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Prognosis for Biodiversity in the Amazon Improves


by Bill Chameides | July 21st, 2009
posted by Erica Rowell (Editor)

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When it comes to biodiversity, the Amazon is pretty much unrivalled. So will the destruction of the Amazon’s unique rain forest ecosystem mean a loss of biodiversity? And if so, how much? (NASA)

The Amazon is a nearly unrivaled repository of DNA, but deforestation and development are depleting the account.

Biodiversity is not just a “treehugger” thing. Each species in the world occupies a niche in the food web and provides a link in the chemical cycles that maintain ecosystem function and keeps life on the planet ticking away. Each species also contains a unique bit of DNA code that could potentially provide the key for new medical cures and pharmaceuticals.

It’s estimated that something like 25 percent of the prescription drugs we use in the United States are derived from plant products. Lose a little biodiversity and you potentially lose a shot at the next miracle drug.

When it comes to biodiversity, the Amazon is the Big Kahuna. The Amazon:

    • encompasses some 2.1 million square miles in South America (about the size of the contiguous United States),
    • holds about half of all the world’s remaining rain forests,
    • is home to an estimated one in ten of all the known species on the planet, including some:
The Amazon rain forest is important to biodiversity. (WikiCommons: Pfly)
    • 40,000 varieties of plants,
    • 427 mammals,
    • 1,294 birds,
    • 378 reptiles,
    • 427 amphibians, and
    • 3,000 fishes.

But between 2000 and 2005, the Amazon rain forest shrank at a rate of about 8,600 square miles per year (based on data from the Brazilian Amazon) due to logging, agriculture, extraction of oil and natural gas, and development. Some sources (see here and here) show a drop-off in deforestation since 2005, while other sources indicate deforestation rates may be increasing. As the rain forest shrinks, so does its biodiversity.

What Does a Shrinking Rain Forest Mean for Biodiversity?

Without significant government intervention to slow deforestation rates, as much as 25 percent of the Amazon’s rain forest habitat could be gone by 2050. That in itself is a pretty devastating statistic, but will that translate into a similar loss of biodiversity?

The scientific literature generally answers that question in the affirmative. For example, one estimate by Stephen Hubbell and colleagues published last year in the Proceedings of the National Academy of Sciences (PNAS) projected that 20 to 33 percent of the canopy tree species of the Amazon will be gone by 2050 as a result of deforestation.

Now a new study by Kenneth Feeley and Miles Silman of Wake Forest University published last week in the early edition of PNAS suggests that the prognosis may not be that bad. Focusing on some 40,000 vascular plants in the Amazon, the authors used much more detailed information on the spatial distribution and extent of these plants, thus improving on previous works.

The greater spatial information indicates that many species will be able to survive deforestation because some portion of their habitat will remain untouched; in other words Amazonian species will have to retreat or lose ground to deforestation but will still have havens to carry on.

Without significant government intervention to slow deforestation rates, as much as 25 percent of the Amazon’s rain forest habitat could be gone by 2050. (NASA)

All in all, Feeley and Silman conclude that only about 9 percent of all vascular plants will go extinct by 2050 as a result of deforestation. With government intervention to slow deforestation, the extinction in the Amazon, they estimate, will decline to 5 percent.

Losing 5-9 percent of all species in the Amazon is not great, but it sure is a lot better than 20-33 percent. Good news for the pharmaceutical industry, good news for all of us humans, and, I imagine, good news for all the vascular plants, who no doubt, having read the latest issue of PNAS are breathing a sigh of relief. Concentrate and you can almost catch that extra burst of oxygen wafting up from South America.

More on Tropical Rain Forests

Tropical Deforestation (nasa.gov)

filed under: animals, deforestation, faculty, plants, rain forest
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