RESEARCH STARTER

Gambia River

The Gambia River is a significant waterway in West Africa, stretching over 700 miles (1,130 kilometers) from the Fouta Djallon highlands in Guinea, through Senegal and Gambia, to the Atlantic Ocean. It features two main ecological zones: a tidal estuary at its mouth and freshwater regions further upstream, each supporting diverse habitats such as mangroves, swamps, and riverine forests. This river is vital for local economies, facilitating agriculture, fishing, hunting, and transportation, while also offering potential for hydroelectric power through proposed dam projects.

The Gambia River basin is home to a rich array of wildlife, including approximately 1,500 plant species, 80 mammals, 330 birds, 26 reptiles, and 150 freshwater fish, although it has few unique species. Migratory birds flock to its mangroves, making it an essential habitat for avifauna. However, the river faces challenges from human activities, including land conversion for agriculture and plans for dam construction, which could disrupt its ecosystem and sediment balance. Conservation efforts are necessary to monitor and mitigate the impacts of these developments. As climate change poses additional threats, the Gambia River represents a crucial intersection of environmental conservation and human livelihoods in the region.

Full Article

  • Geographic Location: West Africa.
  • Summary: The last remaining undammed river in West Africa is an important reserve of biological diversity and support for human well-being, but is threatened by human activities.

The Gambia River winds over 700 miles (1,130 kilometers) from the Fouta Djallon highlands of northern Guinea through southeastern Senegal and the Gambia into the Atlantic Ocean. It is one of the largest rivers in West Africa and is composed of two distinct habitat types: estuary at the mouth and freshwater further upstream. Each of these supports a collection of flooded areas, swamps, mudflats, and riverine forests.

As part of the broader Senegambia Catchment area, the Gambia River is an important ecosystem for biological diversity, though it has few endemic species (those found nowhere else on Earth) in its waters. The river supports various economic activities, from agriculture to fishing, hunting, and transportation. It also shows promise for potential hydroelectric power. Like many of the world's aquatic and coastal systems, it is under direct threat from these anthropogenic factors.

Mangroves, Salt Marsh, Wetlands

The estuarine and freshwater zones, which are largely a function of the reach of the tide and saltwater from the sea, create different communities of flora and fauna. At its mouth, the Gambia is an 8-mile-wide (14-kilometer-wide) permanently flooded ria, or funnel-shaped estuary, formed from the submergence of the lower portion of the river valley. This estuary is a matrix of mangrove swamps and creeks with riverside mudflats on elevated ground formed from silt deposition.

The river narrows as it travels further inland, though it remains about half a mile (1 kilometer) wide, even 124 miles (200 kilometers) from the mouth. As the influence of the tide wanes, so does the level of flooding. The middle section of the river is only seasonally flooded, and the early stages of the river in the Fouta Djallon and southeastern Senegal, before the Gambia meets with any of its important tributaries, do not experience any flooding.

The basin of the Gambia River contains thousands of species, including over 1,500 plant species, 80 mammal species, 330 bird species, 26 reptile species, and 150 freshwater fish species. This diversity results from the broad range of habitats, including mangroves, freshwater swamps, salt mudflats, and Sudanian-Guinean riverine forest. Though the Gambia is important for biodiversity, it is not unique among other river ecosystems in the area. It possesses only a few endemic species. Most species are held in common with the Senegal, Bafing, and Faleme Rivers and are known together as the Senegal-Gambia Catchment, or the Senegambia Catchment. Thus, the Gambia River ecosystem is part of the broader Sudan-Guinean Savanna biome, and shares several species from the Guinea-Congo Forest biome and the Sahelian biome as well.

The mangroves and wetlands of the Gambia River reach 62 miles (100 kilometers) inland from the Atlantic and comprise one of the 200 most biologically valuable ecoregions of the Earth, as listed by the World Wildlife Fund. The river supports nearly 111,000 acres (45,000 hectares) of mangrove swamp dominated by trees such as Avicennia africana, Sesuvium portulacastrum, and Rhizophora spp. Much of this area is covered with salt marsh herbs and halophytic (salt-loving) grasses. The mangroves support a diverse community of avifauna, both as breeding and wintering grounds.

