Q&A: Reef restoration approaches taken by RRAP initiative

Background information and frequently asked questions about coral reef restoration and the approaches taken by the RRAP initiative to develop tools to enhance the natural resilience of the Great Barrier Reef.

Coral reefs are in decline worldwide. Climate change has reduced coral cover and surviving corals are under increasing pressure. Rising ocean temperatures and marine heat waves led to mass coral bleaching on the northern and central Great Barrier Reef in 2016 and 2017, compounded by cyclones and outbreaks of coral-eating crown-of-thorns starfish.

The frequency and severity of bleaching events is forecast to increase, in line with climate change predictions. Many corals already live close to their temperature tolerance limit and their ability to naturally adapt to rising temperatures may not be sufficient given the magnitude and rate of global warming.

Despite the alarming outlook, the Great Barrier Reef still has high biodiversity, natural beauty and resilience. Commitments by governments to the targets of the Paris Climate Agreement could limit global warming to between 1.5 and 2 degrees Celsius above pre-industrial levels (noting the Reef has already warmed by ~0.7 degrees). This gives us a window of opportunity to develop additional actions to support the resilience of coral reefs and to sustain their values and services.

The RRAP program looks into ways we can assist the Reef's capacity for recovery and adaptation. The ultimate aim is to help protect coral species that provide critical habitat for 35 percent of the world's fish, thousands of other marine species, and support livelihoods and economies worth hundreds of billions.

Climate change mitigation is critical to give the Reef a chance into the future. However, even if global warming can be kept within 1.5 degrees Celsius above pre-industrial (the most optimistic goal of the Paris Climate Agreement), the world is set to warm another 0.5 degrees Celsius in the coming decades (http://www.ipcc.ch/report/ar5/syr/).

Because corals already live close to their temperature tolerance limit, this amount of warming will likely be too much for many sensitive coral species, including those that build important fish habitat. This means that safeguarding the Reef requires new interventions in addition to strong carbon mitigation and continued conventional management.

The additional warming that the Reef will experience will depend not only on the latent warming already in the system, but also future emission trajectories (http://www.ipcc.ch/report/ar5/syr/). The RRAP will evaluate the costs, feasibility and risks across multiple scenarios - climate change trajectories and social/economic futures. The Reef will have its best chance of maintaining biodiversity and ecological value if additional warming can be minimised and if people continue to care about the Reef and support its management (http://www.environment.gov.au/marine/gbr/publications/reef-2050-plan-review-options-final-report). If global warming exceeds 2 degrees C above the pre-industrial level, then we will need to consider more radical interventions and measures of adaptation to build resilience. The RRAP proposes to evaluate a range of active interventions such as assisted gene flow, assisted evolution and gene editing so that they are ready and safe if or when we need them. Using these approaches to protect key species in key places could maintain critical Reef values under less favourable climate scenarios. Importantly, CO2 mitigation and continued water quality management, starfish control and no-take areas will be more important than ever, and the prerequisite for a successful reef adaptation program.

The RRAP program will use the Reef's natural processes of larval dispersal to help spread resilient species or populations to reefs that need climate tolerance urgently. Where possible, we will help the Reef help itself, which will make our work cost-effective. A small subset of the Reef's 3000 individual reefs can help colonize corals on large areas of the Reef in a short time frame (http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2003355). Understanding and designing strategies for when and where RRAP interventions will be most effective is a key focus of our work in 2018. The RRAP will focus on the recovery and survival of coral species that serve key ecological functions and underpin multiple Reef values. These include species that build important fish habitats. In addition to using natural Reef processes to help us scale up interventions in key areas, we will work closely with engineering and technology sectors to develop innovative deployment solutions that can be delivered cost effectively at scale.

Corals have adjusted and adapted to their environment over decades to millennia. For example, corals in the Persian Gulf survive temperatures that are too extreme for coral species elsewhere, while certain coral species naturally tolerate water with lower pH. On the GBR temperatures vary by several degrees from North to South and large temperature differences also exist within reefs between habitats and depths. The thermal tolerance of corals reflects their local temperature environment. This means corals in the northern Great Barrier Reef bleach at higher temperatures than those to the south. With rapid global warming, including all Reef regions, the key question is whether rates of natural adaptation are fast enough to keep up.

