The Foreign Service Journal, February 2008

Convention, where it was approved in principle. Until now, the forest segment of the greenhouse gas/climate change threat has been treated as a side issue. But the time is now at hand for a grand bar- gain that provides incentives for forest protection and REDD, plus aggressive reforestation and afforestation. A Fragile Giant Worryingly, the Amazon River Basin is itself vulner- able to the effects of climate change. Several global cli- mate models, in particular the one run by Britain’s Hadley Center, show a potential drying trend in the eastern Amazon, a process often called Amazon dieback or savannaization. Were this to happen, there would be massive loss of forest and biodiversity, as well as the release of a significant amount of carbon into the atmosphere. The model is too imprecise at this time to put an actual number on the amount of carbon that would be released as a positive feedback loop, but a sense of the scale can be derived from the fact that at present the Amazon forest contains a carbon stock equivalent to about 15 years of the current annual increase in atmospheric CO 2 . Complicating matters, changes within ecosystems like the Amazon jungle are not simply gradual and lin- ear. Instead, such ecosystems are known to experience threshold responses to past climate changes. The most notable example is the dieback of the coniferous forests in parts of North American and Europe, where longer summers allow native pine bark beetles to spawn another generation every year, leading to massive tree death. One Amazon Basin threshold relates to its remark- able ability to recycle water. About 25 years ago, through the brilliant analysis of isotope ratios of oxygen in rain samples from the Atlantic to the western fron- tier of the Brazilian Amazon, Brazilian scientist Eneas Salati demonstrated that the region generates half its own rainfall. As moisture comes off the Atlantic, it falls as rain in the eastern part of the Amazon; then as much as 75 percent of the water evaporates off the complex surfaces of the forest, is transpired by trees and carried westward toward the Andes. When the moisture-laden air reaches the Andes, it is deflected north and south. Conse- quently, a significant fraction of the rain south of the Amazon in Mato Grosso, São Paulo and northern Ar- gentina comes from the Amazon and the hydrological cycle. That means that an important part of Brazil’s powerful agro-industry and some of its hydroelectric power depend on the Amazon rain machine. Salati calculated that approximately 50 percent of Amazon rainfall was generated within the basin in this fashion. His findings shattered the previous paradigm, under which vegetation was simply the consequence of climate and had no effect on meteorological condi- tions. It has been clear for decades that at some point deforestation can undercut the cycle, causing the Ama- zon rain machine to begin degrading. The difficulty has been how to define where that threshold would be before it has already passed. It is a complicated ques- tion because not all parts of the Amazon contribute equally to the recycling, but a Brazilian Ph.D. thesis calculated the tipping point as occurring when the for- est would be about 40-percent deforested. With official deforestation in the Brazilian Amazon at something shy of 20 percent, a threshold double that would seem to give considerable comfort. But unfor- tunately, deforestation is not the only way the hydro- logical cycle can be affected. Since the demonstration of the existence of the hydrological cycle, the El Niño phenomenon off the west coast of South America has gone from something considered a local problem, mainly affecting the an- chovy fishing industry, to one with almost global cli- matic reach. In El Niño years, there is extensive rain up the coast into North America, and strong drought in Southeast Asia and Indonesia. In addition, the effects reach across South America to cause drought in north- eastern Brazil and the eastern Amazon. In 1997, the El Niño effect was so severe that satellites revealed a smoke cloud as big as Brazil hanging over South America. Quite separately, the Brazilian Amazon experienced a severe drought in 2005 associated with the changes in the Atlantic circulation that spawned Hurricane Katrina. This was the most severe drought in record- F O C U S 24 F O R E I G N S E R V I C E J O U R N A L / F E B R U A R Y 2 0 0 8 Several global climate models show a potential drying trend in the eastern Amazon.