Far too many governments have failed to grasp the scale of the threat from invasive species, warns UN Environment Programme's executive director Achim Steiner. In this week's Green Room, he issues a call to arms to halt the alien invasion.
Ask an Asian rice farmer about a brown or green-coloured snail, some 10cm in length, and you could well be asking about sinister creatures from Mars.
The golden apple snail has become a scourge in the paddy fields, damaging a staple crop as a result of its voracious appetite and 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 (£913bn) a year, if not far more.
Free from natural predators and checks and balances, alien invaders - like the golden apple snail - can experience massive population surges in their new homes.
Native species are ousted, waterways and power station intakes clogged. Aliens also bring 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.
South Africa has 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.
In the 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 ships' 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 the snails proved less than popular for diners, importers released the creatures and perhaps their eggs into Asia's rivers and lakes, from where they spread to about 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 about 1990, travelling 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.
The plant has now invaded more than 50 countries around the world and annual costs to the Ugandan economy alone may be $112m (£73m).
In sub-Saharan Africa, the invasive witchweed is responsible for annual maize losses amounting to $7bn.
Overall losses to aliens may amount to more than $12bn in respect to Africa's eight principle crops.
Damage to river banks in Italy by the introduced coypu rodent, brought in from Latin America for fur, is estimated at $2.8m annually, according to data compiled by the Global Invasive Species Programme (GISP).
In the Philippines, the golden apple snail causes damage to the rice crop of up to $45m.
The challenge is both a developed and developing economy one, but perhaps the true scale is perhaps only now unfolding.
Scientists with the Delivering Alien Species Inventories for Europe (DAISIE) say there are now 11,000 invaders in Europe, of which 15% cause economic damage and threaten native flora and fauna.
Meanwhile, climate change is also 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. Rainbow trout, introduced into the UK, is a case in point.
In the War of the Worlds, the Martians were defeated by an Earthly infection - perhaps a bout of flu - to which they had no resistance. Real world aliens are often made of sterner stuff.
Improved international co-operation is needed alongside support for initiatives, such as GISP, and the work of organisations like the International Union for the Conservation of Nature (IUCN).
It is 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 (IMO).
Improved management of affected habitats can also assist. 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.
This year, the Japanese government 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. Raising awareness among policymakers and the public, and accelerating a comprehensive response via the CBD, when governments meet in Nagoya later this year, is long overdue.
As the economy recovers, global trade including via shipping, will resume the risk of further invasions.
Alien invasive species are part of the overall biodiversity challenge; for too long they have been given an easy ride.
Achim Steiner is UN Under-Secretary General and executive director of the UN Environment Programme (Unep)
The Green Room is a series of opinion articles on environmental topics running weekly on the BBC News website
Do you agree with Achim Steiner? Are too many nations failing to address the threats posed by invasive species? Do we need to tighten national bio-controls to limit the spread of alien plants and animals? Or is it impossible in a globalised world to close our borders to unwanted arrivals?
Perhaps a new global balance of power for species must be established. This will probably take many years and result in a great loss of species diversity globally. Given the nature of life and human travelling and transporting behaviour, a globalized world inevitably leads to globalized species. This is another consequence of living in the Anthropocene, the age where humans influence almost all natural processes. Invasive species will only aggrevate the mass extinction event we are currently experiencing. I seriously doubt this problem can be prevented completely in the long term.
Paul Siersma, Utrecht, Netherlands
Mr Steiner, Check on numbers of invasive species is fine but without regulating the growth of human numbers and their aggressive behaviors, we would not be able to fix these challenges substantially.
Sanjay Singh Thakur, Indore, India (Presently from Gangtok, India)
It is impossible not to agree. But why do we have to keep mentioning Global Warming and as an example the Rainbow Trout? This fish was physically introduced here in the early 1900s from the US where I would have thought climate conditions were/are/have been/will be harsher than here. So we have to mention the 'threat' from unspecified "sleepers" while there are 11,000 real invaders already here in Europe. So how exactly is the Rainbow Trout a sleeper and how destructive is it?
Stephen Skinner, Winchester
Stricter controls should be planned and implemented in each nation.
