Recent Trends in Local-Scale Marine Biodiversity Reflect Community Structure and Human Impacts

Abstract

The modern biodiversity crisis reflects global extinctions and local introductions. Human activities have dramatically altered rates and scales of processes that regulate biodiversity at local scales. Reconciling the threat of global biodiversity loss with recent evidence of stability at fine spatial scales is a major challenge and requires a nuanced approach to biodiversity change that integrates ecological understanding. With a new dataset of 471 diversity time series spanning from 1962 to 2015 from marine coastal ecosystems, we tested (1) whether biodiversity changed at local scales in recent decades, and (2) whether we can ignore ecological context (e.g., proximate human impacts, trophic level, spatial scale) and still make informative inferences regarding local change. We detected a predominant signal of increasing species richness in coastal systems since 1962 in our dataset, though net species loss was associated with localized effects of anthropogenic impacts. Our geographically extensive dataset is unlikely to be a random sample of marine coastal habitats; impacted sites (3% of our time series) were underrepresented relative to their global presence. These local-scale patterns do not contradict the prospect of accelerating global extinctions but are consistent with local species loss in areas with direct human impacts and increases in diversity due to invasions and range expansions in lower impact areas. Attempts to detect and understand local biodiversity trends are incomplete without information on local human activities and ecological context.

Community assembly and the functioning of ecosystems: how metacommunity processes alter ecosystems attributes

“…Uninvasible local communities consist of pairs of species with adjacent positions along the R opt gradient (with consequent resource levels shown as filled circles) or of single species closest to the R opt constraint (dashed line). While there is certainly some evidence for local biodiversity losses, especially in the face of anthropogenic change (Murphy andRomanuk 2014, Newbold et al 2015), local diversity in a many ecosystems has remained stationary for decades, and has even increased in some (Vellend et al 2013, Dornelas et al 2014, Elahi et al 2015, even when local communities are perturbed (Supp and Ernest 2014). Other possible local communities (pairs of species with non-adjacent positions along the R opt constraint or single species more distant from the R opt line) are possible but are not endpoints for community assembly.…”

Consequences of biodiversity loss diverge from expectation due to post-extinction compensatory responses

“…Whilst we were unable to incorporate the occurrence of co-extinctions10, non-indigenous invasive species57 or other cascading effects that can have further consequences for community structure and ecosystem functioning, we were able to establish divergent patterns in response for alternative extinction scenarios that hold promise for exploring new strategies of ecosystem management and governance. An important next step in predicting future biodiversity change, however, is to quantify the prevalence of local extinction drivers in the ecological landscape58 and understand how these interact in natural systems5960 to influence the risk of extinction, altering community dynamics and ecosystem properties, both locally and across regional scales.…”

Biodiversity enhances reef fish biomass and resistance to climate change

“…Biodiversity is declining on average at marine sites impacted by human activity (15), and is decreasing globally at rates orders-of-magnitude above historical background levels (6,16), with some suggesting that biodiversity loss is already approaching a planetary tipping point beyond which ecosystems may be irreparably compromised (17). This information raises a practical question: how does declining biodiversity affect the resilience of ecosystems to other stressors, specifically climate change and human harvesting?…”