Comparing Ips typographus and Dendroctonus ponderosas responses to climate change with the use of phenology models

Abstract: Bark beetles are a subfamily of insects living in and breeding on woody plants. Some of the bark beetle species have the ability to attack living trees, and thereby the potential to cause major forest damage. These forest damages can have a significant ecological and economic impact to forest ecosystems and foresters. In this study, phenology models were used to compare the responses to climate change of two species, the European [i]Ips typographus[/i]and the North American [i]Dendroctonus ponderosa[/i], focusing on the beetles’ voltinism. One existing model for [i]I. typographus[/i] was used, and then adjusted to fit for the conditions demanded by [i]D. ponderosa[/i]. In addition, it was evaluated how [i]D. ponderosa[/i] could develop if the species was established in Sweden, and if it potentially could imply a threat to Swedish forests. The modeled results reveal that as a consequence of climate change, the potential geographic extent and phenology of bark beetles will be altered. By the end of the 21st century, bark beetles populations will have expanded further north and to higher altitudes, and their bivoltine potential will be increased. As a consequence, the outbreak potential might increase. According to climate conditions, [i]D. ponderosa[/i] has the potential to establish in Europe. Due to its shorter generation time, [i]D. ponderosa[/i] has a higher bivoltine potential than [i]I. typographus[/i] in European conditions. However, the susceptibility of host plants also plays an impotent role for bark beetle establishment, and how much of a threat [i]D. ponderosa[/i] could imply to Swedish forest ecosystems depends substantially on the vulnerability of the main Swedish tree species to [i]D. ponderosa[/i] infestation. Regarding all bark beetles, appropriate forest management is vital to reduce the bark beetle outbreak risk.