As anyone who has ever been rockpooling before knows, these little pools of seawater can be a haven for marine life.
But when a natural shoreline is replaced with a vertical seawall, the gently sloping foreshore, along with its rockpools, vanishes.
The problem with sea walls is that when they are built, the intertidal area (a sloping area between marine and the terrestrial environment, usually containing important micro-habitats known as rock pools) is effectively compressed onto a sheer, featureless vertical slope.
Without rock pools the number and diversity of animals and plants species in the intertidal area plummets.
Two ecologists at the University of Sydney, Dr Mark Browne and Prof. Gee Chapman have come up with a solution that is so simple you wonder it hasn’t been done before.
Flower pot pools
It was Gee Chapman’s idea to use flowerpots as replacement tidal pools. When attached to existing sea walls, the receding high-tide causes water to collect inside the pots during periods of low tide and gives organisms like molluscs and starfish a habitat similar to naturally occurring rock pools.
The flowerpots themselves are very durable and built from a custom mould, in two different sizes. Browne and Chapman searched many weeks for a provider and eventually settled on Antique Stone and ECS Services.
Once a supplier was secured and the flowerpots prepared, Browne and Chapman were able to install 80-90 pots in a matter of days. Ten months on and the flowerpots appear to be holding up admirably to the rigours of Sydney Harbour.
After speaking to Mark Browne, it became clear that this project involved a lot of inter-disciplinary collaboration. In addition to the flowerpot manufacturers, the two ecologists worked extensively with engineers on the North Sydney Council.
Browne attests to the importance of working with engineers. As the project involves drilling into the sea wall to attach the flowerpots, it was crucial to have engineers involved to make sure the structural integrity of the wall would not be compromised: as much of Sydney Harbour, including the famous Sydney Opera House, relies on the support offered by sea walls, any damage done to them could have serious consequences.
Browne and Chapman’s work falls under the category of 'ecological engineering.' Browne explains: 'We’re not trying to restore [the natural intertidal habitats]. The only way to do that is to rip out the wall, which is not realistic or practical.
'Instead we’re trying to rehabilitate these areas. While all engineering projects must take into account structural and aesthetic qualities, our projects are novel as we are seeking to add ecological criteria as a third pillar.'
This greener form of engineering has been around for a while in terrestrial environments – just think of green roofs – but has yet to be fully explored in the marine context. This flowerpot installation is a pioneer in the field.
If you live in a coastal community and are concerned with the ecological impact of its sea walls, Browne suggests that you talk to his research team and lobby your local council to try flower pots. He emphasises that sea walls are not safe places for people to start attaching flowerpots without permission.
This could, however, be a great opportunity to build a dialogue between council-members, ecologists, engineers and the people in your community. Browne believes that the flowerpot installation is easily adaptable with careful local planning and wants to see the idea spread beyond Australia.
With 50 per cent of the global population living within 100 km of the sea (this number is expected to rise to 75 per cent) and 75 per cent of major cities being coastal and constructed on sea walls, Browne and Chapman’s research is timely and relevant.
Centre for Research on the Ecological Impacts of Coastal Cities, University of Sydney
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