Guidance Exotics

Index section Exotics

• Exotics in fresh water
• Exotics in the coastal zone
• The colonisation of the IJsselmeer by Caspian mud shrimp
• Trapped muskrats

Introduction

Over the centuries humans have deliberately or unintentionally introduced hundreds of terrestrial and aquatic exotics into the Netherlands. Exotics can pose a threat to the native flora and fauna, as has been demonstrated elsewhere in the world - the rabbit in Australia and the Nile perch in Lake Victoria, for example. So far, the Netherlands has escaped such dramatic negative effects, though there are species (such as the killer shrimp and the Caspian mud shrimp) that are ousting the native fauna. Furthermore, exotics sometimes bring in diseases that attack native species: for example, crayfish plague, which is threatening the native river crayfish. And some exotics - the oak procession moth, for example - can damage native crops.

Some of the exotics have been deliberately introduced into Europe or the Netherlands. They include the Japanese oyster (for oyster culture), the muskrat (for fur) and the Rum cherry (for forest improvement). Others have arrived by themselves, often by accident, such as the Asian tunicate and American razor shell, which hitched a lift from ships, Haliclona xena, which seems to have been imported with oysters, and the species that reached the Netherlands after canals were built to link rivers.

Relevant sections and indicators in the Environmental Data Compendium

• The number of species in the Netherlands
• The common oyster and the Japanese oyster in the Zeeland delta
• River crayfish: trends in numbers
• Oak processionary moth and climate change