Abstract: Report on methodology for vulnerability assessment
The aim of this deliverable is to report ways to assess the vulnerability of lakes to global change in an ecologically sound way. Our initial aims were to cover a EU-wide scale in the analysis, using data sets collated during the WISER project. However, this approach proved unfeasible because data sets were highly deficient in terms of description of sampling and analysis protocols, confounding studies of inference. Instead of focusing on broad spatial scales, we decided to use long-term data from the Swedish Lake Monitoring Program. The rationale being: 1) Data series from lakes across the country were available, including lakes situated in subarctic/arctic regions which are predicted to be especially vulnerable to environmental change. These lakes could be compared with lakes in other climatic regions, allowing for an assessment whether vulnerability to environmental change is contingent on climatic zones. 2) Long-term data spanning a period from 1988 to 2010 were available for analyses. Previous research has documented substantial change in local and regional abiotic and biotic lake conditions across these lakes. With environmental change being evident for this period, our analyses focused on how lake vulnerability is linked to this environmental change.
The term “vulnerability” is intuitively appealing to invoke the sensitivity of ecosystems to global change. However, little effort has been made to operationalize the term within an ecosystem context that would make empirical testing straightforward. Consequently, scientists have to cope with the paradox that ecosystems apparently withstand many forms of environmental change, despite reported mass extinctions in the Anthropocene. To move vulnerability from a myth to a testable hypothesis novel empirical approaches are needed. Resilience and complex adaptive systems theory can enlighten vulnerability assessments and provide the foundations for innovative ways of measurement. In this report, we use subarctic and hemiboreal lakes as case studies to show how a resilience approach to study the vulnerability of ecosystems to global change can be made explicit.
We used multivariate time series modelling, and identified and tracked community change at distinct temporal scales. We determined the distribution of functional feeding groups of invertebrates within and across temporal scales, and identified cross-scale linkages thought to be important in driving positive feedbacks necessary for reinforcing observed patterns. Such feedbacks maintain ecosystem processes, despite changing environmental conditions. Results showed that subarctic and hemiboreal lakes shared overall similar functional attributes (richness, evenness, diversity) and redundancies of functions within and between the observed temporal scales. The effects of global change were particularly strong at one temporal scale, causing monotonic change in communities that can eventually lead to a loss of important ecosystem services upon reaching a critical threshold. Temporal dynamics at different scales were unrelated to environmental change. We conclude that an understanding of scale-specific processes provides managers with a realistic assessment of vulnerabilities and the relative resilience of ecosystems to environmental change. Explicit consideration of ‘intact’ and ‘affected’ scales in analyses of global change impacts provides opportunities to improve management.
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