ECOLOGICAL CLEANSING - The New Wild: Why Invasive Species will be Natures Salvation - page 56

trolling invader species, researchers argue, is a more cost-effective way of maintaining water supplies
than building dams. 4
Faced with such advice, the post-apartheid government quickly decided to start eradicating the alien
water-guzzlers. 5 A nationwide program began in 1995 under the name Working for Water. It is a valu-
able job-creation scheme. And the backbreaking work is portrayed as heroic and patriotic. Poor un-
employed people from the country's slums are recruited to rappel down cliffs, wade through wetlands,
dangle from helicopters, and brave snakes in their war on the aliens. The initiative has also enhanced
South Africa's reputation as a world leader in fighting invasive species, helping it to secure the home
for the headquarters of the IUCN's Global Invasive Species Program, established in 1997 at the Kirsten-
bosch National Botanical Garden near Cape Town. Ironically, Kirstenbosch is the place from where
many of the alien species either escaped or were deliberately distributed.
But does this alliance between conservation and job creation deliver what it promises? Hydrologists
point out that the figures for how much water is “taken” by the invader trees may not be the same as
the amount of water that would be “saved” if the trees were removed. This is because without the alien
trees, other vegetation would be taking water. And if there were no vegetation, then evaporation losses
from the ground would soar. 6 Elsewhere in Africa, the same trees are being promoted by ecologists to
protect soils that store water. For instance, the UN Food and Agriculture Organization and aid agencies
have encouraged farmers in arid Africa to plant species blacklisted in South Africa, such as black wattle,
to improve the water-holding capacity of soils and generate income for farmers. It is, says Christian Kull
of Monash University in Melbourne, far from clear why those trees are regarded in such a different light
when growing in South Africa. 7
A second critical question is whether the massive project is eradicating the trees as intended. For
several years, the South African government has been claiming that it has purged around five million
acres of aliens. It looks like progress. Except that, according to a 2012 assessment by some of the aca-
demic pioneers of Working for Water, the claim does not stand up. According to van Wilgen, despite
the billions of dollars spent, the amount of land covered by the target species increased by more than 4
percent between 1996 and 2008. 8
A huge amount of hacking and spraying has gone on. A great deal of sweat has been expended.
Some areas have been cleared, notably in Table Mountain National Park. But van Wilgen tells me that
job-creation priorities have taken precedence over making sure the job gets done: “The ability of Work-
ing for Water to provide employment has become its major attraction to politicians.” Meanwhile, there
has been very little official monitoring of what the project has achieved, and in particular whether alien
species have returned to cleared areas. It now appears, van Wilgen says, that seeds persist in the soil,
and plants readily regrow after the work gangs have moved on, continuing their colonization. Often they
invade new lands faster than they have been cleared from other areas.
Despite such setbacks, conservationists worldwide have grown increasingly ambitious in their plans to
restore ecosystems through eradication schemes. Most attempts have concentrated on remote islands.
These are places where there are some of the most visible signs of the presence of invaders. They are
also places where eradication is much more achievable. Once they've been gotten rid of, there is a fair
chance that many aliens will stay away for good. But even on islands, such programs are rarely simple.
Effects can cascade through ecosystems in unexpected ways. Sometimes the cure is worse than the dis-
ease.