Visible from space, Africa's Great Rift Valley runs four thousand miles from the Red Sea to the mouth of the Zambezi - a diverse landscape of erupting volcanoes, forest-clad mountains, spectacular valleys, rich grasslands, vast lakes and mighty rivers. Home to the greatest concentration of animals on Earth - lions, crocodiles, elephants, hippos and flocks of flamingos - and pastoralists such as the Maasai - this is a land in constant geological turmoil. Great Rift takes you to another world - a world of exotic extremes, where the forces of nature have shaped the landscape and so created a hotbed of evolution. It is the very cradle of mankind.
Episode 1 | Fire
The unique wildlife of East Africa’s volcanic mountains.
The Great Rift Valley provides the stage for an epic battle between trees and grass – its course influenced by volcanic eruptions, landscape and rainfall. On its outcome rests the fate of Africa’s great game herds. In the Rift’s savannas, grazers and their predators struggle to outwit each other, forcing one group of primates to develop a social system that paved the way for the evolution of mankind.
What connects the abyssal depths of the Red Sea to Tanzania’s active volcanoes, the scorching lava fields of Ethiopia’s Danakil Basin to the glacier-capped peaks of Mount Kenya? These extreme landscapes were all created by the Earth’s huge geological forces – and are now home to some of Africa’s toughest survivors.
As we travel through the Great Rift, we see the most dramatically altered landscape in the Earth’s recent history, and reveal the forces that are still building it. It is at its most dynamic in the Afar Depression, an alien landscape of volcanoes, glittering salt pans and fierce temperatures. Here, where the Earth’s crust is at its thinnest, the whole area seethes with volcanism as the land visibly stretches and cracks and the Great Rift continues to make its mark on the Earth.
Over 30 million years of this activity has created some of the world’s most stunning landscapes. In this time, half a million cubic kilometres of lava have poured out of the rift: it Is this that has made spectacular wildernesses, like the Ethiopian highlands, home to wildlife found nowhere else. We reveal the survival strategies that allow these specialists to make this harsh landscape their home: sure- footed Walia ibex and Gelada baboons using their extraordinary agility to find safety on the vertiginously steep cliffs; and the rare Ethiopian wolves, unlike their counterparts around the world, living as solitary hunters in order to survive.
Many of the Rift’s loftiest volcanoes now lie extinct, like the majestic Mount Kenya. Astride the tropical Equator, this snow-capped mountain gives rise to an extreme freeze-at-night, fry-by-day climate, creating an unusual home for some of the weirdest wildlife of the valley. Only here are frostbitten giant lobelias pollinated by beautiful iridescent sunbirds.
Beneath the volcanic lava slopes of nearby Mount Suswa, mysterious lava caves are visited by bats and baboons, while, up above, resident Maasai pastoralists condense their drinking water from steaming volcanic fumaroles and a still-smouldering crater encloses a secret garden of strange succulent plants.
Travel West, and the valley changes from grassland to true African jungle. Here, in the little-known mountains of southern Tanzania and Rwanda, we explore the mysterious lives of the unique animals found here, including the kipunji (a type of tree-living baboon). Often shrouded in mist, the Rwenzori Mountains of the Moon are Africa’s Noah’s Ark, providing a last refuge for the world’s largest primate, the mountain gorilla.
This incredible variety of life appears throughout the Great Rift, creating oasis after oasis of extraordinary diversity and unique adaptation to strange and challenging landscapes – a profusion of life to challenge anywhere on Earth.
Episode 2 | Water
Looking at the colourful wildlife of East Africa’s lakes and rivers.
The Great Rift Valley channels a huge diversity of waterways – rivers, lakes, waterfalls, caustic springs and coral seas – spanning from Egypt to Mozambique. Some lake and ocean deeps harbour previously unseen life-forms, while caustic waters challenge life to the extreme. But where volcanic minerals enrich the Great Rift’s waterways, they provide the most spectacular concentrations of birds, mammals and fish in all Africa.
