Going to Blazes

Fueled by a record El Niño, tropical forest fires are a whole new kind of disaster--and could spur runaway global warming

| Tue Jul. 7, 1998 3:00 AM EDT

Florida's still on fire, its forests parched and set ablaze by abnormally hot, dry weather, forcing more than 112,000 people from their homes last week alone. Earlier this season it was Mexico's turn to burn, sending smoke as far as North Dakota. Before that, vast fires swept Indonesia's tropical rainforests, and the greatest of them all, Brazil's Amazon.

Scientists agree El Niño is largely to blame, but some say there's more to the story: If this year's fires are a sign of what's to come, the world's tropical rainforests may be headed for an entirely new kind of future, a future where lush, moist jungles burn all the time—and global warming could get markedly worse than predicted.

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"A Runaway Climate"

These fires aren't just incinerating homes and habitat and causing temporary smog—they may be helping to heat up the entire planet. The most terrifying of all climate change scenarios are those in which global warming stokes itself by releasing the greenhouse gases locked in forests and soils. Huge fires in the tropical forests sucked dry by the monster '97-98 El Niño could be an early sign of just such a runaway feedback loop.

As last year's Indonesian fires were smoking out Southeast Asia, they were also pumping more carbon dioxide into the atmosphere than a whole year's worth of fossil fuel burning in the entire European Community, peatland ecologist Jack Rieley estimates—and he quickly adds that the figure could run twice that high. Scientists are still working up greenhouse emission figures for the more recent blazes in Amazonia and Central America, the latter which sent smoke over the southern U.S., but they are sure to be substantial. And Florida's fires, which may also be tied to El Niño, have been the worst in 50 years.

While it is impossible to distinguish carbon dioxide emitted by the fires from other effects of El Niño,which overall tends to increase atmospheric CO2,"The rate of rise since the middle of 1997 is as fast as it's ever been," notes oceanographer Charles Keeling, who pioneered global CO2 monitoring back in 1958.

Jack Rieley's field, the study of the tropical peat swamp forests, is particularly relevant to the Indonesian conflagrations. Those fires took place in and upon one of the planet's great carbon sinks, peat bogs up to 60 feet deep which underlay Southeast Asian tropical forests. The bogs have been accumulating biomass for up to 15,000 years, and contain 10 percent of all the carbon locked in world soils. Burning down three feet or more, they were a key source of the Indonesian fires' greenhouse emissions. While apparently extinguished when rains returned in fall, peat fires can burn underground for years and even centuries. If global warming is intensifying El Niños and bringing them on more frequently, as many scientists suspect, this could set up conditions for just such long-term fires.

And major wildfires in the tropics are truly something new. In fact, as a recent Union of Concerned Scientists report notes, before the droughts induced by the massive 1982-83 El Niño caused huge fires in Borneo, "it was thought that undisturbed rain forests simply could never dry out enough to burn." Now scientists are beginning to suspect that in both Asian and Latin American tropical forests, El Niño may pull the climatic equivalent of a coup d'etat, with long hot droughts introducing a new fire regime—a regular pattern of fire in an ecosystem—to humid forests where large "stand-replacing" wildfires are not a natural occurrence.

"Droughts caused by El Niño would have a measurable effect on fires and therefore on carbon dioxide concentration in the atmosphere," says Harvard biologist Fakhri Bazzaz, one of the world's leading scientific authorities on carbon feedbacks from tropical forests. "The fear is you will have a runaway climate. These scenarios are not unreasonable."

Biodiversity Burnup

Not just a climatic catastrophe, a shift to drier, more fire-prone conditions in tropical forests would also be a biodiversity tragedy, because these forests are by far the world's leading biodiversity reservoirs.

"In our nightmares we have visions of what this might mean," says Worldwatch Institute researcher Janet Abramovitz. "It's a rather frightening prospect that we can change the fire regime of these forests, and all the species that depend on them."

This year's fires, for instance, threatened the Chimalpas biological reserves in Mexico, home to hundreds of endangered plant species. And that's just the ones we know of. In the vast Amazon, dozens of animals and plants unknown to science are still discovered every year, including a tiny new monkey announced just last week.

