the British in the 1950's faced up to the need for a painful reappraisal of their former status as rulers of a world empire set apart from Europe. They are now finding a different avenue to wealth and power, as part of a united Europe.

In this New Year, we Americans have our own painful reappraisals to face. Historically, we viewed the United States as a land of unlimited plenty, and so we practiced unrestrained consumerism, but that's no longer viable in a world of finite resources. We can't continue to deplete our own resources as well as those of much of the rest of the world.

Historically, oceans protected us from external threats; we stepped back from our isolationism only temporarily during the crises of two world wars. Now, technology and global interconnectedness have robbed us of our protection. In recent years, we have responded to foreign threats largely by seeking short-term military solutions at the last minute.

But how long can we keep this up? Though we are the richest nation on earth, there's simply no way we can afford (or muster the troops) to intervene in the dozens of countries where emerging threats lurk - particularly when each intervention these days can cost more than $100 billion and require more than 100,000 troops.

A genuine reappraisal would require us to recognize that it will be far less expensive and far more effective to address the underlying problems of public health, population and environment that ultimately cause threats to us to emerge in poor countries. In the past, we have regarded foreign aid as either charity or as buying support; now, it's an act of self-interest to preserve our own economy and protect American lives.

Do we have cause for hope? Many of my friends are pessimistic when they contemplate the world's growing population and human demands colliding with shrinking resources. But I draw hope from the knowledge that humanity's biggest problems today are ones entirely of our own making. Asteroids hurtling at us beyond our control don't figure high on our list of imminent dangers. To save ourselves, we don't need new technology: we just need the political will to face up to our problems of population and the environment.

I also draw hope from a unique advantage that we enjoy. Unlike any previous society in history, our global society today is the first with the opportunity to learn from the mistakes of societies remote from us in space and in time. When the Maya and Mangarevans were cutting down their trees, there were no historians or archaeologists, no newspapers or television, to warn them of the consequences of their actions. We, on the other hand, have a detailed chronicle of human successes and failures at our disposal. Will we choose to use it?

Jared Diamond, who won the 1998 Pulitzer Prize in general nonfiction for "Guns, Germs and Steel: The Fates of Human Societies," is the author of the forthcoming "Collapse: How Societies Choose or Fail to Succeed."