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Bill Chameides

Bill Chameides

Posted: September 22, 2010 02:08 PM

Where Nature Does Her DNA Banking

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Crossposted with www.thegrengrok.com.

When it comes to biodiversity, all land is definitely not created equal.

Diversity, our financial analysts and H.R. reps tell us, is a good thing. In the natural world, when we speak of diversity we usually mean "biodiversity," the range and variability of the species in a biome or on the globe. If you like to think in terms of double helixes, then biodiversity is the range of different kinds of DNA strands hanging out on the planet. And as with financial diversity, ecologists generally agree that biodiversity is a good thing.

Singing the Praises of Biodiversity

2010-09-22-yosemite.jpg
California's biological riches are one reason the United States is considered a megadiverse country, and yet hundreds of the state's species are threatened or endangered. (National Parks Service)

Biodiversity is like money in the bank. Ecologists have found that greater biodiversity can provide a greater measure of stability to enhance the productivity of some biomes. (See discussions here and here.) All those extra, biologically diverse strands of DNA give us models for developing new medicines, new seed stocks, and perhaps that new something we've yet to create because we haven't come across that particular DNA strand yet.

But we can't use that special strand of DNA if the species carrying it has vanished. And that, unfortunately, is a problem. As best as we can tell, global biodiversity has been falling precipitously for quite some time. It's estimated that current extinction rates are some 100-200 times greater than the background rate estimated from the fossil record. Why the increase? Just ask the gorilla called Ishmael. Humans.

The advent of agriculture about 10,000 years ago has been a major cause of biodiversity loss. One driver, not surprisingly, has been the loss of habitat as humans converted more and more land to cultivation and livestock; currently more than 40 percent of the Earth's land area is used for agriculture. What I was surprised to learn was that agricultural practices (such as the use of monocultures) have led to significant losses in the number of varieties of crop plants. For example, according to the Convention on Biological Diversity, 90 percent of the wheat varieties in China have been lost since 1949. In the United States, 80-95 percent of the varieties of apples, maize, cabbages, peas, and tomatoes have been lost since the 19th century.

If plants and animals have fared poorly since the dawn of agriculture, the future doesn't look too rosy either. According to the 2010 Millennium Development Goals Report [pdf], almost 17,000 plant and animal species are known to be threatened with extinction.

I often think that folks tasked with trying to preserve global biodiversity must feel like they're on the Titanic trying to keep the ship afloat using a coffee can to bail water. The pressures of development can be overwhelming.

But they have at least one thing going for them -- they know where to bail.

Focus, Focus, Focus on the Hotspots

When it comes to biodiversity, there are the haves and the have-nots: those rich with species and those poor. Amazingly, most of the world's land species are found in a surprisingly small fraction of the world's surface area.

In 1988, British ecologist Norman Meyers (Time magazine's 2007 Hero of the Environment and part-time faculty member at Duke's Nicholas School of the Environment) coined the term "biodiversity hotspot" to describe this phenomenon. In a paper published in Nature in 2000 Meyers and colleagues identified 25 biodiversity hotspots around the world that collectively contain up to half of the plant's biodiversity but cover only about 1-2 percent of the Earth's land surface [pdf]. For an indication of how things have been going, consider that Meyers et al estimated that those hotspots had previously covered almost 12 percent of the land surface.

At least Meyers and his cohorts know where to take the coffee cans to bail: to that 1-2 percent of land where the hotspots remain. (See map.)

We're Among the Megadiverse

While the concept of hotspots divides the world into regional haves and have-nots, another way to do it is by nation. The term "megadiverse" was created to describe those countries that "account for a high percentage of the world's biodiversity by virtue of containing very large numbers of species." While species know no borders, using official states to categorize biodiversity is helpful to ecologists who have to develop conservations plans within the parameters of local laws.

In 2000 the UN Environment Programme identified 17 megadiverse countries, which hold some 60-70 percent of the world's species [pdf]. (Since the term was first coined in the late 1980s, a variety of scientists and scientific groups have tweaked the megadiversity list, including slightly different sets of countries.) Identifying megadiverse countries instead of regions is spatially courser and concentrates biodiversity over a larger percentage of the globe: collectively the 17 nations cover about 40 percent of the world's non-glacial land area.

Those of us who count ourselves American will be proud to know that the United States is usually one of the 17. And while many of the other megadiverse countries (e.g., Congo, China) could conceivably fall out of that category because of threats on their habitats from development, poverty, or civil strife, I think we can be confident that the United States is there to stay. Our enlightened populace and progressive legislation designed to protect our natural wealth of biodiversity mean we're past the bailing game and into the protecting, preserving, and stewarding game. Really, no kidding.

Turns out, when it comes to DNA banking, we're pretty good savers.

 

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