When marine biologist Nancy Knowlton began studying coral reefs in the early 1970s, the world’s scientists had little understanding of just how diverse and complex these ecosystems were — and the key role they played in the health of the planet’s oceans. Nor did they fully grasp the scale of the threats that would bear down on coral reefs in the coming decades.
Today, however, thanks to the work of Knowlton and other marine biologists, science understands not only how varied and numerous coral species are, but also how extraordinarily diverse life is in the world’s oceans: At least 2 million species are estimated to exist in the marine world, and the figure could be far higher. Knowlton, a scientist at the Smithsonian Institution, has simultaneously been elated by the rapid pace of discoveries, while also growing increasingly alarmed by the perils facing coral reefs, including overfishing, disease, and climate change.
These days, Knowlton is focusing on solutions and has launched a series of events called “Beyond the Obituaries: Success Stories in Ocean Conservation,” inspired, in part, by the desire to reassure young scientists that there is still time to save the world’s corals and to safeguard marine biodiversity. In an interview with Yale Environment 360 Web editor Kevin Dennehy, Knowlton highlights projects that are stemming coral losses, including a comprehensive conservation program on the Great Barrier Reef and smaller-scale efforts in places like Mexico. “I felt it was really important to give people a reason to think that there is something you can do,” says Knowlton. “We all need more than doom and gloom.”
Yale Environment 360: An important element of your research has been determining just how biodiverse the world’s coral systems are. How much more do we know today about this biodiversity than we knew when you began your career?
Nancy Knowlton: We know a lot more, but there are still a lot of unknowns out there. When I started my career people assumed that even if marine organisms came from very different places but looked reasonably similar, they were all one species. And that’s a problem I worked on for a long time when I first started, just trying to figure out how many of these so-called cryptic species there were. And we know a lot more about that now”¦ It’s not that we have discovered all the cryptic species on the planet, but I think at least people are prepared to recognize that there’s a lot more biodiversity than we ever thought.
e360: Just how important have new technologies, including genetic testing, been in getting to this better understanding?
Knowlton: Well, with DNA barcoding there are some groups where it doesn’t work very well, just because it turns out they don’t have that much variation in the genes that are typically used for barcoding. But in general genetics are really helpful. In some groups it confirms what you already
“There are still huge numbers of coral species and places that have never been studied.”
knew, but in other groups — things where the species are really similar — it gives you a clear indication whether they are the same species or not.
But on the other hand there are still huge numbers of species and places that have never been studied… We don’t really know how many species live in the ocean. The most recent estimate was about 2 million species, 95 percent of which have never been described. But even that could be too small.
e360: Beyond determining just how many different species there are, much of your research has involved the relationship between corals and the countless other organisms they support.
Knowlton: Yes. I started working on just how many species are out there. No one had actually ever even done a complete count of everything in one place. And since many of these species were likely to not be described, we thought we’d just go straight to the genetics and say, ‘How
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many genetically distinct things are out there?’ And so we started doing things like collecting small bits of dead reef or putting out little apartment-like houses for organisms to settle into and then bringing them back at the end of the year and see how many things we could find. And we didn’t even try to put a name on anything. We just used barcoding. Because in this case we were working with crabs and shrimps, and for those barcoding actually works really well. And we found, for example, using samples from around the world, there are almost as many crab species in six square meters of coral reef as in all of Europe.
e360: Why is the biodiversity and complexity of these reef ecosystems so important?
Knowlton: Part of it is just that we care a lot about all the different stars in the universe and these are the creatures that we share our planet with. So just understanding the diversity in terms of knowing who we share the planet with I think is important and interesting. Are there two million species? Are there 10 million species? It’s a basic question of what life is like.
In addition, this kind of diversity on reefs supports big tourism industries. And some of that diversity turns out to be important for medicine. The classic example for that are cone snails. There are hundreds of species of cone snails, and each species has quite a complex cocktail of toxins. Some of these have already been commercialized for use as pain relievers, and people have really just begun to explore how many possible medicines might be derived just from that single group of snails.
e360: Among other things that scientists have learned is that the health and abundance of coral species haven’t always been consistent through the planet’s history. Could you describe some of the ups and downs for coral throughout the history of the planet and some of the factors that have influenced these changes?
