Bogging down in the sinks.

• Author: Mattoon, Ashley T.
• Position: Using trees as carbon sinks in the prevention of global warming

Under the Kyoto Protocol, a country may be able to reduce its obligation to cut carbon emissions by "sinking" some carbon in trees. But greenhouse forestry won't necessarily be good for the forests - and it certainly won't prevent climate change.

Last year saw some of the worst forest fires in history. Indonesia lost 100,000 hectares of virgin tropical rain forest, much of which had probably never burned before. Brazil's burning season swallowed 2 million hectares of forest. Overall, more than 5 million hectares of land went up in flames - an area roughly the size of Costa Rica.

This year again, vast stretches of tropical forest have been reduced to charcoal. Another 3.9 million hectares in Brazil were lost. To the north, fires raged here and there through central America, and up into the highland "cloud forests" of southern Mexico, one of the last places in that country where it was still possible to find the quetzals, jaguars, and other species that have shaped thousands of years of indigenous culture.

During the 1980s, the last time an estimate was made, the fires and other forms of deforestation were releasing around 1.4 billion tons of carbon into the atmosphere annually. Deforestation accounts for roughly one-fifth of humanity's annual emissions of carbon dioxide (C[O.sub.2]), the primary greenhouse gas. In the oddly nondescript language of climatology, the burning tropical forests have become a net carbon source - that is, they are pumping more carbon into the atmosphere than they remove through photosynthesis, the process that pulls C[O.sub.2] out of the air to build plant tissues and ultimately, forest soils.

But in the temperate and northern forests, an opposing process seems to be occurring. The regrowth of woodland and various other ecological changes have made these forests a net carbon sink. They are absorbing more carbon than they give off. The size of this sink is uncertain but by a rough estimate, it takes in about 700 million tons more carbon than it releases through burning and decay.

Given the links between forests and climate, it's not surprising that forestry has always loomed in the background of the climate negotiations. The 1992 Framework Convention on Climate Change specifically calls for the "conservation and enhancement" of carbon sinks. That idea proved crucial to the negotiations last December in Kyoto, where the actual mechanics of the treaty were being worked out. The principal task at Kyoto was to get an agreement among the "Annex I parties" (essentially, the industrialized countries) on how much they would reduce their greenhouse gas emissions below their 1990 levels by the time of the "commitment period" - the five years from 2008 through 2012. To measure a country's progress towards the treaty target, its total emissions over those five years will be compared to its 1990 emissions level multiplied by five.

The agreement that emerged called for a collective 5.2 percent reduction of industrialized-country fossil fuel emissions below their 1990 level. (Fossil fuels account for 75-80 percent of humanity's C[O.sub.2] emissions.) Fossil fuels contributed some 6 billion tons of carbon to the atmosphere in 1990. The contribution is now in excess of 6.3 billion tons and rising, so the treaty would appear to require substantial reductions in fossil fuel use. But cutting back on coal and oil is a tough sell politically. Planting trees, on the other hand, has nearly universal appeal. That's why the industrialized country delegates at Kyoto were so interested in the carbon their forests were socking away. Was there some way such a country could use its expanding forests as a "credit," which would partly offset its obligation to cut back on fossil fuels?

RETROACTIVE PROGRESS

The world's forests contain less than 5 percent of the immense lode of carbon - 42.8 trillion tons of it at least - that is circulating through the air, soil, water, and the tissues of living things in a process known collectively as the carbon cycle. But of all the cycle's natural links (that is, excluding the fossil fuel input), the forests are among the most susceptible to human influence.

At present, according to one recent overview of the cycle, terrestrial plant growth in general absorbs some 61.9 billion tons of carbon from the air every year. Decay and burning (both natural and human-caused) release 61.6 billion tons. So despite the fires, terrestrial vegetation on the whole still seems to be a net sink. [ILLUSTRATION FOR CHART OMITTED].

Our biggest effect on the cycle involves, in a sense, the burning of fossil forests. Those fossil fuel emissions - all 6.3 billion tons of them - are additional carbon, which is being injected into the cycle through the combustion of coal and oil. Fossil fuel use is releasing the carbon that ancient forests pulled out of the atmosphere hundreds of millions of years ago.

There is no serious debate over the level of fossil fuel emissions. But at Kyoto, many scientists argued that we do not understand the cycle in its entirety well enough to predict whether the carbon moving into industrialized-country forests will actually stay there. In their view, carbon sinks shouldn't have entered into the treaty until more solid data on them had been collected. But intense pressure to reach some sort of agreement before the conference broke up pushed the sink negotiations ahead anyway. In the scramble to come up with something that everybody could endorse, participants fumbled with their calculators and computer models, and new algorithms came spilling out of convention center doorways every few hours. Kevin Gurney, an atmospheric scientist at Colorado State University who attended the meetings, likened the tangle of resulting proposals to spaghetti. Many of these strands, in Gurney's circumspect way of putting it, had "limited scientific merit."

Whatever the scientific value of the resulting provisions, their diplomatic importance was enormous. The sink concept proved to be a wonderful fudge factor - or "flexibility mechanism," to use the diplomatic euphemism. For example, the United States, the world's largest greenhouse gas emitter, agreed to reduce its emissions to a level 7 percent below its 1990 levels - as long as it could invoke its forest sinks, among other things, when the time comes to do the accounting. Without recourse to the forests, the United States would likely have adopted a more modest limit.

But the U.S. reaction reveals the basic flaw in this approach: it builds too much weasel room into an agreement that may already be too weak to accomplish its ostensible purpose. (See "Last Tango in Buenos Aires," page 10.) Even a straight emissions cut of 7 percent would really only be a start. Consider this: it will take a global reduction on the order of 60 to 80 percent just to prevent atmospheric C[O.sub.2] from more than doubling beyond its preindustrial level by the end of the next century.

Yet precisely because it is such a useful "flexibility mechanism," the sink concept will probably have a long legal life. A growing international cadre of consultants, lawyers, and biologists already makes a living off it. And this sink sector may exert a strong influence not just on the international climate debate, but on the management of the forests themselves.

In a way, the basis of that influence is this rather ungainly equation, which is the Kyoto formula for squeezing a carbon credit out of the forests:

Gross industrial emissions + emissions from LUCF activities - removals from LUCF activities = total net...