Covering one tenth of all species on the planet, Freshwater is a rich, diverse habitat filled with never-ending surprises. The fourth episode is set beneath the Yucatan Peninsula and spanning diverse locations like the rainforests of Costa Rica and the Kalahari Desert and presents a vivid exploration of how freshwater shapes life on Earth. The narrative journeys through the unique breeding rituals of gliding tree frogs in Costa Rica, the strategic hunting methods of mugger crocodiles in Sri Lanka, and the astonishing adaptations of wildlife in the Okavango Delta. It highlights the critical role of freshwater in supporting diverse ecosystems, from the teeming fish species in Lake Malawi to the perilous journey of gobies in Bioko.
The episode also addresses human impact, showcasing the extensive irrigation system in Pakistan and its unintended consequences on local wildlife, like the endangered Indus river dolphin. This captivating chapter not only showcases nature's marvels but also underscores the delicate balance between human needs and wildlife conservation.

Grasslands cover one quarter of all land and support the vast gatherings of wildlife, but to survive here animals must endure the most hostile seasonal changes on the planet. From Asia's bizarre-looking Saiga antelope to the giant anteaters of Brazil, grassland animals have adapted in extraordinary ways to cope with these extremes. In the flooded Okavango, lions take on formidable buffalo in epic battles, on the savannah bee-eaters take advantage of elephants to help catch insects and, on the freezing northern tundra, caribou embark on great migrations shadowed by hungry Arctic wolves.

The great flood in the Okavango turns 4,000 square miles of arid plains into a beautiful wetland. Elephant mothers guide their families on an epic trek across the harsh Kalahari Desert towards it, siphoning fresh water from stagnant pools and facing hungry lions. Hippos battle for territory, as the magical water draws in thousands of buffalo and birds, and vast clouds of dragonflies. Will the young elephant calves survive to reach this grassland paradise? The experienced mother elephants time their arrival at the delta to coincide with the lush grass produced by the great flood.
In a TV first, the programme shows the way they use their trunks to siphon clean water from the surface layers of a stagnant pool, while avoiding stirring up the muddy sediment on the bottom with their feet. Lechwe swamp deer, zebras, giraffes, crocodiles and numerous fish and thousands of birds arrive in the delta. And, in a phenomenon never before filmed in the Okavango, thousands of dragonflies appear - seemingly from nowhere - within minutes of the flood arrival, mating and laying eggs. As the flood finally reaches its peak, elephants and buffalo, near the end of their epic trek across the desert, face the final gauntlet of a hungry pride of lions. In a heart-wrenching sequence, a baby elephant is brought down by a lion in broad daylight.

Planet Earth is quite simply the greatest nature/wildlife series ever produced. The ultimate portrait of our planet looks at the key factors that shape our natural history. The sun and fresh water dominate the lives of all animals and plants on Earth and trigger seasonal migrations, small and large.