Filmed over four years and 31 countries, this latest collaboration between David Attenborough and the BBC Natural History Unit has presented a compelling portrait of how our planet works. In the final episode of A Perfect Planet, however, we find out how our fragile ecosystem is under threat as never before because of the impact of one rampant species — humans. In previous episodes we’ve learnt how the sun, weather, volcanoes and the oceans have shaped our uniquely hospitable environment and made an astonishing biodiversity possible. Now, though, a century and a half of human dependence on fossil fuels is bearing ugly fruit, as huge releases of CO2 have destabilised our climate, perhaps fatally.