Article: The Aliens aren't leaving....

THE ALIENS AREN'T LEAVING ANY-TIME SOON by Delphi Carstens Despite legislation and brave efforts by the likes of Working for Water and Ukuvuka (Operation Firestop), alien invaders are still proliferating, choking out South Africa’s indigenous bio-diversity.. "Environmentalists are saying 'if you don't get them (the alien invaders), they will get you,' and we are being heard," noted Guy Preston, National Leader of the Working for Water (WWP) Programme, an alien-busting initiative launched by SA’s ministry of Water Affairs and Forestry in 1996. With the support of President Thabo Mbeki's administration and the popular press, rallying cries against the invaders are indeed being heard and heeded. The burning question, however, is whether the problem hasn’t already grown way beyond control. A recent holiday along the Garden Route undertaken by the humble author of this article and a friend confirmed just how pressing the alien-invader problem had become. Uninformed eyes that had once indiscriminately seen a uniform green-mass now suddenly distinguished seas of black-wattles, Silky Hakeas and a host of other invaders throttling the beautiful but unfortunately hapless indigenes. Knowing that Working for Water had been active in the Hoekwil area (close to Wilderness), we decided to look in on the results. Driving along the old George-Knysna forestry road towards Hoekwil, however, we beheld an alien problem that seemed beyond any help - black wattles were quite literally everywhere, some standing in seemingly endless clumps so thick and impenetrable that even Guy Preston would balk. Although WWP had done some good work in the Hoekwil environs (the results of which could clearly be seen here and there), locals informed us that their alien-buster program had unfortunately drawn to a halt due to dwindling funds. No one knew when they would be back to tackle the seemingly endless mass of black-wattles. Removing alien invaders is no mean feat. Most, like Wattles, seed prodigiously and - if cut down, sprout up thicker than ever. To make matters worse most alien weeds wither and dry into a highly combustible mass during dry months, and can ignite in high intensity veldt fires such as the one that recently swept across the slopes of Table-Mountain. According to WWP, invasives sometimes burn with 10 times the heat of indigenous plants. Such an intensely hot fire invariably kills the seeds of whatever indigenous plants had managed to eke out a living amongst their more hearty alien counterparts. The alien seeds, of course, survive to germinate in greater profusion once the fire has passed. Evidence of this phenomenon can be found all over South Africa where all-too-frequent droughts have resulted in many fires that have left thick stands of invaders (particularly black wattles) in their wake. Wattles and other alien invaders love to grow near rivers, as we discovered when we went hiking along the banks of the Diep and Touws rivers. Having beaten our way down the area’s once-pristine gorges through monstrous seas of wattles, we found - much to our dismay - wattles practically growing in the rivers themselves. Everywhere great chunks of riverbank had been dragged into the water by the notoriously unstable wattles. Greedy invaders drink much more water than indigenous plants and many, like the black wattle, have contributed significantly to the erosion of SA’s riverbanks and watercourses. The Garden route isn’t the only invaded territory. Any drive taken through the Cape flats will reveal seas of Port Jacksons - a rather prolific problem throughout the Western Cape. Introduced from Australia in the early 1800s, these trees were used to bind the driftsands alongside the first road constructed across the shifting dunes of the Cape Flats. Two hundred years later and they’re everywhere - even along the Garden Route, as we discovered much to our horror. Hiking along the Outeniqua hiking trail, however, we found large fungus ‘galls’ growing on the branches of these alien-invaders. Apparently, this fungus was introduced in the mid-1990’s as a way to combat the burgeoning Port Jackson problem and has since met with some success (the fungus weighs down the branches of the tree, eventually leading to its death). The fungus that attacks Port Jacksons is unfortunately the exception to the rule. Unlike indigenous vegetation, alien invaders have no native insects or diseases to keep them in check. Controlling their numbers, therefore, is mostly a question of arduous clearing operations with annual follow-ups necessary for years thereafter. Sadly, even with strict legislation that forbids landowners from planting invasives and requires the elimination of certain of their kind, the problem isn’t going to go away all too easily. "Hearty exotic species, if not stopped, will push out indigenous species until only the stronger foreigners survive," cautioned Guy Preston. "With remarkable speed, a single species can crowd out a diversity of plants and trees, wreaking irrevocable damage." Apart from wattles and Port Jacksons, SA has eight other major invaders (alongside hundreds of other equally pernicious contenders). These are Lantana (Lantana camara), Triffid Weed (Chromoleana odorata), Water Hyacinth (Eichhornia crassipes), Mesquite (Prosopis glandulosa), Rooikrans (Acacia cyclops), Bugweed (Solanum mauritianum), Prickly Pear (Opuntia imbricata), and Silky Hakea (Hakea sericea). SA is by no means alone in its dilemma. Internationally, the direct destruction of habitat and invasion by alien species are considered to be one of the single greatest threats, aside from humans themselves, to the survival of biological diversity. "After habitat loss, this biological invasion constitutes the greatest threat to biodiversity, and it has already had devastating consequences for the planet," avers Jeffrey McNeely chief scientist for the IUCN. "The economic bill runs into tens of billions of dollars every year. Pests, weeds and pathogens, introduced deliberately or accidentally, reduce crop and stock yields, and degrade marine and freshwater ecosystems."