More than 576 bird species are found in the Gambia River basin, including many migratory species arriving from Europe each winter to take refuge among the mangroves. The yellow-billed stork (Mycteria ibis) and African sacred ibis (Threskiornis aethiopicus) can be spotted along the Gambia's banks, along with the long-crested eagle (Lophaetus occipitalis), pelicans, and other birds that find food and shelter in the area. Owls such as the African scops owl (Otus senegalensis) may also be found in this area, as well as threatened species, such as the black-tailed godwit (Limosa limosa) and the European turtle dove (Streptopelia turtur), which rely on intact wetland habitats for wintering.

Small-bodied mammals, such as the spotted-necked otter and greater cane rat, and larger-bodied mammals, such as duikers, crocodiles, hippopotamuses, and the vulnerable African manatee (Trichechus senegalensis), call this area home.

As the influence of the Atlantic tide and saltwater wanes, the Rhizophora mangroves thin and transition into a collection of freshwater swamps, salt flats, and seasonally flooded grasses, trees, and agriculture. The freshwater swamps are dominated by Phragmites karka grasses and are a habitat for many species of wintering birds. The swamps create a breeding ground for mosquitoes and tsetse flies, which are vectors for malaria and sleeping sickness, respectively. The most efficient malaria vector in sub-Saharan Africa and host to the deadliest malarial parasite is Anopheles gambiae, named for the region in which it is common. Native fish diversity and abundance are an essential control of mosquito populations and provide a key ecosystem service by regulating the malaria vector.

Human Interaction

The importance of the Gambia River to human communities is apparent from the names of the five administrative divisions of the Gambia: Western, North Bank, Lower River, Central River, and Upper River. Many Gambians outside of the capital depend directly on agriculture and fishing for their well-being. Wood is the most common fuel source and comes from the riverbanks and floodplain. These economic activities both depend on and severely impact the health of the river.

Nearly one-third of the Gambia has been converted to arable land dedicated to the production of rice, maize, groundnuts, millet, and sorghum. Similar land transformations have occurred in southeastern Senegal and are beginning in the mountainous Fouta Djallon of northern Guinea. These transformations began centuries ago. Flood rice cultivation has been the dominant land use on the banks of the Gambia River for recorded history. The system of flood rice cultivation used in the American South was a direct application of the system used along the banks of the Gambia; evidence suggests that American enslavers and traders targeted enslaved people of ethnic groups because of their experience in rice cultivation along the Gambia's banks.

In addition to its role in cultivation, the river and its tributaries are fished from source to mouth. Prawns are caught in the estuary, while fish are consumed over the river's entire course. Fish populations in the river remain relatively healthy. Hunting for wildfowl and mammals of all sizes is common in the riverine wetlands. Crocodiles, African manatees, and hippopotamuses have been hunted nearly to the point of local extinction in The Gambia, though hippopotamuses can be found in southeastern Senegal, where human populations are less dense.

In 2021, construction of the Sambangalou Multipurpose Dam officially began on the Gambia River in Senegal’s Kédougou region. The Gambia River Basin Development Organization (OMVG) leads the project, with support from the African Development Bank and the Exim Bank of China. When completed, the dam will generate approximately 128 megawatts of electricity and produce 402 gigawatt-hours annually, delivering power to Guinea, Gambia, Senegal, and Guinea-Bissau.

However, the dam poses ecological risks, including disruption of sediment flow, alterations to the estuarine saltwater boundary, and potential degradation of water quality. These changes may lead to mangrove depletion, habitat loss, and shifts in aquatic species populations. Conservation groups and research institutions have worked with OMVG to develop adaptive mitigation strategies to minimize biodiversity loss; ongoing environmental impact assessments track shifts in the river’s sediment load, salinity patterns, and mangrove distribution. As a potential source of electricity and a significant contributor to biodiversity and other ecosystem services, the Gambia River is a frontier for managing ecosystems for environmental and human well-being.

One potential effect of this dam, the modification of the salt front, will likely be exacerbated by global warming. With higher average temperatures and projected lower annual rainfall, the average evaporation rates along the river will increase faster, driving higher salt deposition rates. Climate change effects also lead to a more acute demand for irrigation water, another factor that will draw water out of the river's mainstem and tributaries. The spread of drier and saltier areas will cause a shift in habitat toward more halophytic plants, altering the range patterns of animals that rely on less salt-tolerant vegetation.

