Mangroves of Kenya and the threats facing them

Mangroves of Kenya

According to Wikipedia, mangroves are ‘salt-tolerant trees and shrubs that usually grow in the intertidal zone throughout the tropics and sub-tropics.’ They are most often located along sheltered shores and can penetrate deep into the estuaries of rivers. Mangroves trees have a very plastic form which means that the same species can grow as a short stunted bush in unfavorable conditions or as a full sized tree reaching heights of 40 meters, forming dense forests several kilometers thick under favorable conditions.

Along the Kenyan coast which is approximately 600 kilometers, mangrove forest form a big to small patches relative to availability of suitable conditions required for their proper development.  The total area of mangrove cover is estimated at 54,000 ha spreads over 18 forest formations along the coast.  The most extensive patch is in Lamu and Tana river counties containing more than 70% of the total mangrove forest area to the North of Mombasa (34,000 ha).  Other smaller and isolated patches of mangroves are found in Kilifi – 1725 ha, Mida and Mtwapa creeks, Gazi bay, Funzi-Shirazi, and around Vanga.

In all these patches there are nine mangrove species which follow a typical zonation pattern.  Sonneratia alba grows closest to the low water line, followed mainly by Rhizophora mucranata, and then comes Bruguiera gymnorrhiza, Ceriops tagal, Avicennia marina, Lumnitzera racemosa and Heritiera litoralis respectively. Other mangrove species include Xylocarpus granatum and Xylocarpus mollucensis.

Why then are mangroves important?

Most of us will find it easy to overlook the seemingly nondescript trees that often line the land found between the sea and the coastline. This is partly because these trees don't grow fruits or nuts, nor are they ideal for shade or breeze, but what they do have to offer far surpasses all of the above qualities.  In fact, Kahindi Charo from Dabaso Creek Conservation Group (DCCG) attests to this fact in saying that, ‘If there were no mangroves, we would be dead, since most of us are fishermen and fish lay their eggs and get their food from mangrove marshes.’

Mangrove forests are among the most productive terrestrial eco systems and are natural and are a renewable resource. Mangroves are not a marvel just for their adaptations but also for the significant role they play in our environment.

• Mangrove ecosystem act as Buffer Zone between the land and sea.
• Mangroves protect the coast against erosion due to wind, waves, water currents and protect coral reefs, sea-grass bed and shipping lanes against siltation. They are also known to absorb pollutants.
• Mangroves host a number of threatened or endangered species, different animal species- mammals, reptiles, amphibians and bird- offer nutrients to the marine food web and provide spawning grounds to a variety of fish and shellfish, including several commercial species among them bats, lobsters, manatees, and birds.
• In mangrove areas water level is shallow, warm water temperatures due to various decaying activities, water current is slow (nearly stagnant) hence ideal place for growing of sea algae and for spawning for fish and marine animals. They are breeding, feeding and nursery grounds for many estuarine and marine organisms.
• Mangroves are known to purify the water by absorbing impurities and harmful heavy metals and also help us to breathe a clean air by absorbing pollutants in the air.
• Mangrove forests are also important in terms of aesthetics and tourism. Many people visit these areas for sports fishing, boating, bird watching, snorkeling, and other recreational pursuits.

In addition to the above ecological importance of mangroves they also possess other attributes that are beneficial to humans in general:

·         They are also a source of a vast range of wood and non-wood forest products including timber, fuel wood, charcoal, fodder, honey, pulp, tannin, medicine and thatch etc.

·         Their ecosystem has a very large unexplored potential for natural products useful for medicinal purposes & also for salt production, apiculture, fisheries products fuel and fodder, etc.

·         Mangroves also provide opportunities for education, scientific research and eco tourism.

Threats to mangroves of Kenya

Despite the significant importance that mangroves have on the environment, they are currently experiencing a major threat: clearance. As the demand for coastal settlements and development continues to increase, so does the elimination of this essential habitat. This is manifested in a study released last year by Landsat, Ocean Coast Management and KMFRI showing that from 2000 to 2010 mangrove depletion in Kenya totaled 1,340 hectares (3,310 acres), compared to 4,950 hectares (12,230 acres) lost in the eight years prior to that.

Kenyan mangroves have not been spared either as shown in the following threats facing them:

ü  Reduction in species diversity due to preferential extraction of certain species and of trees of given specification.

ü  Overexploitation of wood resources for building poles, fencing, fuel wood, fishing stakes, charcoal burning among others.

ü  Pollution effects including oil spills, solid waste and sewage disposal.  Oils are harmful to the mangroves since they clog the breathing roots leading to suffocation.

ü  Opening up beaches have led to chocking of mangroves through beach sand accumulation.

ü  Conversion of mangrove forest areas to other uses including salt mining or even settlement.

ü  Over reliance on mangrove products due to lack of suitable alternatives.

ü  Poverty has been outlined as the main contributing factors towards overexploitation of mangrove forests. 

To curb these threats, Kenya Forest Service (KFS) has embarked on the preparation of the first ever national mangrove forest management plan. By developing this management plan, KFS aims at reducing the loss and degradation of the mangrove ecosystem. This will in turn result in an increased availability of mangrove resources and in the maintenance of biodiversity, and ultimately, would contribute to the wellbeing of the coastal communities. This will greatly contribute to poverty alleviation and to the promotion of sustainable coastal development.