The data on wildlife migrations in East Africa shows a dramatic decline in populations over the past several decades. In Kenya, wildlife numbers declined by 68% between 1977 and 2016, both inside and outside protected areas. Specifically focusing on migratory wildebeest populations:
- The Mara-Loita population decreased by 81% from over 123,000 in 1977 to under 20,000 by 2016.
- The Serengeti-Mara population, though initially growing from 190,000 in 1957 to 1.3 million in 1977, has seen a 73% reduction in wildebeest migrating to the Masai Mara, dropping from 588,000 in 1979 to 157,000 in 2016.
- The Athi-Kaputiei population plummeted by 95%, from 27,000 in 1977 to under 3,000 in 2014.
- The Amboseli population saw an 85% decline, going from 16,300 in 1977 to less than 2,400 in 2014.
- The Tarangire-Manyara population fell by 72% from 48,800 in 1990 to 13,600 in 2016.
Four of the five major migratory populations are now severely threatened. These sharp declines are mainly attributed to human activities such as unplanned agricultural expansion, infrastructure development, and competition with livestock for resources, which have fragmented critical migratory pathways. Urgent conservation actions, including regulation of land use and restoration of degraded rangelands, are required to prevent further collapses and local extinctions of migratory wildlife species.
The study published in Koedoe highlights the significant threat posed by invasive alien plant species in the Serengeti-Mara ecosystem, a critical wildlife area in East Africa. Through field surveys and analysis, 245 alien plant species were identified, with 62 of them having established self-sustaining populations away from human habitation. Among these, 23 species were identified as invasive, posing substantial risks to the ecosystem, particularly to the migration and habitat of large mammals like wildebeest, zebras, and gazelles.
The most concerning invasive species include Parthenium hysterophorus, Opuntia stricta, Tithonia diversifolia, Lantana camara, Chromolaena odorata, and Prosopis juliflora. These species spread rapidly, reduce biodiversity, and degrade rangelands, directly affecting the food supply of grazing animals. If unchecked, these invasions threaten not only the ecological balance of the region but also the tourism industry, which is economically vital to both Kenya and Tanzania.
The study emphasizes the urgent need for management interventions, including the removal of invasive species from tourist facilities, implementing control programs to eliminate outlier populations, and introducing biological control measures. Without effective management, the invasive plants could drastically alter the ecosystem, leading to a decline in wildlife populations and negative impacts on tourism.\\
The study found that climate change, particularly reduced vegetation quality, has a more significant impact on impala stress levels in the Serengeti than human disturbances. Impala showed elevated faecal glucocorticoid metabolite (FGM) concentrations when vegetation was poor, indicating higher stress. Rainfall improved forage quality, reducing stress. Human activities, such as settlement density and proximity to park borders, also increased stress, but not as strongly as the availability of nutritious vegetation. The findings suggest that maintaining forage quality through habitat protection and addressing climate change effects is critical for conserving impala and other herbivores in the region.