On naked patches of land in western Canada and United States, scientists are planting trees that don't belong there. It's a bold experiment to move trees threatened by global warming into places where they may thrive amid a changing climate.

Take the Western larch with its thick grooved bark and green needles. It grows in the valleys and lower mountain slopes in British Columbia's southern interior. Canadian foresters are testing how its seeds will fare when planted farther north - just below the Arctic Circle.

Something similar will be tried in the lower 48 US states. Researchers will uproot moisture-loving Sitka spruce and Western redcedar that grace British Columbia's coastal rainforests and drop their seedlings in the dry ponderosa pine forests of Idaho.

All of this swapping begs the question: Should humans lend nature a helping hand?

With global warming threatening the livelihoods of certain plants and animals, this radical idea has moved to the forefront of debate and triggered strong emotions among conservationists.

About 20 to 30 percent of species worldwide face a high risk of becoming extinct possibly by 2100 as global temperatures rise, estimated a 2007 report by the Nobel-winning international climate change panel. The group noted that current conservation practices are "generally poorly prepared to adapt to this level of change."

Deliberately moving species has long been opposed by some, who believe we should not play God with nature and worry that introducing an exotic species could upset the natural balance and cause unforeseen ripple effects.

Others counter that given the grim realities of a warming planet, it would be irresponsible not to intervene as a conservation strategy. Otherwise, trees may suffer from ravaging disease epidemics while critters unable to head north may find themselves trapped in a declining landscape.

"A tree that we plant today better damn well be adapted to the climate for 80 years, not just the climate today," said Greg O'Neill, a geneticist with the British Columbia Ministry of Forests and Range. "We have to think long-term."

O'Neill is heading the experiment that will transform certain North American forests into climate change laboratories. The large-scale, first-of-its-kind test involves purposely planting seeds from more than a dozen timber species outside their normal comfort zone to see how well they survive decades from now.

Outsiders are also keenly watching the experiment as a test case for what is professionally known as "assisted migration."

"We'd all prefer species to move naturally," said Duke conservation biologist Stuart Pimm. But "sometimes you just can't get there from here."

This spring, crews fanned across rugged mountains and began the first dozen plantings on cleared forestland in British Columbia's southern interior and on a private plot near Mount St Helens in Washington State.

Each test site contains some 3,000 seedlings, on average 30 centimeters tall, planted side-by-side on two hectares. Fluorescent pin-flags and aluminum stakes dot the corners so that scientists can come back every five years to document their health.

The project will eventually include 48 plots around British Columbia, Washington State, Oregon, Montana and Idaho. It will test the ability of 15 tree species to survive in environments colder and hotter than they're used to.

O'Neill knows that some trees will die and others will go through erratic growth cycles. He estimates about 50 percent of the plantings may die, but he needs to collect the data to get an idea of how much they can tolerate.

"It will take several extreme climatic events to find out the winners and losers," he said.

(China Daily via Agencies July 21, 2009)