By David Okul
Like in many parts of the world, invasive species in Kenya are a threat to the native wildlife and vegetation. Consequently, human health and economies become a risk from the invasive species as a bulk of the commercial, agricultural, and recreational activities depend on a healthy native system.
But how can we define if a species is invasive or not? In general terms, invasive species refer to species not native to the ecosystem and causes harm to the environment, ecosystem, or human health. The species are also likely to reproduce quickly or spread aggressively. Although most invasive species come from different countries, it is not often the case. A species may be invasive even it’s native to a different region in the same country.
Whether intentionally or by accident, humans are the major spreaders of invasive species. Intentional in the sense that some are released pets (e.g. Burmese pythons in the everglades), while some are intentionally planted (such as landscaping plants). Under the Wildlife and Conservation Act of Kenya (2013), various species are classified as invasive. This article will outline these species.
Not Many Mammals are listed as Invasive in Africa
The only mammal listed as invasive in Kenya is the Coypu rat (Myocastor coypus). The large semi-aquatic rodent is native to South America but is nominated by IUCN as one of the “100 of the World’s Worst invaders.” Today, the Coypu rat is found in every continent except Australia and Antarctica. Initially, they were kept for their fur, but many farmers learned that its fur is not premium in the market like a rabbit, minx, or fox furs. The rats eat a lot of vegetation and reproduce fast. A breeding pair can create 16,000 individuals within three years. Crazy numbers! But the species has a gestation period of 130 days resulting in a litter of 4-6 young ones on average, and a female can reproduce 48 hours after giving birth. Also, consider that the nutria can eat vegetation 25% of its body weight. It is no wonder that the Kenyan government is cautious about it.
Nevertheless, some mammals should be a concern for Kenya and across Africa because of their invasive nature. Examples of invasive mammals in Africa include feral cats, goats, house rats, and European rabbits. Feral cats are particularly nasty to any ecosystem as they kill any species they can. All in all, the impacts of invasive mammals are not as severe when compared to plants.
Invasive plant species in Kenya
Various plant species are known to be invasive in Africa. They take up pastureland and some are persistent weeds in cultivation lands. Regardless, all invasive plant species tend to limit the production of indigenous species.
- Mathenge (Velvet mesquite) (Prosopis juliflora): It is perhaps the most notable invasive woody species in Kenya and some parts of Africa. In Kenya, it was introduced in the Baringo region, but it did spread to other parts. It spread aggressively leading to the loss of pasture. Among its other negative impacts include punctures to tyres, reduced biodiversity, loss of agricultural land, injury to livestock, and blocking challenges.
- Tickberry (Lantana camara): Lantana camara is native to South America but graders have moved it across the tropics, mainly because of its showy flowers, which produce berries. The berries are eaten by birds that further disperse the seeds. The species push native plants because livestock cannot its leaves or stems.
- Nile Cabbage (Pistia stratiotes): the plant was introduced to Africa from South America. It is grown as an ornamental and often used to provide cover for fish in aquariums or ponds. However, its devastating effects in East Africa outpower its positive effects. It has clogged water bodies and irrigation channels.
- Yellow oleander (Thevetia peruviana): The plant is naturalized in many parts of Africa as it is commonly used for fencing. As the plant is poisonous to humans and most animals, it tends to spread fast.
- Mauritius thorn (Caesalpinia decapelata): The woody plant has its origin in Southern and Eastern Asia but has been naturalized in East Africa. Because of its thorns and fast growth, it is often used as a live fence in Africa as it can prevent invasion from notorious animals, like baboons. Regardless, the species chokes native vegetation. It has also been reported to clogs water infrastructure.
- Jimsonweed (Datura stramonium): The origins of the noxious weed are relatively unknown, but it is suspected to be native to the Americas region. The species has spread to most parts of the world. In Africa, it is common in roadsides, agricultural lands, disturbed areas, and riverbanks. The plant is used as medicine and narcotics. It is invasive because of its tendency to spread fast in agricultural areas reducing crop yields.
- Yellow bells (Tecoma stans): The plant is native to the Americas and has spread over the world because of its ornamental appeal. However, its seeds are dispersed by the wind at a rapid rate leading to weed-like tendencies in riparian areas and roadsides.
