For millions of years, mammals have evolved to master every environment on Earth, but the planet is changing rapidly, all thanks to one mammal in particular - humans. As mankind reshapes the face of the world, mammals must change with it if they are to survive, let alone thrive. Today, some are finding clever and surprising ways to make the most of this new wild, while others need a helping hand from us.

Water presents air-breathing mammals with some of the greatest challenges of any environment on Earth. Less than 2% of mammal species are considered truly marine mammals. Witness some of the most intimate and surprising behaviours of marine mammals.

Having honed their survival strategies over millennia, mammals have evolved to be masters of the cold. We journey across the globe, exploring a frozen world, from icy seas to snowcapped mountains and meet the unique mammals that call them home.

By pushing themselves and their bodies to the absolute limit, mammals have found remarkable ways to survive in the hottest places on Earth. From baking deserts, harsh dry spiny forests, barren desolate salt pans and even raging bush fires, mammals, with their remarkable intelligence, unique behaviours and incredible adaptations, have found ways to beat the heat.

Sir David Attenborough reveals why forests are the ultimate test of survival for mammals and how they have overcome the challenges of life in this multidimensional, complex and continually changing environment.