5.3: Habitat Loss’ Impact on Africa’s Ecosystems
5.3.1 Tropical forests
Occupying about 7% of all land surfaces, tropical forests are estimated to contain over 50% of the world’s terrestrial species (Corlett and Primack, 2010). Due to these high levels of biodiversity, the complexity of biological interactions in tropical forests is unparalleled in other ecosystems, and consequently also their importance to humans. On a local scale, the timber and non-timber products from tropical forests sustain the traditions (Box 5.2), livelihoods, and financial well-being of millions of Africans. Tropical forests also have regional importance including protecting catchment areas (Section 4.2.4) and moderating climate (Section 4.2.3). Lastly, as reservoirs of carbon, tropical forests play a globally important role in mitigating the negative effects of anthropogenic climate change (Section 10.4), and with 17% of Earth’s tropical forests, Africa plays a globally important role in tropical forest conservation efforts.
John R. S. Tabuti
>College of Agricultural and Environmental Sciences,> Makerere University,
>Kampala,> Uganda.
Ethnobotany, as a scientific discipline, studies the relationships between people and plants: how people affect the survival and distribution of plants, and how plants influence human behavior and cultures. For instance, local cuisines are shaped by available plant species, and people cultivate species that they consider useful. Conservation of plant diversity can be aided in many ways by recognizing the importance of plants to people’s livelihood and spiritual practices.
The people of East Africa identify and use a great many plant species that are essential for their well-being (Tabuti, 2006). Native plants are used for food, for construction, to treat the diseases of both people and livestock, and in numerous other ways. Some of the most important species include White‘s ginger (>Mondia whitei) and red stinkwood (>Prunus africana, VU) for medicine, African teak (>Milicia excels, NT) for timber, shea tree (>Vitellaria paradoxa, VU) for food and cosmetics, and African sandalwood (>Osyris lanceolate, LC) as a source of fragrant oil.
Some plant species (and sometimes entire ecosystems, such as forests) are valued for religious or cultural reasons. The plants or forest areas themselves are considered sacred, the site of a deity or spirit, with certain rituals performed using those special plant species or the habitats they occupy. These sacred sites and species are protected by local taboos. For example, the powderbark gardenia (>Gardenia ternifolia) is not harvested for firewood among the Balamogi people of Uganda because it is believed to bring bad luck. Among the Mijikenda people of Kenya, sacred forests known as Kaya are protected because people believe that the forests are inhabited by spirits and are places of prayer and held as a source of ritual power. Cutting down trees, grazing livestock, and farming are prohibited within the Kaya. One protective belief holds that cutting a tree in the Kaya with a machete can result in the machete rebounding and causing injury to the woodcutter. Another belief is that food cooked using wood from these sacred forests can cause sickness, and that a dwelling built with timber drawn from the forest will collapse. Consequently, more than 50 Kaya—ranging in size from 0.3 to 3 km 2 and home to 187 plants, 48 birds, and 45 butterfly species—have enjoyed unofficial protection due to religious and cultural beliefs.
Today, however, the plants and their natural communities on which people rely for their well-being are being threatened. By far the greatest threat is land use change and habitat conversion to agriculture to grow food for a growing population. Changing cultural and spiritual values in East Africa, as well as social and economic pressures, are threatening the existence of even sacred forests. For instance, the coronation site of the Paramount Chief of the Balamogi in Uganda was previously protected as a sacred forest by local lore, but it has now been cut down and converted into gardens by local people who no longer follow ancient traditions. Harvesting of plant species, such as the red stinkwood and East African sandalwood, for international markets is also a significant threat no longer held at bay by cultural norms.
Thankfully, several species continue to be actively protected by local communities and governments. According to Greger (2012), traditional healers aid conservation by replanting around 50% of the medicinal plant species that they consider to be important to their practice. For the relationship between people and plants to survive, scientific conservation and local tradition must work together. An example of such collaboration is on display in Uganda’s Budongo Forest Reserve (Figure 5.B), where researchers at the Budongo Conservation Field Station are working with local communities to refine methods for sustainable management and utilisation of the region’s local plants.
