Alien Invaders

The threat to wildlife from invasive species is now one of the greatest across the world and it is growing. Killer shrimp are the latest non-native species to be found in a formerly quiet and respectable area of Cambridgeshire. In the UK we have endlessly debated the problem of the grey squirrel and Japanese knotweed but in Spain the invaders are being driven out permanently. Can their plan work and would eradication return native species to abundance or simply create new problems in our ecosystems?

Recent studies suggest the rise in invasive species stems from international trade. Global warming has also contributed to species migration and survival in the wild. The Spanish authorities have drawn up a list of 168 offending species including the raccoon and mink, zebra mussels, and one of the worse offenders the ruddy duck.

In New Zealand rats are driving the yellowhead bird to extinction and the chrytrid fungi is causing a worldwide decline in amphibians but can species really recover after competition is successfully eradicated? It seems that in some cases they can. The near extinct black vented shearwater is recovering on a Mexican island after the eradication of cats, goats and sheep. The wallaby is also recovering after red fox were taken out in Australia.

However, there are also a growing number of scientists who argue that to eradicate invasives is costly, cruel and ultimately unnecessary. In Puerto Rico invasive species have been the only plant and wildlife able to survive in eroded soils. Their encroachment has returned lifeless areas to thriving jungles, eventually providing a more encouraging environment for native species to return.

If we can't beat them then it may even be time to learn from these ecological survivors. Producer Helen Lennard Repeated on 31:03:2011 13:31:00.