Pristine lands, by the strictest definition, no longer exist, scientists say. Atmospheric pollution has settled on every earthly surface...

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Pristine lands, by the strictest definition, no longer exist, scientists say.

Atmospheric pollution has settled on every earthly surface. Human-induced climate change is affecting ecosystems across the planet. Untrammeled landscapes are fragmented and shrinking.

Where is the last of the truly wild? The Wildlife Conservation Society, with the Center for International Earth Science Information Network at Columbia University, assembled satellite and land-use data to plot the extent of the global human footprint. On its colorful maps, the zones closest to pristine pop out as patches of leafy green.

Worldwide, the society found that 17 percent of land is still virtually untouched — mostly because it is inhospitable to humans. In areas capable of growing basic crops, and therefore most able to support people, untouched lands have diminished to 2 percent of the total.

Alaska holds the vast majority of least-altered lands in the United States. In the more settlement-friendly lower 48, the wildest areas have become islands ringed by interstates, farms, towns and cities, making up 0.9 percent of land.

Disputes on managing these areas, and other nearly pristine lands, continue. In May, the Bush administration canceled the so-called roadless rule imposed by the Clinton administration. The rule banned road-building in nearly 60 million acres of national forest, about the land mass of New York and Pennsylvania combined.

State governors now can recommend building in their roadless areas, perhaps for mining, logging or fire control, although final decisions on road construction come from the Forest Service.

On Thursday, Reps. Jay Inslee, D-Wash., and Sherwood Boehlert, R-N.Y., introduced a bill to restore the road ban.

Here are four of the wildest areas, which are largely, but not entirely, off limits to commercial uses.

Central Idaho wilderness

A crown jewel of American natural areas. National-forest lands surround protected wilderness zones in a rich, self-sustaining ecosystem.

Conditions: A Forest Service study found this area to be the healthiest part of the Columbia River basin.

Outlook: There is little pressure from sprawl or recreational development, given the rugged and remote terrain. But logging and road-building on national forest lands are possible.

Jarbidge wilderness

Of the lower 48 states, Nevada is the least imprinted by humans overall, according to the Wildlife Conservation Society. This wilderness region in the northern part of the state also includes parts of Idaho and Oregon.

Conditions: Heavy grazing in the 20th century damaged soils; mining also was prevalent early in the century.

Outlook: Grazing is now limited, and recreational use is light, owing to the region’s remoteness, so the wilderness is recovering well. It has some of the best air in the United States, and also good water quality.

Pennsylvania mountains

A rugged area in north-central Pennsylvania that includes the Tioga State Forest, home to elk, bald eagles and other wildlife.

Conditions: Deer overpopulation; mine waste in the watershed. A once-busy railway through the canyon is now a trail.

Outlook: The canyon area is protected wilderness. State officials are working with nearby communities on sustainable development.

Gulf coastal prairie

Conditions: About 1 percent of the wild grassland remains, in patches as small as 10 square miles.

Outlook: These areas are being rapidly degraded. Three percent of Texas land is under public control; conservation efforts rely mostly on private landowners.