Visible from space, the Okavango Delta is Africa's largest remaining intact wetland wilderness. This shining delta in landlocked Botswana is the jewel of the Kalahari, more valuable than diamonds to the world's largest diamond producer and celebrated in 2014 as our planet's 1000th UNESCO World Heritage Site. Now, what you see here are the two major tributaries, the Cuito and the Cubango, disappearing up north into the little-known Angolan highlands. This is the largest undeveloped river basin on the planet, spanning an area larger than California. These vast, undeveloped Angolan watersheds were frozen in time by 27 years of civil war. In fact, Africa's largest tank battle since World War II was fought over a bridge crossing the Okavango's Cuito River. There on the right, disappearing off into the unknown, into the "Terra do fim do mundo" -- the land at the end of the earth, as it was known by the first Portuguese explorers. In 2001, at the age of 22, I took a job as head of housekeeping at Vundumtiki Camp in the Okavango Delta ... a patchwork mosaic of channels, floodplains, lagoons and thousands upon thousands of islands to explore. Home to the largest remaining population of elephants on the planet. Rhinos are airlifted in C130s to find sanctuary in this wilderness. Lion, leopard, hyena, wild dog, cheetah, ancient baobab trees that stand like cathedrals under the Milky Way. Here, I discovered something obvious: wilderness is our natural habitat, too. We need these last wild places to reconnect with who we really are. We -- all seven billion of us -- must never forget we are a biological species forever bound to this particular biological world. Like the waves connected to the ocean, we cannot exist apart from it -- a constant flow of atoms and energy between individuals and species around the world in a day and out into the cosmos. Our fates are forever connected to the millions of species we rely on directly and indirectly every day. Four years ago, it was declared that 50 percent of all wildlife around the world had disappeared in just 40 years. This is a mass drowning of 15,000 wildebeests that I witnessed in the Maasai Mara two years ago. This is definitely our fault. By 2020, global wildlife populations are projected to have fallen by a staggering two-thirds. We are the sixth extinction because we left no safe space for millions of species to sustainably coexist. Now, since 2010, I have poled myself eight times across the Okavango Delta to conduct detailed scientific surveys along a 200-mile, 18-day research transect. Now, why am I doing this? Why am I risking my life each year? I'm doing this because we need this information to benchmark this near-pristine wilderness before upstream development happens. These are the Wayeyi river bushmen, the people of the Okavango Delta. They have taught me all I know about the Mother Okavango -- about presence in the wild. Our shared pilgrimage across the Okavango Delta each year in our mokoros or dugout canoes -- remembers millenia living in the wild. Ten thousand years ago, our entire world was wilderness. Today, wilderness is all that remains of that world, now gone. Ten thousand years ago, we were as we are today: a modern, dreaming intelligence unlike anything seen before. Living in the wilderness is what taught us to speak, to seek technologies like fire and stone, bow and arrow, medicine and poison, to domesticate plants and animals and rely on each other and all living things around us. We are these last wildernesses -- every one of us. Over 80 percent of our planet's land surface is now experiencing measurable human impact: habitat destruction and illegal wildlife trade are decimating global wildlife populations. We urgently need to create safe space for these wild animals. So in late 2014, we launched an ambitious project to do just that: explore and protect. By mid-May 2015, we had pioneered access through active minefields to the undocumented source lake of the Cuito River -- this otherworldly place; an ancient, untouched wilderness. By the 21st of May, we had launched the Okavango megatransect ... in seven dugout canoes; 1,500 miles, 121 days later, all of the poling, paddling and intensive research got us across the entire river basin to Lake Xau in the Kalahari Desert, 480 kilometers past the Okavango Delta. My entire world became the water: every ripple, eddy, lily pad and current ... any sign of danger, every sign of life. Now imagine millions of sweat bees choking the air around you, flesh-eating bacteria, the constant threat of a landmine going off or an unseen hippo capsizing your mokoro. These are the scenes moments after a hippo did just that -- thrusting its tusks through the hull of my boat. You can see the two holes -- puncture wounds in the base of the hull -- absolutely terrifying and completely my fault. (Laughter) Many, many portages, tree blockages and capsizes in rocky rapids. You're living on rice and beans, bathing in a bucket of cold water and paddling a marathon six to eight hours every single day. After 121 days of this, I'd forgotten the PIN numbers to my bank accounts and logins for social media -- a complete systems reboot. You ask me now if I miss it, and I will tell you I am still there. Now why do we need to save places we hardly ever go? Why do we need to save places where you have to risk your life to be there? Now, I'm not a religious or particularly spiritual person, but in the wild, I believe I've experienced the birthplace of religion. Standing in front of an elephant far away from anywhere is the closest I will ever get to God. Moses, Buddha, Muhammad, Jesus, the Hindu teachers, prophets and mystics, all went into the wilderness -- up into the mountains, into the desert, to sit quietly and listen for those secrets that were to guide their societies for millennia. I go into the Okavango on my mokoro. You must join me one day. Over 50 percent of the remaining wilderness is unprotected. A huge opportunity -- a chance for us all. We need to act with great urgency. Since the 2015 megatransect, we have explored all major rivers of the Okavango River basin, covering a life-changing 4,000 miles of detailed research transects on our dugout canoes and our fat-tire mountain bikes. We now have 57 top scientists rediscovering what we call the Okavango-Zambezi water tower -- this vast, post-war wilderness with undocumented source lakes, unnamed waterfalls in what is Africa's largest remaining Miombo woodland. We've now discovered 24 new species to science and hundreds of species not known to be there. This year, we start the process, with the Angolan government, to establish one of the largest systems of protected areas in the world to preserve the Okavango-Zambezi water tower we have been exploring. Downstream, this represents water security for millions of people and more than half of the elephants remaining on this planet. There is no doubt this is the biggest conservation opportunity in Africa in decades. Over the next 10 to 15 years, we need to make an unprecedented investment in the preservation of wilderness around the world. To me, preserving wilderness is far more than simply protecting ecosystems that clean the water we drink and create the air we breathe. Preserving wilderness protects our basic human right to be wild -- our basic human rights to explore. Thank you. (Applause)