Revisiting the evidentiary basis for ecological cascades with conservation impacts

Abstract

Complex ecological interactions are widely utilized to deliver conservation benefits but their efficacy is often debated. Using a coral reef trophic cascade as an example, we reveal that outcomes can be surprisingly difficult to detect. Even important impacts of marine reserves can go undetected (20% more coral with power < 0.5). This evidentiary challenge is compounded by misinterpretation of "nonsignificant" results as evidence of failed conservation practice. We illustrate a more appropriate analytical approach using a Bayesian Region of Practical Equivalence (ROPE) whereby many tests of conservation practice would be interpreted correctly as "undecided" rather than "negative." Practitioners working with ecological cascades will increasingly be faced with "undecided" evidence of conservation benefits. Since one solution is to consider a wider diversity of evidence, we provide a hierarchy of evidentiary quality. In this way, even reductionist evidence of the component ecological interactions can be utilized, which is far easier to collect and evaluate.

Evaluating annual severe coral bleaching risk for marine protected areas across Indonesia

“…The role of local management interventionssuch as MPAsin protecting and building the resilience of coral reefs in the face of global climate change has been debated (e.g. [1,38,61]). Resilience-based management approaches for coral reefs aim to protect reefs from local stressors, increase the resistance of reefs to damage during disturbance and/or increase recovery rates of reefs from damage sustained during disturbance [33].…”

“…While the role of MPAs in improving reef resilience under climate change has been criticised, given the limited evidence for increased recovery rates following bleaching within MPAs (e.g. [1,39]), more recent work has suggested that the limited evidence should be interpreted as a lack of statistical power in ecological monitoring to detect impacts, rather than MPAs having no impact on coral reef resilience [61].…”

Coral reefs benefit from reduced land–sea impacts under ocean warming

“…As a result, whereas local resource managers have aspired to an integrated land–sea approach 19 , evidence of its efficacy above either approach in isolation remains wanting and difficult to test. Detecting conservation benefits in highly dynamic ecosystems is challenging 20 , but recent studies have identified salient connections between local conditions and coral reef resistance to and recovery potential following mass bleaching 2 , 11 , 21 – 23 . Managers therefore require unambiguous targets for the combination of land–sea human impacts they should mitigate to support coral reef persistence under climate change.…”

Insights from the 2-year-long human confinement experiment in Grand Cayman reveal the resilience of coral reef fish communities

“…Coral reef fishes are a salient group of organisms for reef habitats, contributing to their ecosystem function and the provision of key ecosystem services, including nutrient cycling 1 , herbivory to prevent macroalgae proliferation over coral 2 , and cascading trophic effects 3 , 4 , among others. These functions promote coral reef resilience 5 and drive key ecosystem services such as nutrient provision from fisheries 6 , storm protection 7 , and other economic benefits for human livelihoods 8 – 10 .…”