Reading time

“Next time you fly over the ocean, try to admire the vastness, the beauty and the rich marine life that can thrive in those waters.”

Ocean Witness Guido shares his story

“Watching the waves crash into the coast, experiencing stunning sunsets above the horizon and looking out over the sea is – I believe – the ultimate therapy.” Guido Leurs has been passionate about the ocean and marine life ever since he was a little boy, so it is no surprise that the ocean later became the central topic of his studies and now his PhD. As a marine researcher, Guido is witnessing a lot of change in the ocean, from pollution to disappearing species. Drawing from his credo that knowledge is power, and based on his studies on sharks and rays, he seeks to advise on more effective conservation strategies that may lead to the implementation of new marine protected areas. This way he hopes to protect his beloved ocean.

become an ocean witness
14 June 2019 | Groningen, the Netherlands

What is your earliest memory of the ocean?

I grew up 200 km away from the nearest sea (North Sea), but we would visit the sea coast on summer breaks. On these holidays, I could be found catching crabs or collecting shark teeth and shells in between rocks or on the waterline. At that time, I was just 4 years old – which means that my interest for animals and nature started when I was still quite young. But my fascination for marine life and sharks especially started around the age of 15.

What does the ocean mean to you today?

To me the ocean is the last true – largely undiscovered – wilderness that we have on our planet. Whenever I look over the ocean, I speculate on what’s beneath the surface. The immense size of the oceans feeds my curiosity, it gives me a sense of freedom and it fuels my devotion to unraveling the mysteries that it holds. Even though we will never understand the ocean completely.

The ocean means a lot to me, but since I work in the city, I do not get to see it every day, unfortunately. However, that makes the moments that I am on or near the ocean even more special. Watching the waves crash into the coast, experiencing stunning sunsets above the horizon and looking out over the sea is – I believe – the ultimate therapy. And once you dive through the surface, you enter another world. As a kid I liked exploring in nature, always looking for small insects or discovering new things. Diving and studying marine life gives me that same feeling; there is still so much to learn!

“I believe knowledge is power. So, to effectively make a long term difference, we need more knowledge of nature.”
Guido Leurs

What changes are you witnessing in the ocean?

I think fellow young Ocean Witnesses will agree: the easiest difference to spot out there is the decline of marine life and more trash in the oceans and on the coasts. Beaches are full of cigarette butts, balloons and plastic waste. Even on reefs you’ll find beer bottles and discarded fishing gear.

One memory that made a real impact on me, is from a fieldwork trip to Banc d’Arguin (Mauritania, West Africa) in 2016. We visited what could have been a very beautiful white sand beach. However, the beach was completely covered with trash, including bottles of alcoholic beverages. As alcohol in Mauritania is banned, at that very moment I realised how big the problem is: the trash came from faraway places.

A change that I personally didn’t experience, but learned of while growing up, was the decreased abundance of, and the threats to many marine species. Overexploitation, habitat degradation and pollution have caused fish populations around the world to decline. And still, in many parts of the world, the pressure on marine ecosystems is high. As one of my major research projects takes place in West Africa, I have spent a considerable amount of time in the field there. High fishing pressure on sharks and rays within and outside of marine protected areas is still a major problem.

“I like to imagine what it must have been like to swim among such an abundance of large fish, sharks and rays; this is a great motivation for me to do my work.”
Guido Leurs

How do these changes affect you?

As a marine researcher, I see species disappear from our fragile ecosystems. Losing these species means that the particular role that this species covers within the ecosystem also disappears. The scary thing is that we often don’t exactly know what that means for the functioning of ecosystems.

For me personally, these changes often leave me wondering what the ocean would look like in its pristine state. I like to imagine what it must have been like to swim among such an abundance of large fish, sharks and rays. This, however, is a great source of motivation for me to do my work. With my colleagues, I demonstrate what the roles of these species are to show why we should do more to conserve them.

