Norway spruce is the most important tree species in Europe in economic terms and provides crucial ecosystem services, including mitigation of climate change and provisioning of carbon-neutral raw materials. However, the future of commercial spruce forests is now threatened by unprecedented outbreaks of the European spruce bark beetle. In 2019 alone, the beetle killed >110 million m3 spruce in Europe – 8 to 48 times more than the baseline mortality rate over the four preceding decades – and beetle epidemics are expected to further intensify with progressive climate change. In this project we will test if current forest management regimes promoting even-aged, long-rotation pure spruce forests is optimal to ensure that Norway’s forests remain a strong carbon sink and timber provider for society, also in a future with climate change and increasing risks of bark beetle epidemics. To evaluate this we will improve the fundamental understanding of the abiotic and biotic drivers of bark beetle epidemics through detailed hydrological modelling of drought stress on trees and improved understanding of how beetles and their fungal associates kill trees. We will develop ‘wall-to-wall’ national-level modelling and monitoring tools by leveraging Norway’s excellent infrastructure of detailed map-based forest information. These tools will include a short-term bark beetle risk assessment and management tool and a simulation framework to test how different forest management regimes and climatic futures impact bark beetle risk, carbon sequestration and timber production. Finally, we will compare ‘business-as-usual’ scenarios using even-aged spruce management with alternative management regimes to evaluate if current management, built around models and simulations that do not incorporate bark beetle attack, will actually be turned upside down when the risk of bark beetle epidemics is factored in.
Norway spruce makes up 25% of the productive forests in Europe, with ca. 7.5 billion m3, and is the most important tree species in Europe in economic terms. Healthy spruce forests also provide crucial ecosystem services, including mitigation of climate change by CO2 sequestration and provisioning of carbon-neutral raw materials that can substitute products with high carbon emissions. However, unprecedented insect outbreaks are now threatening the future of commercial spruce forests over large areas. The European spruce bark beetle (Ips typographus) mass-attacks and kills healthy spruce trees, and beetle activity is promoted by climate change both directly (faster development, longer reproductive season) and indirectly (stressed host trees). In 2019 alone, the spruce bark beetle killed >110 million m3 spruce in Europe – 8 to 48 times more than the baseline mortality rate over the four preceding decades – and beetle epidemics are expected to further intensify and expand northwards with progressive climate change. Despite the enormous impact of the beetle, there is still insufficient science-based knowledge about how to manage spruce bark beetle populations effectively, particularly at a landscape scale. In the SPRUCEBEETLE project, we will first develop robust scientific projections for long-term bark beetle damage in Norway by analyzing the main drivers promoting build-up of beetle populations, and then evaluate the effect of short- and long-term risk-reducing management measures. We will determine how forest structure (spatial structure, age and species composition) and biotic/abiotic stressors influence bark beetle damage and estimate the effect of different short- and long-term management measures using simulation models. This ambitious project requires close coordination between researchers from different subject areas, spanning from the chemical ecology of spruce-insect-microbe interactions to molecular biology, forest production and climate modelling.