Reefscape: a global reef survey to build better satellites for coral conservation

Photo courtesy of Greg Asner /

Reefscape: a global reef survey to build better satellites for coral conservation

Coral reefs are special places. They contain thousands of species often  assembled in kaleidoscopic patterns that defy both our scientific  understanding and our imagination. Reef ecosystems feed millions of  people and protect our shorelines, acting as buffers to waves and  storms. The corals, fish, invertebrates and other creatures residing in  reef ecosystems vary greatly from region to region, generating an  exciting global-scale tourism industry: a trip to the Caribbean turns up  species that can’t be found in the Pacific Ocean; swim off a beach in  Indonesia, and you’ll find reef inhabitants different from those in the  Red Sea. Coral reefs are said to be the rainforests of the ocean, and  indeed, the untrained eye often finds that discerning coral species on a  reef is similar in experience to telling tree species apart in the  jungle.

Coral reefs around the world.

Photo courtesy of UNEP-WCMC

While science has documented only a small portion of reef species that  occur around our planet, we do know that human activities have taken an  extensive toll on reef ecosystems worldwide. Massive areas of reef have  been physically removed by society’s seaside and offshore activities.  Even larger areas of coral reef have been degraded by global stressors  linked to carbon dioxide emissions from industry, transportation and  other human activities. Ocean temperatures are spiking, resulting in  coral-bleaching events that destroy vast swaths of reefscape, and ocean  acidification is having a negative impact on coral health and growth.

Coral bleaching in the 2015 ocean warming event in the Hawaiian Islands. 

Photo courtesy of Greg Asner

Despite our growing knowledge of how coral reefs are changing around  the world, the geography of these changes remains extremely hard to  piece together. Reefs in one region respond to stressors differently  than reefs in another, and within a reef, individual species react  differently. During coral-bleaching events, for example, there are often  winners and losers within a given reef, making it difficult to predict  whether the ecosystem as a whole will bounce back. This variation among  corals is matched by unknown variation among key reef-dwelling fish and  invertebrates, the fates of which are linked to that of corals. Given  that coral reefs span an estimated 500,000 square kilometers (193,000  square miles) in total area, spread over more than 200 million square  kilometers (77.2 million square miles) of ocean, it is no wonder that  the state of global reefs remains poorly known today.

To gather a  more comprehensive understanding of the condition of global reef  ecosystems, we need a way to assess and monitor them on a large  geographic scale. New satellites, such as those from Planet (formerly Planet Labs), are, as of 2017, able to capture near-daily  imagery of coral reefs worldwide. Planet’s high-resolution imagery of  reef location provides us with an at-your-fingertips understanding of  the extent of shallow, horizontally oriented reefs. Satellites miss the  vertically inclined reefs — the so-called reef walls — but are evolving  to facilitate monitoring the most vulnerable shallow horizontal reef  areas over time. Currently, no satellites can provide a way to assess  reef health at the resolution of individual or clusters of corals and  other reef inhabitants. For this, we need a new satellite mission.

Planet imagery allows for mapping of shallow coral reefs, such as on Lighthouse Reef Atoll in Belize.

Photo courtesy of Planet Inc.

With our partners, we are planning a new satellite mission for global  reef ecosystems, a mission that will advance our ability not only to map  reef extent, as we can do now with Planet’s current fleet of  satellites, but also to monitor changes in coral reef health. The  mission concept centers on global-scale reef monitoring using detailed  spectral information, which we and others have advanced from high-flying  aircraft. A high-tech approach called imaging spectroscopy measures the  spectrum of sunlight scattered and absorbed by an object. These  spectral patterns differ based on a given object’s unique chemical  signature, and so can be used to assess changes in reef health over  time.

Imaging spectroscopy provides a detailed mapping of coral reefs including some coral species and their health. 

Photo courtesy of Carnegie Airborne Observatory .

To lay the groundwork for a new satellite mission, it is important to  develop a baseline understanding of current reef extent, and to pair  that information with field-based assessments of reef condition. In  addition, improved spectral libraries of corals are required to drive  the new satellite design and approach for global monitoring.

Divers collect the spectral properties of corals in preparation for future satellite missions.

Photo courtesy of Chris Balzotti

The Reefscape project aims to improve our understanding of the  condition of coral reefs worldwide, while simultaneously developing  spectral libraries needed to advance the development of a new satellite  mission. A global-scale field study is a daunting task, and we will need  to select regions that maximize our understanding of global reef  conditions while collecting the field-based spectral data. Given the  magnitude of this undertaking, we and our sponsors decided to take  advantage of the unique information and perspectives we will gain in the  field and start an outreach component to the project. We  hope that our combination of hard-core biology and old-fashioned  naturalist reporting will elevate awareness of the state of coral reefs  in 2018, as viewed through the lens of spatial ecologists like  ourselves. With your help, we can use the Reefscape project to  communicate the geography of reef conditions and to get the conservation  community prepared for a high-tech satellite mission that will  transform how we monitor coral reefs in the next decade and beyond.

This article was originally published on Mongabay.

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