Knowlton: Well, corals depend on certain kinds of conditions. In fact, the earliest reefs weren’t built by corals at all. They were built by bacteria. And then there have been times in Earth’s history when most of the reefs
We’ve lost a lot of living coral actually in the last couple of decades.”
were built by large clams. Corals themselves probably date back at least to the time of the dinosaurs… And there have been places where at times there have been lots of coral reefs, and times when there haven’t been that many. Right now we happen to be in a time when there are quite a few. Or at least there used to be quite a few. We’ve lost a lot of living coral actually in the last couple of decades.
e360: We seem to be living in a time when their very existence seems to be at risk. Could you talk about some of these threats?
Knowlton: Traditionally, the biggest threats to corals were considered to be overfishing and poor water quality. And in both cases what happens is that corals are in a kind of a never-ending struggle with seaweed. Seaweeds grow a lot faster. And in order for you to have corals around rather than just a lot of seaweeds, you need fish that eat seaweeds. And also if there’s too many nutrients in the water seaweeds go crazy. And corals do better in sort of nutrient-poor water. So those two things have until relatively recently been the biggest threats to corals.
Increasingly climate change is a serious problem. Because what happens is that the corals have in their tissues little single-celled algae that they depend on for food. It’s a really wonderful example of a mutualism where the coral
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provides shelter and nutrients to the algae and the algae through photosynthesis provide food for the coral. And the corals die if they lose
their algae. The problem is that these algae are very sensitive to even small increases in temperature above the normal maximum. You only need about one or two degrees centigrade above the normal seasonal maximum before you start having these algae being unable to photosynthesize properly. And then they wind up being kicked out of the coral, and the coral turns kind of ghostly white because it loses all these algae that were in their tissues. It’s called coral bleaching, and if you look at a bleached coral you can see right through the tissue, which becomes almost transparent to the skeleton, which is stony white.
e360: And, as you say, it doesn’t take much warming to trigger these changes.
Knowlton: It doesn’t take much, which is why coral reef biologists are so worried about global warming, because the trajectory for the future is just more and more of the same. And we’re already at the edge for some corals. For example in 1998, about 80 percent of the corals in the Indian Ocean bleached and about 20 percent of them died. And that would be like if in New England you had a really hot summer, and 80 percent of the trees lost their leaves and 20 percent of them never got them back again. They [corals] grow really slowly. They are the trees of the marine environment in the tropics.
So when you look at climate change models that suggest these hot temperatures [could] become even an annual event by 2020… I mean, it’s hard to know how many things will go extinct, but reefs as complex three-dimensional ecosystems can only tolerate so much before they
“Reefs… can only tolerate so much before they really are going to start vanishing everywhere on the planet.”
really are going to start vanishing everywhere on the planet.
In addition, you’ve got the side problem of having too much carbon dioxide in the atmosphere, and it dissolves in the ocean, making the ocean more acidic. And that’s also really bad for corals because it makes it much harder for them to build their skeletons. In the past the stressors have been mostly local, and now they are increasingly becoming global.
e360: It seems that some of these stressors might be making the coral more vulnerable to disease. It’s draining all their energy.
Knowlton: Yes. And we actually know, for example, that if you have a big coral-bleaching event, corals don’t always die. But what sometimes happens is after a big bleaching event even the corals that recover subsequently succumb to disease and die from disease. And we’ve seen that in a number of places. So disease is actually a huge problem on coral reefs.
In the Caribbean, in particular, another coral that used to be really common on the reef were the branching corals — the staghorn corals and elkhorn corals — and they’re now listed under the Endangered Species Act because disease has essentially decimated their numbers throughout their entire range. Sort of like Dutch Elm disease underwater.
e360: Much of your earlier research was done in the Caribbean, in Jamaica. What was the state of the coral reefs in that part of the world at the time? And what kind of changes physically have you seen in recent decades?
Knowlton: You know, I always start my talks by showing a picture that I took as a grad student in 1975. And at that time there was living coral everywhere. The bottom was about 70 percent living coral. And we knew the reefs weren’t in pristine condition because there were essentially no
“There were a lot of distinguished coral reef biologists working in Jamaica… None of us really predicted what would happen.”
big fish. In fact there weren’t that many fish at all because Jamaica is a really poor country and subsistence fishing had basically stripped the reef of most of the fishes because people were desperate to just feed their families… It’s very hard to say, ‘Don’t fish for five years and then they’ll come back.’ So we knew the fish communities weren’t in great shape, but the corals were spectacular. And I have to say there were a lot of distinguished coral reef biologists working in Jamaica at the time… None of us really predicted what would happen.
