Nairobi — Virtually every protected area in Africa suffers from invasive species threatening biodiversity and peoples' livelihoods, a meeting called to address the problem has heard.

Africa's protected biodiversity areas are under increasing threat from the species introduced - usually through human activities - to areas outside their natural range where they damage biodiversity, agriculture and human health.

The poor - who depend almost exclusively on ecosystems for their survival - are particularly affected by invasive species, experts said at the 14th meeting of the Subsidiary Body on Scientific, Technical and Technological Advice to the Convention on Biological Diversity held in Nairobi over the last two weeks (10-21 May).

"It is a very serious problem because the potential damage to biodiversity is huge," said Geoffrey Howard, a Nairobi-based coordinator for invasive species at the International Union for Conservation of Nature, Switzerland.

"People are generally only worried about wildlife in parks and may not know that invasive plant species have invaded native vegetation in Africa's protected areas and pose a major threat to the future of biodiversity conservation."

In Zambia, he said, giant mimosa (Mimosa pigra) - a spiny shrub native to Latin America and introduced to Africa - established itself on the Kafue flood plain in a national park in the early 1980s, and now covers 3,000 hectares of prime floodplain habitat - fast displacing important indigenous animals, birds and plants from their natural environment.

"The government is now spending substantial amounts of money on trying to control this insidious weed," Howard said.

The problem is made worse because many protected area managers and their staff, as well as relevant policymakers, seem to lack knowledge about recognising invasive species and deciding on the best methods for dealing with them, said Arne Witt, coordinator for invasive species at CABI Africa, a non profit, science-based development and information organisation based in Kenya.

"Most African countries lack the necessary policy and legal frameworks to prevent the introduction of invasive and potentially invasive species," Witt added.

"There are few national or regional programmes in Africa to manage them."

Lack of scientific research and institutional capacities also contribute to the situation, and thus little is known about the invasive species that are present, what impact they have and how best to manage them, the meeting heard.