Ecological Viability of East African Parks and Wildlife Sanctuaries

Over the last twenty years, local communities have exploited the resources provided by Nechisar National Park in southern Ethiopia. With an increasing population, there are now hundreds of families grazing their livestock on Nechisar’s grassland plains, greatly reducing the amount of grass cover and increasing the occurrence of bushes and bare soil. The sicklebush (Dichrostachys cinerea) is one of the most common shrubs covering the plains, and it is continuing to grow in large quantities, replacing the original habitat. Livestock and other herbivores may contribute to the increasing bush cover by ingesting the seeds of these bushes and then passing them intact within their dung. If the seed-filled dung is deposited in grassland habitats, the seeds may successfully grow and increase the risk of bush invasion. This project, which formed the basis of my Master’s thesis, investigated how the vegetation in the plains has changed over the last 25 years, and how well seeds from the sicklebush (and two other bushes) germinate after being defecated by herbivores; this knowledge is further enhanced by mapping the locations of these herbivores throughout the plains.

Results indicated that sicklebush patches tend to cluster together. While most patches are likely the result of natural processes like wind dispersal, small patches are particularly isolated, suggesting the movement of animals may be more responsible for their location. The greater kudu was the only ungulate to prefer grasslands with sicklebush patches, while all others preferred open grasslands. The sicklebush seeds were more successful at germinating after being defecated by lesser kudu, cattle, and goats, and these seeds germinated more often than the other two bushes. The influence of herbivores on sicklebush invasion via seed dispersal may be minimal, however, and factors such as habitat alteration and the reduction of grass-shrub competition may be the primary mechanism encouraging the proliferation of the sicklebush in the Nechisar plains.

The establishment of wildlife sanctuaries and dispersal areas is becoming a more common method to try to combat the increasing loss of wildlife in Kenya in an effort to allocate specific areas that can be solely used by migratory and free-ranging wildlife. However, there are challenges to creating an efficient wildlife sanctuary or dispersal area. Those responsible for the creation of these refuges must ensure there is little human-wildlife conflict, a minimum amount of spatial overlap and competition between wildlife and livestock, a diverse range of habitats to accommodate for a diverse amount of wildlife, and enough space to fully and comfortably house the species that utilize the area. This project investigated five sanctuaries in the Amboseli ecosystem: Kimana, Osupuko, Kilitome, Elerai-Rupet, and Motikanju Wildlife Sanctuaries. Geographic information systems (GIS) were used to map the boundaries of Kimana (for the first time), conduct transects within all the sanctuaries, and create a grid displaying spatial overlap between wildlife and livestock in each sanctuary.

Spatial overlap occurred in 7.53% of the total area covered, with a minimal rate of potential competition, and habitat preference was exhibited. Overall, the four habitats recorded (bushland, grassland, wooded grassland, and shrubland) were relatively equal in frequency, yet Simpson’s diversity indices showed no significant difference in diversity between each sanctuary or each habitat. Although the sanctuaries in the Amboseli ecosystem do not have a significant difference in diversity, they hold a high level of diversity of wildlife. A good dispersal area must accommodate for a wide variety of species, and these sanctuaries do meet this criterion under the data from this study. It is also important for dispersal areas to have minimal amounts of wildlife-livestock spatial overlap and competition, which this study illustrates for these areas. However, it is difficult to make a clear assessment as to the overall ecological viability and usefulness of the sanctuaries based on one study alone. What is clear is that wildlife is, in fact, utilizing and gaining something from these protected areas. In essence, this suggests that the sanctuaries are working as migratory corridors and dispersal areas, but more, long-term research must be carried out to properly assess the sanctuaries’ overall ecological viability.