Blue carbon
There’s huge potential for the continent’s coastal habitats to help balance Australia’s carbon emissions. Australia is ringed by seagrass beds, mangrove forests, tidal marshes and kelp forests, all of which sequester and hold huge amounts of ‘blue carbon’. These coastal ecosystems are driven by photosynthesising plants, so they absorb C02 from the atmosphere just as terrestrial vegetation does. But carbon isn’t stored only in plant tissues in these habitats, it’s also sequestered in huge amounts in their sediments.
“So they can hold up to 40 times more than terrestrial forests,” explains Dr Oscar Serrano, a marine ecologist with expertise in biogeochemical cycles at Edith Cowan University’s Centre for Marine Ecosystems Research in Western Australia. Australia is a blue carbon ecosystem hotspot, having about 10 per cent of the world’s total. Even so, up to 20 per cent of these habitats in Australia have been destroyed or badly degraded. Rehabilitating what has been lost would not only sequester and store carbon but also have other significant benefits. Mangroves, for example, protect coastlines from severe weather and are significant fish nurseries, contributing enormously to marine productivity.
Oscar was a lead author on a 2017 CSIRO report exploring the potentially huge opportunities for the ERF to tap into blue carbon. “There are a large number of activities an industry, institution or NGO can do to restore these carbon ecosystems,” Oscar says.
“It was concluded the activity with the largest potential is the reintroduction of tidal flow in coastal wetlands. Since
1900 there has been [much] construction in Australia of levees or walls to restrict tidal flow, [mostly] for agriculture and human settlements. If we removed these levees so tidal flow can re-enter and flood all these wetland areas, it’s expected mangroves and tidal marshes and seagrass will recolonise them.”
“Massive” is how Oscar describes the potential impact of recovering Australia’s blue carbon ecosystems. “We estimated that if just 10 per cent of the area that has been lost – roughly 1000sq.km – could be restored, it could reduce emissions from land-use change in Australia by 7–8 per cent,” he says.
That’s carbon that many large companies in industries such as oil, mining and fishing would be interested in buying credits for to offset their carbon footprints.