Blocked migratory corridors and loss of dispersal areas are limiting the migratory movements of animals like the wildebeest.
tHE iconic wildebeest migrations of East Africa are an important ecological phenomenon and massive tourist attraction. However, many wildebeest populations are in drastic decline across the region.
Their dispersal areas and migratory corridors are being lost due to high human population densities, increasing urbanisation, expanding agriculture and fences. Their loss would contribute to biodiversity decline, and jeopardise tourism and other ecosystem services. Urgent efforts need to be made to protect wildebeest migratory corridors and dispersal areas to ensure these great migrations for the future.
Large-scale animal migrations were once common around the world, but many have now collapsed, and others face serious decline.
For example, on the Great Plains of North America, the American bison once numbered as many as 30 million animals. Today, only a few remain due to over-hunting.
In Central Asia, the Saiga antelope has declined from over one million animals in 1980 to less than 200,000 in 2000.
In Kenya, the migration of vast herds of zebra and Thomson’s gazelle between the Lake Nakuru-Elementaita region and the Lake Baringo disappeared in the early part of the 20th century due to over-hunting, habitat loss and other human disturbances.
The East African savannas are well known for the large-scale seasonal migrations of grazing herbivores.
Perhaps one of the most wellknown is the annual migration of 1.3 million wildebeest, 600,000 zebra and Thomson’s gazelle in the Serengeti-Mara ecosystem. The significance of this migration is huge: it is the largest and most species-diverse large mammal migration in the world. It is of iconic importance for tourism and has huge ecological significance, resulting in the Serengeti National Park in Tanzania being listed as a World Heritage Site.
The East African savannas are highly variable ecosystems, so migration enables animals to track spatially and temporally varying resources across the landscape. This gives migratory populations an advantage over resident popula- tions, and allows these populations to rise to very high abundances. Migrants may also move to access breeding grounds, to reduce the risks of predation and disease, and to enhance their genetic health.
Wildebeest migrations are important both ecologically and economically. They play a vital role in ecosystem function and provide a number of important ecosystem services. They also have a direct effect on predator populations and other wildlife species, and on grass food resources.
Economically, wildebeest migrations are important because they draw in tourism and thus contribute significantly to national economies. Tourism generated an estimated US$1.2bil (RM3.9bil) revenue in Kenya in 2012 and US$1.3bil (RM4.3bil) in Tanzania in 2011.
Wildebeest depend on migratory corridors and dispersal areas as they migrate out of protected areas to their seasonal habitats, often located in pastoral lands. Migratory corridors and dispersal areas usually cross human-dominated landscapes where land use practices are becoming increasingly incompatible with wildlife. As these areas are degraded or lost, severe declines in the wildebeest populations can result.
In East Africa, the white-bearded wildebeest, found across Kenya and Tanzania, is facing large declines due to incompatible land uses in their migratory corridors and dispersal areas. This has occurred as their migratory corridors and dispersal areas have become blocked or lost, limiting their migratory movements. The result has been the near collapse of many wildebeest populations.
The exception to this general pattern is the Serengeti-Mara population, which increased six fold between 1963 and 1977 following the eradication of rinderpest, before stabilising to its current population of approximately 1.3 million. In southern Africa, the blue wildebeest is stable or increasing, although their numbers are still far lower than their 1960’s levels.
In Kenya, all four wildebeest populations are declining dramatically as indicated by the latest trends. In particular, in the Mara ecosystem found within Narok County, the wildebeest population that migrates annually between the Maasai Mara National Reserve and the Loita Plains declined by more than twothirds, from approximately 113,000 animals in 1977 to 35,000 by 2009 due to the expansion of agriculture and continues to decline.
In the Athi-Kaputiei ecosystem, the wildebeest migration between the Nairobi National Park and the adjoining Athi-Kaputiei Plains declined by more than 90%, from over 30,000 in 1978 to under 2,000 by 2011 as a result of increasing urbanisation, fencing, settlements, mining and other developments.
In Tanzania, in the Tarangire-Simanjiro ecosystem, the wildebeest migration from Tarangire National Park to the Simanjiro Plains declined by 88%, from 43,000 in 1988 to 5,000 in 2001 due to expanding cultivation and settlements blocking their migratory corridors.
In each of these cases, wildebeest are prevented from accessing their wet season ranges due to the blockage of migratory corridors or the loss of habitat in their dispersal areas.
Wildebeest are especially vulnerable to human impacts in their wet season ranges. Many protected areas in East Africa primarily conserve the dry season habitat for migratory wildlife, with the wet season ranges occurring almost entirely outside of protected areas on adjacent communal or private lands.
Protected areas also tend to be small and were not designed to conserve all of a migratory species’ habitat requirements. As a result, wildebeest must journey outside of protected areas to reach their wet season ranges. Here they face a number of pressures due to human population growth, land use change and increasing development.
In the past, protected areas were able to sustain large migratory wildebeest populations because human population densities were low enough to allow them to migrate outside of protected areas to their wet season ranges. However, this is becoming increasingly difficult as human populations surrounding protected areas rise, and land use changes and habitat loss intensifies.
Today, nearly all the world’s
remaining large wildlife populations exist in unfragmented migratory systems. For example, the Serengeti-Mara ecosystem migration has been sustained because it has survived in a relatively intact ecosystem contained within a network of protected areas that encompass all the grazing habitats required to support a large migratory population. However, this migration too now faces a number of threats.
The loss or fragmentation of habitats is one of the main threats to wildlife migrations globally. In East Africa, wildebeest migrations are in decline due to a number of land use activities causing habitat loss and fragmentation in their wet season dispersal areas. These land use activities, which include cultivation, land subdivision, settlements, fencing and other infrastructure, disrupt migratory movements and cause wildebeest populations to decline.
