Joaquim Garrabou: "I never thought I would witness this collapse of species in the Mediterranean Sea"

The sea off the Costa Brava and Costeau's documentaries aroused the fascination for the ocean of Joaquim Garrabou, a researcher at the Institut de Ciències del Mar (ICM-CSIC) in Barcelona. This attraction took shape when he investigated one of the most emblematic and diverse habitats in the Mediterranean: the coral reefs. He wanted to understand the functioning of these ecologically important communities and decode the processes that made them places of such high biodiversity.

However, in the summer of 1999, following abnormally high temperatures, a mass mortality event occurred along hundreds of kilometres of coastline on an unprecedented scale. What he was studying was collapsing and he was forced to redirect his research. Since then, Garrabou has focused on the study of climate change in coastal marine ecosystems and is now one of the most recognised experts.

From the outset, it was clear to him that in order to understand the magnitude of the effects of climate change, it was necessary to promote collaborative initiatives. In this sense, he is the coordinator of the citizen science platform Observadores del Mar and responsible for the Mediterranean network T-MEDNet, dedicated to monitoring the effects of warming.

The ultimate goal of his research is to contribute to climate change adaptation strategies by promoting Marine Protected Areas (MPAs) and reconnecting society with nature. He has recently participated in a study revealing that marine heatwaves associated with the climate crisis are seriously affecting the two most emblematic coral species in the Mediterranean: the red gorgonian and the red coral. In this interview we talk about all this, as well as the solutions needed to halt this trend.

What does it mean that coral populations in the Mediterranean are collapsing?

We have been observing over the last decades that gorgonian populations, which are a type of coral, are losing abundance, in many cases up to 80-90% of their biomass, due to the impact of warming waters and, in particular, to the increased frequency of extreme heat events in the sea. We also call these events marine heat waves.

Why do these corals have such a difficult recovery period?

These species are long-lived, they can live for tens or hundreds of years and have very slow growth rates. A red coral, for example, one of the most emblematic coral species in the Mediterranean, grows about a quarter of a millimetre per year in diameter. Therefore, when these populations are impacted by a disturbance, it takes a long time for them to recover. In fact, to have a colony of a similar size to those before these extreme events, it would take between 60 and 100 years. Heat waves or the impact of climate change in warming waters is a new disturbance to which these species are not adapted, which means that populations are losing individuals and gradually disappearing from our coasts.

How long have you been doing this study and how did you carry it out?

A: We have been studying these populations for about 30 years. For the study we have just published, we installed marks on the rocks that allow us to go back to exactly the same areas and follow the evolution of the coral colonies. In this case, we started monitoring more than 15 years ago, and we return every year to photograph or take measurements directly in situ to recognise the different colonies, which allows us to assess how they are evolving over time.

Why are corals so important for marine ecosystems, and how important is it for the rest of biodiversity if these animals die?

The most important role that these coral species play is that they structure the marine habitats where they develop. It would be the equivalent of trees on land. If the trees disappear in a forest, then the diversity and functioning of that habitat completely changes, and all the accompanying species that would be in the forest may disappear. It is the species in which they find shelter, food, which allows them to carry out their functions. It is exactly the same thing that is happening in the sea. Those structural species that are the key to these ecosystems are disappearing, and with them we may lose other species that need these marine trees to live. But this not only has consequences for biodiversity, it also has a great impact on the services provided by these ecosystems. Many of these gorgonian-dominated habitats are home to fishery species such as lobster or fish species such as grouper. Also, in these habitats we find species that secrete bioactive substances that can have many applications in pharmacology or in the chemical industry. For example, recently some species living in these habitats are enabling the development of drugs to fight cancer or diseases such as Covid-19.

To what extent are these heatwaves increasing due to climate change?

Indeed, we are observing an increase in the frequency, intensity and extent of these waves over the last 15 to 20 years, in the same way that occursin the air. This is associated with the warming of the Mediterranean. We have evidence that it is warming up to three times faster than the average ocean. This warming has not happened progressively, but is associated with extreme heat events that are occurring and intensifying over time.

What does it mean that the level of warming in the Mediterranean is so rapid?

The Mediterranean is considered a hotspot for climate change. In terms of air temperature, we are on the verge of exceeding 1.5°C, which is what the Paris agreement sets as a limit that we have to fight not to exceed. In the Mediterranean we are already in this situation and we are seeing the consequences of this phenomenon. According to our last study, the mortality events are spreading and have a much higher incidence not only in specific locations, but all across the Mediterranean.

What other changes are you observing?

Another observation we are making is the shift in species distribution. This affects native species, i.e. species that were already in the Mediterranean, but because conditions are changing, they are now moving to areas that are more favourable to them. The problem in the Mediterranean is that cold-water species from the north of the western Mediterranean cannot move further north because there is no water and, therefore, they are disappearing or reducing their abundance while other species more suited to warmer waters arrive and colonise these areas. On the other hand, there is the arrival of non-native species, that are moving rapidly from east to west through the migrations of species that are entering through the Suez Canal. These are species of tropical origin that are colonising the Mediterranean because they find themselves in a sea where they can develop much more peacefully, and this is generating very dramatic transformations in Mediterranean ecosystems.

Is this problem already affecting our coasts?

