In mid-July 2016, satellites observed dense smoke over north-central Russia. Many of the fires appeared in the tundra-taiga intersection, where boreal forest gives way to low-lying vegetation and permafrost. The tundra is an important carbon sink, storing greenhouse gases in its soils. But the tundra is vulnerable to rising global temperatures, which dry out peat and turn it into prime kindling for wildfire. Fires in the far north, particularly in peatlands, produce huge quantities of carbon dioxide and methane, further fuelling global heating.

Photograph: MODIS/Aqua/NASA