First in Jamaica we had this huge hurricane [Hurricane Allen in 1980], which broke corals up into little bits and killed a lot of them. And then there was this big disease — not of corals, but of the black spine sea urchin. Because there were no fish around it was the most important seaweed-eater on the reef. And this disease wiped out almost all of the sea urchins throughout its range and, as a result, the seaweeds went absolutely crazy. And throughout the Caribbean most of the reefs flipped from coral-dominated state to a seaweed-dominated state. So within about ten years of my starting to work in Jamaica the reefs effectively vanished.
e360: What are some of the other more vulnerable regions in the world as far as the state of reefs?
Knowlton: Well, anywhere near people is potentially vulnerable, unless people really get together and figure out what they’re going do to make sure they don’t lose their reefs. The Australians are the gold standard for reef protection, the Great Barrier Reef Marine Park Authority. A third of it is off limits to fishing and that is incredibly important in terms of giving reefs resilience, which is the ability to bounce back if something bad happens.
e360: What part can and should marine protected areas play?
Knowlton: Well, in the developed countries, marine protected areas — in the tradition of take a part of the habitat and put it off limits to fishing — is a critical component of reef management. Because fishing pressure can be so intense elsewhere that you need those pockets of protection where big fish are allowed to grow up and make lots of babies.
“It is very important to pay attention to what is working, to try to replicate successful models in other places.”
And those big protected areas — or big networks of areas — can also work in some of the remote places where there aren’t many people.
But a lot of reefs are in places in the coral triangle in New Guinea, Indonesia, the Philippines, where it’s very difficult, for socioeconomic reasons, to just put reefs off limits. But there you can take advantage of more traditional management schemes that people have used for decades or centuries. It’s more about managing fishing than putting fishing off limits.
e360: Does it make sense to target certain areas where the stressors are less and the coral systems are still relatively biodiverse?
Knowlton: Well, I think that’s in fact what people have done. For example the big marine protected areas that were set aside in the Pacific under the Bush Administration, those were very important because so many of them are so remote they are in pretty good shape. They still have pretty intact fish communities and very healthy coral communities. That is an important part of the approach that you need to take. Now, those areas are not protected from warming waters or ocean acidification. But what you see when you look at those places is that they do have a lot of resiliency. They have bleaching, but they are able to bounce back. So that kind of protection does play an important role.
Ultimately, if we don’t do something about carbon dioxide concentrations in the atmosphere, local management will not succeed. But effective local management actually buys incredibly important time while we figure out how we’re going to deal with the carbon dioxide problem.
e360: In the face of some of the grim projections you started this ‘Beyond the Obituaries’ series of events. What was your thinking in setting this up?
Knowlton: When I was at Scripps [Institution of Oceanography], I created something called the Center for Marine Biodiversity and Conservation, and a big part of what that center did was graduate education. And I used to stand up in front of fundraisers and talk about what the center did and why it was important. I’d talk about the students, and I started thinking ‘Why did they come to the center to get a graduate degree?’ And I started realizing that they thought of themselves as medical students, except their patient was the planet instead of a person. And I started thinking, in medical school we don’t train everyone to write obituaries. We train them to solve medical problems, not just record the demise of people. So I started thinking about how what a disservice we are doing to these students. They really needed more than doom and gloom. We all need more than doom and gloom.
Not to undersell the enormous severity of the problem and the future prospects and future threats. But it is true that there are some things that are working out there. I just feel that it is very important to pay attention to what is working, to try to replicate successful models in other places.
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What’s interesting about these success stories is that almost all of them were due to the actions of one or a small number of people initially. For example there’s this wonderful story about the success in Cabo Pulmo, where in this tiny very poor village in Baja California, this single family decided they could not continue to fish the way they were doing. They stopped fishing, and the fish rebounded incredibly. Tourism now provides much more income to the community than fishing ever did. And it was initially just a tiny number of people that were responsible for creating this really big change.
And so I felt it was really important in terms of the narrative of conservation to talk about the role of individuals, because so often when you talk to the general public they say, ‘Oh, it’s so sad. But there’s nothing we can do.’ And I felt it was really important to give people kind of a reason to think that in fact there is something you can do. Everybody can do something.