Brightening clouds and coral larvae: study picks best Great Barrier Reef rescue ideas

<span>Photograph: James Cook University/AFP via Getty Images</span>
Photograph: James Cook University/AFP via Getty Images

Brightening clouds with salt crystals and deploying slicks of coral larvae to try and limit the impacts of global heating on the Great Barrier Reef are among more than 40 concepts being backed by the Australian government in an ambitious $150m research and development program.

A two-year feasibility study released by the government on Thursday has reduced about 160 potential ideas to a list of 43 that will be funded for further investigation under the Reef Restoration and Adaptation Program (RRAP).

About $100m for the program comes from $443m of previously announced government funding being administered in a partnership with the not-for-profit Great Barrier Reef Foundation.

Related: More than half of remote reefs in Coral Sea marine park suffered extreme bleaching

A further $50m will come from a consortium of the Australian Institute of Marine Science (AIMS), CSIRO, the University of Queensland, QUT, James Cook University, Southern Cross University and the Great Barrier Reef Foundation.

The Great Barrier Reef Foundation said it wanted to raise a further $100m from the private sector, and said research and development providers had committed to matching that with a further $50m to create a potential $300m fund.

The world’s biggest coral reef system is under intense pressure from global heating. The summer of 2020 saw the third and widest outbreak of mass coral bleaching in five years.

Ocean heating, caused by rising levels of greenhouse gases in the atmosphere, is threatening coral reefs around the globe.

The UN’s Intergovernmental Panel on Climate Change has said most tropical coral reefs would disappear even if heating was limited to 1.5C and would be “at very high risk” at 1.2C. Global heating is already at about 1C since the industrial revolution.

The federal environment minister, Sussan Ley, said a “global response” was needed to tackle rising greenhouse gas emissions.

She said: “For the average Australian and the average citizen of the world that cares deeply about the reef, this is our chance to shine and demonstrate that while we know climate change is the number one challenge to our reef, we also know there is much we can do to prepare the reef and put it in the best possible position for it to become as resilient as it needs to be.”

The feasibility study, led by AIMS, said: “Even if the world manages to stabilise global warming at 1.5C above the pre-industrial average, mass-bleaching events are predicted to increase in frequency and severity in the coming decades. Critically, the reef’s resilience may already be significantly impaired.”

The study added: “In short, we are facing the very real prospect that, within a generation and without concerted action to reduce emissions and help drive adaptation and faster recovery from damage, the Great Barrier Reef as we have known it will cease to exist.”

Last week, the chief scientist of the Great Barrier Reef Marine Park Authority, Dr David Wachenfeld, told Guardian Australia that measures to improve the reef’s resilience were needed, but their success was underpinned by “dealing with the climate problem.”

Related: Snow-white coral of once-vibrant Great Barrier Reef a sign urgent action must be taken | Adam Morton

Dr Paul Hardisty, the chief executive of AIMS, said the “best and brightest scientists” from across Australia had been brought together to work on the feasibility study.

“What we have found is pretty profound. There is real hope for the reef,” he said.

“RRAP is all about finding ways to help protect the reef from the effects of future warming and to prevent the kinds of bleaching that we have seen going on and to help damaged reefs recover.”

He said the research effort was “at the forefront of any science being done anywhere in the world”.

Some methods previously discussed as having potential to lower temperatures on reefs during heat stress events – including using pumps and fans to circulate cooler deeper water onto shallower corals – have been ruled out for further research.

But other concepts have been approved for further research in programs that will run over the next five to 10 years. They include:

  • Shading reefs by brightening clouds using nano-sized ocean salt crystals, or creating fog and mist over smaller reef areas

  • Using “micro-bubbles”, ultra-thin natural films and farmed algae to reduce light over smaller areas

  • Stabilising and enhancing damaged reef structures with mesh, frames, concrete shapes and 3D printed forms that could recreate the complexity of natural reefs

  • Dispersing slicks of natural and tank-raised coral larvae onto reefs

  • Breeding corals that are naturally more heat tolerant and then using their larvae in mass dispersal

David Mead, the AIMS director of strategic development, who helped coordinate the feasibility study, told Guardian Australia: “The outcome we want is to retain the fundamental resilience of the Great Barrier Reef.

“This is to progress a broad range of ideas and some will get eliminated along the way.”

On cloud brightening, Mead explained the concept was to spray nano-sized droplets of salt water to increase the reflective capabilities of clouds.

While the effect was “subtle” he said over a period of weeks initial modelling suggested it could keep water temperatures below the threshold where corals bleached.

“It sounds scary and we need to do a lot of detailed studies on any downstream impacts,” he said.

The feasibility study also estimated the annual cost of the 43 different concepts being researched. While the costs seemed high – cloud brightening, for example, would cost an estimated $158m a year – Mead said the benefits were also very large.

The study modelled likely benefits from deploying the interventions, which ranged from $10.7bn over 60 years to figures in the hundreds of billions.

But the cost benefits from deploying the measures were dependent on future greenhouse gas emissions and diminished as temperatures went higher.

Hardisty said the study had shown it was “technically feasible to act at scale” but he said “it’s going to be a combination of measures applied at different scales and in different areas that will work together to achieve real success.”

He said: “If we can get the science right and intervene on the reef at scale to prevent this kind of damage and build that resilience, then the benefits for Australia environmentally, socially and economically, especially for reef communities, is going to be in the tens of billions of dollars.”

Anna Marsden, managing director of the Great Barrier Reef Foundation, said the feasibility study had shown that 71% of the Australian public supported large-scale efforts to help reefs adapt.