Every year the Serengeti-Mara ecosystem becomes the stage of the greater wildlife spectacle on Earth, the annual migration of approximately 1.2 million wildebeest accompanied by more than half a million zebras, Thomson’s gazelles and other mammals.
The significance of this migration is huge: it is not only the largest and most species-
diverse large mammal migration in the world, but it is also one of the few greatest animal migrations left in our planet.
More than an amazing and very dramatic spectacle, the great migration is critical to the survival of the entire Mara-Serengeti ecosystem. Wildebeests, also known as gnus, shape the ecosystem as they move. They crop grass and fertilize the land with their droppings, while lions, cheetahs, hyenas, crocodiles and other predators depend on them for protein. In fact, one of the most iconic portions of the migration is the crossing of the Mara River during which thousands of animals die every year either as they fall prey to the hungry crocodiles waiting for their annual feast or just by drowning while trying to cross to the other side of the river.
When a keystone species disappear the entire ecosystem is threatened
While the death of so many animals is very sad, it is part of the circle of life. A lot of research has been done on the migration’s role in facilitating terrestrial nutrient cycling and promoting vegetation, prey, and predator biomass in the savanna grasslands of the Serengeti Mara Ecosystem. New studies are also showing that this animal migration has also a positive impact on the ecology of the aquatic ecosystems.
Unfortunately, many wildebeest populations are in drastic decline across the region (Estes and East, 2009). Their dispersal areas and migratory corridors are being lost due to high human population densities, increasing urbanization, expanding agriculture and fences, and habitat fragmentation (UNEP Global Environmental Alert System, Dec 2013). Another big threat to the area has been the more intense variations in seasonal flooding and drought, which might be the result of climate change. As the Indian Ocean warms and prevailing winds transport moisture over East Africa, more intense periods of rain and drought result, raising the prospect of a new threat to the Serengeti’s keystone species and their migration (Pool, 2010 Smithsonian Magazine).
If nothing is done to protect this million-years-old phenomenon we might soon face the collapse of an entire ecosystem that depends on these clumsy animals for their survival.
Want to learn more about the great migration? Read the Greatest Spectacle on Earth a post I wrote seven years ago from the perspective of the wildebeest.