Helen F Yan

The University of Sydney · School of Geosciences

Extinctions on land are often inferred from sparse sightings over time, but this technique is ill-suited for wide-ranging species. We develop a space-for-time approach to track the spatial contraction and drivers of decline of sawfishes. These iconic and endangered shark-like rays were once found in warm, coastal waters of 90 nations and are now pr...

Nonnative marine species are increasingly recognized as a threat to the world's oceans, yet are poorly understood relative to their terrestrial and freshwater counterparts. Here, we conducted a systematic review of 2,203 research articles on nonnative marine animals to determine whether the current literature reflects the known diversity of marine...

Aim As anthropogenic stressors on the biosphere intensify, understanding how communities respond to disturbances is critical. Biodiversity is often thought to promote the stability of communities over time and enhance ecosystem functioning. However, results have been inconsistent, and the multifaceted linkages among diversity, stability and functio...

Individual growth is a fundamental life history trait1–4, yet its macroevolutionary trajectories have rarely been investigated for entire animal assemblages. Here we analyse the evolution of growth in a highly diverse vertebrate assemblage—coral reef fishes. We combine state-of-the-art extreme gradient boosted regression trees with phylogenetic com...

Under current trajectories, it is unlikely that the coral reefs of the future will resemble those of the past. As multiple stressors, such as climate change and coastal development, continue to impact coral reefs, understanding the changes in ecosystem functioning is imperative to protect key ecosystem services. We used a 26‐year dataset of benthic...

The true state of ocean biodiversity is difficult to assess, and there are few global indicators to track the primary threat of overfishing. We calculated a 50-year Red List Index of extinction risk and ecological function for 1199 sharks and rays and found that since 1970, overfishing has halved their populations and their Red List Index has worse...

The abundance of herbivorous fishes is known to vary strongly with latitude. However, our understanding of this pattern is largely based on the examination of nominally herbivorous fishes (i.e. both herbivores and detritivores) as a single group. Therefore, we do not know how this collective classification may have confounded our understanding of d...

Epilithic algae dominate cover on coral reefs globally, forming a critical ecological interface between the benthos and reef organisms. Yet, the drivers of epilithic algal composition, and how composition relates to the distribution of key taxa, remain unclear. We develop a novel metric, the Epilithic Algal Ratio, based on turf cover relative to to...

Herbivorous fishes play important roles on coral reefs, acting as key trophic conduits of primary productivity. Whilst these roles are widely appreciated on tropical reefs, the relative contribution of fishes which inhabit marginal reefs, such as Prionurus surgeonfishes, is not well understood. Here, we examine the extent to which herbivorous fish...

Function-based studies have opened a new chapter in our understanding of coral reefs. Unfortunately, we are opening this chapter as the world’s reefs rapidly transform. In this context, one of the most important roles of function-based studies is to inform coral reef conservation. At this critical juncture, we have a chance to reflect on where we h...

Herbivorous fishes, and the productivity of algal turfs, are widely viewed as central to the functioning of coral reefs. This understanding is largely based on clear-water reefs. Our knowledge of herbivorous fishes and the nature of their nutritional resources on turbid reefs, by contrast, remains relatively limited. We therefore explored the natur...

Overfishing is the most significant threat facing sharks and rays. Given the growth in consumption of seafood, combined with the compounding effects of habitat loss, climate change, and pollution, there is a need to identify recovery paths, particularly in poorly managed and poorly monitored fisheries. Here, we document conservation through fisheri...

Sharks and rays are key functional components of coral reef ecosystems, yet many populations of a few species exhibit signs of depletion and local extinctions. The question is whether these declines forewarn of a global extinction crisis. We use IUCN Red List to quantify the status, trajectory, and threats to all coral reef sharks and rays worldwid...

The first baited, video-based global survey of coral reef sharks reveals widespread depletion and functional extinction from eight nations. The authors identify priority ‘Goldilocks’ nations with the necessary combination of governance and shark abundance to recover depleted shark populations.

A key question for coral reef conservation is whether reefs dominated by macroalgae can recover. Since the near-disappearance of the herbivorous urchin Diadema antillarum in the Caribbean, a prevalent management paradigm has focused on protecting herbivorous fishes to trigger shifts back to a coral-rich state. However, in the absence of D. antillar...