The diverse landscapes of the Great Rift capture seasonal rains into a network of life-giving rivers – feeding the Nile, Congo and Zambezi – but also some of world’s deepest inland lakes, scalding geysers, crystal springs and shallow toxic soda lakes. During the long dry seasons, these water bodies become the focus for some the Africa’s most dramatic natural spectacles.
We reveal how the faulting and rifting that gave rise to the Red Sea has channelled East Africa’s rivers to provide a sanctuary for mighty gatherings of hippos and birds, and to provide a stage for encounters between thirst-crazed game herds and Africa’s greatest predators: lions and crocodiles.
Those same turbulent forces also created the valley’s spectacular freshwater lakes, thousands of feet deep. In glorious isolation, each lake has evolved its own unique species; Lake Malawi alone has more
species of fish than any other lake in the world, with over 500 species of cichlids (living jewels that are one of the evolutionary wonders of the world).
Swirling clouds far out on Lake Malawi turn out to contain literally billions of insects, the basis for an extraordinary ecosystem, involving co-operative spider-gangs, sardine-like fish shoals, swooping flocks of swifts and rare saucer-eyed cichlids lurking in the perpetual darkness of the lake depths.
Further North, chemicals leached from the Rift’s alkaline volcanoes have created some of Africa’s most inhospitable habitats: the caustic soda lakes. Yet even here, life here has managed to flourish. Flamingos are the only large animals that have adapted to life in this harsh world, and they gather in their tens of thousands.
At the Rift’s far northern end, Lake Asal lies 152 metres below sea level. It is the lowest point in Africa, and the most saline, barren body of water on Earth, but it may not always remain so. One day the activities of the Great Rift may lead to it flooding, joining it with the nearby Red Sea, itself created by the Rift over 30 million years ago, and now one of the most glorious underwater habitats on Earth.
The forces that created Africa’s deepest lakes are still at work. Djibouti is one of the few places on Earth where you can actually see the Earth’s crust tearing itself apart. Here, where the Great Rift enters the ocean, we plunge into the abyss, using state-of-the-art submersibles to reveal the Rift’s darkest secrets
Episode 3 | Grass
The spectacular game herds of East Africa’s grasslands.
The valley is the product of deep-seated geological forces which have spewed out a line of cloud-wreathed volcanoes stretching from Ethiopia to Tanzania. Their peaks provide a refuge for East Africa’s most extraordinary wildlife, including newly discovered and previously unfilmed species which have evolved surprising survival strategies to cope with their challenging mountain environment.
The dramatic split of Africa’s Rift Valley led to the formation of a habitat never before seen in Africa: open grassland savannah. As the tropical forests retreated and the savannahs encroached in their place, a raging battle commenced between the woods and the grasses. Shaped by fire, rain and the greatest concentration of wildlife on Earth, these savannahs are the most volatile landscapes in the Rift Valley.
The Great Rift’s active volcanoes of Ol Doinyo Lengai and Nyiragongo hint at a past that has seen thousands upon thousands of eruptions fill the valley floor with volcanic ash, providing the raw ingredients for tremendous diversity.
In the rain shadow of the Rift’s great volcanoes, the dry conditions and unique ash soils have stunted the growth of trees, but have created the perfect conditions for grasslands to flourish – home to Africa’s largest and most charismatic animals and the setting for its greatest wildlife spectacles.
This patchwork landscape of open spaces has created a unique challenge for primates, such as baboons, who have adapted their behaviour to savannah life by living in large social groups and forming strong emotional bonds.
All the wildlife here has a role to play in shaping the savannah. Huge elephants tear down trees and keep the woodlands at bay, whilst at night hefty hippos haul themselves out from the rivers and lakes in their thousands and attack the grasses. Kob perform a surprisingly intricate mating ritual in the short grass plains, and in the long grasses of Mountt Kenya widow birds entertain with spectacular leaps to attract a mate.
At night, the carnivores take over the savannah, and for the very first time new technology allows us to see a mother lioness teaching her cubs to kill, behaviour that has never been seen or filmed before. Also filmed for the first time, chimps sleep tight in their nests and one family that has been trapped in a forested gorge for 20 years find themselves stepping out into the savannah – could this be a reflection of the first steps of our early human ancestors?