Remotely sensed habitat diversity predicts species diversity on coral reefs

Abstract

The ability to map coral reef biodiversity from orbit would greatly advance marine spatial planning. Presently, reef biodiversity is measured in situ by divers, but this method is inefficient and expensive. Remote sensing techniques have been developed in the terrestrial realm to lever the “habitat heterogeneity hypothesis,” which contends that the biodiversity of organisms is directly linked to the diversity of habitats which they occupy. Here, we evaluated this hypothesis using satellite-derived reef habitat maps across 880 shallow-water field stations distributed on a global transect through the Atlantic, Pacific, and Indian Oceans where we measured the taxonomic and functional diversity of reef fish and corals. Benthic habitat maps produced from WorldView-2 and PlanetScope were compared as proxies for coral reef species diversity. We found satellite-mapped habitat heterogeneity to be positively correlated with both fish (R ≤ 0.64) and coral diversity (R ≤ 0.56), at an optimum spatial scale between 110 and 320 ha, even when the data were partitioned across global biodiversity gradients. Best results were realized when using the WorldView-derived habitat maps, indicating that the enhanced spectral and radiometric resolution of this sensor is better poised for retrieving species biodiversity than PlanetScope. Our study offers an efficient method for monitoring coral reef ecosystems by leveraging satellite maps as a surrogate for species biodiversity.

Satellite imagery of the Neulka Islands (New Caledonia), along with the three types of satellite-derived habitat maps considered in our study. (a) True-color image from Maxar WorldView-2. The Khaled bin Sultan Living Oceans Foundation Global Reef Expedition (“GRE”) benthic habitat maps for the Neulka Islands at 4×4 m resolution (b) contain 14 of the total 37 Indo-Pacific classes. The Allen Coral Atlas (“ACA”) offers two map types at 5×5 m resolution – benthic (c) and geomorphic (d). The full six ACA benthic classes are shown, while nine out of 12 geomorphic classes are present at this site.

Meet IFAN: Helping Bring Navigate with Care to the Next Generation

If you’ve ever seen a lighthouse flashing from the shore or a brightly colored buoy bobbing in the water, you’ve seen Aids to Navigation at work.

Aids to Navigation, often called AtoNs, help mariners navigate safely. They can mark channels, warn of hazards, help vessels determine their position, and provide other information people need to make safe decisions on the water. Around the world, these systems help guide everything from small recreational boats to large commercial or container ships.

But safe navigation isn’t only about protecting vessels and the people aboard them. The choices mariners make can also affect the animals and ecosystems beneath and around them.

That connection between maritime safety and ocean conservation is at the heart of this year’s Science Without Borders® Challenge—and of our partnership with this year’s theme sponsor, the International Foundation for Aids to Navigation (IFAN).

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Coral Bleaching Awareness Month: Giving Coral Reefs a Chance to Recover

For hundreds of millions of years, coral reefs have supported life in our oceans. Although they cover less than 1% of the ocean floor, they provide habitat for at least 25% of all marine species. They also support people around the world by sustaining fisheries and tourism, providing food and livelihoods, and helping protect coastlines from waves and storms.

But coral reefs are under increasing pressure. Pollution, overfishing, coastal development, physical damage, and increasingly warm ocean temperatures can all affect reef health. One of the most visible signs that a coral reef is under stress is coral bleaching.

This September, in recognition of Coral Bleaching Awareness Month, we’re taking a closer look at what happens when corals bleach, why bleaching matters, and what scientists around the world are doing to better understand, protect, and restore coral reefs.

Abstract

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