Vulnerability of the Great Barrier Reef to climate change and local pressures

Abstract

Australia's Great Barrier Reef (GBR) is under pressure from a suite of stressors including cyclones, crown-of-thorns starfish (COTS), nutrients from river run-off and warming events that drive mass coral bleaching. Two key questions are: how vulnerable will the GBR be to future environmental scenarios, and to what extent can local management actions lower vulnerability in the face of climate change? To address these questions, we use a simple empirical and mechanistic coral model to explore six scenarios that represent plausible combinations of climate change projections (from four Representative Concentration Pathways, RCPs), cyclones and local stressors. Projections (2017-2050) indicate significant potential for coral recovery in the near-term, relative to current state, followed by climate-driven decline. Under a scenario of unmitigated emissions (RCP8.5) and business-as-usual management of local stressors, mean coral cover on the GBR is predicted to recover over the next decade and then rapidly decline to only 3% by year 2050. In contrast, a scenario of strong carbon mitigation (RCP2.6) and improved water quality, predicts significant coral recovery over the next two decades, followed by a relatively modest climate-driven decline that sustained coral cover above 26% by 2050. In an analysis of the impacts of cumulative stressors on coral cover relative to potential coral cover in the absence of such impacts, we found that GBR-wide reef performance will decline 27%-74% depending on the scenario. Up to 66% of performance loss is attributable to local stressors. The potential for management to reduce vulnerability, measured here as the mean number of years coral cover can be kept above 30%, is spatially variable. Management strategies that alleviate cumulative impacts have the potential to reduce the vulnerability of some midshelf reefs in the central GBR by 83%, but only if combined with strong mitigation of carbon emissions.

Spatial resilience of the Great Barrier Reef under cumulative disturbance impacts

“…However, such spatial patterns of coral bleaching on shallow reefs are typically patchy (up to a 10‐100m scale; S. Heron, unpublished data) and are currently difficult to resolve at the scale of the GBR. Given that coral bleaching is predicted to increase both in frequency and severity over the next decades (van Hooidonk et al, ; Wolff et al, ), its impact on coral cover will also likely increase and potentially surpass that of tropical cyclones in the future.…”

“…By accounting for key ecological processes (coral growth and recovery potential), environmental drivers of coral cover, and observed disturbance history, we reconstruct coral cover trajectories for >1,500 reefs at a 0.01° (~1 km) resolution over the last 22 years (1996–2017). Importantly, for the first time, our model includes a spatially explicit index of water quality for the frequency of river plume‐like conditions (Petus, Silva, Devlin, Wenger, & Alvarez‐Romero, ), which can negatively affect corals (Fabricius, ; Wolff, Mumby, Devlin, & Anthony, ). We independently validate our model predictions and provide quantitative estimates of model uncertainty—a critical requirement for informing decision‐making and risk analyses (Mumby et al, ).…”

3D Printing: Applications in evolution and ecology

“…3D printing has also been used to help recreate coral reefs. The Great Barrier Reef is experiencing widespread coral bleaching and coral death (Wolff, Mumby, Devlin, & Anthony, ), but advances in 3D printing are enabling the production of coral shaped objects, 1 m in height (Sustainable Oceans International, ). These large‐scale 3D printed forms replicate the complexity of natural coral, providing organisms such as fish with suitable habitats while corals colonize the external surfaces.…”

Ultra-Violet Radiation Has a Limited Impact on Seasonal Differences in the Acropora Muricata Holobiont

“…The effect of seawater temperature variations on coral physiology has also received a lot of attention; in particular because episodes of temperature extremes can induce coral bleaching (loss in symbionts and photosynthetic pigments), resulting in decreased photosynthesis and calcification rates (HoeghGuldberg, 1999;Hoegh-Guldberg et al, 2017;Hughes et al, 2017;Wolff et al, 2018), as well as shifts in the composition of coral-associated microbial communities (Littman et al, 2010(Littman et al, , 2011Ziegler et al, 2017). However, little is known about the response of coral holobionts to seasonal changes in ultraviolet radiation (UVR) levels.…”