- Mexican poppy (Argemone mexicana): It is native to Mexico and Texas but has spread as a weed to most tropical areas of the world. It is poisonous to livestock but deaths are few because it is not readily eaten. Its seed remains dormant for a long time making its control difficult.
- Opuntia exaltata Long spine cactus
- Opuntia ficus– indica Sweet prickly pear
- Opuntia vulgaris ” Drooping prickly pear: Most of the Opuntia species were introduced to Kenya by the British as ornamental plants. The plant thrives in arid conditions suppressing grass and other indigenous vegetation. The cacti have sweet fruits, but they are dangerous to livestock because the spine can cause injury to animals feeding. Regardless, animals like baboons and elephants help the spread of the plant as they feed on the seeds and help disperse. A species of opuntia was considered Australia’s worst weed before a series of biological agents were deployed to fight it.
- Water hyacinth (Eichhornia crassipes): Water hyacinth has numerous negative effects on Lake Victoria including obstructing waterways, the spread of water-borne diseases, and increase of water loss through evapotranspiration.
Acacia reficiens is a species that is native to Kenya but is treated as an invasive species in some areas. For instance, the species has colonized former grasslands in parts of northern Kenya. As such, local NGOs with the community are cutting down the trees and planting grasses. Similarly, Acacia mellifera in southern parts of Kenya is also not desirable by the pastoralists.
In some areas of Africa, a list of invasive plants also includes the Acacia wattles (especially Acacia mearnsii), Eucalyptus species (probably because of its negative impacts on wetlands), and castor oil plant (Ricinus communis).
Other animals listed as invasive in Kenya
Apart from mammals, other animals including birds, reptiles, and anthropoids are classified as invasive. The following section outlines them
Birds
- Speckled Mousebird (Colius striatus):
- Ring-necked pheasant (Phasialus colchicus)
- Mute Swan (Cygnus olor)
- Chaffinch (Fringilla coelebs)
- House Finch (Carpodacus mexicanus)
- Common Indian Myna (Acridotheres tristis)
- Rose-ringed (Ring-necked) Parakeet (Psittacula krameria): It is a common ornamental bird across the world. However, it is known to escape cages and free itself from captivity. The species is recognized as invasive in most parts of Africa.
- Common (European) Starling (Sturnus vulgaris)
- Rock Dove (Feral pigeon) (Columba livia): It is thought that the first rock doves came to Africa from Dutch settlers in South Africa in 1652. They are a menace to the agricultural landscapes.
- Beautiful fruit dove (Ptilinopus pulchellus)
- Black-chinned fruit dove (Ptilinopus leclancheri)
- Coroneted fruit dove (Ptilinopus coronulatus)
- Mariana fruit dove (Ptilinopus roseicapilla)
- Pink-spotted fruit dove (Ptilinopus perlatus)
- Wompoo fruit dove (Ptilinopus magnificus)
- House Crow (Corvus splendens): Urban pest that damages crops and is a hazard at the airports. It was introduced in Kenya in about 1947, and is responsible for killing fruit bats.
- Red-billed Quelea (Quelea quelea)
Reptiles
- Red-headed agama lizard (Agama agama)
- Brother’s Island tuatara lizard (Sphenodon guntheri)
- Orange-throated whiptail lizard (Aspidoscelis hyperythra beldingi)
- Rainbow kopje skink (Lampropholis delicata)
- Brown tree snake (Boiga irregularis)
- Red diamond rattlesnake (Crotalus exsul)
- Burmese star tortoise (Geochelone platynotan
Invertebrates
Crown of thorns starfish (Acanthaster planci)
Fishes
Although not listed in Kenya’s wildlife Act, an invasive species of interest to conservationists is the Nile Perch (Lates niloticus). The species was introduced to Lake Victoria in 1954 to address the issue of overfishing. However, Nile Perch is the main cause for the disappearance of over 200 endemic fish species in the lake.
It is apparent that invasive species have a devastating impact on the native species. In Kenya, the impact of invasive species is particularly significant. Because the economy depends on natural resources for industries like tourism and agriculture. Even more concerning is the growing list of endangered species in Kenya, whose habitats are destroyed by the invasive species.
David Okul is an environmental management professional with over 10 years experience on donor projects, conservation, forestry, ecotourism, and community-based natural resources management. When not working on environmental projects, I spend my time writing for Silvica on a variety of topics.