Adaptation can occur through a variety of ways and can be fast under the right conditions. Genetic adaptation occurs through changes in the organism's DNA and can be rapid if standing genetic variation and heritability of fitness traits are high. Under these conditions the spread of tolerant genes may be limited by reproductive constraints and barriers to dispersal. Epigenetic changes involve modifications to the chemical switches on the DNA and can sometimes be passed from parents to offspring similar to DNA markers. The RRAP research program will focus on understanding how adaptation in stress tolerance can be harnessed and enhanced over short time frames to help coral become more temperature tolerant. This builds on ongoing research at AIMS

The current rate of environmental change, and back-to-back bleaching events in 2016 and 2017, has raised concerns that most reef-building coral will not be able to adapt fast enough. This could result in a catastrophic loss of coral. Because corals build habitats and reef structure, they are foundational for much of the Reef's biodiversity. Losing coral therefore means losing functions, and consequences could be devastating for all reef life and the people and economies who depend on it. The result could be a Reef with few ecological, social and economic values intact.

The Great Barrier Reef is home to around 600 different species of corals, many of which serve different functional roles. For example, some coral species are important as fish habitats, whereas others promote reef recovery after disturbances. Loss of coral means loss of habitat and food for fish, themselves potentially also directly impacted by climate change. This can lead to changes to the ecosystem, for example an increase in seaweeds that make it difficult for coral larvae to recruit to the reef and for adult corals to survive and recover. The RRAP will explore solutions that will assist the recovery and survival of coral species that serve both key ecological functions and underpin multiple Reef values.

Conventional coral reef management on the Great Barrier Reef is currently focused on protecting reefs through zoning, managing and improving water quality and removing Crown of Thorns starfish (http://www.gbrmpa.gov.au/). These efforts remain critical to support reef recovery between bleaching events and storms. However, the gain in reef resilience from conventional efforts, even if they are intensified, cannot compensate for the stress caused by more frequent and severe bleaching events. In short: climate change will increasingly affect the Reef's natural resilience despite the best conventional management efforts.

Keeping the Reef healthy into the future will require a multi-pronged strategy that combines (1) climate mitigation, (2) continued and intensified conventional management to minimize multiple, cumulative stressors, and (3) additional interventions designed to boost climate tolerance and resilience (https://theconversation.com/the-great-barrier-reef-can-repair-itself-with-a-little-help-from-science-85182.).

The Great Barrier Reef and all other coral reefs in the world are changing as a result of impacts from human activities including climate change - with or without our best interventions. The RRAP aims to provide solutions to maintain the ecological functions and species that support biodiversity, tourism and fisheries are given the best chance of survival into the future.

The Great Barrier Reef is home to many thousands of species, so the challenge will be to identify the species that most urgently need help while considering what species provide values for the ecological health of the reef and society. Some species of coral that are homes for fish are also the most sensitive to climate change so they should be considered a priority.

Some species are seen to play more important roles in ecosystems than others. This importance is of course judged by people and relate to whether species support functions that underpin biodiversity and ecosystem services. This program will work with Reef stakeholders to develop a set of criteria against which we will develop strategies and alternatives for interventions. This includes the evaluation of "ecosystem engineers" (e.g. coral species that build structure and habitats), "keystone species" (which impact on other species), and species that have high aesthetic, recreational or commercial values.

The RRAP will look at combining conventional and novel approaches to produce effective solutions - that is, approaches that work to build the Reef's resilience.

The techniques we are assessing can be split into two categories: prevention and repair.

Prevention techniques are tools to reduce susceptibility to elevated water temperatures that cause coral bleaching. They propose to develop corals with a higher temperature-bleaching threshold, using a range of techniques. These range from identifying and moving existing corals with elevated temperature resistance to selectively breeding corals whose temperature tolerance has been enhanced. We are also considering other approaches that adjust the physical environment at a reef-scale to reduce the exposure of corals to acute temperature stress events. Repair techniques include enhancing recovery after disturbance from coral bleaching, crown-of-thorns starfish outbreaks, cyclones or ship groundings. These techniques include developing biological supports to accelerate natural recovery. This includes modifying the reef surface to improve coral recruitment or facilitating the recovery of bleached corals.

AIMS current research aims to understand the adaptive capacity of corals and how to apply this knowledge to Reef conservation and management.

The term assisted evolution (AE) refers to a range of approaches that aim to accelerate naturally occurring evolutionary processes to enhance certain traits that are important for health and survival. These approaches range from assisted gene flow, selective breeding of stress tolerant coral stock to active selection and manipulation of microbial symbionts with the aim of enhancing the stress tolerance of the coral animal. The thermal tolerance of corals may also be extended by genetic engineering and synthetic biology tools. For example, future research and development may potentially use existing gene editing technology (https://www.aims.gov.au/seasim-spawning-research-2016) to very precisely engineer the temperature tolerance of corals. AIMS researchers are currently engaged in a number of experiments to measure epigenetic changes and genetic adaptation and the conditions under which it can be promoted (https://www.aims.gov.au/reef-recovery).

