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The Life Aquatic: Marine Scientist Callum Roberts Talks About the Conservation of Coral Reefs

The Life Aquatic: Marine Scientist Callum Roberts Talks About the Conservation of Coral Reefs

Rich coral growth, with a pair of exquiste butterflyfish (Chaetodon austriacus), flourishes beneath the barren desert cliffs in the Red Sea. Taken at sunset. Ras Katy, Sinai, Egypt. Gulf of Aqaba, Red Sea.

The unique marine ecosystems that are the ocean’s coral reefs are under threat like never before. With the rise of climate change, these magical and vital ecosystems have experienced an increase in bleaching events that have left their very existence in jeopardy. As a result coral reefs around the world have been severely damaged and are beginning to disappear.

One man who’s dedicated his life to understanding and protection these incredible underwater habitats is Britain’s pre-eminent marine conservation scientist Callum Roberts. In a thirty-year career, he’s travelled the world researching reefs all over the world, working out the best ways to reduce the severe stresses they face.

With his book Reef Life having just been released, we sat down with Callum to talk about where his initial interest in marine habitats came from, the human-made threats facing coral reefs and his hopes for their future.

The MALESTROM: When did your love of the ocean begin?

Callum Roberts: I grew up in a pretty wild place. Wick on the North coast of Scotland. It was an amazing location, full of wildlife. Particularly on the coast where these incredible seabird-filled cliffs were. So that really got me interested in the sea.

I spent a lot of time in and around it, falling in love with it and getting a sense of a world beyond Wick. In the sea, I saw a connection to other places which were definitely warmer and more exotic than the one I was in.

TM: And you always wanted to be an adventurer? You read Jaques Cousteau…

CR: That’s right. Jacques Cousteau was a great inspiration and obviously he brought the underwater world into the living rooms of everybody in the country who had a TV really. It transported you to another place and showed there was a world ready and waiting to be explored.

So that piqued my interest in learning to scuba dive and I did that as soon as I could as a student in the first year of University. That was very fortunate as it gave me the opportunity to help out my supervisor, Rupert Ormand, who had this expedition to Saudi Arabia going on and he needed divers. So I was there ready and waiting, trained and able to lend a hand.

TM: Tell us about that first dive. What was it like?

CR: It was incredibly surprising really because when you stand on the shore of the desert, there’s almost nothing living in that parching heat. Saudi Arabia is one of the most hostile countries on land for life of almost any kind so it was literally barren.

Then you look out over this turquoise expanse of sea which hides the shallow reefs and becomes a dark indigo beyond where the reef drops off into the depths of the Red Sea. Very, very steeply in this place. So within 100 metres of the edge of the reef, it’ll be half a kilometre deep, maybe even more.

There’s this very sudden transition and when you get underwater you suddenly realise there’s this incredible abundance of life. It’s staggering, there’s fish everywhere, blizzards of them. The other thing that’s quite striking is the sheer diversity of species. The richness is just breathtaking.

If you’re used to going into a park in the UK, you might struggle to make a list of about fifteen different bird species over the course of an hour, then you go into a coral reef and literally in a second you’re seeing a hundred species right in front of you. It gives you a sense of the difference there is.

Maaga Reef Maldives 2015 pre-bleaching
Maaga Reef Maldives 2015 (pre-bleaching)

TM: How do coral reefs sustain such amazing biodiversity?

CR: That’s one of those great mysteries that I tried to unlock as a student. I made some progress towards that, but I think the jury is still out and it will be for a very long time on exactly how many species occur there. Some of the major theories are based around the large area of habitat.

If you look at the tropics they have a larger area of habitat than say the polar regions do. So taking a slice of the planet, it’s really fattest and biggest around the middle, and as you move towards the poles, the amount of area shrinks. So for any latitudinal band, say 10 degrees of latitude near the pole, there’s far less habitat than ten degrees of latitude at the equator.

In short, more habitat equals more species, there’s certainly a very strong relationship between that in ecology where the bigger the area the more species it supports. The other thing is, over the course of planetary history the tropics have been much less affected by major catastrophes.

So the last two million years or so of ice ages coming and going have really caused immense stress for anything that lives in temperate and polar regions. Whereas the tropics remained habitable over that time and so there were probably fewer species disappearing in the tropics than there were from higher latitudes.

