Wild forests are magnificent, but they are also incompatible with lots of things that human societies like to do. In the 1990s, a Scottish geographer, Alexander Mather, coined the phrase “forest transition” to describe – roughly speaking – how nations cut down their trees, realise they have cut down their trees, and start, eventually, haltingly, to plant trees again.

One of the easiest things to forget, living in a deforested nation, is that people cut down trees to improve their lives

Papua New Guinea has not gone through its forest transition yet. According to the Center for International Forestry Research, it is probably at stage two, known as “frontier conditions”, where things really start to speed up. According to the government, some 15m of its 37m remaining hectares of forestthe early 1990s. He and his research partner, a Czech entomologist named Vojtech Novotny, were besieged by business offers during the carbon craze just over five years ago. They steered clear, and have largely stayed out of the sensitive politics of REDD+ ever since. But they happen to possess some of the most detailed data ever compiled about Papua New Guinea’s trees, including how much carbon they contain.

In 2010, Weiblen and Novotny established a 50-hectare rainforest research plot about 100km west of Madang, as part of a network of international sites administered by the Smithsonian Tropical Research Institute in Panama. Over the next three years, researchers – mostly local villagers – proceeded to count, measure, and record the stem of every tree in the plot more than 1cm