Climate Change Leaves Mark on Coastal Ecosystems

Extreme climate events are exacerbating the impact of climate change in Australian marine ecosystems causing, in some cases, irreversible change underscoring the importance of adaptation and innovative solutions in the marine environment.

Researchers at CSIRO, Australia’s national science agency, have for the first-time collated published works by leading researchers of climate impacts around the whole of Australia’s coast to reveal that around 45 per cent of our coastal marine ecosystems have suffered from the impact of climate extremes.

The study was published in Frontiers in Marine Science.

Marine heatwaves, heavy rainfall from tropical storms, cyclones and droughts have all played a role in fundamentally changing our coral, kelp, mangrove and seagrass communities.

“The length of coast impacted by extreme climate events in the last decade is more than 8000 km, almost four times the length of coastline impacted by the much better known Gulf of Mexico oil spill,” lead author of the study Dr Russ Babcock said.

“Corals, kelp, mangrove and seagrass ecosystems provide important habitat and food for thousands of biodiverse marine creatures, plus make vital contributions to the biotic productivity and resource economy of coastal habitats and nearby towns and cities.

“We’ve already seen major climate events rock these marine food webs and create changes that will take decades to fully recover from.

“Some of them are potentially irreversible.”

The CSIRO Oceans and Atmosphere research team have studied events like the 2011 Western Australian marine heatwave, the 2016 and 2017 back-to-back coral bleaching events and major cyclones like Cyclone Yasi to paint a full picture of the accumulated impact of extreme climate events.

Ecosystem modelling approaches have also been used to reveal the likely scale of these impacts into the future.

They found that ongoing human-induced climate change, such as gradual increases of sea surface temperature, are exacerbated by extreme climate events which leave most marine organisms and habitats unable to acclimatise or adapt in rapidly changing habitats.

CSIRO Senior Researcher and paper co-author Dr Beth Fulton said that if extreme climate events occur more often and are more intense marine habitat recovery is unlikely to occur.

“Our modelling indicates that the average recovery time for major species groups is around 10 to 15 years. If climate shocks happen more often than this, then ecosystems may never fully recover,” Dr Fulton said.

Different types of extreme climate events can also happen concurrently or one after the other, creating additional pressures for marine ecosystems.

“In February 2011 Cyclone Yasi destroyed swathes of seagrass meadows along the north Queensland coast. When the associated flooding reached the sea the turbid and nutrient rich waters blocked sunlight preventing growth of any remaining seagrasses,” Dr Babcock said.

Dr Babcock and colleagues have been working across Australia’s marine ecosystems to understand climate impacts and strategies for effective adaptation.

“Adaptation responses will be required at species and ecosystem scales,” he said.

“Our research, for example in developing new methods for restoring coral reefs, may be one way to help maintain ecosystems.

“We have developed industrial scale methods to harvest coral spawn, grow it out in at-sea aquaculture systems and redistribute across damaged reefs.

“This is one example of a flexible and adaptable strategy that can be used to help reefs recover in the short term.

“But in the long-term adaptation efforts will need to be coupled with efforts to reduce atmospheric greenhouse gases that drive climate change.”

Climate impacts on four major marine ecosystems

Coral Reefs

• Coral habitats are home to more than 83,000 animal and plant species, and are susceptible to diminishing water quality, overfishing, construction, warming oceans and ocean acidification.
• Between 2011 and 2017 coral reefs along thousands of kilometers of Australia’s west and east  coasts were affected by four separate coral bleaching events. Mortality of corals in WA was as high as 90 per cent in some places while in the north of the GBR average coral cover declined by around 50 per cent.

Kelp Forests

• Kelp forests are important marine habitats and sources of food, kelps are threatened by overfishing, eutrophication and climate change.
• During the 2011 Western Australian marine heatwave several species of kelp became locally extinct depriving important fishery species of habitat, they are unlikely to recover in the foreseeable future

Seagrass meadows

• Seagrasses stabilise sediments, store carbon, feed turtles and dugongs and provide habitat for fish, invertebrates and birds, many of which are economically important.
• Following the 2011 Queensland floods and seagrass loss there was a marked rise in the number of turtle and dugongs found stranded which has been linked to the decline in food availability.

Mangrove forests

• Mangrove ecosystems support fish and fisheries in northern Australia through providing shelter and a stable substrate for plants and animals, as well as protecting low-lying coastlines.
• During summer 2015-16 over 1000km of mangrove forest died around the Gulf of Carpentaria, home to one of Australia’s most valuable fisheries, leaving this otherwise pristine ecosystem severely damaged.