Jean-Pierre Gattuso is a CNRS Senior Research Scientist at Université Pierre et Marie Curie-Paris 6. He investigates the response of marine organisms and ecosystems to global environmental changes such as ocean warming and acidification.
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Stories of Change
Jean-Pierre Gattuso interview
RH: = Roger Harrabin, interviewer
JPG: = Jean-Pierre Gattuso, Research Professor at the Centre National de la Recherche Scientifique (CNRS) National Centre for Scientific Research, France. participant
RH: So this is Jean-Pierre Gattuso. Where are you from?
RH: Jean-Pierre, what sort of a state are the oceans in as result of our CO2 emissions?
JPG: The CO2 emissions trigger two major changes, that is the warming of the water because the ocean is absorbing more than 90% of the extra heat released and generated by increased CO2 in the atmosphere, and also the ocean absorbs 28% of the CO2 we release in the atmosphere. So in effect the ocean is moderating climate change and also we see a lot of the water, almost 100% of the water, coming from the melting of ice sheets and glaciers. So the ocean is really moderating climate change but at the same time there is a cost to that - that is warming, acidification and the sea level rise.
RH: And what’s going to be the result of that do we know?
JPG: Well, we have just released a thorough review on the impact and we looked at seven key organisms, among which corals, molluscs (that is oysters and mussels) and marine plants, and also we looked at ecosystems services, coastal protection, tourism, fisheries, agriculture. And what we found is with RCP 2.6, that is the high mitigation scenario that is consistent with the Copenhagen call to limit global warming to 2°, it’s a compromise that is relatively useful for the ocean, that is most of the impacts will be either moderate, or unfortunately there is high risk for corals and molluscs, oysters and mussels, but the rest of the impacts are quite moderate in context.
RH: Hang on a second, so what you’re saying is that if we hit the two Celsius maximum agreed by the international community then there won’t be too much damage on the ocean except for on corals and molluscs?
RH: And you’re saying that as though that’s a good thing.
JPG: I’m not saying it’s a good thing but what we did, we contrasted this scenario with the business as usual scenario, RCP 8.5, the track of which we are today. Today we are even a little above this scenario and then that is dramatic for all the organisms and ecosystem services we looked at, all of them, almost, are in the very high risk of impact. So when you contrast those two scenarios you really realise that it’s not very wise to go beyond the 2° target, recognising that there will be significant impact for a few corals and molluscs.
RH: I think you’ve concluded that reefs as we know them, as we understand them with branching corals and table corals, won’t be able to survive this century if we continue on in the way we are.
JPG: That is correct, the increase in temperature triggers coral bleaching and eventually coral mortality. And starting 2050 or so, ocean acidification will also have an impact on coral reefs by limiting calcification, that is the build-up of the structure of coral reefs, you know, the calcium carbonate that is making those huge ecosystems in the tropics, and ocean acidification will also trigger dissolution of the calcium carbonate framework. The very existence of coral reefs is in danger.
RH: OK, so the good scenario is that we dissolve our coral reefs, what’s the bad scenario?
JPG: The bad scenario is that there is a very high risk of impact on all other organisms, not only corals and molluscs but also marine plants, ecosystem services, such as coastal protection will be greatly affected … also the moderation of the ocean will also diminish with the high scenario.
RH: Sorry, what does that mean, so the ocean will no longer help to buffer against continuing climate change?
JPG: The buffering effect of the ocean will be less in the high risk scenario, yes.
RH: The evidence on this is not perfectly smooth, is it? I mean there was one paper from Rodolfo-Metalpa, who found that mussels and corals grew faster at high CO2 levels. I was reading another paper today from Palau which suggests that corals there can grow at a level of acidification that you’d expect by the end of the century; somehow they’ve managed to survive. So not all the evidence points the same way, does it?
JPG: Absolutely not, it is true that some coral species have some resistance mechanisms that enable them to withstand this warming and acidification, but in this study we did an overall review and found that overall the impacts are very negative, even though some species are able to withstand those changes, if you like.
RH: Do you know the study, Rodolfo-Metalpa, which found that corals and mussels actually improved, grew faster than normal at higher CO2 levels; are you aware of that study?
JPG: I am. In fact Rodolfo-Metalpa did his work near a CO2 vent in the Mediterranean and we have to recognise the fact that those vents are windows to the future, but they are imperfect windows to the future because they don’t incorporate the warming effect; only ocean acidification is manipulated by those CO2 vents, not the warming of the water. So this is not something that is taken into account by Rodolfo-Metalpa et al. Also the resistance has to do with the food that is provided to those organisms, for example, in the Baltic, which is naturally acidified, the mussels are resisting quite well to ocean acidification, but there is a lot of food, and experimentally we show that organisms provided with enough food can resist ocean acidification better than those which are impoverished with food, which is the case in many tropical areas.
RH: It seems that in this area, like in so many others, that climate change is one of many stresses and if you can reduce the other stresses then you can actually delay the onset of the impact of climate change. That would be true say for coral reefs, for instance; if we stop mining them and eroding them and polluting them, they would be able to withstand climate change better.
JPG: Yes, there are ways that we can help some organisms and ecosystems to withstand… to buy time, in fact, and there are options to repair, to adapt or to protect those organisms or ecosystems. But we show in our study that those options to mitigate the impact are becoming less effective with the high risk scenario, with the RCP 8.5, the business as usual, the number of options declines and their efficiency declines as well.
RH: You speak to policy makers from time to time. Do you get the sense that they have really understand the potential impact on the oceans?
JPG: I think they do now - the coverage of the ocean in the IPCC report is quite extensive and there is a lot of arguments provided in the report to reach ambitious emissions scenario at COP 21. In the past I think ocean acidification, for example, was seen as an additional problem for them to deal with and they didn’t want to engage in that problem because there was so much trouble already to solve this issue of temperature. But I think the result of our study is that we have compelling arguments to be successful in those CO2 emission predictions because of the ocean. I mean it’s an additional argument to climate change to be ambitious and successful at COP 21 in Paris.
RH: Jean-Pierre Gattuso, thank you very much.
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