Some large sections of permafrost in Siberia have been thawing out in the last few years due to climate change. If the thaw continues apace (or speeds up) researchers worry that much more organic matter — leftover plant and animal leavings from thousands of years ago, like mammoth dung, that never fully decayed due to sustained below-freezing temperatures — will thaw out and start decomposing, which could significantly speed up climate change with massive doses of methane and carbon dioxide. “The deposits of organic matter in these soils are so gigantic that they dwarf global oil reserves,” says climate scientist Sergei Zimov. “This will lead to a type of global warming which will be impossible to stop.” The United Nations agreed in a recent report that large-scale permafrost thaw could be quite nasty, climate-wise, but since the bulk of permafrost is still frosty, it’s regarded as mostly a potential threat for now. But even the current thaw isn’t all bad, at least for some cash-strapped locals who comb Siberia’s no-longer-perma frost for mammoth tusks and skeletons which can net thousands of dollars apiece from museums and private collectors.