Vulnerability of ten major Nordic cities to potential tree losses caused by longhorned beetles

Henrik Sjöman,Johan Östberg

doi:10.1007/s11252-019-0824-8

Henrik Sjöman, Johan Östberg

Open Access

https://doi.org/10.1007/s11252-019-0824-8

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Abstract

Urban forest and urban trees are currently facing several challenges arising from a changing climate, complex inner-city environments and severe threats of pathogen and insect attacks. The latter have already had serious consequences for many cities, with outbreaks of diseases and pests causing large-scale tree losses that will take a long time to resolve. The pest species Asian longhorned beetle (Anoplophora glabripennis) and citrus longhorned beetle (A. chinensis) have large numbers of host species and genera and can hence be classified as one of the most serious future threats to the urban (and natural) tree landscape. The question is not whether these new threats will arrive in northern Europe, but rather when an infestation will occur and how well prepared are cities to deal with it. This study presents an up-to-date compilation of the urban tree population in 10 major Nordic cities, based on recent tree inventories, and investigates and discusses the effects of an outbreak of the two longhorned beetle species, based on information taken from a review of 35 papers presenting host-related data on these species. Evaluation of the data on host susceptibility to the two longhorned beetles revealed clear differences in tree losses between scenarios, with predicted tree losses of 15–98% in the different cities.

Highlights

Recent research clearly shows the importance of urban trees for sustainable urban development through their capacity for delivering numerous important ecosystem services
On analysing the genus diversity among the individual cities, Tilia was found to be the most common genus in Copenhagen, Espoo, Gothenburg, Helsinki, Oslo and Stockholm, while Sorbus was the dominant genus in Malmö and Aarhus and Betula was the dominant genus in Tampere and Turku (Table 3)
The dominance of Tilia was pronounced in Helsinki, where it accounted for almost 44% of the total tree population (Table 3)

Summary

Introduction

Recent research clearly shows the importance of urban trees for sustainable urban development through their capacity for delivering numerous important ecosystem services. Urban forest and urban trees are currently facing a number of challenges arising from a changing climate, complex inner-city environments with locally tough site situations and severe threats of pathogen and insect attacks (Sjöman et al 2012) The latter have already had serious consequences for many cities, with outbreaks of pathogens and pests causing large-scale tree losses that will take a long time to resolve. In Europe and North America, the elm (Ulmus spp.) was one of the most common urban trees until Dutch elm disease, caused by Ophiostoma novo-ulmi, was introduced to the two continents and killed millions of trees in urban environments and in natural habitats (Sinclair and Lyon 2005) This has resulted in cities losing a large proportion of their tree canopy, which will take a long time to recover to the point it was at before the outbreak of Dutch elm disease. Europe is experiencing a similar scenario with Ceratocystis platani on

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