many countries have committed to planting more trees to soak up c02 but my guide gwyn says the mix of trees planted is crucial to success. when there is a mixed amount of tree species within a forest, so the more biodiverse we have in terms of what's above the ground, the more biodiverse is below the ground and the more carbon ends up in the soil, where it's stored for a very, very long time. so does he think nature alone could lead us to carbon neutrality? this is a recent plantation. there's around about 15—20 different tree and shrub species and this was planted last year, in the last winter, which is a year ago for us now but, as you can see, they're really not getting anywhere above waist height. that really puts emphasis on how we have to conserve our mature forests because this plantation here is going to probably take maybe 20, 30