Comm: "The world is engaging in a new defensive battle against invasive species.

"Here in the Seychelles, more than 200 years of devastation by rats is coming to an end.

"It was man who first brought rats here, and it's man who must now repair the damage.

"Scientists are now rising to a new challenge: to control and eradicate these alien invaders and restore the balance in disrupted ecosystems.

"Throughout history, alien species invading the territories of others have fueled the motor of extinction. But as human economic activity has spread to every corner of the globe, the process is speeding up.

"After direct habitat destruction invasive species now pose the second greatest threat to global biodiversity.

"Tropical ocean islands were the very first ecosystems to become the victims of alien invaders. In the Seychelles several unique species have already gone extinct and many of those which survive are critically endangered."

Nirmal Jivan Shah, Director Birdlife Seychelles: "So everything that evolved here including the plants evolved in an environment that was free of mammalian predators so the moment that you have something like a rat come on an island and invade an ecosystem which had been isolated perhaps for millions of years and evolved in that isolation then you can imagine the kind of devastation that kind of predator will bring.

"Hitchhiking aboard ships with the first human visitors, rats escaped to a bountiful paradise."

John Nevill, Birdlife Seychelles: "They're very competitive animals and they feed in a very broad niche they'll eat seeds of plants, birds they have an enormous impact right across the spectrum and particularly of course on the endemic species.

"The magpie robin, the seychelles brush warbler the Seychelles Fody for example these cannot coexist with rats."

Comm: "The worlds leading experts on island eradications have been drafted in from New Zealand to tackle the rat problem on three Seychelles Islands, Fregate, Denis and here on Curieuse."

Dr. Don Merton, New Zealand Department of Conservation: "In getting rid of rats from an island it's very important to get total coverage very quickly before the rats realise what's going on so we've developed a technique of covering the entire island using a helicopter.

"The helicopter flies along predetermined GPS lines - the transect lines - which makes for very very accurate bait application."

Comm: "In order to minimize the risk to native species they have been rounded up and kept in captivity for at least six months."

John Nevill, Director of Conservation, Seychelles: "On Curieuse we've built three pens on different locations around the island and we've been collecting up the tortoises and putting them in there. I have to say of course its extremely unlikely that a tortoise would suffer it would have to eat several kgs of the bait to be affected and I think that's extremely unlikely but of course we want to take all the precautions we possibly can to minimize any unwanted impact of the poison."

Comm: "Rats are highly intelligent animals, so the poison bait has been specifically designed to outwit them."

John Nevill: "Rats are bait shy and certainly the mature rats will not take a new food source which appears in the environment they will allow other rats, the younger rats to take it and then observe those rats, um and of course if those rats fall ill and die they will not take the bait - now this is an adaption to being poisoned persistently through time - they don't suffer any ill consequences of this bait for 3-4 days and its designed to smell good, be the right colour, taste good to the rats and so they gorge themselves on it."

Dr. Don Merton: "We generally wait two years before we can start claiming success - even if its not successful the effects are dramatic. Often the response from indigenous wildlife is quite spectacular the reptiles for instance within a couple of years are likely to far exceed their original densities some birds will recover very very quickly too so within a year or 2 even some of the rarer ones are likely to show massive increases in the population."

Comm: "The long term aim for this programme is to restore some of the species that are thought to have lived on these islands before the arrival of man. They will also become safehavens for species like the Seychelles Paradise Flycatcher which for a dangerously long time now has only existed on two tiny islands."

John Nevill: "It's an ongoing struggle the issue never ends we must maintain it rat free afterwards to justify that investment and even more so once we start introducing what are critically endangered species of birds numbering sometimes less than 100 in global population to these islands so they can reproduce it's essential that we maintain the island rat free."

Comm: "While many invasive species like rats are introduced accidentally, sometimes seemingly harmless species are deliberately introduced into a new environment.

"In the Outer Hebrides, on the west coast of Scotland someone released seven hedgehogs onto South Uist to help control garden slugs."

John Love, Scottish Natural Heritage: "I don't think in 1973 or 74 anyone could have predicted the consequences of bringing a few hedgehogs to the Uists - Hedgehogs in their proper place are totally innocuous indeed quite useful animals but because they have never been here the wildlife are just not used to having to deal with them."

Comm: "With no natural predators of their own on the islands the hedgehogs have bred prolifically and there are now more than 6000.

"The problem is that the islands are a vitally important breeding site for huge numbers of wading birds that nest on the ground.

"While hedgehogs feed mainly on worms and beetles, they are also opportunistic feeders, they will have a go at almost anything they bump into.

"With so many hedgehogs in one place, bird populations are crashing dramatically."

