subscribe
Apple | Spotify | Amazon |iHeart Radio | cast box | Podcast Republic | RSS | Patreon | fluoride | Facebook | IMDB
podcast transcript
The African Great Lakes are some of the largest bodies of freshwater on Earth, but rather than being carved out by ice, the continent literally ripped itself apart.
This lake is older, deeper and more biologically diverse than any other lake on Earth. It is home to thousands of unique species and tens of millions of people who depend on these lakes every day.
But their story is not just geological or ecological, it is human, evolutionary and ongoing.
In this episode of Everything Everywhere Daily, learn more about the Great Lakes of Africa and why they are unlike any other lake on Earth.
The African Great Lakes are one of the most extraordinary freshwater systems on Earth, a massive chain of lakes stretching across eastern and central Africa along the tectonic scar of the East African Rift.
These lakes span 10 countries and collectively hold about a quarter of the world’s unfrozen fresh water.
Unlike the North American Great Lakes, which undoubtedly have only five, the number of African Great Lakes varies from one list to another. Key lakes commonly included include Victoria, Tanganyika, Malawi, Turkana, Albert, Edward and Kivu.
With the exception of one, which I will explain in a moment, all of these lakes have similar origins and were created through the same process.
Although these lakes are superficially similar to the North American Great Lakes, they are very different.
The North American Great Lakes are very young. They were created near the end of the last Ice Age about 10,000 to 12,000 years ago. As the glacier retreated, it created massive depressions that were later filled with meltwater.
In contrast, the African Great Lakes have large structural origins and are much older. They were created millions of years ago when the African continent split apart.
In the last episode, we explained how the East African Fault is slowly dividing Africa, and that in tens of millions of years from now, eastern Africa will become a new continent.
As the shell stretches, it breaks and falls into a long trough called a graben. Over millions of years, precipitation, rivers, and groundwater filled this basin, forming deep rift lakes.
Lakes can be found in Africa spanning a region shaped like the letter Y, with two branches called the Eastern Rift Valley and the Western Rift Valley. With one important exception, all lakes are created by this process.
This is why lakes tend to be long, narrow, and extremely deep. Lake Tanganyika has a maximum depth of 1,470 m (4,823 ft), making it the second deepest lake in the world.
The exception is Lake Victoria, the largest of the Great Lakes.
On the surface, Lake Victoria, the largest of Africa’s great lakes and the world’s largest tropical lake, is shaped quite differently. It occupies a shallow depression between the two arms of the crack rather than being located within the crack itself.
It is thought to have dried up almost completely during a dry period about 17,000 years ago and then refilled when the environment became wet again.
The differences between the North American Great Lakes and the African Great Lakes extend beyond what created them.
In terms of climate, the North American Great Lakes are in a temperate zone with distinct seasons, winter ice cover, and seasonal temperature hierarchies.
Most of Africa’s Great Lakes are near the equator, in tropical or subtropical climates. Lake Tanganyika and Lake Malawi are permanently stratified.
This means that warm surface water and cold deep sea water rarely mix, greatly affecting oxygen levels and nutrient cycling.
The deep waters of Tanganyika are largely anoxic, or devoid of oxygen, essentially a dead zone below a certain depth, whereas North American lakes are more completely mixed and oxygenated.
Lake Tanganyika is special not only for its depth, but also for what that depth means in terms of time. The deepest layers of water have been isolated from the surface for potentially tens of thousands of years, and sediment cores drilled from the bottom contain an uninterrupted record of climate and environment dating back millions of years.
Lake Kivu, shared by the Democratic Republic of Congo and Rwanda, has huge reserves of dissolved methane and carbon dioxide in its deep waters.
In the last episode, we covered a rare natural disaster called a marginal eruption. It occurs when CO2, which is heavier than air, erupts in large quantities from lakes and spreads into rural areas.
It’s silent, completely invisible, and incredibly lethal. The 1986 metamorphic belt eruption in Cameroon killed more than 1,700 people.
If such an eruption were to occur in Lake Kivu, it could affect more than 2 million people.
Lake Malawi is so deep and clear that visibility exceeds 20 meters, making it one of the world’s best freshwater diving destinations. The water here is surprisingly clean by African standards, but this purity is threatened by agricultural runoff and population growth.
If there’s one aspect of Africa’s Great Lakes that truly amazes scientists, it’s their biology. Lakes, especially Lakes Tanganyika, Malawi and Victoria, are considered one of the world’s most important laboratories for understanding how species reproduce.
The best known example of adaptive radiation from the African Great Lakes is the cichlid fish. These freshwater fish began as a single ancestral species that colonized a new environment and 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.
It is estimated that there are between 500 and 1,000 cichlid species in Lake Malawi alone, many of which are found nowhere else on Earth. Lake Victoria is thought to have generated hundreds of species from a single ancestor in just 15,000 years, making it one of the fastest examples of vertebrate speciation.
Lake Tanganyika, the oldest and deepest, is home to approximately 250 species of cichlids and is considered the source of cichlid diversity throughout the region.