Robert Drown, Bison, SD, USA
I run an invasive terrestrial plant outreach program for The Nature Conservancy. It is so difficult to get people to understand how quickly the problem can spread. The whole story needs to be told - these non-native species have such an enormous impact on biodiversity of not only native plant populations, but also native insect populations, and on up the food chain. These non-native invasive plants are not inherently 'bad'. When they are brought over for commercial purposes or inadvertantly, they do not come with the diseases and predators that kept them in check in their homeland. Here, purple loosestrife, buckthorn, Japanese barberry, goutweed, etc. all are horticultural plants that have taken off in wetlands, fields and forests, reducing the quality of wildlife habitat and forest regeneration. We all need to learn to be better stewards of the landscape, and learning to prevent and manage invasives is a piece of that puzzle.
Sharon Plumb, Montpelier, Vermont
I agree, it needs government commitment everywhere plus border controls,controls on imports implemented.It is going to be more difficult with hotter climates and maybe less rainfall to grow crops wihtout impact of aline species.Also it needs GRAPHIC communication of what species look like to all people in countries.
alastair clarke, Leamington Spa
I am afraid that the problem of invasive alien species is being taken too lightly both by governments and also by other international bodies. The reason for such a laissez-faire attitude is the myopic definition of progress based on the greed of short term economic gain, despite the ever growing negative economic social and ecological impacts. It is only when the damage done is irreversible and unbearable that man's economic greed will perhaps start to realise.
Alfred E. Baldacchino, Attard, MALTA
I think if an indigenous species is suddenly faced with extinction because a predatory species was brought in, by humans, then action of course is needed to protect the threatened species. If, however, it's simply a question of the species identity changing as a result of cross breeding with another related species introduced by humans, we should simply let evolution take its course and not interfere. By intervening we might think we're somehow protecting the first species, but what if there's an evolutionary advantage in allowing the two species merge? This is how new species are born, and while we should protect the environment and its flora and fauna, this isn't the same as attempting to stop evolution as a whole.
Charles Benjamin, Edinburgh
None native invasive species represent greater threats than those of competion for space and resources. Plague associated with north american signal crayfish has driven our native species to near extinction and Phytopthora ramorum using Rhododendron as an intermediate host threatens our woodlands with the devastation experienced on the US Pacific west coast. Both of these phenomena have an association with international trade. We need to act on current threats and from this learn how to make make informed choices in the furure. Yes, no doubt, there will be a bit of a sting economically.
Christine Smith, Stone. UK
The problem of alien invasive species is easy to identify and respond to when it is obvious, such as in the cases in your report, but not for marginal aliens, and where we need to predict the risk of an invasion. For example, Black Wattle (Acacia mearnsii) is listed as one of the world's top 100 alien invasives, but recent peer-reviewed research and long experience in South Africa shows that it is invasive only under certain conditions, and that otherwise its benefits outweigh its environmental costs. We need better risk:benefit assessments, and better biology that explains both the case where an alien species invades, and where it does not. Current policies and programmes are too indiscriminate.
Fred Kruger, Pretoria, South Africa
Although unwanted species transfer to places where they displace native species or cause other harm should be avoided wouldn't it also be a good idea to facilitate species transfer from places which no longer have viable habitat to areas where such natural assemblages can be maintained. Only a fraction of species existing in the world are known and loss of biological knowledge stored in Nature with every one lost is a blow to the Earth's ability to mend itself. Even if mankind doesn't get its act together in time it seems such efforts should be a cost of doing business placed upon continued slash and burn economics of the concrete jungles of today. I'm thinking specifically of coral reef assemblages which will be lost and for which if I'm not mistaken mankind still can not even come close to sustaining in a captive environment.