In 2021, the United Nations' Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report predicted that West Africa would face increased variability in rainfall and more frequent drought conditions. For the Gambia River basin, this may amplify the spread of saline soils, reduce wetland resilience, and increase pressures on freshwater availability for both ecosystems and agriculture. In addition to climate and development pressures, the Gambia River faces growing threats from artisanal gold mining in the Fouta Djallon highlands. These activities introduce mercury and other pollutants into upstream tributaries. Invasive plant species such as Eichhornia crassipes (water hyacinth) also spread in slower-moving sections of the river, threatening native biodiversity and clogging fishing channels.


Bibliography

Boussouga, Youssef-Amine, et al. “Water Quality of the Gambia River: A Prospective Drinking Water Supply.” The Science of the Total Environment, vol. 878, 20 June. 2023, p. 162794, doi:10.1016/j.scitotenv.2023.162794. Accessed 14 Mar. 2026.

"Contract Awarded for Sambangalou, Senegal." The International Journal on Hydropower and Dams, 17 Feb. 2021, www.hydropower-dams.com/news/contract-awarded-for-sambangalou-senegal. Accessed 14 Mar. 2026.

“Fifth National Report to the Convention on Biological Diversity: Gambia.” Department of Parks and Wildlife Management, May 2014, www.cbd.int/doc/world/gm/gm-nr-05-en.pdf. Accessed 14 Mar. 2026.

Gomez, Rose Zahra. "Gambia Set for Hydroelectricity." The Point, 4 May 2017, thepoint.gm/africa/gambia/article/gambia-set-for-hydroelectricity. Accessed 14 Mar. 2026.

Jones, Michael. Flowering Plants of the Gambia. CRC Press, 1994.

Louca, Vasilis, et al. “Fish Community Characteristics of the Lower Gambia River Floodplains: A Study in the Last Major Undisturbed West African River.” Freshwater Biology, vol. 54, no. 2, 2009, pp. 254–71, doi:10.1111/j.1365-2427.2008.02105.x. Accessed 14 Mar. 2026.

Sheridan, Michael, and Celia Nyamweru, editors. African Sacred Groves: Ecological Dynamics and Social Change. Ohio UP, 2008.

Skinner, Jamie, et al. Sharing the Benefits of Large Dams in West Africa. International Institute for Environment and Development, 2009.

"The Gambia." NASA Earth Observatory, 27 Sept. 2020, earthobservatory.nasa.gov/images/147335/the-gambia. Accessed 14 Mar. 2026.

Verkerk, M. P., and C. P. M. van Rens. Saline Intrusion in the Gambia River after Dam Construction. University of Twente, 2005.

Webb, James L. A., Jr. “Ecological and Economic Change along the Middle Reaches of the Gambia River, 1945-1985.” African Affairs, vol. 91, no. 365, Oct. 1992, pp. 543–65. doi:10.1093/oxfordjournals.afraf.a098561. Accessed 15 Mar. 2026.

Full Article

  • Geographic Location: West Africa.
  • Summary: The last remaining undammed river in West Africa is an important reserve of biological diversity and support for human well-being, but is threatened by human activities.

The Gambia River winds over 700 miles (1,130 kilometers) from the Fouta Djallon highlands of northern Guinea through southeastern Senegal and the Gambia into the Atlantic Ocean. It is one of the largest rivers in West Africa and is composed of two distinct habitat types: estuary at the mouth and freshwater further upstream. Each of these supports a collection of flooded areas, swamps, mudflats, and riverine forests.

As part of the broader Senegambia Catchment area, the Gambia River is an important ecosystem for biological diversity, though it has few endemic species (those found nowhere else on Earth) in its waters. The river supports various economic activities, from agriculture to fishing, hunting, and transportation. It also shows promise for potential hydroelectric power. Like many of the world's aquatic and coastal systems, it is under direct threat from these anthropogenic factors.

Mangroves, Salt Marsh, Wetlands

The estuarine and freshwater zones, which are largely a function of the reach of the tide and saltwater from the sea, create different communities of flora and fauna. At its mouth, the Gambia is an 8-mile-wide (14-kilometer-wide) permanently flooded ria, or funnel-shaped estuary, formed from the submergence of the lower portion of the river valley. This estuary is a matrix of mangrove swamps and creeks with riverside mudflats on elevated ground formed from silt deposition.

The river narrows as it travels further inland, though it remains about half a mile (1 kilometer) wide, even 124 miles (200 kilometers) from the mouth. As the influence of the tide wanes, so does the level of flooding. The middle section of the river is only seasonally flooded, and the early stages of the river in the Fouta Djallon and southeastern Senegal, before the Gambia meets with any of its important tributaries, do not experience any flooding.

