June 5, 2007

Alien plants invading agricultural land

Alien vegetation is preventing food production on vast tracts of Swaziland's agricultural land, compounding the country's worst ever harvest, which has led to more than a third of the population requiring food aid. "Invasives have been troubling the country for a decade in quantities that do real harm. Government has not done enough thus far, but now there is a recognition of the problem. There is new budgeting to combat the foreign plant intruders," said Moses Ngwenya, a conservationist in the northern Hhohho Region.
A prolonged dry spell has left about 400.000 vulnerable people in need of approximately 40.000 metric tonnes (mt) of food assistance until the next harvest in April 2008, according to a recent report by the United Nations' Food and Agriculture Organisation (FAO) and the World Food Programme (WFP), which was based on a joint assessment mission.
Foreign plant species, such as fast growing Eucalyptus trees - used for windbreaks - and the decorative bougainvillea have been imported into the country for a century, but the introduction of other exotic species, hardier than the indigenous flora - the most noxious being the triffid weed, or sandanezwe in the local Swazi vernacular - is thriving in the country's climes. No one knows where it [sandanezwe] came from, but it is everywhere. It crowds out other plants. It takes over land that might be cultivated. Fire has no effect on the plant. Cutting it does nothing," said Ngwenya.
The taxonomic name for sandanezwe is chromolaena odorata, a fast-growing perennial shrub native to South America and Central America. It is an aggressive plant and forms dense stands that prevent the establishment of other plant species. One of the popular named given to it, triffid, is derived from John Wyndham's 1951 post-apocalyptic novel 'The Day of the Triffids', about marauding plants, with animal-like mobility and a deadly sting, devouring the planet. The Hhohho region’s largest government farm, used for grazing cattle, has become almost entirely overgrown by the tangled small-leafed vines, which have no nutritional value for livestock.

In Parliament, Prime Minister Themba Dlamini, delivered a cabinet report on the impact invasive species were having on the country’s environment and economy to a Senate select committee. "The proliferation of Invasive Alien Species (IAPS) in the country, particularly sandanezwe, is a serious concern because these plants are a threat to bio-diversity and socio-economic development," Dlamini said.
IAPS were declared a national disaster in 2005 and government this year has committed R10 million (US$1.4 million) to the eradication of invasives, an amount conservationist say would be insufficient to address the problem. "Any threat to agriculture is a double threat this year, when food production is down to emergency levels," said Ngwenya.
The WFP estimates that four out of ten Swazis will require emergency food assistance this year, following the dry spell that caused devastation to both commercial and subsistence farming alike, in all four of Swaziland’s regions. Although autumn rains softened the effect of the dry spell on grazing lands, invasive plants, if left unchecked, could colonise 90 percent of the grazing areas within the next few years, the government believes.
Like other invasive plants, sandanezwe is difficult to eradicate, the agricultural ministry's principal secretary, Noah Nkambule said. "The problem with this weed is that even if you have cleared one area, you have to keep the momentum up by going back again after an interval and do more clearing. It can only be terminated by pulling it up by its roots, and burning the entire plant." As is the case in neighbouring South Africa, the opportunism of invasive plants is burdening the country's already stressed water resources, where ponds, rivers and small dams have become clogged by the intruduers and the invasives' aggresive roots systems have crowded out their indigenous counterparts. (IRIN)

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