Fences are used to stop disease transmission between wildlife and livestock, to prevent poaching and to protect crops and homes, but they obstruct migratory routes.
Fencing is one of the main causes of the crash in the wildebeest population in the Athi-Kaputiei ecosystem in Kenya. More than 20% of the ecosystem is now fenced, and a number of migratory corridors linking the Nairobi National Park and the Athi-Kaputiei Plains have been blocked by fences. Now, only few wildebeest enter Nairobi National Park during the dry season.
Roads, too, obstruct migratory routes, cause wildlife mortality due to vehicle collisions, and decrease landscape connectivity. Due to increased access, roads can also open up new areas for development, leading to land uses incompatible with wildlife. These are many of the concerns in the development of a new road through the Serengeti National Park.
In Kenya, a similar threat faces the wildebeest migration in the Athi-Kaputiei ecosystem due to the upgrading of the Athi RiverNamanga Road and the proposed Greater Southern Bypass Road along the southern boundary of Nairobi National Park.
Poaching is another threat to many migratory populations. In the Serengeti National Park it is estimated that local consumption of bush meat is responsible for approximately 70,000 to 129,000 wildebeest deaths per year. A high intensity of poaching is also linked to a decline in wildlife numbers in the Mara area of Kenya.
Climate change is a new and growing threat to wildlife migrations in the East African savannas. The increased frequency and severity of droughts and floods that is expected to occur will modify vegetation growth and hence food availability for the migrating animals.
In the Amboseli ecosystem, a severe drought caused the wildebeest population to crash by more than 85% in 2009. By 2010, the population numbered only 3,000 animals, down from over 15,000 animals before the drought, the lowest observed for more than 30 years.
The ability of migrants to respond to changing climatic conditions is likely to be impaired by such manmade threats as habitat loss and fragmentation.
What is being done?
Since most migrants wander outside of protected areas, it is crucial to include communities and landowners in conservation efforts through participation in wildlife management and benefit-sharing. In the East African range lands, economic benefit to local communities from wildlife has been meagre with little incentive to help protect migrants or their dispersal areas and migratory corridors.
Efforts are now being made to secure wildlife dispersal areas and migratory corridors through the use of community conservancies, payments for ecosystem services and other economic incentives.
For example, in the Mara, eight wildlife conservancies have been formed, which offer land lease payments of US$25 to US$40 per ha (RM82 to RM132) per year to land- owners. These schemes, financed by ecotourism operators, aim to keep land open for wildlife and provide landowners with a regular income stream. They now cover over 90,000ha, securing vital migratory corridors and dispersal areas for wildebeest from both the Serengeti and the Loita Plains.
In the Athi-Kaputiei ecosystem, the wildlife conservation lease programme, supported by a number of donors, offers participating landowners US$10 (RM33) per ha per year to keep their land open for wildlife and livestock in the wildebeest dispersal area. This programme is being targeted to secure wildlife migratory corridors and critically reduce fencing in this ecosystem and by 2012 covered 24,200ha.
In another approach, environmental easements are being applied to protect privately owned land adjacent to Nairobi National Park, including placing it under park management.
Also in this ecosystem, the community and other stakeholders have recently developed the first community driven landuse masterplan to sustainably manage wildlife dispersal areas alongside livestock grazing, settlements and other land uses in the ecosystem.
In the Tarangire-Simanjiro ecosystem in Tanzania, payments for ecosystem services, financed by tour operators, are being used to protect the dispersal area of migratory wildebeest and other wildlife in the Simanjiro plains.
Conserving migratory routes requires implementing conservation plans beyond protected area boundaries. Dispersal areas and migratory corridors can be kept open for wildlife, by encouraging wildlife-friendly land uses, and the co-operation and participation of community and private landowners.
Governments need to provide the correct enabling policy and legislative environment to support the types of initiatives already emerging to protect migratory habitat.
Due to the transboundary nature of wildebeest migration in East Africa, the respective countries and governments need to work together to mitigate threats to the migrations.
Good scientific information on where, when and why wildlife migrations occur is needed to inform conservation and management decisions. This includes mapping the movements and ranges of wildebeest, the ecological drivers of migration, population levels, and a good understanding of the threats to migrants and their habitats.
The Kenya and Tanzania governments are already mapping wildlife corridors and migratory routes with the aim of securing critical wildlife areas.
In other initiatives, researchers are collaring wildebeest to track their movements to understand how landscape fragmentation and climate change are affecting wildebeest, and reporting their movements online.
Efforts to secure dispersal areas and migratory corridors will require an integrated approach to land use planning both inside and outside of protected areas. By taking into account wildlife and their migratory routes, people, livestock, landscapes and natural resources, a more comprehensive conservation effort can be made.
Thus, there is a need to work collaboratively with landowners and users to identify threats along migratory routes so these critical areas can be effectively protected.
The rapid and dramatic wildebeest population declines in East Africa calls for urgent, comprehensive and decisive remedial steps to protect the remaining populations and rehabilitate their habitats. This will enhance their resilience to the intensifying droughts and contribute to the sustainability of local livelihoods. – UNEP
Moving house: Wildebeest and zebra mount the opposite bank after crossing the Mara river, in the Maasai Mara Game reserve in Kenya. The annual migration of wildebeest, zebra and Thomson’s gazelle in the Serengeti-Mara ecosystem is the largest and most species-diverse mammal migration in the world. – aP
crocodiles devour a zebra as it attempts to cross a river.