Dale Lanan, Longmont, Colorado, USA
We see this with the almost indestructible Japanese Knotweed, the govUK's thought out answer is a Japanese predator insect. This will thoughtfully not eat our succulent plants but only the knotweed. Man's carelessness, thoughtlessness and arrogance has created more problems than it solves. Look at the Cane Toad in Australia. The rabbit in Australia, mouse - ditto, one being "controlled", now no longer by Myxomatosis, with all the harm this has done. Bees are dying in this country; some say it is mobile phones, climate change, disease (from where) and seek grants to study it! Early flowering plants from NZ sold in garden centres have brought flat worms that decimate our earth worms. When will man learn, if it lives in that hemisphere, in that country, then it is meant to be there. Want to see it, go there, do not bring it hear. Cheap imports, need cheap transport, therefore corners are sometimes cut. Result Chinese midden crabs, and the algae! We must demand the highest standard in transport. They also need to export, as we "need" to import. With an industrial manufacturing base the problems would be reduced.
Confusus Theytry, South Wales
In the UK this is a case of shutting the stable door a bit late. There are already thousands of species of flora and fauna in gardens and the countryside that that have been introduced from foreign climes. As the UK land use changes and climate changes (I don't want to go there) certain of these species will blossom (pun intended) and spread as environmental niches change. This is all pretty normal but instead of a local inhabitant slowly adapting to fill the vacancy there will be a queue of aliens whose CVs tick all the boxes. Many of our animals and plants that most of us think of as native to Britain are not so. All those deer ,squirrels, carp, zander as well as those rhododendrons all arrived by sea and air. When it comes to commercial crops we are already trying GM methods that scare me more than any accidental introduction.
Max Hutchinson, Gunnislake, Cornwall
As a specialist in invasive species, I can assure you that until all countries can move past the political barricades and change from "black list" policies (where only designated species are excluded from import and all others are accepted), to "white list" policies (where only designated species are approved for import and all others are excluded), we will continue to lose the battle with invasive species. With each new species imported, we again gamble massive impacts on our environments and economies, all so that an importer can make a profit (for which we often pay the resultant irreversible costs many times over).
Dr. Richard Old, Pullman, Washington USA
I know that trials are being carried out with knotweed predators but not enough is being done in the UK to halt invasive species, especially along our waterways. We always pull up Himalayan Balsam when we go for walks, but even in national parks and English Heritage land it is everywhere. A concerted effort needs to be made in Springtime to pull Balsam up before it flowers. And don't get me started on Harlequin ladybirds...
Claire Butler, Sheffield
Three of the examples in this article were all brought in to their new environment purely to make money, they are:
* golden apple snail brought in an aquarium pet and a gourmet food
* water hyacinth brought in to decorate ornamental ponds
* copyu rodent brought in from Latin America for fur
So, for the limited financial gain of a few, there is an enormous cost to everyone else. Therefore it would seem prudent to restrict companies and people from importing flora and fauna to countries where they do not exist already. Additionally, given the potential consequences, severe penalties must be applied to those individuals and companies that do import non-native plants and animals.
Ian Becket, Manchester, UK
I agree as a farming region we have experienced a dozen or so aggressive new weeds and pests on maize and wheat crops most of them alien to the region. Use of chemicals to control them have significantly increased the cost of farming.Most farmers postulate that they were introduced with fertilizer imports. Thus concerted efforts to manage spread of invasive species is highly welcomed.
Joshua Cheboiwo, Eldoret, Kenya
I strongly agree with this article. Here in Brazil we have a huge problem with the giant african snail. In the Tijuca forest, the world's largest urban forest, Indian Jack fruit trees are strong competitors and are dominating the ladscape. In Angra dos Reis, a forest-islands-mountain paradise 150km west of Rio de Janeiro, Sun Coral has invaded local ocean fauna, coming from ship's ballast water... Even hydro plants are suffering from the introduction of Zebra mussels, that clog the power generating turbines. The examples are all over and once infested, full control is virtually impossible!
Bruno Boni de Oliveira, Rio de Janeiro, Brazil
As an ecological consultancy, we are very concerned about the spread of invasive species in Ireland including Japanese Knotweed, Himalayan Balsam and Giant Hogweed. We are untertaking a pilot invasive species mapping study in The River Deel catchment County Donegal, Northwest Ireland this summer and hope to publish the results as widely as possible on web-based and print media.
John Wann, Whitehead, Co. Antrim