That Darned El Niño

Much of the damage can be traced to El Niño, the climate pattern which reshapes weather around the Earth by altering the track of the jet stream. This shifts global rainfall patterns, bringing killer floods to places such as Peru and harsh droughts to Asia and parts of Latin America. While scientists are increasingly confident that humans are warming the planet, they are more cautious about ascribing specific weather variations to climate change. However, a strong case is emerging that global warming is indeed fueling El Niño.

El Niño is believed to act as a great valve, opened by the ocean on a regular basis to discharge accumulated heat. Most heat coming from the sun is trapped in the oceans, and most of that is in the tropics. The Pacific as the largest ocean is the biggest heat-catcher, and the western equatorial Pacific is usually the world's warmest patch of ocean. But when what El Niño researchers Mark Cane and Stephen Zebiak describe as the "equatorial heat reservoir" fills, the El Niño release valve opens. Winds and currents move the warm pool toward the central Pacific and South America, and El Niño pumps heat around the world.

In a warming world, there is more heat to feed El Niño. The ocean surface overall has grown one degree Fahrenheit hotter over the last century, and ocean warming has been particularly pronounced over recent decades. Sea surface temperatures in parts of the tropics have been like "a furnace room in the last 20 years, the place where the heat has been going in," notes Nicholas Graham, a climate scientist at the Scripps Institute of Oceanography.

In those 20 years, the El Niño heat valve seems to have been stuck on open. The Pacific has been in an El Niño phase much of the time. In 1982-83 arose the most powerful El Niño known up to that point. By some measures the 1997-98 El Niño was even stronger, causing the greatest total rise in sea temperature ever recorded. In between, 1990-95 witnessed the longest El Niño on the books.

Human Fingerprints

When a condition tied to ocean heat breaks so many records, at the same time that the planet overall is experiencing its record hottest years, the question naturally arises: Is there a human global-warming fingerprint on this? One El Niño research pioneer has few doubts. Kevin Trenberth, who back in 1976 used statistical methods to nail down El Niño's then-typical recurrence rate—once every 4-7 years—has now applied his models to El Niño's recent odd behavior. With fellow scientist Timothy Hoar at the U.S. National Center for Atmospheric Research (NCAR), Trenberth concluded the present odd sequence of El Niños has a probability of occurring naturally only once in 2,000 years.

Wrote the scientists in the peer-reviewed Geophysical Research Letters, "Is this pattern of change a manifestation of global warming [or] a natural variation? We have shown that the latter is highly unlikely."

"What my result showed was the degree of unusualness," Trenberth says. "And the main thing we can point to is global warming. I think El Niños are being changed by global warming."

Other scientists find Trenberth's conclusions less persuasive because they are based on a statistical record that runs back only around 120 years. But a five-century anecdotal track drawn from the writings of Spanish explorers and colonists in South America also points to the weirdness of the last 20 years. In their historical survey, Oregon State University oceanographers William H. Quinn and Victor T. Neal identified eight very strong El Niños from 1525 to 1982-83, and found that in the past three centuries, major El Niños averaged one every 42 years; the two recent record-breakers came just 14 years apart, closer together than any two big ones since 1525.

Various computer models also show El Niño-like conditions becoming more prevalent as carbon dioxide doubles over current levels. NCAR researchers Gerald Meehl and Warren Washington published the results of one such simulation in Nature in July 1996. With carbon dioxide already up 30 percent since 1750, they said their models indicate the recent increase in El Niños could indeed be a global warming signature.

This year's El Niño certainly contributed to yet another record spike in global temperatures, which were half a degree higher than the previous record for the first five months of the year, "far exceeding anything we've seen in the past," National Climatic Data Center chief Thomas Karl announced in June.

At the White House briefing announcing those figures, Al Gore gingerly approached the climate change connection. The vice president noted that "as a result of global warming there is more heat in the climate system, and it is heat that drives El Niño. So when El Niño comes, the effects are likely to be compounded by global warming."

An Endless Cycle?

"Maybe we're sending El Niño spinning out of control," says Adam Markham, climate campaign director for World Wildlife Fund. "Even without El Niño we see a warming trend which is going to cause a general drying. That threatens rainforests."

That was the conclusion of a scientific conference on tropical forests and climate change WWF held three years ago. The group expects to release updated proceedings later this month.

"The worst case scenario is a combination of existing threats to tropical forests plus climate change virtually wiping them out," Markham says. "The combination of human development plus global warming plus fires is a cycle that cannot go on forever."

