Using two decades of cloud stored NASA satellite measurements, scientists recently assessed the vulnerability of Belize’s famed coral reefs to bleaching and collapse. The findings help administrators protect reefs from human impacts such as development, overfishing, pollution and climate change.
The 185-mile-long reef system off the coast of Belize includes a vibrant marine environment that supports thousands of animal and plant species and fuels the Central American country’s largest industry, tourism. The system is one of about 1,200 UNESCO World Heritage Sites around the world.
In a study published in Frontiers in Remote Sensing, researchers ranked 24 marine protected areas off the coast of Belize based on the risks corals face from murky water and rising temperatures. How researchers at NASA’s Jet Propulsion Laboratory in Southern California and counterparts in Belize used free cloud data on Google Earth Engine in their analysis.
Emil Cherrington, a native Belizean and co-author of the paper says “We depend on the reef for many things, so preserving these resources is important, Studies like this give the government of Belize more tools to conserve the resources the country has”.
The hard skeletons of stony corals form a barrier reef structure that keeps Belize’s shallow coastal waters calm and allows marine life to thrive there. Coral needs clean water and constant temperatures to grow. Changes in both factors can affect the survival of the symbiotic algae that live in the coral and provide food.
NASA Moderate Resolution Imaging Spectroradiometer
When the algae die or die, the corals lose their color, a phenomenon called bleaching. Coral can survive under these conditions, but the changes may put it at greater risk of mortality. To collect data on water clarity and surface temperature over large areas, scientists turned to the Moderate Resolution Imaging Spectroradiometer (MODIS), which was developed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and launched in 2002 as one of several instruments on board the ship.
Analyzing MODIS images collected between 2002 and 2022, the researchers developed a vulnerability index that characterizes the risk to corals in marine environments that Belize manages to protect biodiversity. The team examined sea surface temperatures in each protected area and assigned a number from 1 to 6 based on how low or high the averages were relative to norms. QRatings of 1 to 6 are then combined to give a coral index, from 2 to 12. Higher numbers indicate greater risk.
The vulnerability index could be used for other reef systems around the world and could be modified to include other water variables such as acidity, said Ileana Callejas, the paper’s lead author and a graduate student at the University of California, Los Angeles. Increasing ocean acidity result of climate change due to higher concentrations of dissolved carbon dioxide in the water threatens the health of corals.
“We’ve tried to make the data and our approach as accessible as possible,” said Callejas, who started the research during his internship at JPL. “Our main goal was to create an easy-to-use toolkit that would create an index that was easy to understand and that could be used to identify which marine protected areas may need more attention.”
While historical records and traditional ship-based field testing have given coastal management authorities an idea of the most vulnerable areas, satellites can shine a light on other locations that may be less accessible or more expensive, said Nicole Auil Gomez, press associate author and director of Wildlife’s Belize Country Program Conservation Society.
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