Coral reefs play a vital role in regulating the climate and sustaining marine life and biodiversity - with 25% of the ocean’s fish relying on them for their nutrition, habitat and reproduction according to the NOAA. They are also crucial to indigenous communities, who are dependent on coral reefs for various socioeconomic reasons including but not limited to employment, nutrition and even medicine.
Anthropogenic stressors, such as ocean acidification, sedimentation, coral bleaching, pollution, overfishing, in conjunction with climate change, pose a direct threat to coral reefs, which leads to degradation and extinction along with the ecosystems they maintain.
To preserve and ensure the survival of coral reefs, scientists often harness satellite technology to monitor spatial and temporal data on coral reef ecosystems, thus reinforcing their restoration.
Mapping
Mapping the coral reef systems is fundamental for marine biologists and conservationists to further comprehend the causes and effects of coral reef health (or lack of, thereof) by visualizing the phenomenon and its alterations through space and time. Specifically, high-resolution images sourced from satellites are used before cartographic means to produce accurate and reliable maps or digital models.
The Allen Coral Atlas project fulfils that exact purpose by mapping the world’s coral reef systems, providing researchers with benthic and geomorphic data. Although the Atlas is unable to locate certain species or detect coral health, it is recommended by the team to be combined with datasets from other platforms, such as dataMERMAID, which might include these features. The consolidation of different geospatial data layers into GIS software leads to general monitoring, thus well-informed decision making. Both aforementioned resources are free to use and accessible to everyone.
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Remote Sensing
According to the Coral Reef Satellite Mission, the most advantageous way to produce a global coral reef baseline map of detailed granularity is through remote sensing, since it can meet the spatial, spectral and orbital requirements of this aim. Remote sensing includes measuring an area’s reflected and emitted radiation using special cameras - commonly from satellites or an aircraft, to discern and observe its physical properties.
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Unlike underwater survey techniques, remote sensing can cover extensive and inaccessible areas while being less costly and time-consuming. However, the process is obstructed by the intricacy of spatial, temporal and optical properties of coral reef ecosystems as well as other constraints, such as overlying air and water, weather conditions, or changes in the bottom of the ocean. Therefore, to obtain valid knowledge, data needs to be processed appropriately with methods that allow the correlation of the satellites’ signal and coral reef attributes.
Multiple geo-registered satellite images of coral reefs over time, especially when combined with in-situ data, can enhance the evaluation of their health.
The Coral Reef Satellite Mission is an initiative by the Planetary Coral Reef Foundation (PCRF). Their objective is to produce the first global baseline map of living corals by conducting a global mapping survey using remote sensing technology. The map will provide accurate, unbiased and most importantly, real-time data of the condition of coral reefs, which will allow the detection of changes in coral reef health on a comprehensive, universal scale. The data is distributed for free and available in several formats via PCRF’s website.
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NOAA’s Coral Reef Watch (CRW) program focuses on observing and predicting the quality of coral reef ecosystems globally harnessing the technology of near real-time remotely sensed satellite images and modelled in-situ data. The CRW focuses on physical environmental changes of coral reef environments via a global early-warning system. The information provided by the system are then processed into modelled outlook predictions, which help scientists fathom how coral reef ecosystems are affected by climate change and stressors, evaluates their condition on an international scale, thus encouraging the implementation of immediate and efficient preservation actions and management.
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Tracking and monitoring
Satellite technology is handy when it comes to tracking, specifically, identifying and monitoring pollution that can occur from space.
A worthwhile mention is ESA’s OptiMAL project, which revolves around the detection of marine plastic litter using software that identifies a distinct spectral signature of plastic detected from orbit. Utilising remotely sensed satellite imagery from the Copernicus missions Sentinel satellites, marine plastic waste can be located in the shortwave infrared.
The datasets are then cross-examined with measurements from aerial and ground surveys.
The project aims to create a global map that will display the amount of plastic litter in the oceans.
ESA used the Sentinel-2 satellite to capture the Great Barrier Reef bleaching event that occurred in 2017.
Plastic litter in global oceans [6]
So as you can see, the survival of coral reefs is of crucial importance for the longevity of life in both our oceans and on land.
To preserve the invaluable coral reefs, we can go as far as space and take advantage of satellite technology.
