Mangroves, saltmarsh under threat

Victoria University researchers say mangroves and saltmarshes are misunderstood by land managers, under-valued by the public and under threat from rising sea levels and coastal development.

A four-year study by Professor Paul Boon, from the university's Institute for Sustainability and Innovation, shows human impacts and development have destroyed up to 20 per cent of the state's coastal marshes, while the future looks even bleaker.

Professor Boon said predicted sea level rises would push these systems inland, where their retreat would be blocked by seawalls, farmland and housing developments along much of the coast.

"These saltmarshes with nowhere to go will simply drown," he said.

Mangroves and saltmarshes are important breeding ground for birds, fish and other marine and estuarine species, protect against erosion and provided filtration of runoff from the land, Professor Boon said.

Despite this, mangroves and saltmarshes are not referred to specifically under Victorian legislation for protection, he said.

Disturbingly, the knowledge of mangroves and coastal saltmarsh across different management agencies is patchy and the management of these areas is poorly coordinated.

In one example, the Department of Primary Industries was promoting Tall Wheat Grass to rehabilitate salty coastal areas even though it is one of the worst and most invasive weeds of saltmarshes, particularly where they occur next to agricultural lands.

Meanwhile surveys of the public in Torquay and Tooradin found knowledge of the environmental role fulfilled by saltmarshes by the broad public to be almost nonexistent.

"Saltmarshes are largely unknown and therefore 'invisible' to the community," Professor Boon said. "Most people saw saltmarshes as little more than muddy, smelly breeding grounds for mosquitoes."

Recommendations in the 500 page report Mangroves and coastal saltmarsh of Victoria include the reservation or purchase of environmental land to support the inland retreat of mangroves and saltmarshes, new buffer zones to coastal development and the creation of a single body to coordinate management of the state's mangroves and saltmarshes.

The study included the first fine-scale mapping of all current mangroves and saltmarshes in Victoria, as well as an analysis of the likely coverage before European colonization of Victoria.

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