Study: Maine Fishermen Should Plan For Accelerated Ocean Warming

Aug 7, 2019

Climate change is triggering more and more surprise variations in temperatures in the world’s oceans, including off Maine, and those spikes are changing ecosystems in ways that looking at the past wouldn’t predict.

That’s one of the conclusions of a new study out Monday from the Gulf of Maine Research Institute, which finds that the bigger-than-expected temperature swings are benefiting some species while hurting others, and that has effects that can be felt up the food chain by the humans that depend on those ecosystems.

Dr. Andrew Pershing, chief scientific officer at GMRI and the lead author of the study, spoke with All Things Considered Host Nora Flaherty about the changes.

Flaherty: This paper looks at ocean temperature surprises becoming more common. What do you mean by surprises, and why are they happening more?

Pershing: So when we talk about a surprise what we’re talking about is an event that is unlikely, that you wouldn’t expect based on your past experience. And so for this study, we were focused on ocean temperatures and we defined it as a temperature that is two standard deviations away from the mean over the previous 30 years. That’s an event that you wouldn’t expect to happen more than about 2% of the time. So a really unlikely event, but not super unlikely.

Why are there more surprises these days, and what are those surprises causing?

We would expect to have more surprises just because of the fact that the ocean is warming. We live on a warming planet, so that’s causing temperatures everywhere to increase. That means that we’re seeing temperatures that fall outside the range of what people have experienced before. But what we tried to do in this study was to even take into account the trend, so over a 30 year period, think about, ‘Is the temperature rising?’ and then say, ‘What should the temperature be even accounting for that trend?’ What we find is even accounting for the trend, we’re seeing more events that are surprising. We call these the surprising surprises, events that are even more than we would expect. And we’re seeing those all over the world.

And these sort of surprise swings in temperature have resulted in things like a lobster glut in the Gulf of Maine in 2012, the Pacific Blob in 2013, and coral bleaching.

Absolutely. We’re seeing these all over the world. The 2012 event in the Gulf of Maine was one of the first marine heat waves that was described, and that had an impact on the lobster population and on the lobster fishery. Australia has had a number of important marine heat waves. And then this summer, people are looking at places like Greenland and the Gulf of Alaska.

So what you’re saying here is that you expect things to be changing, but things are changing faster than you’d predict, and these changes hurt some species while they help others? Broadly, who wins and who loses here and how does that impact the food chain?

So what we were really interested in with this study was thinking about the process of adjustment or adaptation. So rather than just assuming that a particular temperature, the ecosystem will just sort of magically appear and function in a normal way at that temperature, what we wanted to think about was how does an ecosystem that’s undergoing warming change? And can it keep up with the changes? So we modeled that replacement process, and what we found was that as you turn up the warming rate, we see that the abundance of species goes down. And we think that we’re going to lose the specialist species — the species that might be really good at a narrow range of temperatures, and they’re going to get replaced by more generalist species.

What are some examples of generalist and specialist species?

In the paper, we talk about coral reefs, which are a really interesting area in which we’re seeing a lot of impact all over the world. And we see in the coral reef ecosystem that a lot of the specialist species often are the really fast-growing branching corals, the really pretty ones that provide a lot of the structure. And they’re the ones that seem to be most affected by these bleaching events. And they’re being replaced by these more generalist species, these kind of moundy brain corals that can withstand a wider range of temperatures but don’t grow as quickly and don’t build reef in the same way that the branching corals do. Here in Maine, we’re looking at a variety of changes. I think one of the things we have an eye out for are jellyfish, which are really weedy species that can do really well when a lot of other things can’t and can grow really quickly, and seem to be able to tolerate a range of temperatures. We might think about squid as another really kind of dynamic species, potentially competing with some of the fish.

This can also impact species that eat these sorts of species, because their eating and breeding schedules may no longer link up.

Yeah, so we think about changes in the timing, we think about changes in abundance, and that’s definitely something that we’re seeing for a number of species. In the Gulf of Maine, we’re watching an ecosystem as it’s being transformed, as we’re losing some of our cool-water species like cod, as we’re gaining warm-water species like black sea bass. What we’re interested in is, from the point of view of the of the ecosystem, of the total amount of stuff that’s out in the water, is that going to hold together as the ecosystem goes through this this transformation?

We’ve been talking about the ecosystem down in the ocean. What about the human communities that depend on these ecosystems?

We were really interested in how people make decisions about natural resources. One of the things that’s striking if you think about fisheries, if you think about conservation, is so much of what we do is grounded in history. When we manage fisheries like cod, that happens by looking at 30 years of data, and you update it with the last couple of years of data. When we’re making the catches, we’re kind of assuming that the fish population is going to function in the same way that it has for the last 30 years. What our work shows, and what we’re trying to get at in this paper is the value of actually accounting for the trends and betting that the future is going to be different than what we’ve observed and not assuming that things are going to stay exactly the same.

You and the other researchers who worked on this paper contrast the usefulness of the two ways of looking at this change, backward looking and forward looking. You find using past trends to predict what’s going to happen isn’t especially useful, because more temperature surprises are on the way, but using models that take that into account will be useful. Why is that, and why do you say it’ll be a hard transition for a lot of people?

We’re trying to really highlight that the world that we’re heading into is going to be really different. One of the ways it’s going to be different is that every year, we have this trend that we’ve unleashed on the world. It tends to get a little bit warmer on average every year. And betting that that’s going to continue is going to give us better outcomes. That’s what our work seems to show and that the trends that we’re seeing in the ocean and many places, including here in the Gulf of Maine, are at the point where that forward-looking strategy really will start to pay off.

People have evolved both through our biology but also just culturally with a way of doing things. We live where we live because we expect the conditions in that place to be able to support us in the way we expect. So we have cod fishermen in Gloucester, Massachusetts, because that’s a traditional cod fishing ground. We’ve adjusted to the conditions that have prevailed on the planet, and we’re going to have to adjust to additional conditions, and the new conditions that are coming. The advantage that we have over something like a coral or a cod is that we can see those changes coming. We think that’s a necessary transformation that people are going to have to go through as we move into this century. But it’s going to be really tough because it’s very different than how we’ve trained ourselves and the institutions that we’ve built.

To be clear, you’re not just talking about change continuing, you’re talking about change continuing to accelerate year over year — snowballing.

Yeah. That’s an additional thing that we saw, and that’s the reason why we’re seeing so many of these surprising surprises, these events that are even more unlikely than we would expect in the ocean, even accounting for the trends.

I know you’re a scientist and you’re not in the business of giving policy advice, but what should policymakers and people who depend on these industries be looking out for?

I think that anytime you’re making a decision, and what you’re doing is looking backwards and you’re thinking about how that would have behaved last year or 10 years ago, or where you’re using data that’s an average over a long period of time, that’s a decision that I think you’re going to want to rethink about how can we look to the future? What are the projections that are out there? What are the trends that we might be able to look to and extrapolate forward? That’s really where we think that the the low hanging fruit is.

This interview has been edited for clarity.

Originally published Aug. 5, 2019 at 4:00 p.m. ET.