The 'devil' and other alien plants have invaded the Maasai Mara, threatening one of the world's greatest natural wonders, according to a new study.
Consequently, conservationists and the Kenya Wildlife Service (KWS) have demanded that the aliens species be taken out of the park.
Most of the plants were introduced innocently for ornamental purposes by hotels.
"It is critical that all invasive or potentially invasive plants be removed from tourism facilities in the Mara - asap," said conservationist Arne Witt of Centre for Agriculture and Biosciences International (CABI).
Mr Witt led a research team from KWS and Stellenbosch University in South Africa, who now want all invasive alien plants in the Mara removed.
In case of resistance from the tourist lodges as happened in South Africa, the conservationists want authorities to invoke the letter of the law.
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In the study, the team identified 245 invasive plant species but zeroed in on six, which they said were an immediate danger to the existence of large mammals in the Mara-Serengeti ecosystem.
If nothing is done, Witt said, this would have a severe impact on the migration of large animals, especially wildebeest, zebras and gazelles.
"This will, in turn, have a substantial negative impact on tourism, which is a major economic activity in the region."
The annual Maasai Mara migration involving more than two million animals is regarded as one of the greatest natural wonders of the world.
According to Witt, the offending plants, which include the devil weed (Chromolaena odorata), are invasive (replace other vegetation), toxic or unpalatable, meaning there's less forage available for wildlife to feed on.
In their study published in the conservation journal Koedoe in May, the researchers had investigated the extent of invasive plant species at the Masai Mara National Reserve and the adjacent Serengeti National Park in Tanzania.
The study done between 2011 and 2016 concluded that six species out of the 245 present immediate and grave danger to wildlife existence and migration.
The six, the researchers said, are known to be aggressive invaders with the potential to reduce the capacity of the land to support grazing mammals. Some are also known to be poisonous, or have the ability to affect the health of livestock or wildlife.
The researchers also investigated the type of ornamental plants — those planted for decorative purposes — at 24 tourist facilities. They reported more than 200 alien species that have been introduced for ornamental purposes.
Of these, 23 species were found to have spread over the limits of the tourist facilities into the wild, with possible serious consequences on native vegetation.
To confront the problem, the team wants all alien plants around tourist facilities, invasive or not, removed immediately.
"If allowed to establish widely, control costs can run into millions of dollars," Witt said.
The devil weed, a name also shared with the Datura species and appearing at the top of the list of six, is from Central and Southern America.
An invasive plants database hosted by CABI indicates that the devil has reduced the chances of survival of Nile crocodiles in South Africa and lowland gorillas in Cameroon.
It is described as having the capacity to smother whole plantations of coffee and cocoa and becoming the dominant plant in grazing lands.
Due to the high nitrate content in its leaves, the devil is poisonous to cattle.
Also called the Siam weed, it may not be a household name in Kenya, but this is not so with Prosopis juliflora, also among the six listed.
Prosopis juliflora, called 'Mathenge' in Kenya, is known for its dominance tendency and poisoning of livestock mainly in Baringo County and other parts of the Rift Valley and Coast regions.