These cichlids display a variety of feeding strategies, body shapes, colors, and behaviors. Some are algae scrapers, some are specialist mollusk crushers, some are open water plankton feeders, and interestingly, some are scale predators that sneak up on other fish and nibble at their scales.
There are also mouth-breeding species where the parents incubate the eggs in their mouths for several weeks.
The lake is incredibly important to the global aquarium industry because of its cichlid fish. African cichlids are prized for their vivid colors, territorial behavior and relative hardiness, and dominate a large portion of the freshwater aquarium trade, supporting the African regional export economy and a global network of breeders and enthusiasts.
Besides cichlids, the lake is home to a variety of other creatures. Lake Tanganyika is home to unique invertebrates, including jellyfish, snails and crabs, which superficially resemble marine life and are a legacy of the lake’s ancient and stable chemistry.
Hippos and crocodiles are abundant in and around almost all lakes. The surrounding wetlands and coastline are important habitats for many birds, including African ospreys, herons, storks, and millions of migratory birds. The papyrus swamps around Lake Victoria provide breeding and habitat for dozens of species of fish.
Tragically, the introduction of Nile perch to Lake Victoria in the 1950s and 1960s led to one of the greatest ecological disasters in freshwater history.
Nile perch is a large predatory fish that was intentionally introduced to increase fisheries production. This devastated the lake’s native cichlid population, causing the extinction of approximately 200 species, the largest vertebrate mass extinction in recorded history.
In comparison, the North American Great Lakes have few endemic species that exist only in the Great Lakes.
Africa’s Great Lakes are not just about geology and biology.
For the estimated 50 million people who live in the immediate vicinity of Africa’s Great Lakes and the millions more who depend on their basins, these bodies of water are more than just scenic spots. They are the foundation of everyday life.
Fishing is the most direct economic link. Lake Victoria alone supports one of the world’s largest freshwater fisheries, directly employing over 200,000 fishermen and millions more in processing, transport and trade.
Despite the ecological costs, the Nile perch fishery generates hundreds of millions of dollars in export revenue each year, with most of the catch shipped to Europe and Asia.
Kapenta and Kariba are important sources of cheap animal protein for landlocked populations in Zambia, Tanzania, and the Democratic Republic of Congo. In Malawi, a sardine-like fish called usipa is central to nutrition and culture.
The lake is a vital freshwater source for drinking, irrigation and industrial uses throughout the region. In a continent facing growing water shortages, lakes represent an irreplaceable resource. Several major cities, including Kampala in Uganda, Bujumbura in Burundi, and Mwanza in Tanzania, lie directly on the lakeshore and depend on it for their city water supplies.
Tourism, although underdeveloped compared to the lake’s potential, makes a meaningful contribution to the local economy. Lake Malawi National Park was designated a UNESCO World Heritage Site in 1984, in recognition of its extraordinary cichlid diversity.
The lake’s clear, warm waters and sandy beaches attract visitors from around the world for snorkeling, diving, and sailing. Lake Tanganyika is equally of interest to divers and researchers, and on its shores lies Tanzania’s Gombe River National Park, where Jane Goodall began her groundbreaking chimpanzee studies in 1960.
The lake also plays an important role in local transportation. In areas where roads are poor or non-existent, lake ferries serve as a lifeline connecting communities.
From Lake Victoria, ferries connect Uganda, Tanzania and Kenya on journeys that require long and difficult overland routes. The sinking of the MV Bukoba in Lake Victoria in 1996, killing more than 800 people, demonstrated both the scale of lake traffic and the dangers posed by overloaded and poorly maintained vessels.
With 10 different countries in the region, it’s no surprise that the lake has been a source of friction. In fact, several issues arose and became a cause of international tension.
First, there are disputes over borders and control. Many lakes are shared, including Lake Malawi and Lake Victoria, and disagreements over where the boundaries lie can cause diplomatic tensions and sometimes lead to confrontations. This is especially true when fishermen cross into conflict zones.
Second, competition over fishing is a major cause of friction. Although fish stocks move freely, national regulations do not, leading to overfishing, enforcement conflicts, and arrests of fishermen when they operate across borders.
Third, controlling water flow and hydropower generation leads to downstream conflict. For example, decisions that affect Lake Victoria have implications for the Nile River, which in turn can have implications for countries beyond the immediate lake region.
Fourth, environmental damage causes common problems, but responsibility is not equal. Pollution, invasive species and deforestation in one country can harm the entire lake, which can lead to criticism and disagreements over who should act.
Fifth, natural resources beneath the lakes, such as oil in Lake Albert or methane in Lake Kivu, create economic competition and territorial disputes.
Despite these tensions, significant efforts are being made to jointly manage the lake. Organizations such as the Lake Victoria Fisheries Organization and the Nile Basin Initiative aim to coordinate policies, share data and reduce conflict. These frameworks recognize basic realities. No country can effectively manage its lakes on its own.
When most people think of Africa, they might think of vast savannas, lush rainforests, or even the Sahara Desert. But Africa is also made of water. It’s actually a huge amount of fresh water.
Due to their ancient origins, Africa’s Great Lakes are one of the most biologically diverse freshwater ecosystems on Earth. Despite being formed millions of years ago, they are still very relevant and important to people living near the coast today.
