Are we being invaded?
It does seem so, from reading the papers recently. There have been quite a few stories in the news in recent weeks about invasive non-native species. The most famous of these is the grey squirrel, but we’ve also been hearing about crayfish, mittened crabs and, ahem, ‘killer’ chipmunks.
For a conservation organisation this certainly a tricky issue. We tracked down the RSPB’s expert on the issue, Paul Walton, to get to the bottom of the matter. Here’s what he had to say…
It is one of the least understood of ecological issues - yet it is one of the main ways that humanity impacts the natural world: the introduction of non-native species.
A huge number of living species – perhaps as much as half of global biodiversity – owes its very existence to the fact that the world is effectively divided-up by physical barriers that stop different ecosystems and ecological communities from mixing.
These barriers are the oceans, mountain ranges, deserts, rain-shadows and currents. They have forced evolution to operate independently in different parts of the world, producing diverse and regionally characteristic floras and faunas - giving us, for example, tigers as forest cats in Asia, but jaguars as forest cats in South America. The effect runs right through the living world.
People, however, have a long history of moving animals and plants around the globe and – either deliberately or inadvertently – allowing them to establish in new areas. This effectively breaks down these geographical barriers to species movements. Free from native predators, pathogens and competitors, the new non-native arrivals often flourish and sometimes – all too often – create severe problems for native wildlife. Islands and freshwater lakes are particularly vulnerable.
The introduction, by people, of mammal species – particularly cats and rats – on islands has probably been the biggest single cause of bird species extinctions over the past 3 centuries. Moreover, with the growth of international trade and the effects of climate change, the problem is set to intensify.
RSPB staff keep a keen eye out for potentially damaging non-native species on our nature reserves, particularly aquatic plants that have escaped from gardens and can have devastating impacts on wetland habitats. We have, moreover, been closely involved with constructing policy and legislation on non-native species issues, both nationally and internationally. We do not advocate the ‘demonisation’ of non-native species, nor the eradication of every plant or animal brought to the UK by people: some non-native species do not have a direct detectable effect on native wildlife, and some species are too well established for any realistic practical response. However, where native wildlife is threatened, and where a practical response is possible, we do promote effective and humane measures to protect species and habitats from damage or extinction.
The principal aim is to improve our ability to prevent damaging introductions before they happen - always better than a 'cure' - and then to establish a rapid response capacity and effective control mechanisms for damaging non-native species that do become established.
We will continue to help develop and implement the government’s GB Non-native Species Strategy, and we are pressing for effective EU legislation on non-native species. Currently national legislation is patchy and inconsistent across the EU, and we need to bring all Member States to a minimum standard in this regard: if any one country allows the preventable establishment of damaging non-native species, wildlife across the whole European Community is then put at risk.