Invasive alien species — pests, insects and weed — threaten to surpass the impact of drought on smallholder agriculture, pastoralism, fisheries and tourism, scientists warn.

These species comprise coloniser plants, insects and animal pests — described by the Centre for Agriculture and Biosciences International (CABI) as non-native organisms.

Besides eating into huge tracts of farmland and suffocating crops, pasture and water bodies, they cause environmental harm which affect human and animal health.

“In East Africa, many plants introduced in the region have escaped cultivation and are wreaking havoc,” said Dr Arne Witt, Africa invasive species co-ordinator at CABI at the opening of a two-day workshop in Nairobi.

Socioeconomic studies of the impact of invasive species in rural livelihoods done in Kenya, Ethiopia, Tanzania, Uganda, Malawi and Zambia showed a major negative economic impact on mixed maize smallholders.

The study covered the erect prickly pear, parthenium weed, siam weed, lantana and tree marigold.

Dr Witt puts the annual losses at $0.9 billion — $1.1 billion, expected to grow to $1billion — $1.2 billion over the next 5–10 years.
“Invasive alien plants outcompete indigenous species, often resulting in changes to the structure and composition of an ecosystem,” Dr Witt added.
These invasive species also affect millions of people living in the region who are dependent on natural resources — a source of future conflicts, according to Dr Witt.

Tackling invasive species

Plant and animal species scientists, who met in Nairobi to develop a strategy aimed at tackling invasive species in Africa, said the rate at which IASs were covering arable and pasture land is going to exacerbate the already bad situation of resource-based conflicts.
“The region must wake up to a new livelihood threat and act immediately. Invasive alien species are quickly swallowing farmlands, water bodies and the environment,” he said.

Recently, the Fall Army Worm (FAW) among a range of other pests, invaded thousands of maize crop plantations in Kenya and left farms dry. It causes 100 per cent loss of crops, and is said to be continuing to devastate more farms in the region.

Dr Witt calls on the government to take this issue seriously; revise its policies, improve airport surveillance by ensuring police are not only focused on contraband but also thoroughly checking luggage of visitors who are coming into the country.
Mr Hiver Boussini, the animal health officer at the African Union Inter-African Bureau for Animal Resources (AU-IBAR), Kenya lists Prosopis juliflora, known as Mathenge weed in Kenya, as a continuing concern among pastoralists for its ability to colonise large areas of pasture land.

“This weed has eaten huge chunks of pasture land forcing pastoralists, in some areas, like Laikipia, Tana River and in Ethiopia to fight for the little grass that is left, in the process resulting in inter-communal clashes,” he said.
The scientists who met at Icipe in Nairobi warned that wild tobacco, known scientifically as Nicotiana glauca, water hyacinth (Eichhornia crassipes), and yellow cestrum (Cestrum aurantiacum) a could be a new breeding ground for the malaria spreading anopheles mosquito.
While invasive species are a global problem, SSA is one of the most susceptible regions, with a long and diverse list, and clear illustrations of the often horrendous destruction of this menace.
Indeed, it is projected that the threat posed by invasive species in the region will directly and indirectly affect the attainment of at least eight sustainable development goals.