Invasives Blog

By Gilbert Nakweya
Reblogged from SciDev.Net

Prosopis and Lantana, two invasive woody shrubs that have been encroaching on Kenyan grazing and agricultural lands. Copyright: Panos

Invasive alien species should not be used in restoring degraded landscapes as their costs outweigh their benefits, experts say.

Invasive alien species, according to the Convention on Biological Diversity, are plants, animals and other organisms that are non-native to an ecosystem, and may adversely affect human health and the environment, including decline or elimination of native species.

The experts who spoke on the sidelines of the Global Landscapes Forum held in Kenya last month (29-30 August), said that long-term workable restoration of degraded landscapes in Africa requires effective management and control of invasive alien species.

“We need to try and link science to the indigenous knowledge that exists.”
Fassil Teffera, Arba Minch University

According to the experts, invasive alien species destroy biodiversity, thus aiding land degradation.

Robert Nasi, the director-general of Indonesia-headquartered Center for International Forestry Research (CIFOR), said that Africa loses about 2.8 million hectares of forests each year due to deforestation and land degradation resulting from rapid population growth, increased demand for food and climate change.

Unless urgent action is taken, land degradation will worsen, Nasi said. “Annually, we must restore at least 12 million hectares globally to reach land degradation neutrality,” Nasi added.

The forum, which was organised by CIFOR in partnership with the United Nations Environment Programme, and the World Bank, assembled over 800 experts from countries such as Ethiopia, Ghana, Kenya, Rwanda, Tanzania and Uganda to discuss and share knowledge on forest and landscape restoration in Africa.

The experts who included research scientists and policy makers were concerned that the control of invasive alien species is not being addressed sufficiently to restore degraded land in Africa.

According to Yussuf Adan, species programme manager of the World Wildlife Fund-Kenya, some of the common invasive plants  in Africa include the Australian Wattles (Acacia species), Mauritius thorn (Caesalpinia decapetala), and water hyacinth (Eichhornia crassipes) and mesquite tree (Prosopis glandulosa).

These species grow fast, inhibit crop and pasture growth and could cause health problems.  Adan explained. For instance, the water hyacinth that has invaded Lake Victoria in East Africa provides breeding grounds for mosquitoes that spread malaria in the region. Also, species such as the mesquite tree found in Ethiopia kill medicinal plants used by indigenous groups to control their health problems.

Arne Witt, invasive species coordinator at the UK-headquartered Centre for Agricultural Biosciences International (CABI, the parent organisation of SciDev.Net), said that land degradation will be worse if scientists and development actors such as governments do not create innovations to control invasive species in Africa.

Witt added that invasion of land by invasive species makes the regeneration process extremely expensive, indicating that using some invasive species as ornamental plants is poisonous to livestock.

About 71 percent of grazing land could be lost in Southern Africa, if invasive alien species are not managed, Witt explained.

Fassil Teffera, assistant professor of aquatic ecology, Ethiopia’s Arba Minch University, said that it scientists should recognise the contribution of indigenous knowledge to invasive species management.

“We need to try and link science to the indigenous knowledge that exists,” Teffera told SciDev.Net, adding that smallholder farmers in Ethiopia have identified indigenous plants that can be used to control invasive plant species.

Read on SciDev.Net →