World Environment Day, June 5th, 2020

Theme - Forests, Biological Diversity and Livelihoods

By James Mwang’ombe- Head Biodiversity, Kenya Forest Service


Biodiversity (Biological diversity) is the variety of life on earth including the ecosystems in which they live. Forests are critical habitats for biodiversity and they are also essential for the provision of a wide range of ecosystem services that are important to human well-being. There is increasing evidence that biodiversity contributes to forest ecosystem functioning and the provision of ecosystem services. The forest ecosystem services include biomass production, habitat provisioning services, pollination, seed dispersal, resistance to wind storms, fire regulation and mitigation, pest regulation of native and invading insects, carbon sequestration, catchment and cultural ecosystem services as influenced by the forest type, structure and diversity.

Forests and woodlands host enormous amount of terrestrial and aquatic biodiversity, increasingly so in moist tropical regions being the richest habitats worldwide. In Kenya, a number of forests have been identified by Conservation International to comprise two (2) of the thirty-six (36) global biodiversity hotspots – the eastern afromontane and Coastal forest of eastern Africa. While the biodiversity hotspots cover only 1.4% of earth, they are home to >60% of species of flora and fauna. Kenya is among the mega-biodiverse countries in the world with >7,004 plants species out which about 577 (>8%) are endemic with tree and shrub species being around 1800 (>25%).

Human activities are among the major pressures causing biodiversity decline through forest loss, fragmentation and degradation worldwide. In Kenya, forest loss has been occasioned through encroachment for farmland, settlements and change of landuse. Infrastructure development is among the major causes of habitat fragmentation leading for loss of connectivity and dispersal areas for wildlife.

Collectively, these trends in forest cover and condition are a major concern, not only because of the implications for the conservation of biodiversity, but also because forests provide a wide range of critically important ecosystem services such as climate regulation, biomass production, water supply and purification, pollination, and the provision of habitats for forest species. There is also increasing evidence that the provision of ecosystem services is related to aspects of biodiversity; there is a positive relationship between biodiversity and most ecosystem services.

The Millennium Ecosystem Assessment of 2005 listed ecosystem services most of which forests are well able to deliver due to their wide distribution, rich biodiversity as well as long history of human use.


Habitat provisioning across forested landscapes

Forest ecosystems support a large proportion of species threatened with extinction. The provision of habitat by forests for multiple taxa and trophic levels is a key ecosystem service, which in turn positively influences forest ecosystem functioning through a range of mechanisms. This role played by forests in hosting multiple taxa and trophic levels is a crucial aspect contributing towards sustainable livelihoods.

The IPBES report of 2016 assessment on pollinators, pollination and food production underscores the importance of this service. Animal pollination is an important ecosystem service that is fundamental to the reproduction and persistence of most flowering plants, As biodiversity contributes to various ecosystem processes, functions and services, the declining diversity and abundance of pollinators (mainly insects and birds) has raised concerns about the effects on both wild and crop plants. Experimental evidence indicates that greater pollinator diversity results in improved seed production in plants.

In agricultural ecosystems, pollination services are provided by numerous species of wild insects and vertebrates, as well as some managed species that also rely on forest ecosystems for nesting and food resources. In diversified farming systems such as mosaic agricultural landscapes, forest remnants and agroforestry play a very important role in providing nesting and floral resources for pollinators and in sustaining pollinator populations and communities throughout the year. The conservation of natural ecosystems such as forests, which may provide habitats for pollinators, is crucial, and the distance from these habitats to farms affects the success of seed and fruit set. Livelihoods based on beekeeping and honey hunting are an anchor for many rural economies and particularly the forest-dwellers where honey and bees have been noted to play several roles such as food, medicine, alcoholic beverages, trade goods and even in cultural aspects such as securing marriage and identity.

Maintaining the quantity and quality of natural or semi-natural forest ecosystems across the landscape is important to conserve and restore habitats for pollinators. Retaining habitats within a landscape helps to safeguard an essential level of pollination services for both agricultural and forest ecosystems. In ensuring that the crucial role played by pollinators in food security, the government has strengthened the protection and conservation of natural forests as well as restoration to ensure their continued well-being.


Effects of forest tree diversity on pest regulation of native and invading insects

More diverse forests provide more diverse and abundant feeding and nesting resources for insect predators and parasitoids, thus increasing their capacity to control populations of prey (i.e., insect herbivores). The pest regulation service provided by forest biodiversity is thus intimately linked with two main ecosystem functions: primary production and biotic interactions. Increasing tree species diversity is likely to result in more complex forest structure and composition, thus providing more habitat for predators and parasitoids that may regulate pest populations. It has been observed there is less pest damage for crops within a landscape with a high tree diversity, although “ecosystem disservice” has also been observed where animals from the forest cause crop losses through raids such as elephants and primates.


Biodiversity and carbon sequestration in forests

Global warming is one of the main challenges facing humanity, which is a result on increasing concentration of greenhouse gases in the atmosphere. Carbon dioxide is the main greenhouse gas and forests have been identified as one of the mitigating factors through their ability to sequester and store carbon. Carbon in forests is sequestered through photosynthesis, and so is directly related to the species level of biodiversity. Carbon is stored in five distinct pools in forests: above-ground and below-ground live biomass, in deadwood including snags, litter, and soil. Carbon in forests is a function of forest productivity, and diverse forests have been observed to sequester and store more carbon than those with low species diversity. It is important to note that, high soil carbon content also influences oil fertility and thus ultimately food productivity.


Cultural ecosystem services in forest ecosystems

Cultural ecosystem services (CESs) are defined as ecosystems’ contributions to the nonmaterial benefits that arise from complex and dynamic relationships between ecosystems and humans. Commonly recognized CES categories include: cultural diversity and identity, spiritual and religious values; knowledge systems, including education; inspiration; aesthetic values; cultural heritage values; and recreation and ecotourism. In Kenya, the appreciation of CES is varied among the urdan and rural communities. The urban communities would likely view this in terms of leisure time through aesthetic value, recreation and tourism. For the rural and especially forest-dwelling, the importance of CES relates to cultural identity and heritage, kinship, knowledge and food abundance (honey, wild meat, fruits, medicine etc).



Forest type and tree species richness affect forest biodiversity and that forest diversity can be an important factor in ecosystem function and the provision of ecosystem services. While canopy trees are the dominant feature of forests, the diversity of understorey plants, vertebrates, invertebrates, fungi and microbes is also very important for optimum provision of ecosystem services.

It is important to raise awareness about the role of natural forests and forest diversity in the provision of ecosystem services to highlight their value beyond the provision of timber, water catchment and recreation in order to have a holistic view.

The relevance of forest ecosystem services does not stop at the forest edge. There is much scope for synergies between forests and farming land uses; for example, even small patches of forest can benefit crop production by enhancing pollinator and natural enemy populations, although they may also provide disservices. Adding planted forests to catchments dominated by dairy farming reduces greenhouse gas emissions and improves water quality.

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