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Science

Lake Tanganyika Experiencing Unprecedented Warming

Lake Tanganyika, the world’s second oldest and second deepest lake, is in the midst of unprecedented warming.

[social_buttons]Geologists led by Brown University have determined that the massive freshwater lake has warmed significantly during the last century, leading to its warmest surface temperatures on record. Such a change to the lake’s makeup will likely affect fish stocks which millions in the region rely upon for survival.

According to core samples taken in 2001 and 2004 the lake’s surface temperature has risen to 26 degrees Celsius (78.8°F), the warmest the lake has been for a millennium and a half.

“Our data show a consistent relationship between lake surface temperature and productivity (such as fish stocks),” said Jessica Tierney, a Brown graduate student who this spring earned her Ph.D. and is the paper’s lead author. “As the lake gets warmer, we expect productivity to decline, and we expect that it will affect the [fishing] industry.”

Lake Tanganyika borders four of the world’s poorest countries, Burundi, the Democratic Republic of Congo, Tanzania and Zambia, according to the United Nations Human Development Index, and supports an estimated 10 million people by providing drinking water and fish. Up to 200,000 tons of sardines and four other fish species are harvested annually from the lake which, according to a report in 2001 by the Lake Tanganyika Biodiversity Project, supports a large portion of the locals.

The Lake is dependent upon the wind to churn the waters so that the surface waters can acquire the nutrients that live much deeper. The majority of the animal species live in the upper 100 metres of the lake, with certain depths of the lake providing absolutely no oxygen at all. But as Lake Tanganyika warms the mixing of waters decreases which means that there is less food for animals in the upper reaches of the lake.

Data collected by the Brown University researchers points to a linkage between prolonged warming and cooling with low and high algal production, which in turn indicates a clear link between temperature changes and biological productivity in the lake’s history.

“The people throughout southcentral Africa depend on the fish from Lake Tanganyika as a crucial source of protein,” noted Andrew Cohen, professor of geological sciences at the University of Arizona and director of the Nyanza project. “This resource is likely threatened by the lake’s unprecedented warming since the late 19th century and the associated loss of lake productivity.”

Climate change models for the region show a general warming which, if proved accurate in time, would see a corresponding warming to Lake Tanganyika’s surface waters. Some researchers have attributed the decline in fish stocks to overfishing, which Tierney and her advisor James Russel agree could be a factor. However they add that the lake’s warming is exacerbating the stocks’ decline, if not causing it in the first place.

Source: Brown University




5 comments
  1. Ismael Kimirei

    I believe that with the new evidence, the critic that Tanganyika has not been affected by climate change will fade – or die a natural death! Which will allow a multidisciplinary approach to protecting the lake and it's stunningly rich biodiversity. The current situation in the pelagic fishery is disturbing. The reasons given for the catch trend, mainly tied to overfishing, does not fully explain the situation. I think it is high time that the classical fisheries theories used to explain the dwindling catches get a boost from this (climate change) angle.

  2. Saskia Marijnissen

    Climate change is one of the many factors that threaten the health of the Lake Tanganyika ecosystem. Human population growth rates are excessively high, and environmental abuse is rampant throughout the African Great Lakes region. The Global Environmental Facility and United Nations Development Programme (UNDP) have recognized these threats and invested significantly in a programme that has joined the four governments of the Lake Tanganyika riparian countries (Burundi, Democratic Republic Congo, Tanzania, Zambia) in an effort to sustainably manage and safeguard their natural resources. There is still hope that the extraordinary biodiversity in Lake Tanganyika can be protected from mass extinction.

  3. Saskia Marijnissen

    Climate change is one of the many factors that threaten the health of the Lake Tanganyika ecosystem. Human population growth rates are excessively high, and environmental abuse is rampant throughout the African Great Lakes region. The Global Environmental Facility and United Nations Development Programme (UNDP) have recognized these threats and invested significantly in a programme that has joined the four governments of the Lake Tanganyika riparian countries (Burundi, Democratic Republic Congo, Tanzania, Zambia) in an effort to sustainably manage and safeguard their natural resources. There is still hope that the extraordinary biodiversity in Lake Tanganyika can be protected from mass extinction.

    But we are fighting a very complex battle. Unfortunately, time does not seem to be on our hand. Temperatures seem to be increasing quite rapidly. If fish stocks in Lake Tanganyika collapse this is likely to intensify the vicious circle of increasing poverty, corruption, and environmental degradation. We need to break this circle before we can mitigate climate change effects.

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