Our current Environment Minister, Sussan Ley (number four to try the job), has just reannounced, for the umpteenth time, our commitment to capturing blue carbon greenhouse gases in mangroves, marshes and seagrasses.
It’s a worthwhile endeavour, as it was when Julie Bishop made the same announcement in 2017. These systems are not just valuable because of the carbon they capture, they are valuable for a whole multitude of reasons around fisheries, around coastal protection, around supporting our marine biodiversity. But they are under threat.
Since European settlement in Australia, we’ve lost about 25% of our sea grasses, 50% of our tidal marshes, somewhere between 50% and 70% of our mangroves, and that loss is continuing. Estuaries and coastal wetlands have been filled in, drained off and dug up to make way for agriculture and urban development. Seagrass meadows and mangrove stands have been decimated by coastal development such as ports, marinas and sewerage outfalls.
Levies have been built for flood mitigation and to hold back the sea, killing mangroves and tidal marshes to turn them into pasture or some other sort of land use. Things like fish farms can damage seagrass meadows; they put nutrients into the water column, they shade the seagrass, and that can have a negative effect.
The government’s active encouragement of rampant development has exacerbated the problem but the potential of blue carbon faces a far greater threat from climate change.
For example, a heatwave event in Shark Bay in 2010 and 2011 caused the loss of about 1,000 km² of seagrass.
A UN oceans report published in 2019 said blue carbon would offset only about 2% of current global emissions and would not be an effective replacement for the “very rapid reduction of greenhouse gas emissions” required to avoid catastrophic climate change.
The report states that “[…] under high emission scenarios, sea level rise and warming are expected to reduce carbon sequestration by vegetated coastal ecosystems.” If emissions keep rising, the speed and scale of climate change will overwhelm blue carbon ecosystems’ ability to adapt. This problem will be compounded by “coastal squeeze” as rising seas butt up against human infrastructure, leaving coastal plants with shrinking habitats.
As is always the case, there are political motives for the government’s pretence at caring about blue carbon. With China’s increasing involvement in the Pacific, we have all of a sudden “stepped up” in announcing things supposedly to help our neighbours. Not only do we want to look like we care, we also want to claim/buy carbon credits for anything we do to protect their coastal vegetation.
As Oli Moraes from RMIT University observed:
Australia is essentially telling our Pacific neighbours, who are on the front line of climate change: “We will protect your coastal carbon sinks in the short term for international credit, while continuing to burn and export coal, oil and gas.”
In the long term, Pacific islands will be devastated and even destroyed by cyclones and storms. Because those mangroves won’t be able to adapt in time to the hot, acidic and rising seas.
Whilst we continue to champion fossil fuels, all other measures to combat climate change are fighting a losing battle.
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