Focus on invasion of plant "invasives"

Southern Africa's conservationists feel they should learn from the AIDS crisis that foresight can lessen the damage of the region's next great disaster. The looming crisis is an environmental catastrophe wrought by non-indigenous plant species. But while inevitable, environmentalists say the crisis is manageable if steps are taken now. The plant invaders are a political and economic issue that transcends environmental concerns. To diminish the amount of lost farm land, grazing land, game park ecosystems, and other maladies guaranteed to come as "invasive alien species" proliferate, the support of politicians and the general public must be rallied for a cause that even environmentalists concede is little understood today. But the brief history of the Working for Water Programme, an initiative of South Africa's ministry of water affairs and forestry begun in 1996, shows that both government and the public can be mobilised. "Environmentalists are saying 'If you don't get them, the 'invasives', they will get you,' and we are being heard," said Dr Guy Preston, National Leader for the programme. The programme enjoys the support of South African President Thabo Mbeki's administration and the popular press, which endorse the effort to eradicate seemingly innocuous-looking trees and weeds that threaten the region's ecosystems. "Not all plant species that are foreign to a place are bad," Preston noted. "The Southern Africa forestry industry depends on pine trees imported for commercial timber forests. But hearty exotic species from Australia and South America, if not stopped, will push out indigenous species until only the stronger foreigners survive." Wattle trees from Australia and mesquite from Mexico proliferate by sinking roots deeper into the soil than indigenous trees, robbing the latter of nourishment. "With remarkable speed — you can actually see it happen - a single species will crowd out a diversity of plants and trees," Preston told IRIN. Encroaching foreign species of weeds consume land used for agriculture and grazing, causing economic hardship and raising the spectre of food shortages. In winter, alien weeds wither and dry into a highly-combustable mass, and can ignite in high intensity veldt fires. The invasives burn with 10 times the heat of indigenous plants, killing the seeds of the latter while the alien seeds survive to germinate in greater profusion. Soil degradation follows, and a drop in water resources. In South Africa, alien plant species consume seven percent of the nation's available water supply, from rain runoff to underground aquifers, in a country that faces perennial water shortages. "If we can rid ourselves of these plants, which are no good to anyone, we can spare ourselves having to build more and more dams, at considerable cost," said Preston. Linda Dobson, secretary for the Swaziland National History Society, recalls that an invasive species called the Demonia weed was blown in with a cyclone in 1984, and has rendered useless tracts of formerly productive agricultural land. The Hakea shrub from Australia was introduced to South Africa to serve as a hedge, and is now infesting whole forests, displacing native trees and smothering smaller plants. "In their native lands, these species were kept in check by natural pathogens, like bugs. But these plant-eating bugs were left at home when the plants were imported to decorate someone's garden, but then got loose into a foreign ecosystem they preceded to conquer," Dobson explained. The resulting loss of biodiversity, the amalgamation of an area's flora and fauna, can be devastating. Environmentalists predict that one-fourth of South Africa's plants and animals will become extinct if invasive plants continue to proliferate. "When alien species displace native species, the insects that depend on those plants die, and birds and small mammals lose their food supply. They, too, become extinct, as do the larger animals that depend on them for sustenance," said Dobson. The regional tourism industry, fearing the loss of attractions as game parks and nature preserves are threatened with species loss, have become aware of the invasive plant threat. Big Game Parks of Swaziland is actively rooting out invasive species, and replacing them with indigenous plants. "The native plants have great cultural importance, and they are what the visitor to Africa wishes to see," said Ted Reilly, director of the park system. Traditional medicines, made from medicinal roots by local healers, are also endangered. Africans who depend on time-honoured traditional medicines may face a crisis. But the problem is worldwide. The Global Invasive Species Programme estimates that the cost incurred by national economies due to destruction caused by invasive plant species represents four percent of annual global economic output. "The problem is here, now, and it will get worse. But we have reason for optimism because containment efforts can turn the tide," said Preston. The Working for Water Programme is Africa's largest conservation effort, employing 4,000 people. Designed to be more than an environmental project, the initiative is aimed at gender equality and poverty eradication. Sixty-percent of all workers are women, with preference given to poor women who head single-parent households. The "poorest of the poor" are employed, but for a limited time to allow others a chance to be wage earners. Pay is higher than the prevailing rate for agriculture workers, to encourage a savings cushion when a worker's term of employment expires. In the five years the programme's crews have attacked the alien plant invasion, evidence from South Africa is accumulating that successes are being achieved. Rivers that had been choked dry by the roots of invasive species now flow once more. Indigenous plants long gone from some areas are returning. Importantly, the public and politicians alike are aware of a problem most had not suspected three years ago. "It will require a regional effort to counter the invasives," said Preston. "Ecosystems know no national boundaries." This year, proposed legislation in Swaziland, Mozambique and Namibia, and strengthened legislation introduced to South Africa's parliament, will address the problem of invasive plant species in ways ranging from an insurance requirement for anyone who wishes to import an alien plant into the region to a requirement that home owners rid their properties of all invasives before they can sell their homes.