Very high resolution mapping of coral reef state using airborne bathymetric LiDAR surface-intensity and drone imagery

International audienceVery high resolution (VHR) airborne data enable detection and physical measurements of individual coral reef colonies. The bathymetric LiDAR system, as an active remote sensing technique, accurately computes the coral reef ecosystem’s surface and reflectance using a single green wavelength at the decimetre scale over 1-to-100 km2 areas. A passive multispectral camera mounted on an airborne drone can build a blue-green-red (BGR) orthorectified mosaic at the centimetre scale over 0.01-to-0.1 km2 areas. A combination of these technologies is used for the first time here to map coral reef ecological state at the submeter scale. Airborne drone BGR values (0.03 m pixel size) serve to calibrate airborne bathymetric LiDAR surface and intensity data (0.5 m pixel size). A classification of five ecological states is then mapped through an artificial neural network (ANN). The classification was developed over a small area (0.01 km2) in the lagoon of Moorea Island (French Polynesia) at VHR (0.5 m pixel size) and then extended to the whole lagoon (46.83 km2). The ANN was first calibrated with 275 samples to determine the class of coral state through LiDAR-based predictors; then, the classification was validated through 135 samples, reaching a satisfactory performance (overall accuracy = 0.75)

The Future of Coral Reefs

This volume contains a series of papers prepared for presentation at the 14th International Coral Reef Symposium, originally planned for July 2020 in Bremen, Germany, but postponed until 2021 (online) and 2022 (in person) because of the COVID-19 pandemic. It contains a series of papers illustrating the breadth of modern studies on coral reefs and the response of the reef science community to the threats that coral reefs now face, above all from climate change. The first group of papers focus on the biology of a selection of reef organisms, ranging from sea fans to coral dwelling crabs. The next group describe studies of coral communities and ecological interactions in regions as diverse as Florida, Kenya, Colombia, and Norway. Further papers describe investigations into the effects of global warming (in the Maldives and in Timor-Leste) and of other impacts (UV blockers, ocean acidification). The final two papers describe the latest applications of satellite and camera technology to the challenge of mapping and monitoring reefs

Coral reef fish and the aquarium trade: ecological impacts and socio-cultural influences in southern Sri Lanka

The chronic degradation of coral reefs globally and its negative impact on coastal communities such as those in southern Sri Lanka dependent on the marine ornamental trade for their livelihood forms the focus of this study. Attempts to improve the conservation status of Sri Lanka's coral reefs and their associated fauna have failed because they omit to address the social circumstances of local people. Such social-ecological systems require an integrated approach, which provides holistic reasons for the degradation of natural ecosystems and livelihoods of coastal people. The aim of this study was therefore to ascertain the current sustainability of the marine ornamental trade in southern Sri Lanka through an interdisciplinary study employing a participatory bottom-up approach, and derive from findings alternative pathways to restore and maintain the health of the reef and thus provide better livelihoods for the fishing communities. Findings confirm both the fragile state of nearshore coral reefs, their fish populations and the precarious nature of local communities’ livelihoods. Historical and recent environmental and anthropogenic impacts reduced resilience in all trade sectors and current fishing practices and the unjust supply chain compound these effects. Therefore, a holistic co-management framework is recommended that recognises local ecological knowledge and involves fishing communities as citizen scientists to improve monitoring and also provides communication channels to facilitate interaction within and across all groups of the ornamental trade. In this way, all actors are involved in making decisions and taking responsibility for the management of the supply chain at their particular level. This single, coherent framework would thus employ diverse groups and ways of doing as a resilience strategy to halt the degradation and reinvigorate the reef for more sustainable utilisation whilst simultaneously developing highly acceptable alternative income generating livelihoods, such as the community-based aquaculture experiment undertaken during this study

11th International Coral Reef Symposium Abstracts

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11th International Coral Reef Symposium Proceedings