The basin of the Gambia River contains thousands of species, including over 1,500 plant species, 80 mammal species, 330 bird species, 26 reptile species, and 150 freshwater fish species. This diversity results from the broad range of habitats, including mangroves, freshwater swamps, salt mudflats, and Sudanian-Guinean riverine forest. Though the Gambia is important for biodiversity, it is not unique among other river ecosystems in the area. It possesses only a few endemic species. Most species are held in common with the Senegal, Bafing, and Faleme Rivers and are known together as the Senegal-Gambia Catchment, or the Senegambia Catchment. Thus, the Gambia River ecosystem is part of the broader Sudan-Guinean Savanna biome, and shares several species from the Guinea-Congo Forest biome and the Sahelian biome as well.

The mangroves and wetlands of the Gambia River reach 62 miles (100 kilometers) inland from the Atlantic and comprise one of the 200 most biologically valuable ecoregions of the Earth, as listed by the World Wildlife Fund. The river supports nearly 111,000 acres (45,000 hectares) of mangrove swamp dominated by trees such as Avicennia africana, Sesuvium portulacastrum, and Rhizophora spp. Much of this area is covered with salt marsh herbs and halophytic (salt-loving) grasses. The mangroves support a diverse community of avifauna, both as breeding and wintering grounds.

More than 576 bird species are found in the Gambia River basin, including many migratory species arriving from Europe each winter to take refuge among the mangroves. The yellow-billed stork (Mycteria ibis) and African sacred ibis (Threskiornis aethiopicus) can be spotted along the Gambia's banks, along with the long-crested eagle (Lophaetus occipitalis), pelicans, and other birds that find food and shelter in the area. Owls such as the African scops owl (Otus senegalensis) may also be found in this area, as well as threatened species, such as the black-tailed godwit (Limosa limosa) and the European turtle dove (Streptopelia turtur), which rely on intact wetland habitats for wintering.

Small-bodied mammals, such as the spotted-necked otter and greater cane rat, and larger-bodied mammals, such as duikers, crocodiles, hippopotamuses, and the vulnerable African manatee (Trichechus senegalensis), call this area home.

As the influence of the Atlantic tide and saltwater wanes, the Rhizophora mangroves thin and transition into a collection of freshwater swamps, salt flats, and seasonally flooded grasses, trees, and agriculture. The freshwater swamps are dominated by Phragmites karka grasses and are a habitat for many species of wintering birds. The swamps create a breeding ground for mosquitoes and tsetse flies, which are vectors for malaria and sleeping sickness, respectively. The most efficient malaria vector in sub-Saharan Africa and host to the deadliest malarial parasite is Anopheles gambiae, named for the region in which it is common. Native fish diversity and abundance are an essential control of mosquito populations and provide a key ecosystem service by regulating the malaria vector.

Human Interaction

The importance of the Gambia River to human communities is apparent from the names of the five administrative divisions of the Gambia: Western, North Bank, Lower River, Central River, and Upper River. Many Gambians outside of the capital depend directly on agriculture and fishing for their well-being. Wood is the most common fuel source and comes from the riverbanks and floodplain. These economic activities both depend on and severely impact the health of the river.

Nearly one-third of the Gambia has been converted to arable land dedicated to the production of rice, maize, groundnuts, millet, and sorghum. Similar land transformations have occurred in southeastern Senegal and are beginning in the mountainous Fouta Djallon of northern Guinea. These transformations began centuries ago. Flood rice cultivation has been the dominant land use on the banks of the Gambia River for recorded history. The system of flood rice cultivation used in the American South was a direct application of the system used along the banks of the Gambia; evidence suggests that American enslavers and traders targeted enslaved people of ethnic groups because of their experience in rice cultivation along the Gambia's banks.

In addition to its role in cultivation, the river and its tributaries are fished from source to mouth. Prawns are caught in the estuary, while fish are consumed over the river's entire course. Fish populations in the river remain relatively healthy. Hunting for wildfowl and mammals of all sizes is common in the riverine wetlands. Crocodiles, African manatees, and hippopotamuses have been hunted nearly to the point of local extinction in The Gambia, though hippopotamuses can be found in southeastern Senegal, where human populations are less dense.