I would like to close with an excerpt from “Dub: Finding Ceremony” by Alexis Pauline Gumps, which is deeply moving and showcases the spiritual importance of coral reefs:
“What the coral said:
breathe. breathe. breathe. sing. let the water move within you. let it be you. let your every cilia dance you into healing. let the warm salt water brighten you. your tears. sleep. and when you dream of working, sleep again. sleep until you dream of floating. dream until your edges soft. dream until you birth yourself in water singing with the bones of all your lost. dream until you breathe not from your mouth, not from your nose but through your hair and through your skin. dream until you claim the ocean. breathe until you feel no need to swim. breathe until your dreams flow out your brain. breathe and let them in your heart. breathe and we will call you again. that’s a start.”
Written by Vicky Georgiadou
References
Allen Coral Atlas. (n.d.). Explore the World’s Coral Reefs. Retrieved April 26, 2021, from https://allencoralatlas.org/
Biosphere Foundation. (n.d.). The Coral Reef Satellite Mission - from Sea to Space. Retrieved May 9, 2021, from https://biospherefoundation.org/project/the-coral-reef-satellite-mission/
Copernicus. (n.d.). Discover our satellites. Retrieved May 16, 2021, from https://www.copernicus.eu/en/about-copernicus/infrastructure/discover-our-satellites
Edmund Optics. (n.d.). What is SWIR? Retrieved May 16, 2021 from https://www.edmundoptics.eu/knowledge-center/application-notes/imaging/what-is- swir/#:~:text=Short%2Dwave%20infrared%20(SWIR)%20defines%20a%20specific%20wavelength%20range,and%20host%20of%20other%20applications.
ESA. (2017, May 24). Sentinel-2 captures coral bleaching of Great Barrier Reef. https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-2/Sentinel-2_captures_coral_bleaching_of_Great_Barrier_Reef
ESA. (2018, March 19). ESA investigating detection of floating plastic litter from orbit. https://www.esa.int/Enabling_Support/Preparing_for_the_Future/Discovery_and_Preparation/ESA_investigating_detection_of_floating_plastic_litter_from_orbit
Foo, S. A. & Asner, G. P. (2019, March 13). Scaling Up Coral Reef Restoration Using Remote Sensing Technology. Frontiers in Marine Science. https://www.frontiersin.org/articles/10.3389/fmars.2019.00079/full
GIS Wiki. (2013, January 16). In-situ data. Wiki.gis. http://wiki.gis.com/wiki/index.php/In-situ_data#:~:text=An%20in%2Dsitu%20data%20is,same%20as%20the%20actual%20location.
Mermaid. (n.d.). Coral Reef Data Collection and Visualisation. DataMermaid. Retrieved April 26, 2021, from https://datamermaid.org/
NOOA. (n.d.). Coral Reef Watch Satellite Monitoring and Modeled Outlooks. Coral Reef Watch. Retrieved May 13, 2021, from https://coralreefwatch.noaa.gov/
NOOA. (n.d.). Four-Month Coral Bleaching Outlook. Coral Reef Watch. Retrieved May 16, 2021, from https://coralreefwatch.noaa.gov/satellite/bleachingoutlook_cfs/outlook_cfs.php
Pauline, A. (2020). Dub: Finding Ceremony. Duke University Press.
Planetary Coral Reef Foundation. (n.d.). Mapping Coral Reefs from Space. PCRF. Retrieved May 12, 2021, from https://www.pcrf.org/remotesensing.php
USGS. (n.d.). What is remote sensing and what is it used for? Retrieved April 28, 2021, from https://www.usgs.gov/faqs/what-remote-sensing-and-what-it-used?qt-news_science_products=0#qt-news_science_products
Wikipedia. (2021, May 6). Remote Sensing. https://en.wikipedia.org/wiki/Remote_sensing
Image Sources
[1] allencoralatlas.org/atlas
[2] wikipedia.org/wiki/Remote_sensing
[3] biospherefoundation.org/project/the-coral-reef-satellite-mission/
[4] coralreefwatch.noaa.gov/satellite/bleachingoutlook_cfs/outlook_cfs.php
[5] coralreefwatch.noaa.gov/
[6] /www.esa.int/Enabling_Support/Preparing_for_the_Future/Discovery_and_Preparation/ESA_investigating_detection_of_floating_plastic_litter_from_orbit
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