How Tiger Sharks Used Cameras to Reveal the World’s Largest Seagrass Ecosystem

Editor’s Note: Call to Earth is a CNN editorial series reporting on the environmental challenges facing our planet, along with the solutions. Rolex’s Perpetual Planet initiative partners with CNN to raise awareness and education around important sustainability issues and inspire positive action.

Tiger sharks, the largest apex predator in the tropical seas, are notoriously fierce. They can grow to more than six meters in height, have sharp serrated teeth, and are second only to great whites in the number of reported attacks on humans. But in the Bahamas, tiger sharks have taken on a less cruel role, as assistants to marine scientists.

Between 2016 and 2020, a team of researchers attached tags with cameras to tiger sharks so they could view the ocean floor from a new perspective. The data collected revealed what is the largest known seagrass ecosystem in the world, an area of ​​up to 92,000 square kilometers (35,000 square miles) in the Bahamas. According to their study, published in 2022, this increases the total known global seagrass cover by more than 40%.

This is important because seagrasses capture and store enormous amounts of carbon in the sediment and are therefore an essential tool in mitigating climate change.

Dr. Austin Gallagher, one of the report’s co-authors and founder and CEO of ocean research organization Beneath the Waves, believes tiger sharks and other marine life could help scientists map ocean ecosystems and lead to other important discoveries. As a guest editor for Call to Earth, he spoke to CNN about what it’s like to work with tiger sharks and the importance of protecting the ocean’s carbon sinks.

The following interview has been edited for length and clarity.

CNN: When did the idea of ​​putting a camera on a tiger shark come about?

In the scientific community, we’ve been putting cameras on animals for decades, and we’ve been doing the same with sharks for many years now. So it wasn’t completely new, but we wanted to further our work on tiger sharks to better understand what a day in the life of a tiger shark was like. To do that, we needed to be able to see what the animals saw, because we can infer all kinds of patterns based on their movements: where they go and how much time they spend in certain areas and habitats. When we did, it opened up a whole Pandora’s box of new questions and ultimately set us on a path of radical discovery here in the Bahamas.

CNN: What did you discover from the tiger shark data?

We knew that tiger sharks spend a lot of time above the carbonate banks in shallow water here in the Bahamas and we knew that there is an extensive seagrass ecosystem here, but that didn’t happen until we got the data back from those camera-equipped tiger sharks. that we really saw how important and extensive the seagrass could be. It turned on the light for the first time: that we need to map out how much seagrass there is here.

We knew we had to map it from space, because while tiger sharks gave us a dozen good tracks with those camera tags, we had to use orbiting satellites and a remote sensing approach to map how much was there. . It would never be possible as a human, or as a tiger shark, to cover the entire exclusive economic zone of the Bahamas. So we did that and we were able to map it out. We put divers in the water to validate all the predictions from space, took photos of the seabed ourselves and then used more data from tiger sharks, including 360-degree camera tags that gave us a full and comprehensive view of what the animals are doing. were seeing.

Ultimately, it validated a prediction of a whopping 93,000 square kilometers (35,000 square miles) of seagrass ecosystem here in the Bahamas, making it by far the largest in the world. It was hidden in plain sight.

CNN: What else is there to discover?

We are only at the beginning of understanding how valuable and how important this seagrass is, and what role tiger sharks, sea turtles and other endangered biodiversity play in that relationship. And let’s not forget humans and the role we play in the future of preserving these ecosystems.

Mapping and discovering it is only part of it. Then creating new protections around them and working with governments and environmental decision makers to really put all this data into the right packages and get it to the right agencies who will ultimately issue things like carbon credits that can be used to provide protection, but also create financial benefits and ultimately long-term financial returns for places like The Bahamas.

CNN: What is blue carbon and why is it so valuable?

Blue carbon is a term for all carbon that ends up in the ocean. It happens naturally and is stored and captured in the ocean in the various sediments, largely through plants – things like seagrasses, mangroves and salt marshes. These are what we call blue carbon ecosystems, and through natural processes such as photosynthesis, these plants sequester and store enormous amounts of carbon – significantly more than their terrestrial counterparts.

If we want to try to create new protections for the ocean, if we want to try to build resilience, especially in low-lying countries and small island states, we have a real goal of building resilience rather than climate change. One of the ways we can do that is by working with nature: seagrasses, mangroves, they are what we call a nature-based solution to climate change. If we want to improve coastal protection and create benefits for communities and biodiversity, it is incredibly important for ocean research to quantify how much carbon and what its magnitude looks like.

CNN: What is the end goal of your scientific research and work?

The ultimate goal of the work I do is to create empathy for the ocean and preserve what we have for future generations. To live harmoniously with these ecosystems, to find ways to live harmoniously with sharks, to protect these ecosystems like seagrass. It’s about creating marine protected areas, improving existing conservation measures for endangered species like sharks, but it’s about ensuring that the legacy of these incredible ecosystems remains as intact as possible for as long as possible.

This story has been updated to correct the size of the seagrass ecosystem in the Bahamas.

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