Sir John Franklin would not recognize today's Arctic.

When the British explorer set out through the vast archipelago at the edge of North America in 1845, he had reason to believe he could find the Northwest Passage -- a valuable shipping route connecting the Atlantic and Pacific. Much of the continent's northern coast had been explored; his two ships, built to withstand mortar blasts and reinforced for polar conditions, had survived a recent Antarctic expedition. But the Terror and the Erebus became icebound short of their goal, and all 129 crewmembers died in the frozen wastes.

The Far North's vagaries and extremes have long shielded it from such incursions and the development that almost inevitably follows, leaving much of its landscape today with the same roaringly silent, unbroken horizons that swallowed Franklin and his men.

In September of 2007, though, the Northwest Passage was ice-free and fully navigable for the first time since satellites began photographing the region. The event was sobering but not unexpected: Arctic sea ice has declined for decades as the region has warmed twice as much as the rest of the globe, thanks to man-made climate change. By mid-century, scientists believe the Passage will be ice-free enough some summers to be accessible even to normal ships, while the North Pole's ice may thin enough for icebreakers to crush their way through.

As the region's natural barriers crumble, companies and nations are rushing to explore, and eventually extract, rich and once difficult-to-reach deposits of hydrocarbons and minerals. It seems that even this inhospitable place will not be beyond the reach of industry for much longer.

Southern California's Mojave Desert is in a similar position, though for different reasons. As contributing editor Judith Lewis Mernit reports in this issue's cover essay, the deadly heat, aridity and glaring sun that have protected the Mojave's overwhelming emptiness are now attracting a spate of gigantic solar power projects meant to help address climate change.

Good planning in the Mojave can spare rare species, key habitats and especially beautiful places from the onslaught of renewable power projects, Lewis Mernit writes. And sacrificing parts of the desert may be necessary to help lessen the transformation not only of the Arctic, but the Mojave itself.

Still, in both places we will witness undeniable, heartbreaking loss. Every new oil drilling platform or strip mine, every six-square-mile solar plant or 23-square-mile wind project that moves into the soaring spaces that until recently so ably rejected our presence -- devoured it with storm, mummified it with heat or cold -- makes the world a little smaller. This loss is as much internal as external, as much cultural as ecological. It is ultimately the loss of humility. The sort of humility that is, perhaps, the only thing that can stop our wholesale remaking of the Earth.