The other thing is the sea level rising and falling would have created opportunities for new species to develop, because new ones tend to develop from old ones when the populations are split. When the sea level fell, places like South East Asia divided into a number of different basins that are separated by land bridges and that means the species can evolve in isolation and when the sea level rises again you’ve got different things where originally there was one.

TM: Have you seen changes to the reefs over the years?

CR: Yes. Immense changes. if you look at places like the Maldives, they’ve suffered twice now from a massive die-off of coral as a consequence of the El Nino disturbance. That’s this big ocean-atmosphere disturbance that begins in the Eastern Pacific and propagates around the world.

On land, it causes drought, wildfires and flooding, in the oceans it causes marine heatwaves. Those heatwaves can lead to the mass death of coral. And as that El Nino propagates across the Pacific towards Australia, it then engulfs the Great Barrier Reef and moves into the Indian Ocean, all along the way there is coral bleaching and death.

There have been two massive ones in the last twenty years or so. There was the 1997/98 one and then 2015/6, in both those cases the Maldives lost two thirds to nine-tenths of its coral. The first time around it was more severe, it lost around 85 – 95% of its coral and the second time around it was more like 60%.

In the aftermath of that, you see reefs that were formerly these amazing coral-rich gardens in deep water, looking as beautiful as any landscaped English garden but covered in fish. That is all essentially destroyed and over time those dead corals break down into fragments and pieces. The structure degrades so it then looks very, very miserable for a time, then gradually it starts to recover with new coral settling and growing.

So by the time of the 2015/16 event, it was looking great again. I was getting all hopeful about the future of coral reefs and then it was knocked back savagely. It looked like a third rate public aquarium with concrete corals. They all looked grey and although the shapes were right and they were in the right positions it was a very bleak and miserable view.

Maaga Reef Maldives 2017
Maaga Reef Maldives 2017 (post bleaching)

TM: Even if you’re trying to be dispassionate from a scientific viewpoint, it must break your heart to see these problems?

CR: It really does. The problem is, even if the coral reef seems to be recovering, and that particular one is in the aftermath of the previous mass death, if the interval between these stresses gets shorter and shorter, just how much recovery is possible in between those events? Unfortunately, more dire predictions for global warming suggest by the end of this century there will be very adverse conditions for coral survival and growth on the reefs.

It doesn’t mean there won’t be a reef there. Many times people confuse between coral loss and reef loss. They say 30% of coral reefs are already destroyed, but that’s not the case because there is a structure there which is inhabited by a whole range of life other than just coral. So the reef itself is still going to be there to some degree and it’s still going to support life and it’ll support more life depending on how protected it is.

We mustn’t give up on coral reefs and say there’s no chance of saving them so let’s not waste any money. Strong protection is the only thing that’s going to help them out and reduction of other stresses like pollution and coastal development are the things we need to do to give them the best chance of having a good outcome. In the meantime, we absolutely have to transition to a carbon-neutral economy. We can’t carry on pumping carbon into the atmosphere. That is a path towards disaster.

TM: You mention pollution and coastal development, are those the key threats the reefs are facing? Most are human-made I guess?

CR: Yes they are. In fact, all the threats are human-made. Global warming is top of the list now for coral reefs and is causing the most widespread, most severe changes with the warming of the sea. What is incredible is that people don’t really understand how fast the planet is warming, even scientists who study this stuff are taken aback by the figures.

There was a study earlier this year that calculated how much heat is trapped by greenhouse gas emissions per unit of time. What the found was that since 1871 the world has trapped heat equivalent to one and a half Hiroshima sized bombs exploding every second!

So, if you then fast forward to now the answer is that three to six Hiroshima sized bombs worth of heat are being trapped by the oceans every second. If you do the math that means a quarter of a million Hiroshima sized bombs of heat that are being trapped every day on planet earth.

That’s why we’re seeing this massive change to global temperatures, that’s why there’s so much more energy in the system driving intense storms, causing sea levels to rise, causing these droughts and wildfires. That is why we are suffering as a consequence of global change, this is not a trivial amount of heat that’s coming onto the planet, it’s absolutely massive.

Callum Roberts on an underwater dive
Callum on a dive. Credit: Julie Hawkins

TM: Those are some disturbing facts. You mentioned well protected before. What does a well-protected reef look like as opposed to one that hasn’t been?

