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More than 100 invasive alien species in forests

Target

1.1 Norwegian ecosystems will achieve good status and deliver ecosystem services.

Indicator

Number of invasive alien organisms in the following major ecosystems: marine and coastal waters, rivers and lakes, wetlands, forest, mountains and cultural landscapes
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Are we moving in the right direction? Published by the Norwegian Environment Agency

Plants are the invasive alien species that are the greatest threat to biodiversity in Norwegian forests. The vast majority of the alien invasive species that are associated with forests are typical garden plants. Many of these have spread spontaneously from parks and gardens to forested areas. In other cases, they have been introduced by people who have dumped their garden waste in nearby forest, even though this is illegal. 

A number of tree species that are not native to Norway have also spread from plantations to natural forest habitats. In 2012, Norway adopted regulations on planting and sowing foreign tree species for forestry purposes, which will make it easier to control the types of tree species that are planted and where they are planted. It should therefore be possible to prevent the use of foreign tree species from having negative impacts on biodiversity in future. 

Three alien mammal species that are on Norway's Black List are associated with forest habitats: raccoon dog, wild boar and fallow deer. There is no established population of raccoon dog in Norway, and the other two species are only found in south-eastern Norway near the border with Sweden at present. Fungi such as Dutch elm disease (Ophiostoma novo-ulmi) and oak mildew (Erysiphe alphitoides) and the fungus-like pathogen Phytophthora ramorum, which causes ‘sudden oak death’, can all cause serious damage or kill trees and thus pose a threat to forest biodiversity.