John Love, Scottish Natural Heritage: "The RSPB have estimated from studies they've been carrying out recently that within probably 20 years at this current rate of decline the Dunlin could disappear entirely."

Comm: "The RSPB have estimated from studies they've been carrying out recently that within probably 20 years at this current rate of decline the Dunlin could disappear entirely."

"Since the arrival of Hedgehogs, however the numbers of Dunlin have declined by over 60%.

"This is the first documented case of hedgehogs threatening an internationally important bird population with regional extinction."

Digger Jackson, RSPB: "There is a certain urgency to start conservation measures to benefit these internationally important bird populations because each year their numbers appear to decline more and if that should continue for many more years eventually there'll be none left and there'll be nothing left to conserve."

Comm: "Faced with such an urgent situation, the Royal Society for the Protection of Birds are studying the hedgehogs and the bird populations to ensure that any measures they take are based on solid scientific research.

"Meanwhile, the hedgehogs are marching up the chain of three islands. They have now reached the southern tip of North Uist and there are plans to build a barricade across the whole island in a last ditch attempt to halt the advance."

Digger Jackson, RSPB: "We'll probably not have just a single fence but 3-4 parallel fences to compartmentalise the frontline area."

Comm: "But the fences won't stop the hedgehogs for long, thanks to rabbits another introduced species, whose burrows provide a handy way through for the hedgehogs.

"The authorities are now facing up to the fact that if the birds are to stay, the hedgehogs will have to go. This raises the prickly question of eradication."

Digger Jackson, Royal Society for the Protection of Birds: "In the UK the hedgehog is an extremely popular animal - we can't just go in and kill lots of hedgehogs because there'd be a public outcry."

John love, SNH: "The major problem is that hedgehogs are perfectly amenable, innocuous little animals and we wouldn't want to do them any harm, but so we either have to trap them and export them from the islands and remove them altogether, or we would have to go down to the extreme case of killing them and we don't want to do that. So we're up against this problem it's a PR problem basically."

Comm: "The islands are officially protected under several International and European designations and the government is under an increasing legal obligation to protect these bird populations."

John Love, SNH: "You have to be optimistic - we know what this place was like at its peak before the hedgehogs arrived - hedgehogs are popular animals on the mainland but when you live on an island you cannot afford to have mainland values you've got to have the values appropriate to the island and I think we've got to take this seriously and we've got to convince people on the mainland that this is a serious problem."

Comm: "As well as the huge ecological impact of invasive species there is also the financial impact.

"In United States alien weeds have a major effect on the agricultural economy.

"The rangelands of North West America have been invaded by a plant from Europe called leafy spurge. Its milky sap is toxic to cattle and they can't graze it."

Dale Maus & Sons, Alex and Nathan, Rancher: "I think if nothing was done by the time, this one is 8 yrs old, by the time he's old enough to take over the ranch there would be probably not be a whole a lot of grass left, it just wouldn't have been much of a ranch to take over; it would have been better to go to town and get a job."

Comm: "The US department of Agriculture estimates the costs to ranchers at 144 million dollars a year.

"Biological control is one cost-effective solution that's been getting results.

"Scientists have found flea beetles from Europe that feed exclusively on leafy spurge, and so have introduced this second foreign species to control the first.

"Government teams are now holding rangeland field days to teach ranchers the basics of bio-control.

"And if you can put down more than 10000 in one spot then your gonna see some big results pretty quickly.

"Sweep nets are used to collect the flea-beetles and move them onto new patches of spurge.

"Hundreds of thousands of flea-beetles collected by government staff are handed out to ranchers at the end of the day.

"Maurice, your name's on the list Maurice. Bio-control is becoming a part of everyday ranching life."

Chad Prosser, TEAM, Leafy Spurge: "These ranchers are managing these insects, much like they manage their own cow herds - they're collecting, they're setting up their insecteries they're moving them to new areas, setting up new insecteries that they can move to every patch of spurge on their ranch."

Chad Prosser: "The ranchers out here everybody had gun racks and guns in the back of their pick-ups well today it's kind of a paradigm shift and now those shotguns and rifles are being replaced by sweep nets."

Dale Maus: "Of course all this was pretty strange to put bugs on some weeds and think they're going to eat them and they wont eat anything else, all this was pretty strange - but I was so anxious to do something about this leafy spurge that I would a' done 'most anything I guess."

Comm: "It has taken seven years of testing in quarantine get to the point of releasing these flea beetles to ensure they only eat the invasive plants and not the native species.

"In the sandhill prairies of Nebraska the ecological side effects of an early bio-control programme have only recently been discovered.

"In the 1960s agricultural authorities were concerned about the introduced musk thistle from Europe and its impact on cattle grazing land.