CR: For one thing it has far more fish. The typical problem reefs have had is that we’ve caught too many fish. So the populations go right down, even though to an observer who jumps in the water it may feel they’re full of fish, but someone like me who’s a scientist can see most of the fish are small and therefore lower in the food chain, which means the reef has been pretty heavily fished.

The bigger-bodied ones, the predators, are the ones we tend to catch first and those populations are easily depleted. So, if a reef is overfished you see the progressive loss of those larger animals higher in the food chain. It may look amazing, but It’s not functioning in the way it should.

There are various processes that aren’t happening on the reef. And if you fish it really hard then you can start taking out animals at the bottom of the food chain, for example, the ones that control the seaweed growth, the herbivores, the lawnmowers of the reef.

When their population falls you can then shift that coral reef into an alternative state which is dominated by seaweed rather than living coral. That’s a really dangerous state in terms of the health of the environment as it’s hard to come back from that. Juvenile corals find it hard to settle and survive if the seaweed dominates the seabed.

The thing to do though is to protect those reefs strongly from fishing and that really helps bring the population of the herbivores back, cutting back the seaweed growth that then providing space for the coral. So you get progressive recovery when an area is strongly protected from fishing.

People obviously need to make a living, but the best way is by fishing off the reef rather than on it. It’s all about managing them differently and trying to maintain reefs as healthy, vibrant, self-repairing breakwaters that protect tropical coasts, that can support sustainable tourism which can also provide an income for people living in local areas.

TM: With you talking about the animals under the water, I feel I have to ask about your personal experiences on the dives, you must have seen some incredible sights?

CR: I always find it difficult to answer that. How do you compare the beauty of a nudibranch, one of these shell-less mollusks that’s about the size of your little finger and can be as gaudy as any parrot, that kind of beauty in microcosm, with something that is as spectacular as a whale shark? I love both ends of the spectrum.

I had a very memorable dive recently where we had a huge hammerhead shark just cruise past us halfway through the dive. The thing about hammerhead sharks, this one was a Great hammerhead, is the sheer barrel chestedness of them.

You can’t imagine being able to wrap your arms around that shark. It looked magnificent. And when we were doing our safety stop on our way back up at the end of that dive a whale shark appeared and came within arm’s length of us and cruised around a few times before disappearing into the blue. That was an amazing memorable experience.

TM: Have you had any moments where you’ve found yourself in danger on a dive? 

CR: There have been times when I’ve felt the impression of danger. When I was young in Arabia, often diving on my own, which is not to be recommended, but that was normal practice. I was really not sure what to make of these sharks. I worried about them, I thought I could be being attacked at any moment.

But over the years I realised that although sharks are dangerous to some degree and they do attack and kill people from time to time, the great majority are very benign, they don’t do that willfully. Usually, they just come and look at you and then disappear or just cruise past indifferent to you.

So, my encounters with sharks are more in awe and wonder at their elegance and incredible streamlined nature that lets them swim against the strongest currents with almost no movement of their fins. They are extraordinary creatures who have a complete mastery of their environment.

TM: You’ve touched on it just before with fossil fuels, but is that the key to resolving these problems?

CR: It’s the key to everything. Cutting down fossil fuel use and transitioning to carbon neutral. We need to base our economies on renewable energy. But it’s not going to be far enough, or fast enough to keep coral reefs in the state they were in 30 years ago. We’ve gone beyond that point now.

Whether it’ll be possible to get coral reefs back there in the next several hundred years, maybe. But in the meantime, things are going to get worse before they get better. And during that time we need to protect them as well as we can from all the manageable sources of stress.

So overfishing and pollution, both from marine and land-based sources. On land, the real pollution that matters is things like agricultural runoffs. When fertilisers go on the reefs they give seaweed a headstart over the coral. And when sediment falls on the reef, it really stresses the corals and the amount of light that they get.

We’ve got to get those sorts of stresses under control too. And if we do so then we’re going to give coral reefs a good chance of continuing to be amazing and wonderful, even as the world becomes a more stressful place for coral itself to exist in.

Reef Life: An Underwater Memoir by Callum Roberts is out to buy now

Reff Life by Callum Roberts book cover

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