Trees are covering more of the land in rich countries

COLM STENSON drives around County Leitrim, pointing out new tree plantations. In this corner of Ireland, close to the border with Northern Ireland, conifers seem to be springing up all around. The encroachment is not just visual. Mr Stenson, who is a police officer as well as a cattle farmer, recently received a bill from his feed supplier. It came with a brochure advertising easy returns from converting farmland into woods. Forestry companies tout for business in the local livestock market. The forest is “closing in”, he says.

In the 1920s, when Ireland became independent, it was thought to have just 220,000 acres (90,000 hectares) of woods, covering about 1% of the land. Once-extensive forests had been shrinking for centuries. Farmers had cut trees for firewood and to clear space for animals and crops since at least the fourth millennium BC; some tree species were wiped out by disease. Beginning in the 17th century, most of the trees that remained were felled to build ships or fed into charcoal kilns to fire the Industrial Revolution.