Date of Award

12-31-2016

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Jarrett E.K. Byrnes

Second Advisor

Ron J. Etter

Third Advisor

Robert Stevenson

Abstract

Biodiversity is declining globally. Locally, however, on average species richness has not changed over time. Rates of local biodiversity change are not uniformly low; rather, they are highly variable. This variability suggests that we need to understand drivers such as human impacts to make sense of recorded changes in biodiversity. To evaluate the effect of different human impacts on local marine diversity, we performed a meta-analysis on a novel dataset of species richness change over time in marine ecosystems. Our dataset contained 144 sites from 35 studies. We paired this data with large-scale drivers derived from geospatial databases: human cumulative impacts, climate velocity, invasion potential, and nutrient loading. We found that these drivers do moderate changes in local diversity but also have opposing effects on diversity change. Specific drivers (nutrients, linear temperature change, and propagule pressure) are better predictors of local change than aggregate metrics such as cumulative human impacts. Further, long-term studies reveal trends obscured in short-term studies and so net change in local biodiversity is dependent on both human drivers and time. These findings begin to explain the high variability observed in species diversity at local scales and reframe previous findings in a human context. We suggest that local species diversity change is a predictable phenomenon and that suggestions of no net change can result when the global distribution of human impacts is not considered.

Comments

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