A new study calls into question the widely accepted principle that gaps in forests caused by tree falls are largely responsible for patterns in tree diversity. Regardless of whether this finding holds up, the point is made abundantly clear that much remains to be known about tropical forest ecology.
Princeton professor of ecology and evolutionary biology Stephen Hubbell, has been painstakingly tracking every square inch of plant life in large patches of tropical forests for the past 20 years, in an attempt to understand what causes biodiversity.
In the latest issue of Science he reported a finding which overturns one of the bedrock beliefs among ecologists about what allows tropical forests to maintain biodiversity. The commonly accepted theory is that infusion of direct sunlight, called a light gap, makes room for new species. This line of thinking has been used to justify selective tree cutting and even clear cuts.
Hubbell found no such correlation, however. He showed that areas with many light gaps are no richer in species than areas with few pockets of sunlight. In fact, roads and development isolate one section of forest from another, making it difficult for seed dispersal.
Another finding is that tropical forests are not the stable, unchanging ecosystems people assume. In just two years, 40 percent of all tree species significantly change; some drop to extinction in a particular location and others become more dominant.
Hubbell will soon be publishing a book which presents his theory, the unified theory of biodiversity and biogeography, or as he calls it, “the E=mc2 of community ecology.” By calculating a “fundamental biodiversity number” for a particular forest – a single number – a scientist can estimate how many species the forest is likely to contain, whether some of those species are more dominant than others, and other factors.
“We’re still in the Middle Ages in biodiversity research,” Hubbell says. “We’re still cutting bodies open to see what organs are inside.”
Worldwide Forest/Biodiversity Campaign News: http://forests.org
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