Researchers have shown that boat activity at Rottnest Island has destroyed a large seagrass meadow that plays a crucial role in storing carbon dioxide.
A team of Australian researchers from Edith Cowan University surveyed the ‘scars’ on the island’s coast and found boat mooring chains had caused irreversible damage to seagrass covering an area of 48,000 square metres. The study was published today in Nature: Scientific Reports.
“As moored boats drift with the currents, wind and waves, they drag a heavy chain across the seafloor and that chain acts just like a razor across the skin removing the seagrass,” says lead researcher Dr Oscar Serrano, an expert in marine ecology from Edith Cowan University.
“But unlike a 5 o’clock shadow – in this case the seagrass doesn’t grow back.”
Valuable carbon buffer
Seagrass meadows are crucial to maintaining the health of marine ecosystems, as they not only provide habitat and food for marine life, but also act as a climate change buffer by storing atmospheric carbon dioxide.
Samples taken from the scarred areas by Dr Serrano’s team showed that on average more than 75 per cent of the CO2 absorbed by the seagrass had been released back into the atmosphere.
“Seagrass absorbs carbon dioxide at more than 40 times faster than tropical rainforests,” says Serrano. “What that also means is that when the seagrass meadows are wiped out, the carbon dioxide which has been absorbed over hundreds of years, is released back into the atmosphere.”
One way to combat the scarring of the seagrass has been to replace the old moorings that use chains with seagrass-friendly moorings, however this has only managed the slow down the rate of destruction.
“Once the mooring chains have started the process of scouring, waves will likely continue spreading those scoured areas,” says Serrano.
Recurring tourism damage
For the last few decades scientists have been concerned about the effects of tourism on various vulnerable ecosystem regions across Australia, with particular attention paid to the already fragile Great Barrier Reef.
In a 2012 report released by the Great Barrier Reef Marine Park Authority, increased boat activity from both recreational and commercial tourism operations, alongside other factors like shipping, catchment runoff and coastal development, was labeled as a source of “additional pressure” on the health of the reef.
The United Nations Environment Programme has also identified boating and other activities like snorkelling could "contribute to over-exploitation of reef species and threaten local survival of endangered species."
Meanwhile Parks Australia, which manages Kakadu National Park and others, has also identified the negative impacts of tourism on these ecological systems and is due for another review of its sustainable tourism plan at the end of the current 2011-2016 plan.