Despite the importance of tropical forests, their destruction has become synonymous with the rapid loss of biodiversity (Figure 5.6). Africa had already lost over 65% of its original tropical forests by 1990 (Sayer, 1992); human activities destroyed an additional 308,000 km 2 (an area larger than Italy) between 1990 and 2010 (Achard et al., 2014). Losses were particularly severe in Burundi, Benin, and Mozambique, with each country holding less than 5% of its original forest cover (Sayer, 1992). Retaining about half of its original forest cover, the DRC is relatively better off, but current deforestation rates in this country are currently second highest globally (Weisse and Goldman, 2019). Current deforestation rates are so severe in Equatorial Guinea that this country will lose all its forests within the next 20 years if current trends hold (Potapov et al., 2017). Despite these alarming trends—the destruction continues nonstop, particularly in Ghana and Côte d’Ivoire, which saw a 60% and 26% rise in forest loss (the highest rise globally), respectively, between 2017 and 2018 (Weisse and Goldman, 2019). Across Africa, logging is currently the dominant driver of tropical forest loss (causing 77% of total losses over the past decade), followed by agriculture (Potapov et al., 2017).
5.3.2 Rivers and deltas
Due to our dependence on freshwater, humans have always preferred to live near rivers, streams, and lakes. Consequently, these aquatic environments have been destroyed at a scale at least equal to that of terrestrial environments. Rivers have taken a particularly hard hit from human activities, being polluted by industries and dammed to ensure a reliable, year-round supply of water for consumption and irrigation, and to generate hydroelectricity.
Dam construction holds several negative consequences for biodiversity and people. Aquatic organisms that cannot survive the altered river conditions downstream (reduced flow and dissolved oxygen, higher temperatures, and increased turbidity) are most vulnerable. For example, a study from South Africa found that native macroinvertebrate populations (often a good indicator of water quality) were reduced by 50%, and some insect orders virtually extirpated following dam construction (Bredenhand and Samways, 2009). Dams also displace aquatic organisms upsteam. In one well-studied example, back flooding of Mozambique’s Massingir Dam facilitated river substrate changes and the spread of invasive species, which in turn forced sharptooth catfish (>Clarias gariepinus, LC), tiger fish (>Hydrocynus vittatus, LC), and Nile crocodiles (>Crocodylus niloticus, LC) to change their diet. Increased stress levels due to these dietary and environmental changes leave the affected animals susceptible to pansteatitis (a condition where body fat becomes inflamed), leading to mass wildlife mortality events in South Africa’s Kruger National Park (Woodborne et al., 2012). Lastly, dams reduce connectivity in freshwater ecosystems, preventing freshwater organisms from exchanging genetic material, migrating between upsteam and downstream areas, and adapting to changing conditions. For example, in West Africa, the damming of the Senegal River blocked the annual migration path for African river prawns (>Macrobrachium vollenhoveni, LC), a major predator of snails which host schistosomiasis (bilharzia). Once the dam was completed, prawn populations collapsed, leading to a schistosomiasis epidemic in villages upstream from the dam (Sokolow et al., 2015).
Damming rivers harms biodiversity and people both upsteam and downstream from these developments.
Terrestrial ecosystems also suffer from dam construction. Of concern is the direct loss of riverine and palustrine ecosystems downstream from the dam due to reduced waterflow. For example, construction of Nigeria’s Kainji Dam in the Niger River caused the drying of large wetlands and floodplains downstream, in the process displacing nearly 400,000 people who depended on the river’s now-compromised seasonal flood cycles (Drijver and Marchand, 1985). Flooding of upland areas next to dammed rivers also displaces terrestrial wildlife and people. For example, construction of Mali’s Manalati Dam flooded 430 km 2 of savannah and 120 km 2 of forest, which fractured the migration routes of the region’s nomadic pastoralists, leading to overgrazing and soil erosion of the remaining grazing lands (deGeorges and Reilly, 2006), in addition to a 90% loss of fisheries downstream (Acreman, 1996).
