Suitability of the Weber-Gut risk assessment methodology used in Central Europe for determining invasive woody plant species in Estonian historical parks

Nele Nutt,Ardo Kubjas

doi:10.2478/fsmu-2020-0003

Abstract

Abstract The main objective of this research was to assess the suitability of the risk assessment methodology developed by Weber & Gut for Central Europe in order to determine the invasive species in the dendroflora of this region's historical parks. In order to do so a region was chosen where the number of old parks is high (Estonia) and then the following characteristics were studied: 1) the distribution of invasive species; 2) the viability of invasive species. Research results showed that the risk assessment for Central Europe developed by Weber & Gut is not suitable for determining invasive tree and shrub species in the historical parks of Estonia. The research viewed 18 species (classified as a high-risk category) and only half of them had characteristics inherent to invasive behaviour (produces reproductive offspring, often in very large numbers, at a considerable distance from parent plants, and thus has the potential to spread over a considerable area). Even in a small territory (45,339 km2), the regional differences in the occurrence of invasive species were substantial. No independent mass reproduction of most of the invasive species was detected during the use of the Weber-Gut risk assessment system. This research showed that the dangers of invasive species cannot be assessed based on one methodology, but each species should be assessed according to their habitat and specifics of the species.

Highlights

The problem of invasive species Invasive alien species are the second largest reason after habitat destruction for the decrease in biodiversity all over the world (European Commission, 2013)
This article gives an overview of the invasion problem of slow-growing and long-living woody plant species in the parks of Estonia
When using the Weber-Gut risk assessment system used in Central Europe, the number of alien woody plant species was 53 in 2013, which were divided into three risk categories (Purik & Ööpik, 2013)

Summary

Introduction

The problem of invasive species Invasive alien species are the second largest reason after habitat destruction for the decrease in biodiversity all over the world (European Commission, 2013). The European Union has taken several measures to preserve biodiversity by limiting the spread of invasive alien species. Compared to herbaceous plants the problem of invasive slow-growing and long-living woody plants has not received much attention. The shorter the lifespan of a species, the faster it reproduces, the greater risk of invasion by alien species. There seems to be no serious danger when talking about species with a long lifespan, such as woody plants. Alien woody plants have not been considered to be dangerous invasive species (Holm et al, 1997) but the problem has become significant in many regions due to greater distribution and naturalisation of woody plants. Seven woody plants (DAISIE, 2017) are listed amongst one hundred most dangerous invasive species in Europe

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