Expressing ecosystem model output and Swedish forestry goals with composite indictors

Abstract

Forest ecosystems provide a wide range of services necessary for maintaining environmental health and human well-being. Ecosystem models help inform how various management strategies respond in different regions to changing climate conditions. They contribute to mitigation and adaptation policy measures and support private forest owners in deciding ideal practices to implement. The complex nature of model output and how ecosystem services have many synergies and trade-offs between environmental, economic, and social sustainability dimensions make communicating findings outside of scientific cohorts difficult. Composite indicators are mathematical simplifications of complex phenomena widely applied to promote and communicate findings to stakeholders. This study developed a composite with existing ecosystem model results for 19 forestry management strategies across three ecoregions and climate scenario projections in Sweden.

Multiple composites were generated around a central framework that considered domestic and international sustainability policy goals by employing several multivariate techniques to account for variation in targets and ecosystem services. Ten ecosystem service indicators were sorted into theoretical sub-component groups based on whether they addressed biodiversity, climate change mitigation and risk management, or production policy aims. A combination of principal component analysis, exploratory factor analysis, Cronbach’s coefficient alpha, and hierarchical cluster analysis was used to re-sort indicators. These hybrid groupings accounted for meaningful statistical relationships between modeled values. Eight composites were generated with either theoretical or hybrid sub-components, two normalization approaches (z-score and min-max), and two weighting schemes. The two weighting schemes were based on policy prioritizations between sub-components that reflect 1) current policy standards and 2) explored a scenario following international recommendations to focus on biodiversity and climate change above forest production.

The eight composite structures were systematically evaluated across all regions and climate scenarios for each structural aspect (i.e., the sub-component grouping, normalization approach, and weighting scheme) to determine significant differences between structures and the ideal combination for representing the original model output. Z-score normalization with hybrid sub-components and both weighting schemes were selected as the most suitable composite. This combination best captured the variation between management strategies and the relationships between ecosystem indicators while offering more than one policy perspective. The final composite agreed with original model findings: a combination of continuous cover and broadleaf-mixture strategies are best for balancing goals under changing climate conditions for all modeled ecoregions. Results highlighted areas of refinement in the model’s parameterization of spruce management strategies. As with all other composites, the subjective nature of decisions made when designing its framework must be justified and clear when applied, especially when dealing with multidimensional model output.

Popular Abstract

Forests provide many ecosystem services (ES) essential to human survival. They range widely from timber and food to providing a sense of place or an area of recreation. A holistic balance of many services is required to ensure a sustainable future. More than half of Sweden is covered by forests, most privately-owned monocultures with only one tree species. Seedlings are planted and clear-cut harvested regularly every 60 to 120 years, known as even-aged forestry (EAF). Changing climate conditions across Sweden raises average annual temperatures and increases the amount of damage from high-wind storms, droughts, floods, and pest outbreaks, threatening forest ecosystems' stability. Ecosystem models can simulate the regional patterns of how different climate change scenarios affect forests.

Models help predict potential change but often produce complex and challenging-to-understand output. A tool to simplify these datasets while preserving their integrity is known as composite indicators (CIs), which are widely applied in creating and maintaining sustainability policy. This study developed a CI to convert already-existing model output to aid decision-makers in selecting the best management practices for different regions in Sweden. A CI structure was designed around a central framework capturing the policy aims of Sweden's Environmental Objectives and the UN's Sustainable Development Goals. ES values were averaged into three different regions and grouped based on which goals they most directly addressed. The CI balanced these theoretical groups by considering the underlying relationships and mathematical dynamics at play between each of the ES. The CI mirrored the Swedish Forestry Agency's emphasis on placing equal priority on environmental conservation and production efforts. Another perspective explored prioritizing ES contributing to biodiversity and climate change mitigation over economic production.

Findings suggest the ideal forest management practices combine continuous cover and EAF mixed broadleaf stands for all simulated regions and climate scenarios. Trees adapted to warmer conditions have an advantage over less tolerant coniferous species prevalent in today's monocultures. Continuous cover stands are not clear-cut, and instead, trees are only removed once they are fully grown. EAF strategies showed a preference for longer growing times and less thinning of branches and non-planted trees. The CI prioritized strategies that retained the most carbon in the ecosystem related to climate and biodiversity goals, even with a trade-off of decreasing production output and heightening storm sensitivity. The best strategy focusing only on protection and mitigation aims is unmanaged forests, which severely reduces the amount of useable timber but are extremely beneficial for ecosystem health. The diverse range of benefits gained when transitioning to these managements is substantial. The CI also highlighted ways to improve the model. Any arbitrary decisions during development show that every choice must be justified; otherwise, CIs may distort findings. Current and future sustainability goals will only be met by preserving the full range of services forests provide. A combination of model simulations conveyed with CIs can help inform policymaker and forest owner decisions.

• author: Tarasewicz, Nicolas
• supervisor: Anna Maria Jönsson
• organization: Dept of Physical Geography and Ecosystem Science
• course: NGEM01 20211
• year: 2021
• type: H2 - Master's Degree (Two Years)
• subject: Earth and Environmental Sciences
• keywords: Physical Geography, Ecosystem Analysis, forest management, multifunctionality, LPJ-GUESS, ecosystem services, composite indicator, climate change, biodiversity, SDGs, Sweden
• publication/series: Student thesis series INES
• report number: 540
• language: English
• id: 9051819
• date added to LUP: 2021-06-10 16:10:11
• date last changed: 2021-06-10 16:10:11