The march of the larch: the Treeline is now encroaching on the arctic tundra

Covering 20 per cent of the Earth’s surface, the boreal forest is the largest living system, or ‘biome’, on land. It contains one third of all the planet’s trees and encircles much of the northern hemisphere in a halo of green. The northernmost extent of this forest, called the treeline, marks the point beyond which it is too cold for trees to grow.

This is perhaps not where you’d expect to find Ben Rawlence, an author and journalist whose previous books have focused on humanitarian crises in Africa. But, as he explains in The Treeline, things are changing alarmingly fast in this biome: ‘The trees are on the move. They shouldn’t be. And this sinister fact has enormous consequences for all life on Earth.’

To tell the story of this changing natural frontier, Rawlence focuses each of his chapters on one of six tree species that dominate the treeline — Scots pine, birch, larch, spruce, poplar and rowan, or mountain ash. Each, he explains, is specially adapted to survive climate change (all bounced back after multiple Ice Ages) and together they can offer us ‘a glimpse of what, after the great transformation currently unfolding on Earth, will remain’.

With the warming climate, however, the natural cycles of these trees are being disrupted. Rawlence describes the annual fires sweeping through the Siberian boreal forest. In 2019, an area larger than Austria burned. Other changes, though less visible, are no less insidious. In Norway, rising temperatures are pushing birch trees north onto arctic tundra, where they are causing the mass die-off of the under-snow lichen that reindeer depend on. In the face of this privation, many reindeer are now choosing to consciously abort their unborn calves.