5.3.3 Wetlands
Throughout Africa, wetlands are being mined for valuable peat, or drained and/or filled in for development and agriculture. Through these activities, the region has already lost approximately 43% of its wetlands, with current rates of loss among the highest in the world (Davidson, 2014). This is a major concern because wetlands serve as spawning grounds and nurseries for aquatic and amphibious wildlife and stop-over sites for migratory birds (Box 5.3). Wetlands also provide multiple important ecosystem services. For example, they prevent erosion and runoff by capturing large volumes of floodwater, which is then released slowly over time. This process also allows sediments and nutrients kicked up during flood events to settle out, creating fertile habitats for a wide diversity of animals and plants, as well as for agriculture. Water that leaves after this settling period is cleaner than when it entered, having been filtered by the soil, plants, and microbes of wetlands. This water purification and filtration service is generally cheaper and much more efficient than man-made filtrations systems. The loss of any wetlands, but especially at such large scales, is thus a grave concern not only because of the countless animals and plants threatened with extinction, but also the people that depend on all the valuable ecosystem services they offer.
Abraham J. Miller-Rushing 1 and John W. Wilson
1 >Acadia National Park,> US National Park Service,
>Bar Harbor,> ME, USA.
How are Africa’s bird migrations, the biggest in the world, faring in a rapidly changing world? Each year, about 2.1–5 billion birds (mostly songbirds, but also raptors, waterbirds, and many others) travel back and forth between their wintering grounds in Africa and breeding grounds in Europe and Asia (Figure 5.C). Of the 126 species involved in this migration, over 40% have continuously decreased in abundance since 1970 (Vickery et al., 2014). At first, populations that overwintered in open dry savannahs declined: examples include the Ortolan bunting (>Emberiza hortulana, LC) and European turtle dove (>Streptopelia turtur, VU) which decreased by 84% and 69% between 1980 and 2009, respectively. More recently, species overwintering in the humid Afrotropics also started declining: this includes songbirds, such as the common nightingale (>Luscinia megarhynchos, LC) and river warbler (>Locustella fluviatilis, LC)—populations of both declined by 63%—and waterbirds such as the black-tailed godwit (>Limosa limosa, NT), which declined by 45%.
To survive their long journeys, migratory birds need favourable weather conditions, adequate food sources, and intact habitat not only at the end points where they breed or overwinter, but also along their routes where the migratory animals can rest and refuel (Runge et al., 2015). Disturbances in any of these places can lead to sharp population declines. For example, recent research showed that the habitat quality of a single stop-over site can determine whether a migration is successful or not (Gómez et al., 2017). Illustrating this point, a drought in the Sahel, an important migratory stop-over site, led to food shortages that killed 77% of the world’s common whitethroats (>Sylvia communis, LC); even today, this population has not yet fully recovered (Vickery et al., 2014).
Human activities have greatly contributed to the declines of Africa’s migratory birds (Kirby et al., 2008; Vickery et al., 2014). For example, each year thousands of hectares of wetlands, forests, grasslands, and savannahs are being converted into farmlands and urban areas or polluted by rampant use of pesticides and herbicides. Migratory birds also need to deal with hunters and trappers, and an increasing number of human-made structures, such as high-rise buildings, wind turbines, and power lines that represent collision and electrocution hazards (e.g. Rushworth et al., 2014). Then there is the threat of inconsistent rainfall, which causes food shortages and direct mortality, and climate change, which causes temporal mismatches between migratory movements and abundance of key food resources (Both et al., 2006; Vickery et al., 2014).
Addressing these declines, governments, conservation organizations, and local communities all over Africa have started initiatives to protect migratory birds and their habitats. One such initiative is happening in Kenya’s Tana River Delta, one of the most important stop-over sites along the Asian-East African Flyway. Every year, Basra reed warblers (>Acrocephalus griseldis, EN) return from their Middle Eastern breeding grounds to overwinter in the Delta, which covers 1,300 km 2 and supports dozens of threatened species. The area, however, has been under serious threat from development for sugarcane and biofuel crops since 2008. These activities could reduce dry season water flow by up to one third. Local people and conservationists strongly oppose these developments because of its threat to local communities’ ways of life and to wildlife populations. Their efforts gained international attention, and in 2012, Kenyan courts halted development until comprehensive management plans were developed that included environmental impact assessments and local stakeholder engagement (Neville, 2015). Today, local people gain benefit from more sustainable industries, including eco-charcoal audited by the Forest Stewardship Council (FSC), and solar-powered energy to reduce the need for wood.