These species have not yet reached the Spanish coasts massively, but in Israel, Syria or Lebanon, fishermen are catching fish they have never seen before, and many of these species are playing a key role in causing dramatic changes in coastal ecosystems. Where we had kelp forests there are now simply bare rock because of the presence of the so-called rabbitfish that eat all the kelp in a very voracious way.

How does what is happening to species in the Mediterranean compare with coral species in other seas or in more tropical latitudes?

It is exactly the same. For the general public, the phenomenon of bleaching or whitening of coral reefs has had a lot of media coverage because they are very iconic ecosystems, but that is exactly what is happening here. Not the bleaching, but the mortality or the effect of temperature change on the mortality of these species. It not only affects corals, but can also affect sponges, bryozoans or other invertebrates, as well as oceanic invertebrates, or different species of calcareous algae. Outside the Mediterranean, in temperate zones, where there are macroalgae forests such as kelps, the same type of mortalities are also observed. This is a global phenomenon.

Is the frequency of these extreme marine heat events a cause for concern?

We are entering a stage in which these events, which when we started studying them more than 20 years ago were exceptional and could occur every five years, are becoming the new normal. In fact, in the first studies we did on these extreme events we called them "unprecedented". In the last five, six, seven years, every year we have seen these mortalities spread throughout the Mediterranean. That this type of phenomenon is the new norm, as is happening in coral reefs, is very worrying. Ecosystems are changing at a very accelerated rate in front of our eyes, in the length of a human life. In fact, I never thought that I would bear witness to this kind of degradation or collapse of populations. When we began to study these phenomena, it was a conclusion we could reach because we knew the dynamics of these species and the consequences of these kinds of events. But I have to admit it, we wrote it in the results, but as an unlikely hypothesis in such a short term.

How do you feel about documenting and warning of this environmental disaster?

It's the same as when there's a fire. When you pass by you think: "my God, what has happened here?” At sea it is not so obvious because it has the problem of being blue. We can't see what happens below the surface, and for many people the sea ends up at the edge of the beach. If I have an image to describe what one feels when one sees a forest of gorgonians that has suffered the impact of a mass mortality event, the most obvious image for me is that of a forest that has been burnt to the ground, sometimes devastated. We are seeing real tragedies which, if they were visible to the people, could not be ignored. When we return to the sampling sites, I ask myself why we placed the transects in areas where there is almost no coral. We put them here because when we started there were hundreds of colonies. Now there are only a few left. What is happening is much worse, much more dramatic than we can explain here. It's almost like being in the presence of a terminally ill person, we know he is suffering, and we know the cure, but we see that he probably won't get there in time, and without an antidote, there will be no way back.

What would be the antidote in this case?

To fight with all our might to avoid the over-scaling of the planet. There is still hope, I don't want to say that there are no possibilities. Nature is very generous and strong, and if we give it the right conditions, it will be able to recover. We have proof of this through Marine Protected Areas (MPAs), in which, by protecting certain areas, if they are well managed, this promotes the recovery of marine ecosystems. And that's what I'm sticking with. It is important to contribute to the fact that measures, including MPAs, can be implemented effectively in order to conserve the marine biodiversity we have in the Mediterranean. The context is very favourable because currently there are agreements to protect up to 30% of the Mediterranean, and of this 30%, 10% must be strictly protected. And that changes the outlook if we can get it implemented quickly and effectively. The problem is that we currently only have 7% protected in the Mediterranean, and of this 7%, less than 0.1% is strictly protected, so we have a lot of work ahead of us. We have a lot to do, and we have to do it quickly.

What could someone who is worried about listening to you do?

One of the tasks is to raise awareness of what is happening, that climate change is a serious problem and affects us directly, it is not something far away that only affects polar bears. Having an educated society is key to better implement the measures that are being taken to transition to a new energy model, etc. On a personal level, I think we should enter a stage of moderation. The option to travel is there, we have it, but perhaps it is time to ask ourselves: is this trip really necessary? Don't I have another alternative to enjoy my friends, my family? And so on with an endless number of activities. If anyone wants to get more involved, I am fortunate enough to be the coordinator of the marine citizen science platform Observadores del Mar, which is a way for people to take action and be part of the solution. Citizens of all kinds can dedicate a part of their time; first to learn, and then to contribute their observations to this common knowledge about what is going on so that we have more complete images of things as simple as species distribution. There are many common species and fish species for which we still don't have a complete map of their distribution. It's as if on land we don't know where the white pine forests are, nobody thinks about it. There is a lot to be done and citizens can help. Nor should we lose sight of the fact that we cannot afford to lose talent and let young researchers go who are not finding options here.

Another solution would be to not eat fish or to reduce fish consumption?

There is evidence that reducing meat consumption or eating a more vegetarian diet can help reduce greenhouse gas emissions. The problem with fish is that many species are overfished. Apart from the stress that this causes on fish stocks, these activities degrade the bottom. So, yes, reducing or having more ecosystem-friendly fishing practices can obviously help recovery. The ocean has absorbed 90% of the excess heat, it is absorbing almost 30% of the CO2, but for that we need a healthy ocean, a functional ocean. Try to think what would happen if we didn't have the ocean. No one can imagine, we might not be here anymore. As David Attenborough says, "we have to find a way to work with nature and not against nature". And this for me is the key to the future.