‘Devil weeds’ threaten wildebeest migrations in Serengeti

13 June 2017

By Andy Coghlan

With names like “devil weed” and “famine weed”, perhaps it’s little wonder that these invasive plant species threaten to disrupt one of the great wonders of the world: the annual migration of 2 million animals across the savannahs of eastern Africa.

Initially planted for decoration at tourist lodges in Kenya’s Masai-Mara National Reserve, the invasive species are now spreading into and displacing natural vegetation out on the savannah. The large animals that cross these grasslands each year depend on them for food.

That’s the grim message from a new survey of the spread of invasive exotic plants in the Serengeti-Mara ecosystem, focusing on six species that pose the most serious threat to the migrating animals.

“Rampant invasions in the Serengeti-Mara ecosystem will certainly reduce forage production, leading to drastic declines in the populations of wildebeest, zebras and other large grazing mammals,” says Arne Witt of CABI Africa in Nairobi, Kenya. “These invasive plants are toxic or unpalatable, meaning there’s less forage available for wildlife to feed on.”

One invader, called famine weed (Parthenium hysterophorus), has already been shown to displace 90 per cent of food in fields for livestock, and the effects would be the same for wildlife, says Witt.

Already, the animals’ food sources have been hit by drought and depletion of the Mara river, so their plight could be exacerbated if the plants continue to spread. The survey shows that the species are already infiltrating areas of grassland, creating impassable thickets of inedible vegetation where once there was only grass.

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