Unearthed from the dungeon-like depths of a government building in Hobart, photographic data from aerial surveys is helping to protect the underwater forest home of Tasmania’s dragons. This dragons’ tale is a data reuse success story set against the threat of a warming world.
Giant kelp (Mycocystis pyrifera) grows in magnificent undersea forests, where it thrives in nutrient-rich, cool waters. Kelp forests can be 30 m high and reach the sea surface to sunbake as a floating canopy 40 m across, clearly visible from the air. Giant kelp is the foundation species for its ecological community, providing habitat to weedy sea dragons, big-bellied seahorses, abalone, sponges, corals and myriad other marine species.
These richly biodiverse habitats were thought to be in decline off Tasmania’s east coast but actual data was lacking. Professor Craig Johnson and Dr Piers Dunstan, researchers from the University of Tasmania’s Institute for Marine and Antarctic Studies (IMAS), found the raw data they needed in archives of aerial survey photos going back to the 1940s. It was then that state governments began using ex-WW2 aircraft and photographic reconnaissance equipment to map coastlines, mostly for planning.
Fellow IMAS researcher Dr Neville Barrett used the same imagery in the late 1990s to undertake the first seabed habitat mapping of Tasmanian waters for marine protected area planning. “It’s classic data reuse. Those aerial surveys were done to map Tasmanian land-based features but we found we could also use the survey photos to study marine habitat,” Barrett said. “Craig and Piers dug up all the aerial photos of the east coast they could find and estimated the percentage of kelp cover in every bay, year by year. They identified a 90% decline in kelp cover between 1945 and 2000.”
Why the decline? Climate change is thought to be the main culprit. Oceanographic shifts first seen off Tasmania’s east coast in the 1970s coincided with IMAS’ observations of reduced kelp forests. During the period studied, noticeable strengthening of the East Australian Current created warmer ocean temperatures and reduced nutrient load, conditions which are unfavourable to kelp growth.
Kelp forests are among the most dynamic and productive ecosystems on Earth, yet are unknown to many Australians. Most people could name iconic terrestrial forests like the Daintree in Queensland but would struggle to name a comparable marine equivalent. In 2012, thanks to the work of the IMAS researchers and others, the giant kelp marine forests of southeast Australia became the first marine ecological community to be protected with an endangered listing under Australia’s national environmental laws.
New types of data, including image data from robotic submersibles (autonomous underwater vehicles or AUVs) and satellite data from advanced sensors, are aiding in conserving and managing marine environments. For example, a recent University of Tasmania project measured kelp beds from hyperspectral satellite data exploiting the species’ unique spectral signature.
Studies on restoring kelp communities are underway and, in a twist to the dragons’ tale, the original archive of irreplaceable aerial photos that helped protect their home has now been digitised. The data is now reusable by researchers anywhere.
“Wonderful outcomes like this become more and more possible every year as ANDS and other organisations enable access to more data and share it more readily,” said Barrett.
But, in the end, if we’re to preserve these iconic forests, we need to tackle the root cause, which is the changing ocean conditions. How the forests will ultimately fare in this warming world is a tale whose next chapter is yet to be written.
Story provided by Refraction Media.