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ARCHIVE: What are non-native species?

"The most important direct drivers of biodiversity loss and ecosystem service changes are habitat change, climate change, invasive alien species, overexploitation, and pollution." Millennium Ecosystem Assessment report.

A non-native species is an animal or plant introduced outside its natural range (present or past) through the direct or indirect action of man. This includes any part, gametes, seeds, eggs, or propagules of such species that might survive and subsequently reproduce.

The vast majority of non-native species introduced to Great Britain over the millennia have caused no significant harm. In fact, many contribute to economic and social well-being through their use in certain sectors such as agriculture, forestry, horticulture and the pet sector.

But, given suitable conditions, some non-native species find themselves un-checked and able to dominate native species, transform ecosystems or cause general environmental harm. These are invasive non-native species.

An invasive non-native species is any non-native animal or plant that has the ability to spread causing damage to the environment, the economy, our health and the way we live.  Invasive non-native species damage our environment, the economy, our health and the way we live.  They threaten our native plants, animals and habitats, cost the British economy over £2 billion pounds per year, and can threaten our health.

Invasive non-native species

Invasive non-native animals and plants have serious negative impacts on native species by predation, competition and/or spread of disease. They can threaten native species and their habitats, and are capable of causing damage to economic interests such as forestry, agriculture and fisheries, probably of the order of several billion pounds annually in Britain. For example, it is expected to cost many millions of pounds to deal with invasive weeds such as Japanese knotweed the sites of infrastructure for the 2012 London Olympics.

Prevention is better than cure

The true extent of the threat posed by non-native species has become much better understood in recent times and past introductions have usually occurred with little knowledge of the potential consequences. The Millennium Ecosystem Assessment report "Ecosystem and Human Well-being: Biodiversity Synthesis" notes that control or eradication of an invasive species once it is established is often extremely difficult and costly, while prevention and early intervention have been shown to be more successful and cost-effective. Changing conditions, such as climate change and greater global movement of people and goods may make it easier for non-native species to become established.

The effect of climate change on non-native species

Climate change will have a substantial impact on species assemblages in the coming years - both by affecting the distribution of our native species, and by enabling some non-native species to become more common. Increasingly we could see more non-native species that are currently benign become invasive as the climate changes. Already we are seeing some evidence of animals occurring outside their usual or expected ranges. Recent research also shows that the (generally northerly) expanding range and abundance of some mobile species including butterflies, marine molluscs, migratory birds and plants are consistent with patterns of climate change seen in the UK over the past 30 years. Climate change response will be one factor driving natural range extensions of species.

Page last modified: 29 March 2010
Page published: 23 October 2008

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