Experts say better regulation on geoengineering is needed.

Specifically, researchers from the University of Tasmania say more robust rules are needed to ensure the public acceptability of new technologies that aim to protect Australia’s Great Barrier Reef from further coral bleaching due to climate change.

The main driver of coral bleaching is the increased frequency and intensity of marine heatwaves.

Warm water temperatures cause coral to expel zooxanthellae, leading to coral bleaching.  Australia’s iconic Great Barrier Reef (GBR) has lost 50 per cent of its coral cover in the past 3 years as a result of just two consecutive bleaching events.

Some bold ideas involving geoengineering have emerged in response.

Proposals to protect the reef include two which involve “shading” the reef to reduce warming of shallow waters from direct exposure to the sun.

One proposal is the application of a biodegradable polymer film that can act like a ‘sunscreen’ for coral. The other involves increasing the brightness of clouds over the GBR so they reflect more solar energy back into space.

This marine cloud brightening proposal is a type of local solar radiation management, and involves spraying minute salt particles into low-lying marine clouds to increase their brightness.

The third approach involves reducing the temperature of shallow waters near corals by mixing them with cooler waters pumped from 10-30 metres below.

Professor of Environmental and Climate Law at the University of Tasmania, Professor Jan McDonald, says she and her colleagues support trials of these technologies, but warns that better regulation and public understanding is needed.

“We think they need to be governed as part of a coherent policy that articulates the role for such interventions alongside Australia’s climate mitigation and adaptation agendas,” she said.

She pointed to the UK’s experience with the SPICE project - a government-funded geoengineering research project that looked at injecting particles into the stratosphere from a tethered balloon for the purposes of solar radiation management.

The field testing of the project had to be cancelled in 2012, and one of the concerns cited was the lack of government regulation of such trials.

“Australia’s current laws do not guarantee robust governance for field testing or eventual deployment of these technologies,” Prof McDonald said.

“We should have clear processes of risk assessment and public engagement early on, to build legitimacy and trust in this suite of climate interventions.”

More details are available in a new article for the journal Climate Policy.