There's three times more carbon in the soil than in the atmosphere - but that carbon's being released by deforestation and poor farming.

Hurting the soil affects the climate in two ways: it compromises the growth of plants taking in carbon from the atmosphere, and it releases soil carbon previously stored by worms taking leaf matter underground.

Fans of re-wilding say the best way to protect soil and fight climate change is to let forests grow back, but some farmers believe they can keep producing food while changing the way they farm to keep the soil in good shape.