Mangrove Buffers

A recent Cairns Post article has reignited debate: Should mangroves be allowed to naturally re-establish along the northern end of the Esplanade, in front of Cairns Hospital, to reduce erosion and better protect against storm-surge flooding? Or should they continue to be removed?

In the conversation on social media since this article, most locals are backing the mangroves.

Why Mangroves Matter for Cairns

Cairns is one of Australia’s most climate-exposed cities. Our low-lying coast is highly vulnerable to cyclones, storm surges, heavy rainfall and sea level rise. Critical infrastructure — including the airport, seaport and hospital — sits right on the frontline.

While both the airport and port benefit from protective barriers provided by mangroves, Cairns Hospital has little buffer between its buildings and the ocean. This makes the site particularly at risk of coastal flooding and erosion.

Mangroves grow naturally on the mudflats adjacent to the Esplanade, but the mangrove seedlings are removed every quarter.

Along with a range of other benefits, there is significant global and local evidence that mangroves could be one of our best natural defences. They’re great for:

• Erosion control – Their dense root systems help stabilise shorelines and reduce coastal erosion.
• Reducing storm impacts – They reduce wave energy by more than 75%, buffering coastlines against cyclones and storm surges. After Cyclone Justin in 1997, Port infrastructure and vessels were damaged by a storm surge but, anecdotally, areas protected by mangroves were not affected.
• Fisheries habitat – Around 75% of coastal fish species depend on mangroves as nursery grounds, which attract birds and support recreational fishing.
• Water quality – They act as filters, trapping sediments and pollutants before they reach the Great Barrier Reef.
• Carbon storage – Mangroves absorb 4–10 times more carbon than other trees and do it up to 50 times faster.
• Cost – Natural solutions are more visually appealing and much lower cost than heavily-engineered structures such as rock walls.

More Than Mangroves: A Living Shoreline

Mangroves are not the only nature-based solution on the table. Terrain NRM has been discussing the potential to trial an integrated solution along a 500-metre section of the Esplanade in front of Cairns Hospital, combining ecological restoration with engineering.

The approach includes:

• Mangrove re-establishment – Allowing mangroves to grow naturally as part of a curated “mangrove garden”.
• Oyster reefs – Installing oyster reefs at the outer edge of the mangroves to reduce wave action, support water quality improvements and encourage sand build-up. Similar projects have been successful overseas and in NSW, including the Wagonga Inlet Living Shorelines Project.
• Dune rehabilitation – Building up and stabilising dunes with vegetation to provide another natural buffer against coastal hazards. Engineered structures would likely be included as part of an integrated engineering and nature-based landscaping solution.
• Education and cultural connection – Creating a living laboratory and boardwalks to showcase Traditional Ecological Knowledge alongside Western science, turning the site into a protective landscape and a learning and tourism experience.

Together, these elements would form a “living shoreline” — a dynamic system that can protect the hospital and restore ecosystems, strengthen biodiversity and enhance the visitor experience on the Esplanade.

Challenges to Consider

As promising as this approach is, it comes with challenges:

• Community values – The Esplanade mudflats are valued for birdwatching, recreational fishing and uninterrupted coastal views.
• Flooding dynamics – Projects need to account for the combined impacts of storm tide, overland flooding and riverine flooding, ensuring new defences don’t worsen risks for neighbouring areas.
• Approvals and governance – Nature-led solutions cross many jurisdictions, involving Cairns Hospital and Health Services (CHHHS), Cairns Regional Council, Ports North and the State of Queensland. Multiple environmental and planning approvals would be required.
• Design and uptake – These are not yet “business as usual” solutions. Pilot projects, new design standards, and codes will need to be developed.