Protecting Western Australia's Big Blue Backyard - The Pew ...

THE POLLUTION CONNECTION
BETWEEN LAND AND SEA
The health of our marine environment is affected
by what happens on land. The connections
between catchment health, marine health and
community health are clearly demonstrated by
disturbing stories from Cockburn Sound and the
Peel Harvey Inlet.
Cockburn Sound off Fremantle has for many years
been a very important area for commercial fishing
and angling, as well as swimming, boating and
other recreational activities.
From the 1950s the Cockburn Sound catchment
and coastline experienced major industrial
and urban development with refineries, port
development, chemical plants, horticulture
and housing.
The amount of pollutants such as nutrients,
herbicides, hydrocarbons, fertilisers and sewage
finding their way into Cockburn Sound has
increased fourfold in the past 50 years, carried
there by surface runoff and groundwater flows.
The ability of the Sound to flush naturally was
reduced by 40 per cent with the construction
of the causeway between the mainland and
Garden Island.
Since the 1950s, the seagrass meadows of
Cockburn Sound have declined by 80–90 per cent.
These critical feeding and nursery areas for marine
life have been lost to pollution and shell-sand
mining. The loss could be permanent because
seagrasses recolonise very slowly. The blue
swimmer crab fishery, which is reliant on healthy
seagrass habitat, has collapsed. Cockburn Sound
is now closed to the recreational and commercial
fishing of the crabs.
The future continues to look grim for Cockburn
Sound. The human population of its catchment is
expected to triple over the next 20 years, the ports
are to be further developed and a desalination
plant is now extracting water and marine life from
the Sound and returning hyper-saline brine.
South from Cockburn Sound, the Peel Harvey Inlet
at Mandurah became badly polluted by agricultural
and urban runoff—massive algal blooms were
the result. As well as impacting on fisheries and
tourism, a community health study revealed that
the rate of respiratory illnesses had doubled, and
children from 11 to 15 years of age were most
at risk.
In the late 1990s a canal costing $50 million was
dug to flush the Peel Harvey Inlet. But algal blooms
still occur and dead zones exist in some places.
Newly flooded areas have attracted mosquitoes
and increased the incidence of the Ross River virus.
Many estuaries along the west coast have been
impacted by urban and industrial development,
resulting in marked declines in fish catches
as habitats have disappeared. Fortunately
the estuaries along the south coast are less
affected because population growth and coastal
development is limited to a number of relatively
small centres. However, the problems on the west
coast should not be ignored by state and local
authorities when planning the management and
protection of the connected catchments, estuaries
and offshore waters along the south coast.
Light penetrates more deeply in
the region’s clear waters, allowing
extensive and globally significant
seagrass meadows to grow at
depths greater than usual
© Glen Cowans
36
Many estuaries along
the west coast have been
impacted by urban and
industrial development,
resulting in marked
declines in fish catches as
habitats have disappeared