A defining theme of the 11th International Coral Reef Symposium was that the news for coral reef ecosystems are far from encouraging. Climate change happens now much faster than in an ice-age transition, and coral reefs continue to suffer fever-high temperatures as well as sour ocean conditions. Corals may be falling behind, and there appears to be no special silver bullet remedy. Nevertheless, there are hopeful signs that we should not despair. Reef ecosystems respond vigorously to protective measures and alleviation of stress. For concerned scientists, managers, conservationists, stakeholders, students, and citizens, there is a great role to play in continuing to report on the extreme threat that climate change represents to earth’s natural systems. Urgent action is needed to reduce CO2 emissions. In the interim, we can and must buy time for coral reefs through increased protection from sewage, sediment, pollutants, overfishing, development, and other stressors, all of which we know can damage coral health. The time to act is now. The canary in the coral-coal mine is dead, but we still have time to save the miners. We need effective management rooted in solid interdisciplinary science and coupled with stakeholder buy in, working at local, regional, and international scales alongside global efforts to give reefs a chance.https://nsuworks.nova.edu/occ_icrs/1000/thumbnail.jp

Mapping the Socio-Economic and Ecological Resilience of Japanese Coral Reefscapes across a Decade

Shallow coral reefs threatened by climate change must be spatio-temporally analyzed in terms of their protection of coastal human populations. This study combines Japanese spatio-temporal gradients of population/asset and coral buffering exposure to stress-inducing and stress-mitigating factors so that the socio-economic and ecological (SEE) resilience tied to coral reefscapes can be regionally mapped (1200 km) at a fine resolution (1 arcsec) over a decade (11 years). Fuzzy logic was employed to associated environmental factors based on the related population/asset/coral buffering responses, as found in the literature. Once the factors were weighted according to their resilience contributions, temporally static patterns were evident: (1) a negative correlation occurs between coral buffering resilience and latitude; (2) the least resilient islands are low-lying, deprived of wide reef barriers, and located on the eastern and southern boundaries of the Nansei archipelago; (3) the southwestern-most, middle and northeastern-most islands have the same SEE resilience; and (4) Sekisei Lagoon islands have a very high coral buffering resilience. To overcome uncertainty, future studies should focus on the socio-ecological adaptive capacity, fine-scale ecological processes (such as coral and fish functional groups) and the prediction of the flood risks in the coming decades

Towards sequence stratigraphy 2.0: Dynamic topography, sea level change and sediment transfer from source to sink

Earth’s sedimentary successions are an archive of past climatic and tectonic events and sea level changes by recording the complex interactions between those processes across a wide range of time and space scales. Numerous efforts have been made to decipher this archive to obtain signatures of deep Earth dynamics (e.g. dynamic topography induced by mantle flow). However, it remains a challenge as the signals generated by dynamic topography are usually concealed by signals generated by plate tectonic processes. Sequence stratigraphy is an effective tool to analyse sedimentary units. Recently, quantitative stratigraphic analysis has been used to achieve more precise interpretations, which will likely advance the quantification of the role of controlling factors in shaping stratigraphic record. This thesis consists of two parts. The first part presents stratigraphic modelling using the surface process code pyBadlands and quantitative stratigraphic interpretations based on two well-established techniques: the trajectory analysis and the accommodation succession methods. This numerical framework contributes to the development of quantitative sequence stratigraphy which is an important component of “sequence stratigraphy 2.0”. The second part further investigates the large-scale and long-term drainage and sedimentary responses to dynamic topography. Our models predict distinct erosional and depositional landscapes, comparing with that induced by eustatic sea level changes, which provides insights into differentiating the geological signals induced by dynamic topography in tectonically-stable regions. The propagating wave of positive dynamic topography under a plateau produces a landscape that is comparable to southern Africa during Cretaceous times. The propagating wave of negative dynamic topography tilts the surface and generates depositional patterns similar to the continental interior of North America during Cretaceous times and South America during Miocene times