Assisted gene flow involves moving heat-tolerant corals (or their young) to cooler reefs that are warming. This technique will improve the heat tolerance of local coral populations and will help the buffer the reef against future bleaching events caused by warmer-than-normal water temperatures. This approach relies on high standing genetic variation for heritable components of heat tolerance, and the capacity for local thermal adaptation (https://www.aims.gov.au/reef-recovery). It can be made operational in the form of assisted larval dispersal or assisted translocation of adult coral colonies. For example, the northern GBR is several degrees warmer than its southern region and contains genetically heat-adapted corals. Bleaching tolerance of corals may also vary among habitats within reefs that experience different temperature regimes. Research at AIMS is currently investigating the feasibility, benefits and risks of assisted gene flow in coral breeding experiments in SeaSim.

Genetic engineering of corals or their symbionts is one of many ways we might help corals become more tolerant to bleaching in the future. Genetic engineering provides a way to precisely edit specific genes that regulate for heat resistance or to insert genes that increase heat tolerance or disease resistance.. However, the application of genetic engineering solutions for the Reef will require extensive research and development, assessments of benefit and risk, plus legislative approvals that do not currently exist. The RRAP will consider all options that meet the criteria of providing a net benefit for the Reef at acceptable levels of risk, scale and cost. Most of the currently proposed interventions will not involve gene technology. For example, we can consider to move warm-adapted corals or their offspring to naturally cooler places or we can use other assisted evolutionary processes to promote heat tolerance in corals. Starting the research and development and rigorously testing these tools soon gives us the best chance to use them safely and effectively in the future if or when we need to.

The right time to start any new intervention is when the risk of inaction is greater than the risk of action. As climate change grows stronger, so do impacts on the Reef. Delaying the use of new interventions means foregoing opportunities to save species and values. But acting too fast with untested intervention can also pose risks from unknown side effects. To strike the right balance of minimising risk and maximising opportunity, the RRAP program will start early on the research and development of interventions that show promise in terms of effectiveness, feasibility and cost. All new interventions will then go through a rigorous assessment and testing phase while we consult closely with partners and stakeholders. The result will be an expanding toolset of interventions that can be ready for safe implementation if or when they are needed (https://www.aims.gov.au/docs/media/featured-content.html/-/asset_publisher/Ydk18I5jDwF7/content/the-great-barrier-reef-can-repair-itself-with-a-little-help-from-science).

The different intervention approaches proposed in RRAP aim to enhance the resilience of coral reefs but vary in their associated risks. For example, assisted gene flow and assisted evolution represent manageable risk because they use genetic material already present on the reef. Assisted colonisation that involves importing coral species from outside the Great Barrier Reef may carry greater ecological risk than other approaches. A full understanding and evaluation of risks is a key component of RRAP and will be evaluated from ecological, social and economic angles. They will be assessed against the risk of "doing nothing" or delaying interventions. Predicted benefits (upside risks) will be presented alongside chances of any potential negative outcomes (downside risks). These analyses will provide clarity for all, inform a prioritisation of techniques for technological development, decision-making, facilitate a license to operate, and promote stakeholder buy-in.

Our vision is that RRAP will help protect values that are critical for the health and ecosystem function of the Great Barrier Reef - its rich biodiversity, continued status as a World Heritage Area, and a place that continues to support recreation, culture and a multi-billion dollar economy. The Reef is a natural asset valued at $56 billion, an ecosystem of global significance and a critical part of the Australian national identity. By working closely with partners and stakeholders to identify interventions that sustain both ecological functions and social and economic values, the RRAP program will help sustain this asset for Australia and the world.

An essential part of the planning and feasibility assessment phase will be to understand not only the likely benefits and costs of possible interventions but also the ecological, economic and social risks. To do this requires a collective effort of all Reef stakeholders. The RRAP will actively engage and consult with all people connected to the Reef. It will build strong partnerships between researchers, government agencies and the wider community, including Traditional Owners.

A range of active reef restoration approaches have been applied on reefs around the world for decades. They have been successful in, for example, increasing coral cover or reducing algal cover on local scales. Many projects have included gardening of corals in land-based or marine nurseries and more recently laboratory reared coral young are used (https://www.barrierreef.org/science-with-impact/baby-coral-breakthrough). Despite positive reports of many restoration efforts, the cost and effectiveness of many interventions remain unclear.

While the RRAP program capitalises on existing knowledge, it aims to provide a step-change in the cost and scale by which active interventions can be delivered on coral reefs. To achieve this we will be working closely with the engineering and technology sectors to develop innovative deployment solutions that can be delivered at the required scale and cost levels. The first stage of the RRAP program consists of a feasibility study that will examine a broad range of potential concepts and then narrow in on the most feasible options.

We are looking for additional partners and there are many ways to engage

Please contact:
Emily O'Regan (RRAP Project Administrator)
e.oregan@aims.gov.au
07 4753 4275