Invasive species plague Mara-Serengeti ecosystem, affecting populations

An oryx at Entumoto Safari Camp at Maasai Mara. Wildlife face a major risk as alien plants destroy grass and other vegetation in the ecosystem. [Photo: Wilberforce Okwiri, Standard]

Alien plants are threatening animals in one of the Kenya's major wildlife reserves, a study has shown. 

The study found that at least 245 alien species, introduced in the Mara-Serengeti ecosystem accidentally or intentionally as ornamental plants, were destroying the grass and native plants the animals feed on.

The plants were displacing grass and other plants animals eat, according to the research by a team of scientists from the Centre of Agriculture and Bioscience International (CABI), the Centre for Invasion Biology of the University of Stellenbosch and the Kenya Wildlife Service.

The alien plant species the scientists identified were intentionally introduced into the Maasai Mara National Reserve and adjacent conservancies and have become a major threat to one of the greatest wildlife spectacles - the Great Wildebeest Migration.

“We encountered 245 alien plant species, which are significantly more than previous studies. Of these 62, or 25 per cent, were considered to have established self-perpetuating populations in areas away from human habitation. These included species which had either been intentionally or accidentally introduced,” says the report published by Koedoe science journal in July 2017 notes.

Another 23 species were recorded as being invasive, within the ecosystem outside of lodges, and away from other human habitation.

Currently, the report states, the Serengeti-Mara ecosystem is relatively free from threat. However, there are extensive populations of the invasive plants outside of the ecosystem, particularly to the west, and could easily spread into the reserve.

These plants include cactus and prosopis juliflora (popularly known as mathenge) grasses. Others are the parthenium weed, lantana camara, also known as tick berry, chromolaena odorata, a species of flowering shrub in the sunflower family.

Without urgent interventions, the scientists predicted  that rapid spread of these alien species would convert much of the Serengeti-Mara ecosystem into a 'green desert', significantly reducing wildlife numbers and impacting on tourism and later the economy of the country. 

“We predict that in the absence of efforts to contain, or reverse the spread of invasive alien plants, the condition of rangelands will deteriorate, with severe negative impacts on migrating large mammals, especially wildebeest, zebra and gazelles. This will, in turn, have a substantial negative impact on tourism, which is a major economic activity in the area,” says the report.

Arne Witt, an expert on invasive plants at CABI, called for measures to contain the spread of the plants.

Control programs

“We need urgent action right now, with a series of control programmes implemented, to reduce the severity of these threats. Failure to act could see the devastation of Serengeti-Mara ecosystem,” Dr Witt said.

She said some of the plants had been spread by wind, water and wild animals.

The study recommends removal of the plants and implementation of strategies to slow down their spread or eliminate them altogether.

“In carrying out this research, CABI together with other scientists have taken the first step in highlighting the threat of invasive alien species to one of the wonders of the world, the Great Migration," Witt said.

The Maasai/Serengeti is known for the annual wildebeest migration voted the Eighth Wonder of the World.