In 2021, construction of the Sambangalou Multipurpose Dam officially began on the Gambia River in Senegal’s Kédougou region. The Gambia River Basin Development Organization (OMVG) leads the project, with support from the African Development Bank and the Exim Bank of China. When completed, the dam will generate approximately 128 megawatts of electricity and produce 402 gigawatt-hours annually, delivering power to Guinea, Gambia, Senegal, and Guinea-Bissau.

However, the dam poses ecological risks, including disruption of sediment flow, alterations to the estuarine saltwater boundary, and potential degradation of water quality. These changes may lead to mangrove depletion, habitat loss, and shifts in aquatic species populations. Conservation groups and research institutions have worked with OMVG to develop adaptive mitigation strategies to minimize biodiversity loss; ongoing environmental impact assessments track shifts in the river’s sediment load, salinity patterns, and mangrove distribution. As a potential source of electricity and a significant contributor to biodiversity and other ecosystem services, the Gambia River is a frontier for managing ecosystems for environmental and human well-being.

One potential effect of this dam, the modification of the salt front, will likely be exacerbated by global warming. With higher average temperatures and projected lower annual rainfall, the average evaporation rates along the river will increase faster, driving higher salt deposition rates. Climate change effects also lead to a more acute demand for irrigation water, another factor that will draw water out of the river's mainstem and tributaries. The spread of drier and saltier areas will cause a shift in habitat toward more halophytic plants, altering the range patterns of animals that rely on less salt-tolerant vegetation.

In 2021, the United Nations' Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report predicted that West Africa would face increased variability in rainfall and more frequent drought conditions. For the Gambia River basin, this may amplify the spread of saline soils, reduce wetland resilience, and increase pressures on freshwater availability for both ecosystems and agriculture. In addition to climate and development pressures, the Gambia River faces growing threats from artisanal gold mining in the Fouta Djallon highlands. These activities introduce mercury and other pollutants into upstream tributaries. Invasive plant species such as Eichhornia crassipes (water hyacinth) also spread in slower-moving sections of the river, threatening native biodiversity and clogging fishing channels.


Bibliography

Boussouga, Youssef-Amine, et al. “Water Quality of the Gambia River: A Prospective Drinking Water Supply.” The Science of the Total Environment, vol. 878, 20 June. 2023, p. 162794, doi:10.1016/j.scitotenv.2023.162794. Accessed 14 Mar. 2026.

"Contract Awarded for Sambangalou, Senegal." The International Journal on Hydropower and Dams, 17 Feb. 2021, www.hydropower-dams.com/news/contract-awarded-for-sambangalou-senegal. Accessed 14 Mar. 2026.

“Fifth National Report to the Convention on Biological Diversity: Gambia.” Department of Parks and Wildlife Management, May 2014, www.cbd.int/doc/world/gm/gm-nr-05-en.pdf. Accessed 14 Mar. 2026.

Gomez, Rose Zahra. "Gambia Set for Hydroelectricity." The Point, 4 May 2017, thepoint.gm/africa/gambia/article/gambia-set-for-hydroelectricity. Accessed 14 Mar. 2026.

Jones, Michael. Flowering Plants of the Gambia. CRC Press, 1994.

Louca, Vasilis, et al. “Fish Community Characteristics of the Lower Gambia River Floodplains: A Study in the Last Major Undisturbed West African River.” Freshwater Biology, vol. 54, no. 2, 2009, pp. 254–71, doi:10.1111/j.1365-2427.2008.02105.x. Accessed 14 Mar. 2026.

Sheridan, Michael, and Celia Nyamweru, editors. African Sacred Groves: Ecological Dynamics and Social Change. Ohio UP, 2008.

Skinner, Jamie, et al. Sharing the Benefits of Large Dams in West Africa. International Institute for Environment and Development, 2009.

"The Gambia." NASA Earth Observatory, 27 Sept. 2020, earthobservatory.nasa.gov/images/147335/the-gambia. Accessed 14 Mar. 2026.

Verkerk, M. P., and C. P. M. van Rens. Saline Intrusion in the Gambia River after Dam Construction. University of Twente, 2005.

Webb, James L. A., Jr. “Ecological and Economic Change along the Middle Reaches of the Gambia River, 1945-1985.” African Affairs, vol. 91, no. 365, Oct. 1992, pp. 543–65. doi:10.1093/oxfordjournals.afraf.a098561. Accessed 15 Mar. 2026.

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