3D ReefscapesLatest update May 5, 2018 Started on May 5, 2018
We are using cutting-edge technological approaches to quantify and predict the structural consequences of climate-associated disturbances on coral reef ecosystems.
In 2016, I was preparing to go to the Great Barrier Reef (GBR) for the first
time – something I have been dreaming about since I was a child, only this time, I was going as a researcher. But it was also in 2016 when elevated sea surface temperatures (SST) set in motion the worst coral bleaching event in the recorded history of the GBR. Scientific reports estimated 47-83% coral mortality throughout the GBR’s northern section. This section includes my PhD field study area, 21 reef sites encircling Lizard Island. The coral reefs at Lizard Island were already severely damaged following the almost direct hits by consecutive category 4 cyclones; Ita in 2014 and Nathan in 2015. Against this backdrop, I prepared myself to face a decaying reef instead of the coral reef from my bucket list.
Nonetheless, when I first jumped in the water in November that year, I was captivated by beauty. I knew the reef was highly degraded, but I still saw impressive corals, sharks, and many colourful fish. Without a clear idea of the previous state of the reef, this became my baseline. Our team spent three weeks on the Island that month. We gathered a large variety of data for my research project, which is rooted within an ongoing long-term effort led by Joshua Madin and Maria Dornelas since 2012.
Back at Macquarie University, I processed the images taken in the field yearly from 2014 to 2017 using photogrammetric techniques to derive scaled photomosaics and 3D reconstructions of the monitored reef sites, each capturing about 130 square metres of the reef. These two data products, which we coined “Reef Records” because of the spiral motion the cameras track the reef, let us * visualise and quantify the change in benthic cover and 3D complexity. Each Record was spatially georeferenced to match the exact field location through time. It was then that I realised the severity of the damage. ***Some of the reef sites were utterly unrecognisable from one year to the next** (Fig. 1), and I too cried.
In a broad range of terrestrial and marine communities, including coral reefs, geometrically complex habitats contain more species and at higher abundances than simple flat habitats. However, climate change projections forecast an increase in the frequency and intensity of tropical storms and anomalous SST that can trigger mass coral bleaching. These large-scale climate-induced disturbances can quickly destroy vast areas of reef-building corals, rendering these habitats vulnerable to flattening and impaired functioning, lower biodiversity, disrupted recovery and reduced ability to provide ecological goods and services that have been valued in the billions per year.
We have yet to learn how coral reef communities will respond to the trends that have been projected by climate scientists. My research aims are twofold: (1) to assess and quantify fine-scale spatial patterns of change in coral reef habitat complexity and composition as derived from the Reef Records and other environmental data, and (2) to determine if local habitat responses can be reliably traced remotely and at larger scales with space-borne imagery. Ultimately, I hope to produce a better understanding of the mechanisms underlying coral reef habitat complexity response and recovery potential under a novel climate regime. Determining how major disturbances drive ecological change is necessary to identify suitable approaches to managing coral reef ecosystems in the face of climate change.
There are plenty of reasons to remain hopeful about the future of coral reefs, but we must reduce CO2 emissions quickly. Not all changes found in the Records are negative, nor do all areas respond similarly. Many corals survived the traumas of the past and are steadily growing (Fig. 2); others show signs of recovery. Thanks to images worth a thousand words, I have learned to put my baselines in historical context.
Acknowledgment: I am honoured and grateful to have been awarded the 2017 Ian Potter Doctoral Fellowship at the Australian Museum’s Lizard Island Research Station, which is helping fund fieldwork-related expenses and expand my horizons. I would like to thank all who have contributed to the Reef Records efforts in the past for the valuable dataset and for welcoming me into the team. The Reef Records data collection methods were developed in collaboration with the Australian Centre for Field Robotics, University of Sydney.
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