IN recent years global warming hasbecome a fact, not a theory; a reality, not apossibility.Few scientists challenge data that theearth’s surface temperature has increasedabout one degree Fahrenheit over the pastcentury. And every day, stronger evidenceis released attributing this warming, atleast for the past 50 years, to human activity,according to the IntergovernmentalPanel on Climate Change.Last month, the Kyoto Protocol, a multilateralagreement to combat globalwarming across the globe, went into effectwith the support of more than 140 countries,excluding the United States (TT, Feb.25).The question scientists are now strugglingto answer is: What does globalwarming mean, and how will the environmentadapt? Can we expect a rising sealevel? A more turbulent climate? Fewerspecies?RESEARCHERS in northeasternCosta Rica are asking this question aboutthe very thing often viewed as a solution tothe excess of so-called “greenhouse” gasesproduced by humans, particularly carbondioxide – the tropical rain forest.A project of the Organization forTropical Studies (OTS) at La SelvaBiological Station, in the Caribbean lowlandsoutside Braulio Carrillo NationalPark, aims to find out how the rain forestresponds to climate change.Scheduled to end in a few months, theproject known as “Towers” has beenunprecedented in its scope of measuringvarious functions of the rain forest canopy.Using a moveable tower, which at itstallest reaches 44 meters (144 feet), scientistshave been able to study the primaryforest from top to bottom in more than 50different locations around the La Selvaprotected area.“THERE is not a place in the worldwhere this is being done,” said OTSresearcher and eco-physiologist JavierEspeleta.Since the study began in June 2003, ateam of 20 researchers and crew membershas been erecting the scaffolding tower ateach of the 50 sites – a job that entails carryingas much as 4,500 pounds of equipmenton backs and shoulders on hikes aslong as one-and-a-half hours throughdense jungle terrain.Scientists then spend eight hours a dayfor two weeks at a time collecting data andleaves that are studied in labs by night.The scaffolding is then deconstructed,moved and reconstructed.Though arduous, the comprehensivepicture of the forest they are capturing hasmade the effort worth it, according to projectcoordinator Paulo Olivas, who has adegree in forestry from the TechnologyInstitute of Costa Rica (ITCR).BY erecting the tower piece by piece,researchers have been able to slowly moveup the forest canopy, collecting informationas they go. They are particularly interestedin data on plant respiration and photosynthesisrates, and the quantity ofleaves in a given area – a figureresearchers say is hugely important butdeceptively complicated to determine.With this data, researchers are hopingto understand how plants may be affectedby global warming.One of the hypotheses of the project isthat increased temperatures mean the forestis respiring more, which in turn wouldmean the forest is absorbing less andreleasing more of the greenhouse gas carbondioxide (see sidebar).ESPELETA said this could result in a“catastrophic cycle” in which the forest isless capable of absorbing carbon dioxide,therefore temperatures would continue toincrease, further affecting plants’ ability toabsorb the greenhouse gas.Olivas is careful not to forecast toomuch, particularly because the project isnot complete so no preliminary conclusionshave been made.“We don’t know if plants are going toget used to it in the long term… if they aregoing to adjust to the situation so theybecome capable of working with high temperatures,”he said.It is not likely the forest will everbecome a significant producer of carbondioxide, Olivas said. The possibility of theforest no longer absorbing carbon dioxideat the present rate is the real threat thatcould have considerable impact, heexplained.SCIENTISTS already point to somemeasurable effects of the global temperatureincrease. According to what some scientistssay are conservative estimates fromthe U.S. Environmental Protection Agency(EPA) – operating under the administrationof U.S. President George W. Bushwho withdrew the United States from theKyoto Protocol – globally, the sea levelhas risen 4-8 inches in the past century,worldwide precipitation over land hasincreased by about one percent and the20th century’s 10 warmest years alloccurred after 1985.The exact level of responsibility ofhuman activity for these effects, and thewarming, is still under study. If temperaturescontinue to rise – and scientistsexpect they will, by 1-4.5 degreesFahrenheit in the next 50 years – theimpact could be even more dramatic.Warmer temperatures would bringmore evaporation, which would increaseaverage global precipitation, and intenserainstorms are likely to become more frequent,the EPA warns. The sea level couldalso rise two feet in areas.Other scientists predict effects couldbe even more severe.IN the tropical forest, species thatrequire high humidity may die if temperaturescontinue to increase. In addition,more extreme climatic conditions usuallymean the forest is more homogenous,Olivas said, pointing to the mountainoustundra and the desert as examples.But these are only possibilities, heemphasized.The research part of the Towers projectwill conclude in May. Scientists will thenbegin analyzing the data and should havescientific models of the forest’s possiblereaction to global warming within a year,Olivas said.These models will offer predictionsthat are more precise in the short term andless exact in the longer term, he said.“Models aren’t perfect or exact withhow things might change. The only thingthat drives evolution is time,” he said. “Thisis the really cool thing. We try to understandnature, and predict what might happen. ButMother Nature is so magical she mightchange, and adapt to the situation.”THE Towers project (www.fiu.edu/~carbono/tower.htm) is funded by theU.S. National Science Foundation andsponsored by Florida InternationalUniversity.