It is amazing how most of us have spent quality time in the coast and have noticed the distinctive trees that live along shores, rivers and estuaries, but have no idea what they are. Those distinctive trees are probably the mangrove trees and shrubs that live on muddy soil and some also grow on sand, peat, and coral rocks! It’s not a surprise that even for those that live along the coast and know a thing or two about mangroves have no idea how important the mangrove ecosystem is. So here is a little write up on the mangrove ecosystem in Kenya, hoping to educate a few of us out there about this important ecosystem!
Mangrove trees are halophyte plants that thrive in salt water. So how are they adapted to survive in salt water? Their roots filter freshwater from the saltwater they live in and the unwanted salt is then excreted through pores in the mangrove’s waxy leaves. The Mangrove forests in Kenya can be found along sheltered sedimentary shores especially in bays and estuaries.
The mangrove forest in Kenya covers more than 60,000 hectares!
The mangrove trees in Kenya represent approximately 3% of natural forest cover, covering more than 60,000 hectares! Around 60% of the mangroves occur in Lamu County, in the northern part of Kenya, while in Kwale county, in the southern part of Kenya, we have about 14% of mangrove cover. The best developed mangroves are found in Tana River County, a region found in the northern part of the Kenya coast. This region has the second most extensive patch of mangrove forest after Lamu County according to the Kenya Forest Service.
Globally, there are about 60-70 species of mangroves. In Kenya we have only 9 species of mangroves. The most dominant species are Rhizophora mucronata locally identified as ‘mkoko’. Mkoko is a highly sought after mangrove species mainly used for poles, dye, firewood, fencing and charcoal. Ceriops tagal, Avicennia marina, Bruguiera gymnorrhiza and Sonneratia alba are the other common species.
A fond memory I have of visiting a mangrove forest in Shimoni which is in the South Coast of Kenya, is of learning a few tricks of mangrove species identification. From my experience characteristics of the leaves and roots is a good place to start when distinguishing the species. For instance, the Rhizophora mucronata are dark green, with a spine at the tip almost resembling the leaves of the Bruguiera gymnorrhiza that are also dark green pointed at the tip but lack a spine present in the Rhizophora mucronata. The roots and the zonation can be used as a guide, too! For example, the Bruguiera gymnorrhiza have what we call knee roots, as they form arches arising from the mud, while for the Rhizophora mucronata have a characteristic prop root. See the photo above for a guide in zonation and next time you come across a mangrove ecosystem, try using these simple characteristic to distinguish between the two species!
Mangrove forests are a major habitat for many species
If you visit a mangrove ecosystem, you will probably come across plenty of biodiversity! From insects to birds, crabs and shrimp all foraging in the fertile mud. You are also likely to come across plenty of small fish! An estimated two thirds of the fish that we eat in Kenya spend part of their lives in the mangroves which act as their breeding and nursery grounds. A mangrove ecosystem is therefore important in enhancing fishery production and since fishery is a main source of income for coastal communities, the fisheries supported by the mangrove ecosystem become an important source of livelihood.
Mangroves are among the most carbon-rich forests in the tropics!
Mangroves are also good carbon fixers. They store huge stocks of carbon in both above and below ground components. This makes them one of the most carbon-rich ecosystems on the planet. On average, carbon stock of one hectare of mangroves, including soil carbon, is approximately 1,000 tonnes, which is more than twice the carbon stock of upland forests and five times that of savannah. Other important roles of mangroves include reduced negative impact of cyclonic storms, control of soil erosion and trapping of organic sediments.
Threats to the mangrove ecosystem in Kenya
Before restoration and rehabilitation became an issue, coastal communities harvested this ecosystem. The extensive logging provided mangrove wood which is generally a cheap, strong and durable building material. In fact, a majority of the beach hotels that emerged when tourism boomed in Kenya used mangrove wood as a building material. Most of these hotels remained intact despite being abandoned for years when tourism dropped in Kenya. Coastal communities also used this wood for building boats and houses! As a result of the unsustainable harvesting of this precious ecosystem, Kenya lost about 20% of its mangrove cover between 1985 and 2009, meaning 450 hectares of mangroves disappeared every year. A new study reports human pressure, erosion, drought, and sea-level changes as the main drivers of changes in mangrove cover in four countries with Kenyaamongst them. The bottom line is, the cost of losing mangrove ecosystems is loss of biodiversity and loss of carbon stores which help reducing climate change!
Our contribution at both Conservation Education Society and Marine Life Protectors is highlighting some of these threats by creating awareness and educating the public on the importance of mangroves through our social media platforms, our education programmes and our eco tours while visiting the Marine Education Centre here in Diani. We have also developed a proposal for a local community to obtain technical support in restoring a mangrove ecosystem.
Creating awareness on the importance of mangrove ecosystems has proven to work through a rise in restoration programmes. There are a number of community groups that work together to restore the deforested mangroves simply because they have now realized they get more in return for conserving the mangrove forests!
One of the most famous projects that has put Kenya on a global radar is a community mangrove restoration project in a small village in South Coast Kenya bordering the Indian Ocean with a mangrove forest. The carbon offset project Mikoko Pamoja (Mangroves Together) is the first of its kind in the world to successfully trade mangrove carbon credits. The sale of carbon credits is used to fund mangrove conservation alongside development programs within the community of Gazi village. This project has been so successful that it has been used as a model for mangrove restoration not only in Kenya but throughout the entire Western Indian Ocean region.