"We are sitting on a bit of time bomb," says the RSPB's Graham Madge.
"New species are becoming established all the time and some have the potential to take hold and accelerate: we've got a watchlist of species that could potentially cause devastation."
In a few year's time, the ecology of the UK could look very different from today.
While many new species will be harmless and add to our rich mix of biodiversity, a few could become problematic, scientists warn.
Ecologists are already keeping an eye on those non-native species that have already established in the UK but have the potential to spread.
Until recently, these birds have been seen as fairly benign
The ring-necked parakeet (Psittacula krameri) is one such species.
This vividly coloured bird, originally from South Asia and Africa, has been adding a spot of exotic glamour to various sites around the south-east of England since it arrived in the 1960s.
Mr Madge said: "Until recently, these birds have been seen as fairly benign and have largely been adopted as part of the British fauna."
However, the population has now increased significantly.
Some scientists now believe that if the numbers continue to grow and the birds' range increases, the parakeets could begin to compete with native species and could cause problems for agriculture.
As a result, the Department for Environment, Food and Rural Affairs (Defra) is currently undertaking a risk assessment to look at the potential impacts of the tropical birds.
Grahame Madge on the exotic ring-necked parakeet
As well as trying to keep track of the species that we have at home, scientists are also keeping a close watch on the invasive species that are currently wreaking havoc in neighbouring European countries.
The citrus longhorn beetle has already reached places like Italy... the alarm bells should be really ringing for the UK
Sara Redstone, Kew
For example, ludwigia, which is also known as water primrose, is currently causing enormous problems in France.
This aquatic plant, which is native to South America, can spread extremely quickly and form dense mats that can clog up waterways to cause huge flooding risks and damage other aquatic plants and vertebrates.
The plant has come into the UK through sales in garden centres - but work by the Centre for Ecology and Hydrology and the Environment Agency has so far kept the spread of the plants under control.
Researchers are also looking further afield to see what creatures can come into the UK through trade and import.
Could new insects spell the end for our native trees?
Sara Redstone from the Royal Botanic Gardens, Kew, said: "There are a number of insects species that we've seen having a dramatic impact in the US and some of these are now being intercepted on material entering the UK.
"For example, the citrus and Asian longhorn beetle and emerald ash borer are having a drastic effect on street trees and natural woodland in parts of North America, where there are no known biological or chemical defences."
Dr Redstone added: "The citrus longhorn beetle has already reached places like Italy and the Asian longhorn has been found in Austria - the alarm bells should be really ringing for the UK."
Climate change could also have an impact on the invasive species that are able to take hold in the UK.
Previously, colder winters meant that many non-native creatures would be killed off by any cold snaps.
But warmer winters and earlier springs are making the UK a much more hospitable base for many species.
The Argentine ant is one such creature that is causing ecologists some concern.
The UK's native ants could be at threat from Argentine ants
David Roy, from the Centre for Ecology and Hydrology, said: "It is a nuisance in buildings and is highly aggressive, wiping out native species. It is very hard to eradicate."
Originally from South America, modelling studies have shown that the ant is able to increase its range from south to north thanks to the changing climate.
It has already been causing problems throughout the Mediterranean, but Dr Roy warns that it could soon be heading even further north.
Scientists are also worried about how a changing climate will affect the spread of disease carrying species such as mosquitoes.
Sara Redstone believes that action needs to be taken - and soon.
"There is a lot we can learn by observing what is happening in other parts of the world.
"Every year we bring in tens of hundreds of species, and only a small proportion are either a problem or a potential problem.
"But I think everyone needs to be more aware.
"Organisations need to have a collective responsibility, the government needs to also accept responsibility, but as individuals we need to be responsible too."
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