The African Great Lakes: Ancient Waters That Shape Modern Africa

Podcast Transcript

The African Great Lakes are some of the largest bodies of freshwater on Earth, yet they weren’t carved by ice, but by a continent literally tearing itself apart.

These lakes are older, deeper, and more biologically diverse than almost any others on the planet, home to thousands of unique species and tens of millions of people who depend on them every day.

But their story isn’t just geological or ecological, it’s human, evolutionary, and ongoing.

Learn more about the African Great Lakes and why they are unlike any lakes on Earth, on this episode of Everything Everywhere Daily.

The African Great Lakes are one of the most extraordinary freshwater systems on Earth, a chain of massive lakes stretching across East and Central Africa along the tectonic scar of the East African Rift.

These lakes span ten countries and collectively hold roughly a quarter of the world’s unfrozen freshwater.

Unlike the North American Great Lakes, of which there are unquestionably only five, the number of African Great Lakes varies from list to list. The core lakes, which are usually included, are Victoria, Tanganyika, Malawi, Turkana, Albert, Edward, and Kivu.

All of these lakes, save for one, which I’ll get to in a bit, have a similar origin and were created through the same process.

These lakes, while superficially similar to the North American Great Lakes, are very different.

The North American Great Lakes are very young. They were created about 10,000 to 12,000 years ago at the end of the last ice age. As glaciers retreated, they left enormous depressions which were subsequently filled with meltwater.

By contrast, the African Great Lakes are tectonic in origin and vastly older. They were created when the African continent split millions of years ago.

In a previous episode, I explained how the East African Rift is slowly splitting Africa, and tens of millions of years from now, the Eastern part of Africa will become a new continent.

As the crust stretches, it fractures and drops down in long troughs called grabens. Over millions of years, rainfall, rivers, and groundwater filled these basins, forming deep rift lakes.

The lakes can be found in Africa across a region in the shape of the letter Y with two branches: the Eastern Rift Valley and the Western Rift Valley. All of the lakes, again save for one major exception, are created by this process.

That is why the lakes tend to be long, narrow, and extremely deep. Lake Tanganyika is the second-deepest lake in the world, with a maximum depth of 1,470 meters (4,823 feet).

The exception is Lake Victoria, the largest of the Great Lakes.

Lake Victoria, the largest of the African Great Lakes by surface area and the world’s largest tropical lake, formed quite differently. It occupies a shallow depression between the two arms of the rift rather than sitting within the rift itself.

It is thought to have dried up almost completely around 17,000 years ago during an arid period, and then refilled as wetter conditions returned.

The differences between the North American and African Great Lakes extend beyond their creation.

In terms of climate, the North American Great Lakes lie in a temperate zone with distinct seasons, winter ice cover, and seasonal temperature stratification.

Most of the African Great Lakes lie near the equator, in tropical or subtropical climates. Lakes Tanganyika and Malawi are permanently stratified.

That means warm surface waters and cold deep waters almost never mix, with major consequences for oxygen levels and nutrient cycling.

The deep waters of Tanganyika are largely anoxic, or devoid of oxygen, and essentially dead zones below a certain depth, whereas the North American lakes mix and oxygenate more fully.

Lake Tanganyika is extraordinary not just for its depth but for what that depth means in terms of time. The water in its deepest layers has been isolated from the surface for potentially tens of thousands of years, and sediment cores drilled from its floor contain an uninterrupted climate and environmental record stretching back millions of years.

Lake Kivu, shared between the Democratic Republic of Congo and Rwanda, sits atop enormous reserves of dissolved methane and carbon dioxide in its deep waters.

In a previous episode, I covered the rare natural disaster called a limnic eruption. It occurs when a massive eruption of CO2, which is heavier than air, comes out of a lake and spreads in the countryside.

It is silent, completely invisible, and incredibly deadly. In 1986, a limnic eruption in Cameroon killed over 1,700 people.

If such an eruption occurred on Lake Kivu, it could affect over 2,000,000 people.

Lake Malawi is so deep and clear that visibility can exceed 20 meters, making it one of the finest freshwater diving destinations in the world. Its water is remarkably clean by African standards, though agricultural runoff and population pressure are threatening this clarity.

If there is one aspect of the African Great Lakes that genuinely astonishes scientists, it is their biology. The lakes, particularly Tanganyika, Malawi, and Victoria, are considered among the world’s most important laboratories for understanding how species multiply.

The best-known example of adaptive radiation in the African Great Lakes is the cichlid fish. This family of freshwater fish began with a single ancestral species that colonized a new environment and then rapidly diversified into numerous descendant species, sometimes hundreds or even thousands. Each new species occupies a unique ecological niche, a process biologists call adaptive radiation.

Lake Malawi alone is estimated to host between 500 and 1,000 cichlid species, the vast majority of which are found nowhere else on Earth. Lake Victoria is thought to have generated several hundred species from a single ancestor in as little as 15,000 years, one of the fastest-known instances of vertebrate speciation.

Lake Tanganyika, the oldest and deepest, hosts around 250 cichlid species and is considered the ancestral source of cichlid diversity across the region.

