Last week the Flatback survey team was back on Avoid Island with Dr Nancy Fitzsimmons. The team was due back on the island on the 30th of January after marking nearly 80 nest sites during late November / December. Our goal was to dig up all mapped clutches and record data on egg numbers, successful hatches, predation events and unviable eggs. However tropical cyclone Dylan changed our plans and made us reschedule the emergence survey for early March.
Bill and I (Andrew) were in Mackay as TC Dylan passed, a relatively minor event as far as cyclones go. However we witnessed first hand large swells and storm surge tides that saw waves breaking well over the marina wall. This did not bode well for the region’s beaches including our study site.
When we arrived on Avoid we found significant erosion and scouring of the beaches and dunes. Images below compare the same large rock surrounded by sand (and us) and then completely exposed three months later post cyclone.
We estimate that some sections of beach have lost up to 1.5m of sand and the berm has shifted significantly. This goes to show what a single large storm event can do. Flatback’s generally dig their nests around 50 – 60cm below the surface anywhere form the water line to well up in the dunes. This meant the majority of our sites had been lost. The good news being that the clutches would have hatched pre cyclone, the remnants just weren’t there for us to count. Anecdotally we saw high levels of hatchling success in the nests we were able to recover.
So this raises the question what if the cyclone was a couple of weeks earlier? Or what happened to any clutches laid later in the season? Simply thousands of hatchlings would have been lost. While no one can control a tropical storm, their increasing frequency and severity due to climate change will be an added pressure for all sea turtle species. Due to this we need to build resilience in populations by reducing other stressors such as;
- Protecting feeding grounds and rookeries
- Restricting predator access to nesting beaches
- Maintaining and improving native dune stabilising vegetation
- Reducing marine debris
We’re now looking forward to returning to Avoid Island Nature Refuge in May with our partners at Reef Catchments and Queensland Trust for Nature this time to survey flora and fauna while removing invasive vegetation from the island’s critically endangered beach scrub rainforest.