Catalog for life on earth

But over the long term, a tree's greatest value may lie in its potential for guiding conservation strategies as the international community strives to preserve the planet's biodiversity in the face of what some researchers term the planet's sixth extinction event.

Unchecked, human activities are conducting an enormous, uncontrolled evolutionary experiment, say biologists Andrew Knoll of Harvard University and Norman Myers of Oxford University in England.

Humans "are 'deciding' on evolution's future in virtually a scientific vacuum – deciding all too unwittingly, but effectively and increasingly," the two scientists have written.

The fossil record suggests that it takes roughly 5 million years for earth's biosphere to recover from a major extinction event, they say. While no one can forecast what may happen to a given species at the end of that period, the two add that biologists can provide a sense for how reduced diversity could affect the broader course of evolution.

For example, they suggest that large mammals, which have relatively slow reproductive cycles, could give way to species that adapt more quickly to changes. This could lead to an increase in the number of ecosystems dominated by organisms that today we would consider pests and weeds. In addition, diversity could be expected to increase among species that thrive in human-affected ecosystems.

In total, while evolution certainly would continue, it could yield a more homogenized set of ecosystems with much less diversity overall than exists today.

Conservation efforts that once focused on high-profile species have largely shifted toward projects that preserve ecosystems inhabited by endangered species.

Yet, researchers say, conservationists may need to take yet another conceptual leap by designing projects in ways that preserve "the evolutionary processes at risk."

Drs. Myers and Knoll posit that it is more important to maintain the "potential for diversity generation" and the "functional groups that increase the potential for recovery" than individual species.

"What do we save that preadapts the world to rediversify?" asks the NSF's Wheeler.

He suggests that the importance of preserving old-growth forests in northern California may rest at least as much on preserving his "favorite poster child" – a group of primitive wingless insects known as bristletails – as it does on preserving the spotted owl.

One species of bristletail in particular was known only from fossils and was thought to have been extinct for millions of years. Then in the 1960s, Wheeler says, live specimens of these insects were found in the old-growth forests of northern California's coast.

New molecular analyses suggest that the "fossil" species is the sister to the line that begat all 800,000 winged-insect species known today. The creature may represent an evolutionary branching point that could in the future repeat its diversification.

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