These cichlids display a spectacular range of feeding strategies, body shapes, colors, and behaviors. Some are algae scrapers, some are specialized mollusk crushers, some are open-water plankton feeders, and, fascinatingly, some are scale-eaters that sneak up on other fish and bite off their scales.

There are even mouthbrooding species in which parents incubate eggs in their mouths for weeks.

The lakes are enormously important to the global aquarium industry because of their cichlid fish. African cichlids are prized for their vivid color, territorial behavior, and relative hardiness, and they dominate large segments of the freshwater aquarium trade, supporting both local export economies in Africa and a worldwide network of breeders and enthusiasts.

Beyond cichlids, the lakes host an array of other life. Lake Tanganyika contains unique invertebrates, including jellyfish, snails, and crabs that superficially resemble marine species, a legacy of the lake’s ancient, stable chemistry.

Hippos and crocodiles are abundant in and around nearly all the lakes. The surrounding wetlands and shorelines are critical habitat for enormous populations of birds, including African fish eagles, herons, storks, and millions of migratory birds. Papyrus swamps fringing Lake Victoria provide breeding and nursery habitat for dozens of fish species.

Tragically, the introduction of Nile perch into Lake Victoria in the 1950s and 1960s caused one of the most severe ecological disasters in freshwater history.

The Nile perch is a large, predatory fish, that was introduced deliberately to boost fisheries production. It devastated the lake’s native cichlid population, driving an estimated 200 species to extinction, the largest mass extinction of vertebrates in recorded history.

In contrast, the North American Great Lakes have almost no endemic species that exist only in the Great Lakes.

The African Great Lakes are not just about geology and biology.

For the approximately 50 million people living in the immediate vicinity of the African Great Lakes and the many millions more who depend on their watersheds, these bodies of water are not merely scenic features. They are the foundation of daily life.

Fishing is the most direct economic link. Lake Victoria alone supports one of the world’s largest freshwater fisheries, employing an estimated 200,000 or more fishermen directly and millions more in processing, transport, and trade.

The Nile perch fishery, despite its ecological cost, generates hundreds of millions of dollars in export revenue annually, with much of the catch shipped to Europe and Asia.

Kapenta and Kariba are a critical source of cheap animal protein for landlocked populations in Zambia, Tanzania, and the DRC. In Malawi, a sardine-like fish called usipa is central to both nutrition and culture.

The lakes are vital freshwater sources for drinking, irrigation, and industrial use across the region. In a continent where water scarcity is a growing crisis, the lakes represent irreplaceable reserves. Several major cities, including Kampala, Uganda, Bujumbura, Burundi, and Mwanza, Tanzania, sit directly on lake shores and depend on them for municipal water supply.

Tourism, while underdeveloped relative to the lakes’ potential, contributes meaningfully to local economies. Lake Malawi National Park was designated a UNESCO World Heritage Site in 1984, recognized for its extraordinary cichlid diversity.

The lake’s clear, warm waters and sandy beaches draw international visitors for snorkeling, diving, and sailing. Lake Tanganyika similarly attracts divers and researchers, and its shores include Gombe Stream National Park in Tanzania, where Jane Goodall conducted her groundbreaking chimpanzee research beginning in 1960.

The lakes also play an important role in regional transportation. In areas with poor or nonexistent roads, lake ferries serve as lifelines, connecting communities.

On Lake Victoria, ferries link Uganda, Tanzania, and Kenya in journeys that would otherwise require long, difficult overland routes. The sinking of the MV Bukoba on Lake Victoria in 1996, with the loss of over 800 lives, illustrated both the scale of this lake traffic and the dangers posed by overloaded, poorly maintained vessels.

With ten different nations in the region, it should come as no surprise that the lakes have been a source of friction. In fact, multiple issues have arisen, becoming international sources of tension.

First, there are disputes over borders and control. Many lakes, such as Lake Malawi and Lake Victoria, are shared, and disagreements over where boundaries lie can lead to diplomatic tension and occasional confrontations, especially when fishermen cross into contested waters.

Second, competition over fisheries is a major source of friction. Fish stocks move freely, but national regulations do not, leading to overfishing, enforcement conflicts, and arrests when fishermen operate across borders.

Third, control of water flow and hydropower creates downstream disputes. For example, decisions affecting Lake Victoria influence the Nile River, which can impact countries far beyond the immediate lake region.

Fourth, environmental damage creates shared problems but uneven responsibility. Pollution, invasive species, and deforestation in one country can harm the entire lake, leading to blame and disagreements over who should act.

Fifth, natural resources beneath the lakes, such as oil in Lake Albert or methane in Lake Kivu, introduce economic competition and territorial disputes.

Despite these tensions, there are also significant efforts to collaboratively manage the lakes. Organizations like the Lake Victoria Fisheries Organization and the Nile Basin Initiative aim to coordinate policies, share data, and reduce conflict. These frameworks recognize a basic reality: none of the countries can manage these lakes effectively on their own.

When most people think of Africa, they might think of vast savannas, dense rainforests, or maybe even the Sahara Desert. However, Africa is also made up of water. In fact, an enormous amount of fresh water.

The African Great Lakes have ancient origins, making them among the most biologically diverse freshwater ecosystems on the planet. Despite having been formed millions of years ago, they are still highly relevant and important to the people who live near their shores today.