As human populations and their impacts on the world increase, tropicalforests are changing in many different ways. Forests are being cleared,burned, logged, fragmented, and overhunted and an unprecedented pace,and they are also being altered in insidious ways by global climaticand atmospheric changes. "The evidence for global effects suggests thata massive reorganization of the structure and dynamics of tropicalforests is already underway" writes ecologist S. Joseph Wright, "Thetropics support over half of all species and over two-thirds of allpeople. Without an appropriate commitment from the scientificcommunity, the two are unlikely to continue to coexist," concludes thescientist.
Tropical forest landscapes are changing rapidly in the eyes ofscientists working on tropical monitoring plots around the globe, whilehuman populations and their economic activities grow. Old-growthforests become agricultural lands, degraded land is abandoned,urbanization intensifies, and the populations of tropical countrieswill increase by two billion over the next 25 years.
But what is happening in protected areas? Globally, 18% of all tropicaland subtropical moist forest and 9% of all tropical dry forests arenominally protected by governments. Increasingly, even these areas seemto be bearing the indelible marks of human activity.
On Barro Colorado Island (BCI) administered by the Smithsonian TropicalResearch Institute (STRI) in the Republic of Panama, the old-growthforest has escaped fire and agriculture for at least 1500 years. STRI'sCenter for Tropical Forest Science (CTFS) has repeatedly censused allsteams one centimeter of diameter or more at 1.3 m height in a50-hectare plot every five years since 1985. Wright notes that theaboveground biomass on BCI was almost constant since the first census.But lianas increased substantially (from 9% to 13% of all leaf biomass)between 1986 and 2002.
In another protected area, the Kibale National Park in Uganda, a30-year record suggests that reproductive activity by forest trees isincreasing; and at La Selva, Costa Rica, diameter-growth ratesdecreased among surviving individuals for cohorts of nine speciesmeasured annually for 17 years. These mysterious changes may be causedby large-scale drivers, such as increasing carbon dioxide in theatmosphere, intense droughts, or other poorly understood phenomena.
Wright, who has studied tropical forests and its plant and animalinhabitants since the late '70 at STRI, encourages tropical scientiststo conduct assessments based on existing long-term records. Basicresearch will help us to understand the dimensions and mechanisms offorest responses to anthropogenic forcing. Conservation scientists musthelp to mitigate the number of species lost to extinction by enhancingthe effectiveness of the network of protected areas. Other appliedresearch will help to rehabilitate degraded lands and to improveagricultural yields and living standards.
According to William F. Laurance, Wright's colleague at STRI andfrequent spokesman for conservation efforts in Africa and the Amazon,"the commitment of tropical biologists must go a step further toinclude effective communication of their findings to decision makersand the general public. It is those who will eventually demand thatgovernments invest in research and conservation of tropical forests andwho will work to slow the rapid, unsustainable growth of humanpopulations in the tropics."
Ref.: Wright, S. Joseph. 2005. "Tropical forests in a changing environment." Trends in Ecology & Evolution Online.
The Smithsonian Tropical Research Institute (STRI), with headquartersin Panama City, Panama, is one of the world's leading centers for basicresearch on the ecology, behavior and evolution of tropical organisms. http://www.stri.org
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