The meteoric rise of renewable energy has consequences for our electricity supply. While coal and gas fired power stations can generate electricity whenever you need it, renewables are intermittent by nature. So we need a backup plan for when the wind stops or the sun goes down.
All over the world, engineers and scientists are racing to solve one key problem; how to safely and efficiently store electricity at a huge scale but at a low cost. The quest is producing some truly remarkable ideas and this episode details three of them.

One man has seen more of the natural world than any other. This unique feature documentary is his witness statement. In his 93 years, David Attenborough has visited every continent on the globe, exploring the wild places of our planet and documenting the living world in all its variety and wonder. Now, for the first time he reflects upon both the defining moments of his lifetime as a naturalist and the devastating changes he has seen. Honest, revealing and urgent, this film is a powerful first-hand account of humanity's impact on nature and a message of hope for future generations.

The last episode explores Mescaline, the psychoactive molecule in San Pedro and peyote cacti, a sacred medicine that Native Americans have had to fight for the right to use. At the Indigenous practices there's always an elder, someone who knows the territory very well, who's presiding. There's usually a group, a community is involved, There's always an intention, a purpose to what you're doing, and you're treating it as sacred, in order to achieve altered states of consciousness, which contribute to worship in various ways, or celebration or healing.
But maybe all this is not so new to Western culture after all. In the old Greek histories of Eleusis, people who were initiated there got the drink, the kykeon, and then they had the illumination. The precise recipe is a mystery, but we know that the kykeon was a psychoactive brew that was used at the Eleusinian mysteries, a sacred annual ritual of enlightenment practiced by some of the world's greatest minds including Socrates, Plato, and Aristotle. So why did this ritual come to an end more than 1,000 years ago? Was the possibility of illumination or achieving a higher consciousness considered threatening to the powers that be? Have the drug wars been merely an extension of that fear?
Psychedelics has a major part in how we can heal as a community, how we can heal as a city, and how we can heal as a country. The current renaissance of psychedelics could not come at a better time as the world confronts a crisis in mental health. But psychedelics have much to offer. The psychedelic experience changes the mind in ways that will help scientists better understand how it works. All these altered states allow us to probe what is the greatest mystery in all of nature. The emergence from mere matter of something as miraculous as consciousness. But an even bigger question is whether psychedelics might help us address the environmental crisis of how we think about our place in nature. One of the greatest gifts of psychedelics is how they reanimate the natural world, allowing us to perceive the subject, the spirit of all species, not just our own. And to feel a deeper sense of interconnectedness with nature.

A guide to plants that thrive in human-dominated environments, including trees that grow across canyons in India, which have developed into living bridges. The programme examines the origins of growing crops and the ongoing influence on the world of wild plants, as well as efforts to preserve species, from snipers firing pesticide bullets from helicopters to fend off invasive plants to plants being painstakingly pollinated using a paintbrush.

Plants that have developed to thrive in the desert, including cacti that grow in the shade of other trees and collect water in pleated trunks that expand and contract - but can also find themselves a host to other plants, like desert mistletoe. This programme also reveals how tobacco plants being eaten by caterpillars are able to summon the creatures' natural predators, and how tumbleweeds roll across the landscape, only unfurling and growing when they encounter rain.

Will explore the strategy, deception and feats of engineering plants use to thrive in the changing weather of different seasons. In the face of conditions ranging from ice and snow to raging fires, survival is often a question of perfect timing - particularly when contending with intense competition and surprising predators.
In this episode, David Attenborough travels to Finland to show one of the most extreme examples of seasonal plant life in the Arctic Circle. He also travels to California to see how climate change is affecting giant sequoias. These ancient trees like all other seasonal plants depend on the predictability of the seasons and our current changing climate threatens their survival.