Research aims to reduce vehicle impact on beaches

20 December 2013

A UC geography student, who graduated this week, has provided management options to authorities to minimise the impacts of beach users on shellfish resources.

A University of Canterbury student who received his doctorate at graduation this week has provided management options to authorities to minimise the impacts of beach users on shellfish resources.

Beaches are increasingly under pressure from a growing population and people’s activities on beaches. As the festive holidays approach, more people will be driving their cars on sandy beaches for a range of activities.

Driving cars on beaches or riding horses on beaches pose a significant threat to shellfish living and feeding in shallow beach water, UC researcher Dr Gareth Taylor (Geography) says.

"My study looked at the impacts of vehicle driving and horse riding on shellfish beds within Pegasus Bay in Canterbury. Tuatua were found to be immediately impacted by both users, and extrapolative modelling predicted that continued disturbance could be highly detrimental to the population.

"The results were then used to evaluate current beach management techniques and provide management options to Environment Canterbury to minimise the impacts of beach users on shellfish resources."

While most light leisure activities, such as sunbathing and running, will have no impact on the environment, other heavier activities could. Dr Taylor looked 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 5 to 10 cm of sediment about 30 metres below the high tide line. This is also where vehicles and horses are frequently are used.

"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."

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, Dr Taylor says.


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