“The immense size of the oceans feeds my curiosity, it gives me a sense of freedom and it fuels my devotion to unraveling the mysteries that it holds.”
Guido Leurs

And what do you do to contribute to shifting this change in a positive way?

I believe knowledge is power. So, to effectively make a long term difference, we need more knowledge of nature. From a young age, my curiosity has always driven me to try and understand objects, nature and animals. Now, working as a researcher, I use this curiosity to study sharks and rays in different parts of the world. Based on increased understanding of their distribution and ecological roles, we can advise on more effective conservation strategies and possibly even on the implementation of new marine protected areas.

Currently, my main focus is on sharks and rays within the large intertidal areas, like the Bijagos Archipelago in Guinea Bissau. While we’ve gained considerable knowledge of these species on a global scale, in developing regions like West Africa this understanding is less advanced. Like in all waters around the world, the pressure on sharks and rays is high in West African waters. Here, sharks and guitarfish are still caught for their fins, and the meat of both sharks and rays is sold on local markets. As a result, we see a decline in especially larger shark and ray species, but we don’t fully understand their role within large intertidal ecosystems, like the Bijagos Archipelago. That is what we set out to study over the next 3 to 4 years. Besides that, I also have projects running in the Dutch Caribbean, for example on the habitat use and trophic ecology (the structure of feeding relationships among organisms in an ecosystem) of juvenile silky sharks on the Saba Bank.

“The scary thing is that we often don’t exactly know what species loss means for the functioning of ecosystems.”
Guido Leurs

In 2030, what does the ocean look like according to you?

Although all the data tells me otherwise, I try to be quite optimistic for the future. For example, the UN recently published their assessment of the state of Earth’s biodiversity: approximately 1 million species of plants and animals are being threatened with extinction. And yet, I believe that, if enough people care about the oceans and act on that, positive change will follow; the number of marine protected areas is growing, the plastic problem is gaining more and more attention and most western countries are implementing stricter fishing regulations.

But, we do have a very, very long way to go…

Thanks for sharing your story, you’re an Ocean Witness now. What do you want to say to other Ocean Witnesses?

Keep inspiring others! I think your own behaviour can have a clear impact – whether it’s cleaning up beaches, studying marine species or showing people the wonders of the underwater world.

But don’t underestimate your indirect impact by inspiring others. You see, for most people, nature is far from their doorstep and therefore not a central part of their daily lives. However, you can bring it to them; through your actions, your stories and your ideas. Bring nature and all its marvel back into their life, and you will see that people start to care!

“To me the ocean is the last true – largely undiscovered – wilderness that we have on our planet.”
Guido Leurs

And if you would give one tip to the reader at home about how they can contribute to a healthier ocean in the future, what would it be?

Keep the oceans in mind the next time you chose to eat seafood or go grocery shopping. Buying more sustainably and locally sourced food with minimum waste is your voting ballot for a healthier ocean. But that, of course, is the obvious.

I also tend to think that people don’t care as much about the ocean simply because they don’t know it that well. As Simon Winchester wrote in his extraordinary book about the Atlantic: “We see the sea more as a burden nowadays, while flying over it, so we close the window and go to sleep.”

I would like to say: next time you fly over the ocean, try to admire the vastness, the beauty and the rich marine life that can thrive in those waters.

About Guido

Guido Leurs is 27 years old and grew up in Venlo, in the south of the Netherlands.

Having wanted to do a PhD ever since he was little, he was very motivated to conduct scientific research projects on sharks, fish and other marine life during his Bachelor’s and Master’s degree. After working as a marine consultant, he moved up north to Groningen for a  PhD position at the Conservation Ecology Group of the University of Groningen.

So far, his projects have taken him to the Bahamas, South Africa, Dutch Caribbean, Mauritania and Guinea Bissau.

share this article

Guido Leurs

Groningen, the Netherlands

Guido Leurs (27) works as a PhD candidate at the Conservation Ecology Group of the University of Groningen. With his research on sharks and rays, he seeks to advise on more effective conservation strategies and the implementation of new MPAs.