Challenge of alien invasive species

　Ask an Asian rice farmer about a brown or green-coloured snail, some 10 cm in length, and you could be asking about creatures from Mars.

　For the Golden Apple snail has become a scourge down in the paddy fields damaging a staple crop as a result of its voracious appetite while costing a small fortune to control via environmentally-questionable chemicals.

　The mollusc is among literally tens of thousands of life-forms classed as alien invasive species. They are thought to be harming the global economy to the tune of $1.4 trillion a year if not far more.

　Free from natural predators and checks and balances, alien invasives like the Golden Apple snail can explode in numbers in their new homes.

　Native species are ousted, waterways and power station intakes clogged and aliens can bring novel infections including viruses and bacteria while poisoning soils and damaging farmland.

　Some governments such as New Zealand are facing up to the challenge with tough customs controls on foreign plants and animals.

　Others such as South Africa have well-funded removal programmes aimed at, for example, conserving the unique Cape Floral Kingdom and its economically-important nature-based tourist attractions.

　But far too many countries have failed to grasp the scale of the threat or are far too casual in their response.

　Next year the government of Japan will host the UNEP-linked Convention on Biological Diversity (CBD). 2010 is when the international community is supposed to have reduced the rate of loss of the world’s biodiversity.

　Conserving habitats, economic incentives for ecosystems, measures to fairly access and share genetic resources and adaptation to climate change will be among the issues high on the agenda.

　But it is time that the challenge of alien invasive species also gets the attention it rightly deserves given their growing impact on economies, livelihoods and the rest of the natural world.

　In British novelist HG Wells’ celebrated science-fiction saga, “The War of the Worlds” aliens invaded in space ships to wreak havoc and mayhem.

　In the real world they are spread from one Continent to another via the global agricultural, horticultural, aquaria and pet trades or by hitchhiking lifts in ballast water and on ship’s hulls.

　The rice-consuming Golden Apple snail is thought to been brought to Asia from Latin America in the 1980s as an aquarium pet and a gourmet-food.

　After proving less than popular on the region’s menu, importers released the snails and perhaps their eggs into Asia’s rivers and lakes from where it has spread to around a dozen countries including Japan.

　The ‘red tides’ seen for example in Europe’s North Sea and linked with fish kills are blooms of algae brought accidentally in ballast water from the seas off China.

　Alien invasive species also challenge the UN’s poverty-related Millennium Development Goals.

　Take water hyacinth as one example: a native of the Amazon basin, it was brought to Continents like Africa to decorate ornamental ponds with its attractive violet flowers.

　But there is nothing attractive about its impacts on Lake Victoria where it is thought to have arrived in around 1990 down the Kigera River from Rwanda and Burundi.

　Hyacinth can explode into a floating blanket, affecting shipping, reducing fish catches, hampering electricity generation and human health.

　Annual costs to the Ugandan economy alone may be $112 million. The plant has now invaded more than 50 countries world-wide.

　In sub-Saharan Africa, the invasive witchweed is responsible for annual maize losses amounting to US$7 billion: overall losses to aliens may amount to over $12 billion in respect to Africa’s eight principle crops.

　Damage to river banks in Italy by the introduced copyu rodent, brought in from Latin America for fur breeding, is estimated at $2.8 million annually, according to data compiled by the Global Invasive Species Programme (GISP).

　The alien comb-jellyfish costs the Black Sea economies close to $20 million a year as a result of a reduced anchovy fishery.

　Introduced agricultural and human diseases are thought to be costing the US economy over $40 billion annually.

　Six alien weeds in Australia are costing farmers there over $100 million a year.

　In the Philippines alone the Golden Apple snail causes damage to the rice crop of up to $45 million.

　The challenge is both a developed and developing economy one and the more scientists look at the issue the more concerned they become.

　In the United States researchers believe they now know why a weed from Europe-garlic mustard-is damaging native hardwoods. The alien produces a poison which kills native fungi which the trees need to grow.

　The scale is perhaps only now unfolding. Scientists with the Delivering Alien Species Inventories for Europe or DAISIE says there are now 11,000 invaders in Europe of which 15 per cent cause economic damage and threaten native flora and fauna.

　Meanwhile climate change is likely to favour some alien species currently constrained by local temperatures.

　Scientists have termed them ‘sleepers’--foreign agents who become embedded in a community to be activated some years later. Introduced rainbow trout into the UK is a case in point.

　In War of the Worlds the Martians are defeated by an Earthly infection-perhaps a bout of flu-to which they have no resistance. Real world aliens are often made of sterner stuff.

　Improved international cooperation is needed and stepped up alongside support for initiatives such as GISP and the work of organizations like the International Union for the Conservation of Nature.

　Important too to boost the capacity of the responsible national customs, quarantine and scientific institutes able to provide early warning especially in developing countries alongside strengthening agreements under the UN’s International Maritime Organization.

　Improved management of affected habitats can also be key-there is some evidence that introducing a variety of native freshwater plants into a Golden Apple snail-infested site can reduce impacts on the rice crop.

　Training and paying people to hand-pick and destroy snails can also work while offering employment in job-needy communities.

　That said, preventing alien species entering a new country is always going to be demonstrably cheaper than the cure of trying to eradicate a well-entrenched species.

　Alien invasive species are not new-for hundreds of years ships have brought cats and rats to islands with devastating consequences on often unique flora and fauna and in particular birds.

　Recently the United States Fish and Wildlife Service reported it had eradicated invasive rats from a remote Aleutian island-more than two centuries after swimming there from a sinking Japanese vessel.

　And Charles Darwin, the 200th anniversary of whose birth is celebrated this year and whose voyage on the Beagle sparked the theory of evolution, wrote in 1893 about Cardoon or Artichoke Thistle after witnessing its impact in Latin America on indigenous communities.

　“I doubt whether any case is on record of an invasion of so grand a scale of one plant over the aborigines,” said the scientist.

　As the global economy eventually recovers, global trade including shipping will resume and with it the risk of alien life-forms spreading from one place to another.

　Alien invasive species have for too long been given a free ride. Raising awareness among policy-makers and the public, and accelerating a comprehensive response via the CBD when governments meet in Nagoya next year, is long overdue.