3 January 2010:
Australian scientists have announced the world’s first
successful large-scale restoration of a coastal wetland being
devastated by acid runoff.
A dramatic improvement in environmental conditions has been
achieved by researchers working on the trial Hills Creek catchment
at the East Trinity site near Cairns in Queensland, using a
combination of natural tidal action and strategic treatment with
lime.
Mangrove and wetlands are returning, birdlife is flocking to the
area and fish abound in creeks that once ran so acid that nothing
could survive in them. Having first demonstrated success in
the trial catchment, remediation is underway on the remainder of
the site.
The acid crisis at East Trinity began in the 1970s, when developers
drained and cleared 800 hectares of tidal wetland to grow
sugarcane. This dried out underlying acid sulfate soils causing
them to release slugs of acid whenever they were soaked by rain,
leading to fish kills and loss of wetlands which alarmed local
residents.
Today East Trinity is a world class demonstration of large-scale
restoration in action, says CRC CARE managing director Professor
Ravi Naidu. ‘There are an estimated 40 million hectares of
similar acid coastal wetlands round the world and at least 4
million in Australia, including the lower Murray-Darling, and areas
along the coasts of NSW, Queensland, SA coasts and WA’,
he says.
‘This is a problem of global proportions, and Australian
scientists have convincingly demonstrated for the first time on a
large scale that it can be reversed and natural values
restored.’
The main restoration work, being carried out by the Queensland
Department of Environment and Resource Management in partnership
with CRC CARE and Southern Cross University, has made East Trinity
a CRC CARE National Demonstration Site, providing a practical
example of remediation in action. World leading, new
scientific research has been published by the team to assist with
understanding the complex problem of remediating acid sulfate
soils.
According to CRC CARE project leader Dr Richard Bush of Southern
Cross University, restoration began in 2001 after the Qld
Government purchased the land to remediate the acidic soils and
protect the natural green backdrop to Cairns. The site was declared
a ‘reserve for environmental purposes’.
‘We decided to take advantage of the enclosing sea wall built
by the original developers to exclude the tide and drain the
site. We re-introduced a partial tidal exchange through
adjustable floodgates, so as to gradually re-flood the most acidic
sediments and prevent them producing more acid.’
‘Where the runoff was still too acid we added hydrated lime
using specially designed equipment.’
Gradually the mangroves began to recolonise, with a wider species
diversity than the scientists had dared hope for.
‘The birds are back too. In fact the bird life is fantastic
with more than 100 wild species observable within a 10 minute boat
ride of the Cairns CBD. How many cities in the world can
claim that?’
The once-sterile creeks, still stained in parts with the iron-red
deposits from the acidification process, now swarm with tiny fish,
creating an abundant nursery to rebuild fish numbers along the
coast and nearby Great Barrier Reef.
‘Essentially we are reversing the chemistry of what took
place when the acidic soils were drained. If you tried to
treat all the acid sulfate soil at East Trinity according to
current recommended practice, it would cost over $300 million and
require complete vegetation clearing. Our process is
returning nature for a mere fraction of that.’
To keep the acid at bay, however, means that for a third of the
site soils will have to remain permanently a tidal wetland, making
it unsuited to major developments such as marinas or high-rise
urban living. However Cairns could inherit a huge nature park with
potential for an eco-tourist attraction right on its doorstep.
Besides developing a solution suitable for tidal wetlands almost
anywhere, Professor Naidu says the approach devised at East Trinity
could form the basis for a new export industry in remediation.
As communities the world over see fish kills, dying estuaries and
vanishing birdlife, the realisation is dawning that we have made
some serious mistakes in how we developed these sensitive
landscapes – and people, indeed cities, are now looking for
answers, Professor Naidu said.
‘The fact that Australia has devised and demonstrated a
large-scale solution to coastal acid-sulfate soils creates a
remarkable opportunity for a new form of knowledge exports, capable
of returning acidified and degraded coastal areas to healthy
natural environments again’, he said.
“East Trinity is a global case study, and a beacon of hope
that this can be achieved.”
Further information and images:
Professor Richard Bush, CRC CARE, Southern Cross University, 02
6620 3361 or 0428 268 587
Professor Ravi Naidu, Managing Director, CRC CARE, 08 8302 5041 or
0407 720 257
Peter Martin, CRC CARE communication, ph 08 8302 3933 or 0429 779
228
For images contact Meredith Loxton on (08) 8302 3925,
meredith.loxton@crccare.com