Daniel Lashof, senior scientist with the Natural Resources Defense Council, notes that a number of researchers over the past several years have projected that worldwide forest "die-back" due to global warming could over the next century dump 100-200 billion tons of carbon dioxide into the atmosphere. That would effectively double the contribution deforestation makes to global warming.

The Intergovernmental Panel on Climate Change 1995 Assessment is regarded as the most authoritative scientific conclusion yet that humans are heating the planet. Yet the computer models the IPCC used assumed that forests will soak up more carbon than they release. Emerging information "at the very least suggests that a lot of the global warming scenarios we have been using are too optimistic on the ability of the forests to take up carbon," Lashof says.

"The world's forests now lose more carbon to the atmosphere than they absorb—a recent shift," notes Abramovitz. "In fact, up to one quarter of all the carbon added to the atmosphere by human activities now comes from cutting and burning forests."

Long-term ecosystem changes are in prospect, and there are questions as to whether tropical forests, once burned, will reestablish themselves.

Forest loss feeds itself, because the rainforests themselves are the source of much of the rain that sustains them. Rainforest Action Network (RAN) president Randy Hayes notes that around half the rainfall in Amazonia is generated through evapotranspiration—trees releasing water vapor into the atmosphere.

And rainforest soils may not stand up to repeat blazes. "When you cook shallow soils, as the tropical forests have, it can cause permanent damage," notes Hayes.

Another concern is erosion and runoff from newly burned forests. The peat forest fires of Indonesia both lowered the ground level and reduced the sponge effect of bogs, so flooding could be a problem. With a new La Niña coming on at a stunning rate—El Niño's colder, wetter counterpart—huge rainfalls can be expected in areas recently hit by drought and fires. This demonstrates how climatic extremes, which are expected under global warming, can generate worst-of-both-worlds scenarios.

Economic Underpinnings

While prospects for tropical forests in a warming world look grim, their death is not inevitable, even if El Niño returns to wreak climatic havoc more often. For while El Niño-induced droughts set the stage for the recent conflagrations, population resettlement and agriculture most often lit the match. Land clearing by fire simply raced out of control when expected rains did not come. And large-scale corporate agribusiness played a huge role. Reuters reported last September on a study from a province in Sumatra which showed 80 percent of fires were tied to plantations. Schemes to dramatically increase palm oil production are behind many of the Indonesian fires. Logging and cattle ranching made similar contributions in Central America.

"This is tied to the globalization of the economic environment," Hayes comments.

Of course, the pattern of human activities in tropical forests can change. "It is not a given thing this has to get worse every time we have a bad El Niño," says forest ecologist Sandra Brown, a key IPCC '95 contributor in the area of tropical forests and the global carbon cycle.

Much depends on whether rich countries are willing to transfer resources to developing nations. The Kyoto climate treaty envisions a Clean Development Mechanism to do just that. Hammering out the details is a key element of the next climate summit in Buenos Aires in November.

"Some fraction of what industrialized countries do to reduce greenhouse warming can be investments in third world countries," says Peter Frumhoff, Union of Concerned Scientists global resources director.

"One doesn't want to see projects implemented overseas reduce the need to cut pollution here," Hayes warns. Nonetheless, investments in tropical forests "could be a useful tool." They will be part of RAN's message in October, when it will focus World Rainforest Week on climate change.

The Sierra Club will also address climate change in a report due this August, detailing the overall impacts of El Niño and global warming over the past year.

"The bottom line," says Dan Becker, director of the Sierra Club's Global Warming and Energy Program, "is some of the people who need to make the decisions that will allow America to curb global warming pollution are not looking at the evidence: the fires, floods, storms, and temperature record. They're looking at political contributions from the oil, coal, and auto industries. It's going to take more to convince them—and there's going to be more."

If there's an overall message of the recent fires, Markham says, it's this: "Reduce greenhouse gases as quickly as possible. Tropical forests are among the most threatened habitats. They are going to have no opportunity whatever to adapt to climate change."

Patrick Mazza is an environmental journalist writing from Seattle, Wash. His work has appeared in Sierra, In These Times, and E Magazine, among other places. He also edits Cascadia Planet, one of the original bioregional sites on the Web.

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