Over thousands of years, the frozen earth swallowed up all manner of organic material, from tree stumps to woolly mammoths. Deforestation and wildfire-both acute problems in Yakutia-remove the protective top layer of vegetation and raise temperatures underground even more. As the air gets hotter, so does the soil. In Yakutia, where the permafrost can be nearly a mile deep, annual temperatures have risen by more than two degrees Celsius since the Industrial Revolution, twice the global average. Russia has the worldвЂ™s largest share: two-thirds of the countryвЂ™s territory sits on permafrost. It now lies beneath nine million square miles of EarthвЂ™s surface, a quarter of the landmass of the Northern Hemisphere. The soil that remained frozen year-round came to be known as permafrost.

Around eleven and a half millennia ago, the last ice age gave way to the current interglacial period, and temperatures began to rise. As the planet cycled between glacial and interglacial periods, much of that frozen ground thawed, only to freeze again, dozens of times. Three million years ago, as continent-Вsize glaciers pulsed down from the poles, temperatures in Siberia plunged to minus eighty degrees Fahrenheit and vast stretches of soil froze underground. It was impossible to tell through the AntonovвЂ™s dusty porthole, but below me the ground was breathing, or, rather, exhaling. The plane rumbled upward, climbing above a horizon of larch and pine, and lakes the color of mud. I was strapped to a hard metal seat inside the cabin of an Antonov-2, a single-Вengine biplane, known in the Soviet era as a kukuruznik, or corn-crop duster.

This content can also be viewed on the site it originates from.ДЇlying over Yakutia, in northeastern Russia, I watched the dark shades of the boreal forest blend with patches of soft, lightly colored grass.

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