"To control the invasive musk thistle, they introduced a Eurasian weevil, but now this weevil is attacking the native American thistles."

Dr. Svata Louda, University of Lincoln, Nebraska: "So the majority of these plants out here now have a significant portion of their seeds destroyed by a weevil that wasn't supposed to prefer them."

Comm: "In some areas of Nebraska the number of seeds produced by native thistle species has gone down by 85% due to the weevil."

Dr. Svata Louda: "Basically what you see is that the flowerhead is filled with larvae and there is no good seeds."

Comm: "They have also found that the introduced weevil is out-competing native insects such as this picture-winged fly which relies on the native thistles for laying its eggs.

"Such subtle changes in the ecosystem can only be discovered through long term ecological studies.

"The case of the weevil and the thistle highlights the importance of strict regulations when introducing one species to control another."

Dr. Svata Louda: "I think its really important to make sure that the research is thorough beforehand - because once you've done this you cant stop it you can't retract it and you cant say oops we made a mistake lets take it back."

Comm: "In the latest insect invasion to hit the United States, the government have resorted to desperate measures."

Dr. Vic Mastro, USDA: "This is a control strategy that man would have used 500 years ago and that's how primitive we are because of our lack of knowledge of this insect."

Faith Campbell, American Lands Alliance: "We don't have a good way of controlling it now and once it gets in the woods we'll have no way of controlling it."

Comm: "The Asian Longhorned Beetle is widely believed to be the most destructive alien insect to ever reach the shores of America."

Joe Gittelman, USDA: "The threat that the Asian Longhorned Beetle poses to the New York area & New England is basically a hardwood threat - if it gets out of these communities here it has the potential of spreading and destroying vast portions of our hardwood forest from the Canadian border way down the coast all the way to the Carolinas at a minimum...it would be devastating on the economy."

Dr. Vic Mastro: "The estimated cost is 522 billion dollars which isn't even a number you can get your arms around - its frightening how much potential damage this species could do."

Comm: "With 50 square miles under emergency quarantine in New York State, fears are growing that the beetle could invade Central Park."

Joe Gittelman: "We do have an infestation on the island of Manhatten and we hope that we have gotten all of the trees however this site one half mile from 5th Avenue on Central Park if the beetle was to get into that area it would drastically alter the landscape of one of the most famous parks in the world itself. You ask people 'bout what park is in NY and they tell you Central Park."

Comm: "US Government scientists are now in a race against time to develop pesticide based controls. They also have to find better ways of discovering new infestations and here the public play a key role."

Joe Gittelman: "Public education is extremely important significant numbers of our new finds have come from public awareness campaigns. We have a limited staff and when you're dealing with a large city and millions of eyes out there everybody helps."

Comm: "It's believed that the beetle came from China entering the country in the wood-packing material that secures the freight in the holds of ships."

Vic Mastro: "We have so few inspectors that we can't possibly inspect all the containers so the chance of wood entering the country infested with some organism is pretty great - we've changed the rules specifically for China to only allow wood to enter the country if it's had a regulatory treatment."

Faith Campbell: "The Asian Longhorned Beetle is just one very damaging invasive species it's by no means the only one that's coming in this way and China is by no means the only country that has insect pests that could really destroy significant places, so the fact that they've now taken emergency action on wood-packing material from China is a first step but its by no means the end of the story."

Comm: "Increasing global trade inevitably raises the risk of transporting organisms to new environments - where they may become invasive."

Faith Campbell: "Because the emphasis is on not interferring on trade there's always this pressure on the agency to do less and be less demanding and allow trade to happen under more circumstances. So countries will do a less effective job of keeping pests out at the very time that the increased volume of trade makes the danger even greater."

Comm: "Under WTO agreements individual countries are required to identify which species they wish to keep out of their country, and have to provide proof that they are harmful."

Faith Campbell: "There are 32 million species in this world we don't know which ones are going to be a problem when introduced to a new environment."

Dr. Vic Mastro: "The world is getting smaller and we're trading species all over the world, the most robust ones will be successful but I don't think the world's ready to have monocultures of single species and that's where it may end up."

Dr. Svata Louda: "There are examples in the ecological literature of humans trying to manipulate their system to improve their lot that backfire to the point where the civilization disappears - I think we could be, by moving species around, both accidentally and deliberately, we could essentially be pushing ourselves that way, into homogenizing the world into something that wont function, you know, eliminating the key pieces that actually make the whole thing work, and we don't know what those key pieces are."

Dr. Vic Mastro: "Globally I think we have to make people aware that moving items around the world is what causes these problems. It's often very difficult to get that message out in the United States and getting that message out globally I think is going to take a commitment of all the countries involved and that still hasn't happened..."