| Massive tree die-offs occur during bark beetle outbreaks worldwide in face of climate change. Recent outbreaks of the spruce bark beetle (Ips typographus) in Europe and Sweden have strongly affected the forest plant health and have been devastating, particularly for coniferous forest. Historically, Sweden has extensively drained forest wetlands to improve forest productivity. However, with climate change these actions are today identified as large unwanted sources for atmospheric CO2 and may contribute to outbreaks by lowering water levels, which are crucial for the tree defences (e.g. resin quality and quantity). Hence, rewetting may not only reduce CO2, but also lead to unforeseen benefits by decreasing the severity of bark beetle infestations, enhance biodiversity and support natural predators. In face of the biodiversity crisis, particularly in forests by draining of wetlands and recent climate-change induced outbreaks of bark-beetles, here is an urgent necessity to seek solutions for sustainable forest ecosystems in equilibrium.
The overall aim of this project is to: (i) investigate historical ditching on bark beetle infestations at landscape- and regional scales and ground water levels (ii) locally compare population dynamics of bark-beetles and (iii) forest biodiversity, including natural enemies after rewetting. Subprojects ii and iii will be studied at the same sites before and after rewetting, as well as with controls (without rewetting), which will account for any natural or preexisting differences, and thus to estimate the “true” effect of an impact.
The potential impact of rewetting previously drained forests on bark beetle infestations and biodiversity has never been studied before. Using a large-scale approach with satellite data, as well as a before-and-after-control design (with data from 80 traps twice), bark-beetle killed trees and bark samples, we will be able to model rewetted-forest and its interplay with bark beetle risks, biodiversity and natural enemies. The project will run for two years, starting in Sep 2024. Funding for the first of these years is already secured from Naturvårdsverket, and this application seeks to cover the second year. Pheromone-baited traps with windows for general biodiversity will be installed in April 2025 (prior to rewetting) and in April 2026 (post-rewetting). Bark samples from killed trees before and after rewetting will give additional information of within-tree dynamics of bark beetles and natural enemies. Securing this funding for a second year (Sep 2025-Aug 2026) is thus crucial for the completion of the study. In collaboration with key stakeholders, a future-oriented view will be summarized and brought to direct impact as a highly sought-after tool on how to plan and implement wetland restorations that will help mitigate and adapt to climate change and at the same time reduce the risk of bark beetle infestations and increase biodiversity. Thus, this rewetting program is highly relevant for policies regarding sustainable forest management and should in a final assessment, be evaluated by including forest pest dynamics and control. As outbreaks will increase even further with climate change it is an immediate need for these kind of studies in order to mitigate any adverse effects.
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