Trapped. Australia's coastal wetlands may be caught without an escape route as rising sea levels push in on them from the front while urban development presses against them from the back. The survival of mangrove forests that act as nurseries for a broad range of species as well serve as a buffer against storms, salt marshes that are important feeding grounds, sedge lands and melaleuca swamps are all threatened by this rock-and-a-hard-place predicament.
University of Queensland reports that Dr Jonathan Rhodes and a team of researchers at the ARC Centre of Excellence for Environmental Decisions (CEED) are looking into how wetlands, which in times of sea level rise in the past have receded farther inland, are affected by urban development projects. Without a place to escape to, mangroves, salt marshes and other systems can go locally extinct, which could cause a severe ripple effect for wildlife species.
The team says that planners and coastal communities can't just think about development today, but must think as far as 100 years into the future if they want to protect these vital ecosystems. And that means thinking about where these ecosystems will be able to move to as the ocean creeps in.
Dr Rhodes and his colleagues Ms Rebecca Runting and Dr Morena Mills have been using a computer model called SLAMM (Sea Level Affecting Marshes Model) to identify areas where coastal wetlands would naturally retreat to as the ocean comes up – and where existing or future urban development may clash with this.
“It's true you can build a one kilometre long sea wall at a cost of about $7-8 million per metre in height and put urban development in behind it – but the reality is that we're not going to be able to defend the entire Australian coastline with such measures, as sea levels will keep on rising as long as the climate is warming and the polar ice melting,” Dr Rhodes said.
This process may last for centuries and eventually even raise sea levels by tens of metres, scientists fear.
These coastal ecosystems are not just a conservation after thought, but should be an important factor in urban planning. Mangroves take the brunt of the beatings by storms, sparing both urban and natural habitats farther inland from damage and flooding. They prevent coastal erosion, and act as carbon capture and storage systems. They act as nurseries for fish, helping to bolster the fishing industry, and they provide natural resources from honey to wood for fishing poles or building materials. Leaving these coastal ecosystems without an escape route from future sea level rise also means leaving urban development near coastlines without resources or a natural defense system.
As states University of Queensland, "Dr Mills says that many cities and towns are proud of the way they are managing to incorporate native Australian landscapes, vegetation and wildlife into their plans for the future. Now, for sea-side communities, these plans need to take account of the area of land needed to accommodate coastal wetlands displaced by the rising tides."