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  • Photo du rédacteurL'équipe de Clim'Adapt

Making the Great Barrier Reef resilient: a challenge for today and tomorrow

In northeastern Australia, a few kilometres from the coast, there is a biological formation visible from space: the Great Barrier Reef. As a reservoir of immense biodiversity, it is increasingly subjected to climatic conditions that destabilize it. Temperature increase, water acidification and predator proliferation are many challenges to making the Great Barrier Reef resilient. The Reef Restoration and Adaptation Program (RRAP), a consortium of more than 100 experts from around the world, led by the Australian Institute of Marine Science (AIMS), has set itself this challenge: to find ways to make the Great Barrier Reef resilient to climate change and thus save a vital ecosystem.

Coral bleaching, a major concern

Corals represent 0.5% of the marine surface area but are nevertheless the reservoir of 25% of known marine species. The Great Barrier Reef is the largest manifestation of this unique and extremely fragile ecosystem. Indeed, the increase in the pressure exerted on corals has been particularly visible since the 1980s. The frequency of coral bleaching episodes, the first step before coral death, has increased by a factor of 10 in 30 years[1], leading to worldwide concern about their disappearance, with episodes every 3 years now. These phenomena are no longer limited to the El Nino episodes, which increase temperatures in the region about every 5 years. Worse, even when temperatures are lower than normal, bleaching episodes now occur during La Nina [1].

The Great Barrier Reef experienced the worst bleaching episode in its history in 2016, and again in 2017, with more than 90% of corals affected and ultimately 30% of corals permanently bleached[2]. The coral dies when the association with microalgae is broken and with only 0.5°C more for the surrounding waters the alga is expelled and therefore the white skeleton of the coral appears.

The mission

Created in 1972 as an exploration agency defining the Great Barrier Reef and its biodiversity, in recent years, its focus has turned to monitoring and understanding the changes in Australia’s marine ecosystems such as the Reef.

AIMS's National Sea Simulator (SeaSim) is a world-class marine research aquarium facility for tropical marine organisms in which Australian and international scientists can research the impact of complex environmental changes with large, long-term, experiments.

In January 2018, the Australian Government provided $6M to establish the Reef Restoration and Adaptation Program (RRAP), led by AIMS.

Over 18 months, RRAP conducted the world’s most rigorous and comprehensive investigation into medium- and large-scale reef intervention, drawing on more than 150 experts from more than 20 organisations across the globe. The aim: to study the feasibility of intervening at scale on the Great Barrier Reef to help it adapt to, and recover from, the effects of climate change.

The study, to be shortly presented to the Australian Government, found successful intervention was possible and could double the likelihood of sustaining the Reef in good condition by 2050. But time was of the essence: the longer we wait, the more expensive and difficult it will be to successfully intervene at any scale, and the greater the risk the window of opportunity will close.

The RRAP Concept Feasibility Study found there was no single silver bullet solution, rather a range of methods would be needed to work together to provide compounding benefits, along with ongoing best-practice reef management and emissions reduction. It recommends a 10-year research and development program to create a suite of methods to help protect the Reef, assist corals to adapt to the changing environment and to help restore damaged reefs.

These interventions correspond to combinations of variables that take into account the climatic conditions given by the IPCC reports for the 2050 and 2075 forecasts. These would need to be combined with best-practice conventional reef management and reduced carbon emissions to maximise their effectiveness.

Some examples of possibilities that have been identified for further research, risk assessment and possible development include:

- The industrialization of coral breeding to reach the 100 million surviving planted corals per year. This solution requires international cooperation and a substantial budget.

- The identification of corals that are naturally more resistant to heat periods, for example. This would delay coral mortality forecasts by a few years.

- Crossing coral species to find new varieties that can potentially express adaptations under extreme conditions.

- Marine cloud brighting : spraying microscopic sea water droploets into the air, to create a mild fog which deflects photons and sunlight, thus cooling and shading large areas of reef

The solutions can be on different scales: on a local scale, i.e. a few dozen reefs - 1 to 10 million surviving corals per year - or on a large scale, i.e. the entire coral reef. The aim of the tracks to be selected will be to make corals resilient through long-term adaptation to climate change and not just restoration after bleaching episodes.

SEASIM, one of the most advanced aquariums in the world

SeaSim is a coral research laboratory that can simulate specific climatic conditions. It has facilities for the long-term holding and propagation, allowing multi-generational studies, which are critical in understanding how marine organisms acclimatise and adapt to a changing environment.

The conditions of the media are modified according to several criteria: water temperature, salinity and acidity, but also the presence of potentially disruptive chemical elements. This allows the resistance of corals to be tested in real conditions. Conditions are modelled on the different scenarios provided by the IPCC. About twenty species of corals are present in SeaSim laboratories.

These corals are collected in situ after obtaining permits from The Great Barrier Reef Marine Park Authority. During transport, most corals experience stress and bleaching. When they arrive at SEA-SIM, they are therefore recovered in aquariums with ideal climatic conditions. These corals are then placed under special study conditions.

Corals are scientifically interesting because they are independent and therefore by cutting a part, we obtain a clone that will serve as a witness to the experiment.

The resources made available

In their research, they are assisted by a mechanical unit, located in the centre of Townsville, which has the necessary tools to design custom parts but also to create new parts ordered by researchers for their field studies.

To know the evolution of corals over a large time scale, they drill holes and study their grooves. Thus, we can notice by the alternation of the grooves the growth of the corals, the salinity of the waters by highlighting them with X-rays, the increase in temperature during bleaching episodes and the past chemical composition of the waters thanks to the identification of isotopes. These cores highlight the increased frequency of stress episodes and therefore the urgency of AIMS' task.

Conclusion :

Driven by public policies but subject to their alternation, the work of Australia’s Reef Restoration and Adaptation Program concerns the entire planet. Saving this ecosystem, which spans more than 2300km and is so rich in biodiversity, will certainly cost billions of dollars. This cost is to be highlighted by the financial manna it represents. A study carried out in 2016 estimated that global corals as a whole generate between 24 and 310 billion euros in revenue per year, largely due to ecological tourism. 2] All in all, it remains profitable to save these biodiversity sinks, fuelling a positive economy. For more information about the Reef Restoration and Adapation Program:

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