Mangroves are among the most productive forest ecosystems in the world. Despite their importance in providing fuel, timber, coastal protection, fishing breeding sites, and pollution amelioration, mangroves in Kenya are endangered. Along with climate change impacts, human activities also contribute to the loss.
There are approximately 60 to 70 mangrove species globally, but Kenya is home to just nine, with the most prevalent being Rhizophora mucronata, commonly known as ‘mkoko.’ Mangroves are unique as the only trees capable of thriving in saline waters, enhancing water quality by filtering nutrients and sediments. Remarkably, they sequester up to five times more carbon than terrestrial forests, storing it in their foliage, branches, roots, and underlying sediments (UNEP 2023).
Kenya loses about 0.7% of its mangrove forest cover annually. However, peri-urban areas have witnessed a higher loss of mangrove forest areas. For instance, between 1992 and 2009, Tudor lost 86.9% of the mangrove forest while Mwache lost 45.4%, representing very high degradation rates of 5.1 and 2.7% per annum, respectively, according to the mapping of mangrove forest land cover change along the Kenya coastline using Landsat imagery.
Causes of Mangrove loss
- Pollution from Sewage and Fertilizers:
Untreated sewage from urban areas, such as Kilifi, Mwache, and Tudor creeks, introduces excessive nutrients into mangrove habitats, causing eutrophication. This reduces mangroves’ resilience to stressors like drought and salinity. Additionally, fertilizer runoff from nearby farms exacerbates nutrient loading, particularly during low rainfall. - Sedimentation from Poor Land Use Practices:
Unsustainable agricultural practices and deforestation in hinterlands lead to soil erosion, increasing sediment loads in mangrove areas. This sedimentation suffocates mangrove breathing roots, particularly affecting species like Avicennia marina, resulting in widespread die-offs. - Oil Spills:
Oil spills, especially in areas near Mombasa Port, have led to the loss of 10,310 hectares of mangroves, or approximately 16.7% of Kenya’s mangrove cover. Oil coats mangrove roots, suffocating them and disrupting key ecosystem processes, such as burrowing by crabs and worms. - Overharvesting and Land Clearing:
Removing mangroves for firewood, construction materials, and infrastructure development, such as roads and ports, alters hydrological patterns, causes shoreline erosion, and disrupts natural regeneration. - Climate Change and Rising Salinity:
Rising sea levels and prolonged submergence due to climate change increase soil salinity. This makes water uptake challenging for mangroves, leading to stress and mortality. Events like the El Niño rains of 1997/1998 submerged mangroves for extended periods, causing significant die-offs in areas like Mida Creek. - Senescence and Natural Aging:
In areas like Kiunga, mature mangroves (Rhizophora mucronata) experience die-backs due to the inability of aging prop roots to support their heavy biomass, particularly when exposed to wave erosion. - Pests and Diseases:
Insect infestations by species like the Bottegia rubra beetle and metarbelid moths have caused widespread damage to mangroves in areas such as Mida, Kilifi, and Vanga, particularly targeting younger trees and saplings.
Management strategies.
According to a report published by the Kenya Forestry Research Institute in 2023, awareness creation among stakeholders including local communities on the need to conserve the mangroves, and the development of site and species-specific restoration technologies are key in addressing the massive mangroves deaths.
This will should be accompanied by several strategies to achieve success among them;
- Sewage Treatment:
County governments and agencies like NEMA must implement efficient waste management systems to ensure sewage is treated before being discharged. Regular quality analysis of effluent can prevent excessive nutrient loading in mangrove ecosystems. - Agroforestry and Establishment of Woodlots:
Encouraging agroforestry in the hinterlands reduces the need for inorganic fertilizers while improving soil fertility. Establishing woodlots with fast-growing species, such as Casuarina equisetifolia, prevents soil erosion, provides alternative wood sources, and reduces pressure on mangroves. - Replanting and Restoration:
Degraded mangrove areas can be restored using species-specific replanting techniques. Removal of dead wood and algae is crucial to improving drainage and reducing submergence periods, creating favorable conditions for regeneration. - Oil Spill Mitigation:
Authorities must improve the handling of petroleum imports and expedite clean-up efforts after oil spills. Preventative measures can significantly reduce mangrove mortality from oil contamination. - Integrated Pest Management:
Biological control methods, such as introducing predators like ants to combat wood-boring pests, offer an environmentally friendly solution. Prolonged submersion of infested areas can also help suffocate pest larvae and pupae. - Public Awareness and Community Engagement:
Raising awareness about the ecological and economic importance of mangroves encourages local communities to adopt sustainable practices. Community participation in restoration programs and nature-based enterprises can enhance conservation efforts. - Climate Adaptation Strategies:
Mangroves must be protected against the impacts of sea-level rise and salinity changes through measures such as sediment addition to maintain elevation and promote species that can tolerate extreme conditions.
Mangroves are vital to Kenya’s coastal ecosystems, offering ecological, economic, and cultural benefits. However, they face numerous threats from human activities, natural challenges, and climate change. Addressing these issues requires a multi-faceted approach, including public awareness, government intervention, and community-driven conservation efforts.
