Reducing the impact on shellfish of vehicles on beaches

UC research looking at how to reduce impact on shellfish of vehicles on beaches

November 2, 2012

As the summer approaches, more people will be driving their cars on sandy beaches for a range of activities.

While most leisure activities will have no impact on the environment, others could. A University of Canterbury (UC) researcher Gareth Taylor is looking at how beaches can be managed to reduce the impact on shellfish.

The intertidal zone, where most people drive their cars on a beach, contains a wide range of shellfish including juvenile tuatua. In addition to being a food source, tuatua naturally filter the water reducing turbidity. This helps to keep water clear and clean for us to enjoy when visiting the beach.

``While adult tuatua are in the subtidal area, juvenile tuatua sit in the top five to 10 cm of sediment about 30 metres below the high tide line. This is also where vehicles frequently are used,’’ UC doctoral student Taylor said today.

``Findings from my research show one vehicle can cause around five percent mortality to tuatua within the tyre tracks, and up to 35 percent after 50 passes. This may not sound like much, but has the potential to add up over time.

``As a vehicle driver on the beach, what can people do to stop this damage occurring? The easiest way is to not drive on the beach; however, if a vehicle is required there are other ways to mitigate impacts."

``Driving within the same tracks made by other vehicles will significantly reduce tuatua mortality caused by vehicles. The initial vehicle will cause about five percent mortality, but if motorists drive through the same tracks this will increase by just 0.27 percent. This is in stark contrast to causing five percent mortality when creating new tracks.’’

The configuration of a vehicle also influences mortality to shellfish, he said. This is because sediment displacement correlates to mortality. A heavy four wheel drive vehicle will penetrate deeper into the sediment than a light vehicle. Tyres designed to grab into the terrain such as off-road tyres also displace more sediment, so more mortality may occur.

Lighter vehicles with wide tyres designed to roll on top of the sediment would significantly reduce the impact on tuatua populations. A lighter car would reduce sediment displacement and the overall mortality to tuatua below the sediment surface.

``Beaches are an amenity for all to enjoy, but like any other ecosystem it is sensitive to human impacts. If treated with respect, this important ecosystem will be there for future generations to enjoy.’’

Taylor will present his research at the New Zealand Coastal Society conference at the Royal New Zealand Yacht Squadron in Auckland from November 14 to 16.

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