According to the Department for the Environment, Food and Rural Affairs (DEFRA), non-native invasive species can prey on, compete with and displace native wildlife. The can spread disease and block waterways. They can completely alter the balance of ecology in a water system.
Fish populations can alter, and they can block up waterways which mean boat users have to take different routes. The financial costs can run into millions of pounds.
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Brighter skies will develop through thisafternoon, though perhaps with the odd shower at times.
It will be a largely cloudy start with a band of rain sinking south across the area from midday.
An MP has provoked anger over comments she made on her Facebook page about junior doctors 'holding the NHS to ransom'.