Written by Louise Anderson
The problem:
Coral reefs around the world are increasingly threatened by the impacts of climate change, posing significant risks to both the ecosystems themselves and the human populations that rely on them for food and income security. The accelerating rate of change also creates a great deal of uncertainty in the context of protecting coral reefs in to the future. It is important that we find ways to reduce some of this uncertainty, and identify key areas in which to target the limited resources available for coral reef conservation.
The paper:
One recent paper takes a multidisciplinary view of this problem to identify areas of coral reefs that are most likely to survive projected climate change impacts, whilst maintaining the capacity to repopulate other reefs once the climate stabilizes (Beyer et al., 2018). This research borrows from economics by employing Modern Portfolio Theory (MPT) as a way to spatially prioritize those key areas on a global scale. MPT originally applies to investment portfolios, and it is essentially a mathematical framework applied to a collection of ‘assets’ so that the expected ‘returns’ are maximized for a given level of risk. Because it considers risk, and values diverse portfolios with high returns, this approach also lends itself well to conservation problems where climate change presents considerable uncertainty.
In the context of coral reefs, this boils down to trying to assemble a portfolio of areas that are most likely to give maximum returns (in terms of surviving and repopulating other areas), whilst minimizing the risk that these reefs aren’t going to survive projected climate change impacts. The analysis uses metrics that focus on thermal history, larval connectivity, cyclone frequency, and projected future conditions to identify individual units of about 500km2 of reefs. The goal of this kind of work is to guide conservation and policy decision-making and facilitate the development of coordinated strategies for coral reefs at large scales.
An important caveat with the MPT approach used in this paper is that it doesn’t account for other human impacts, such as the use of destructive fishing methods or significant sources of pollution. However, it argues that identified units can then be targeted to additionally reduces stressors at these key sites.
The results
Several regions have been identified as more likely to escape the worst of the projected climate change impacts, including parts of the Red Sea, East Africa, Southeast Asia (Fig. 1) and the Great Barrier Reef. Identifying these areas is based on some key assumptions:
- Localized human impacts can be managed and reduced in these areas to improve outcomes for coral reef ecosystems.
- The goals set out in the 2015 Paris Climate Agreement are met.
- The global climate stabilizes in the future, and surviving reefs are able to repopulate more degraded areas.
What does this mean for coral reef conservation?
Several of the regions identified don’t currently receive significant conservation attention (i.e. Southern Red Sea) (Fig. 2), and there may be opportunities for local management to mitigate the effects of other human stressors. Minimizing the impacts of human activity in these areas represents a key goal for coral reef conservation in the context of climate change. This research provides possible frameworks for countries to collectively develop strategies for steering reefs through the projected changes in coming decades.
This paper is in many ways hopeful that coral reefs can weather the changes already set in motion in our climate, but it is also unequivocally clear that this kind of research must be coupled with immediate, coordinated global action to reduce emissions and limit the effects of climate change. Unless current emissions trajectories are significantly reduced, the scope for strategic management to protect coral reefs in to the future is extremely limited.
Further reading:
References:
BEYER, H. L., KENNEDY, E. V., BEGER, M., CHEN, C. A., CINNER, J. E., DARLING, E. S., EAKIN, C. M., GATES, R. D., HERON, S. F., KNOWLTON, N., OBURA, D. O., PALUMBI, S. R., POSSINGHAM, H. P., PUOTINEN, M., RUNTING, R. K., SKIRVING, W. J., SPALDING, M., WILSON, K. A., WOOD, S., VERON, J. E. & HOEGH-GULDBERG, O. 2018. Risk-sensitive planning for conserving coral reefs under rapid climate change. Conservation Letters, e12587. https://doi.org/10.1111/conl.12587
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