Also, in West Africa, collaborative conservation initiatives are taking steps to protect the critical East Atlantic Flyway. For example, under the guidance of BirdLife International, Guinea-Bissau residents are now monitoring several wetlands in the Bijagós Archipelago to track how well migratory waterbirds are doing at this critically important stop-over site. Also, in Senegal, where two important stop-over sites (Saloum Delta and Djoudj wetlands) are located, the local non-profit NGO Nature Communautés Développement initiated an extensive conservation education program aimed at safeguarding the region’s birds.
Conserving migratory species that cover huge distances and rely on habitats in many areas is not easy. However, efforts like these in West Africa and Kenya (which combine the interests of local people and wildlife) provide excellent models for others to build from.
Mangrove swamps (sometimes called mangrove forests, though technically a wetland because their function and structure are primarily determined by hydrology, Lewis, 2005; Gopal, 2013) are one of Africa’s most threatened wetland ecosystems. Characterised by woody plants that can tolerate saltwater, mangrove swamps occupy brackish waters in tropical coastal areas, typically where there are muddy bottoms. These areas are sparsely distributed; globally, mangrove swamps cover only 53,000 km 2 of land scattered across 118 countries (Dybas, 2015). Protecting Africa’s mangrove swamps, comprising 21% of Earth’s total, is important both biologically and economically. In addition to holding many unique species, mangrove swamps also protect coastal cities and villages from cyclone/hurricane and tsunami damage and provide important breeding and feeding grounds for marine shellfish and fish. One study estimated that mangrove swamps provide an estimated US $57,000 worth of ecosystem services per hectare (van Bochove et al., 2014). Yet, only 7% of Africa’s mangrove swamps are protected. With so little protection, it comes as no surprise that a large percentage of Africa’s mangrove swamps have been destroyed or damaged by agriculture, urban expansion, pollution, and commercial shellfish farming (Giri et al., 2011). In West Africa, the situation is particularly dire. Wood extraction for commercial fish smoking is one of the biggest drivers of mangrove losses, even within protected areas (Feka et al., 2009). With so much destruction, it should come as little surprise that about 40% of vertebrate species endemic to mangrove swamps are currently threatened with extinction (Luther and Greenberg, 2009).
Mangrove losses around Africa have been extensive despite them providing an estimated US $57,000 worth of ecosystem services per hectare.
5.3.4 Seasonal drylands
Africa is also rapidly losing its semi-arid savannahs, scrublands, and grasslands through conversion to agriculture (Box 5.4) and desertification—the systematic degradation of formerly complex and adaptive seasonal drylands into barren wastelands (Figure 5.7). When human populations were low, nomadic pastoralism and shifting cultivation enabled people to utilise seasonal drylands in a sustainable way. Today however, population growth, combined with restrictions placed on free movement by administrative borders and competition for land, forces people and animals living on drylands to be more sedentary. While these areas may initially support some agriculture and livestock, unsustainable techniques, such as overgrazing and excessive tilling, lead to soil erosion and the depletion of soil nutrients and natural seed banks. With the cover vegetation gone, the unprotected topsoil is easily lost to wind and flooding, leaving behind the deeper, infertile, and compact subsoil layers with little capacity tfo hold water. The result is something that closely resembles a man-made desert. However, rather than a functional ecosystem characterized by species adapted to life in the desert, these wastelands have lost their original productivity and biological communities, only to be revived through expensive and/or time-consuming land reclamation methods.
Africa is rapidly losing semi-arid ecosystems due to desertification, the conversion of productive ecosystems into barren wastelands.
Bruktawit Abdu Mahamued 1,2
1 >Biology Department,> Kotebe Metropolitan University,
>Addis Ababa,> Ethiopia.
2 >Edge of Existence Fellow,> Zoological Society of London,
>London,> UK.
We are currently witnessing the start of the sixth mass extinction of species on our planet. From here onwards, biodiversity losses are expected to increase rapidly: a recent UN report estimated that about one million species are already threatened with extinction (IBPES, 2019). While the reasons behind these losses vary by region, in Africa, a major driver is habitat loss. With the current push for development, the impacts of habitat loss are increasing dramatically, affecting species both inside and outside of protected areas. Two Ethiopian birds (Figure 5.D), the Liben lark (>Heteromirafra archeri, CR) and white-winged flufftail (>Sarothrura ayresi, CR), exemplify many of the dilemmas associated with protecting biodiversity on unprotected lands where habitat loss is severe.
