How do you achieve net-zero carbon emissions in just fifteen years? In Finland, a fisherman-turned-climate scientist believes he has part of the answer: re-wilding the country’s peat fields. Gabriel Gatehouse travels to the country's frozen north to meet Tero Mustonen, as he battles lobbyists and vested interests in government and the peat industry, in a race to mitigate the consequences of climate change. Michael Gallagher producing.