Fisherman turned climate scientist Tero Mustonen set up Snowchange, a co-operative, to help rewild his native Finland. But, as peatlands and lakes slowly recover, a new question emerges: how much should humans continue to intervene with nature?

Millions of people need but can’t afford an air purifier. But a social entrepreneur, who just “happened to be in Beijing breathing dirty air”, decided to set off to understand the science, build his own devices and bust the myth that clean air had to be expensive.

The ambitious Great Green Wall project could have a huge impact – if, that is, it can be driven not just from the corridors of power but also by local citizens. In the Gambia, that’s starting to happen. But the clock is ticking.