The Liben Plain is part of the Borana rangelands, managed by Borana pastoralists under their traditional rangeland management system which is generally compatible with conservation ideals. The Borana’s way of life was disrupted about 40 years ago due to pressure from a former Ethiopian government who wanted the Boranas to adopt a more sedentary lifestyle. For example, drilling of water wells in dry season grazing areas disrupted seasonal grazing systems, while fires that the Boranas used to maintain productive grazing lands and prevent shrub encroachment were prohibited. The Boranas also face pressure from changing land tenure systems. The Liben Plain grasslands are located on communal lands upon which nobody can claim ownership. However, if someone wants to farm here, they just pay a tax that in effect assures ownership of the land. The Boranas were initially slow to adopt this farming lifestyle, but when outside settlers started taking advantage of the government’s farming incentives, the Boranas were pushed to do the same to prevent all their ancestral land from being turned over (Mahamued, 2016). The subsequent loss of fire management (and associated shrub encroachment) and cropland expansion, together with increased human and livestock populations, have led to a major loss of the Liben Plains’ natural ecosystem.
The Liben lark is a ground-nesting bird that is near-endemic to Ethiopia (a second population in Somalia may already be extinct; Spottiswoode et al., 2013). Here, its main population is restricted to the open grasslands of the Liben Plain. Although it was previously common in this ecosystem, habitat loss and degradation have reduced the availability of suitable feeding and nesting sites. Further, the reduced population is also increasingly vulnerable to direct threats such as nest predation and trampling of nests by cattle (Spottiswoode et al., 2009). Due to these threats, the lark’s numbers have decreased so dramatically in recent years that it was classified as >Critically Endangered in 2009.
To prevent the extinction of the lark, the Ethiopian Wildlife and Natural History Society (EWNHS), BirdLife International, and other organizations collaborated with local authorities and community leaders in 2016 to establish enclosures for grassland regeneration. These enclosures are in effect communally-managed grassland reserves regulated under a subset of customary laws. These areas not only secure suitable habitats for the Liben lark, they also provide benefits to the Borana community like securing grazing lands for the dry season when the lark is not breeding. This initiative shows early promise—over 350 ha of grassland reserves have already been established, and over 1,000 ha of shrub have been cleared (Kariuki and Ndang’ang’a, 2018). But to truly secure the future of the Liben lark, more support is needed from the Ethiopian government, particularly in preventing further land conversion, supporting ecosystem restoration, and encouraging the Borana pastoralists’ traditional way of life.
Another species facing imminent extinction due to habitat loss is the white-winged flufftail. One of Africa’s most enigmatic birds, the flufftail is an intra-African migrant restricted to a few seasonal high-altitude wetlands in South Africa and Ethiopia. Like the lark, the flufftail is a ground-nester that struggles to find suitable nesting sites relatively free from disturbance. The Berga floodplain, the flufftail’s Ethiopian stronghold, used to be covered by productive grasslands. This unspoiled landscape is now being replaced by settlements, crop farms, and eucalyptus plantations that generate quick profits. This, together with overgrazing, has led to extensive soil erosion, which in turn has altered the structure and grass composition of the floodplain. Today, the floodplain is encroached by invasive weeds and other less desirable vegetation (seen during EDGE project surveys in 2018) which, together with others forms of disturbance, have reduced the amount of suitable habitat available for the flufftail to such an extent that it is now considered >Critically Endangered.
To prevent the extinction of the flufftail, the EWNHS along with the Middlepunt Trust and BirdLife South Africa have taken several steps to improve the outlook for the flufftail. Much of this work involved working with the people at Berga to improve their livelihoods, and to instil a sense of ownership of their local biodiversity. A prominent outcome of this collaboration was a primary school named after the flufftail; results from the project also contributed to a species action plan (Sande et al., 2008). But without continued maintenance, the progress made by this short-term initiative will have limited long-term value. The flufftail’s future thus continues to be dire, as unsustainable land use practices continue to destroy the Berga floodplain. There is an urgent need for joint long-term efforts to reverse the fate of the species, including taking steps to establish protected areas, to initiate carefully-planned ecosystem restoration efforts, and to develop a new species management plan that will provide lasting benefits.