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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Leah Washington, 17, had to have her left leg amputated after being trapped for hours on The Smiler rollercoaster at the theme park.
Fine and dry this evening and overnight with showers on Sunday afternoon.
Warm sunny spells through the evening, followed by dry conditions throughout the night.