New study highlights impact of sea level rise on islands

The Northern Agricultural Region has more than its fair share of spectacular islands situated right off the coast.

To the north there is the iconic Houtman Abrolhos island group and in the south, the no-less important islands of the Turquoise Coast Nature Reserve.

These islands are valuable fishing, tourism and recreational industry assets, however less well known is their importance as conservation assets. For a mainland overrun with feral predators such as cats and foxes, feral-free offshore islands are often vital sanctuaries for rare and threatened animals such as Dibblers, Painted Button Quail and Australian Sea Lions. Endangered plants too, can find safe haven on islands free from grazing species such as goats and rabbits.

The climate change-induced threat of sea level rise to coastal infrastructure is frequently hitting the news these days, but what about its impact on important conservation assets like the Abrolhos islands? Rising seas and increasing storm frequency and intensity will gradually eat away at coastlines, reducing the size of islands as well as increasing the likelihood of coastal flooding with seawater. Neither of these impacts are good news for infrastructure or conservation.

Fortunately, a process has been developed to assist managers to plan for these eventualities. Areas of coastal land at risk from erosion and inundation (collectively known as Coastal Hazards) can be estimated using models that take into account all the complex factors such as sea level rise, storm surge predictions, height of land above sea level and whether the coast can resist erosion (i.e. is it sandy or rocky).

These planning tools are generally applied to the protection of infrastructure, however NACC has recently completed a study that investigates the effect of climate change on the medium-term conservation “life-time” of our islands. Around thirty islands in the Abrolhos group and Turquoise Coast Nature Reserve were identified as having significant terrestrial environmental values. Maps were then generated for each of these that show how erosion and inundation might shape each island in 25, 50 and 100 year timeframes. This information can help managers ensure resources are appropriately allocated to islands that have high conservation values and are at low risk of inundation.  Check out the plan here on the NARvis website.

Dr Mic Payne, NACC’s Coastal and Marine Program Coordinator, was the instigator of the study which he hopes will raise awareness of the need to consider how climate change is reshaping our coastlines and how that will impact on critical conservation assets.

“Coastal Hazard modelling is constantly on the improve and as time progresses we will have the opportunity to compare actual changes to coastlines versus those predicted as likely, by studies such as this,” he said.

“It is still too early to say whether the likely effects shown in this study are best or worst-case scenarios, it could go either way, and only time will tell. In the meantime, we have a report that can guide forward-planning of some of our most important conservation assets in the region”.

NACC would like to thank all island stakeholders who provided input to the study – the Department of Biodiversity Conservation and Attractions, the Department of Primary Industries and Regional Development, the Conservation Council of WA and the Batavia Coast Maritime Institute.

For more information please contact Dr Mic Payne (e) (p) 08 9937 0123.

This project is made possible through funding from the Australian Government’s National Landcare Program.

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