Understanding and assessing cumulative impacts to coastal ecosystem services

Anthropogenic impacts to the environment are often co-occurring and cumulative. While research on cumulative environmental impacts has historically focused on biophysical attributes, anthropogenic activities also pose risks to ecosystem services. This dissertation evaluates the state of environmental impact assessment, particularly the characterization of cumulative impacts, and pilots new methods in two sites with varying data availability: coastal British Columbia (relatively high data availability) and Tasman and Golden Bays, New Zealand (relatively low data availability). First, I assessed the state of cumulative impact assessment in its most common legally mandated form, Environmental Impact Assessments (EIAs), from seven nations. EIAs generally identified a large number of impacts, though a consistently minute subset was deemed “significant” for decision-making. Many EIAs considered spatiotemporal scopes smaller than justifiable, presumed mitigations effective without justification, and determined significance by consultants (paid by developers) with minimal stakeholder input. Next, I piloted two novel cumulative impact assessment procedures for contexts with available data. These procedures combined spatial analysis with expert elicitation for the first, and used Bayesian networks for the second. First, I found that some ecosystem services in British Columbia face higher risk from global stressors, while others face higher risk from local stressors. Changes to ecosystem service access and perceived quality may be as important as changes to biophysical attributes. Second, I show that management plans for the herring fishery are likely ineffective because important impacts were unaddressed. Finally, I piloted a novel expert elicitation approach to characterize and quantify impacts on ecosystem services in data-poor contexts. Local New Zealand experts were tasked with estimating impact before and after group deliberations, and describe causes of impact. This methodology simultaneously reduces the variability among experts’ best estimates, while also increasing individual uncertainty. Despite high uncertainty of individual stressor impact, cumulative impacts were consistently high across ecosystem services. The key stressor was sedimentation, caused by interacting climate change and activities based on land and in the water. As a whole, this dissertation advances the nascent state of cumulative impact assessment for ecosystem services, and pioneers diverse methods to synthesize understanding of these crucial considerations for management and policymaking.Science, Faculty ofResources, Environment and Sustainability (IRES), Institute forGraduat