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Brian Lehrer: It's the Brian Lehrer Show on WNYC, and now our climate story of the week. Melting polar ice caps and rising sea levels are two of the most referenced concerns of global warming but these are not the only two factors that will be most impacted in the oceans of the world by climbing temperatures. Marine life is also expected to be adversely affected. Here's how much that could potentially be the case. A paper published in the journal Science last month was titled, Avoiding Ocean Mass Extinction From Climate Warming. Ocean mass extinction.

It was authored by Princeton professors, Curtis Deutsch and Justin Penn. We'll talk to Professor Deutsch in just a second but according to the study, if nothing or not enough is done to lower carbon emissions, the majority of marine life is expected to be wiped out in the next 100 to 300 years. Now, that's a long timeline and maybe hard to get your head around when we have our families to feed or the atrocities in Ukraine or abortion rights hanging in the balance right now, and many other things, but a mass extinction, like this possible scenario, has not been seen in millions of years, they tell us. Since something known as the Great Dying.

Decreasing the release of greenhouse gases into the atmosphere, a major contributor to rising temperatures, could still avoid mass extinction in the oceans, so let's get into it. Here to speak with us today is a co-author of this study, Curtis Deutsch, Professor of Geosciences and the High Meadows Environmental Institute professor at Princeton University. Professor Deutsch, welcome to WNYC.

Curtis Deutsch: Thanks, Brian. It's great to be with you.

Brian Lehrer: Your study began with the words, or the article in Science began with the words, "Global warming threatens marine biota with losses of unknown severity." In general, what's the mechanism? How do rising temperatures threaten the well-being of marine life? Can you talk a little more about how this works beneath the surface of the ocean?

Curtis Deutsch: Sure. There are two key things that we've learned have a really big influence on where species can live in the ocean and where they can't live. Those two things are rather simple. One of them is temperature, which we're all familiar with as a leading indicator of climate change. The other is a little bit more obscure, especially for land animals and humans that take it for granted, and that is the amount of oxygen available to breathe.

The reason we take it for granted is that the atmosphere has a high amount of oxygen and it's pretty much the same amount anywhere you go unless you're an extreme mountain climber, but in the ocean, that's really not the case. The ocean has far less oxygen than the atmosphere and there are parts of the ocean that become completely devoid of oxygen. In between, animals can be their geographic range, the habitats they can live in, and the ones that they can't, can be sorted according to how much oxygen there is.

Now, it turns out that these two things are closely related. The temperature of the ocean and the oxygen that it contains are really fundamentally connected at both an organism level and also at the scale of an entire ocean. At an organism level, temperature increases the demand for oxygen. Fish and crustaceans and mollusks, and all kinds of marine animals that are not mammals, they breathe faster when the water that they live in is warmer.

That's a problem because the ocean has a different kind of connection between temperature and oxygen. That connection is that the ocean, as it warms up, it gives away some of its oxygen to the atmosphere. Marine animals of almost all kinds are subject to a real conundrum. They're caught between a rock and a hard place where they need more and they're getting less of this really key resource oxygen to breathe.

Brian Lehrer: Listeners, your questions about global warming and marine life are welcome now. Call us at WNYC 212-433-9692 or tweet @BrianLehrer. I want to get you to name some species here. In your study summary, you wrote, "Polar species are at the highest risk of extinction, but local biological richness declines more in the tropics." I wonder if you can talk about some specifics in each case. Like how are the mechanisms and possible outcomes different in colder waters versus warmer waters, and what kinds of marine life does this affect?

Curtis Deutsch: There's pretty big differences between the types of species that live in warm tropical oceans and the types that live in cold polar oceans. One of those key differences is how warm those animals can tolerate their environments to be and the other is how much oxygen they need to be able to breathe there. The warm tropical oceans tend to have less oxygen, to begin with, for perfectly natural reasons, that's just the way that the ocean works. Whereas the organisms that live in the poles and the cold waters tend to have a very high amount of oxygen.

Now, what happens as you warm up the planet is that the tropical organisms that can stand warm water with relatively low oxygen, they might suffer locally but they can always move to find waters that keep that condition that they find habitable by moving away from the equator, say, closer toward the poles. The tropical ocean might begin to lose species that are moving out because the conditions are no longer favorable.

If you think about what would happen to an animal living in the very coldest ocean as it warms up, it might like to find new habitats that remain cold in the face of this warming planet but they're not going to find that because they're already living in the coldest water. They have nowhere to go. When you have nowhere to go and your habitat is degrading, that's when you suffer the greatest risk of extinction because if you run out of habitat where you can survive and maintain a reproducing population, that is a recipe for the ultimate irreversible impact on life, which is the extinction of species.

Brian Lehrer: Can you give a species example or is that too hard?

Curtis Deutsch: Well, the ocean has hundreds of thousands of species. It turns out that probably many more that are not even known to science. There are tons of species that we know of and I could give you an example of a tropical species and a high latitude cold ocean species, but our prediction is not one that's based on individual species but whole categories and types of species. There's an ice fish that lives in Antarctica, there are several different species of fish that live around Antarctica, the coldest part of Earth. They live in freezing temperatures and they don't like temperatures that get too much warmer than that.

An example of tropical species would be all the famous charismatic corals that you see in the Great Barrier Reef or in the Caribbean, and many, many, many more fish and crustaceans and all kinds of animals that live within the coral reef. The tropics are very rich in biological diversity. A lot of that centered in warm shallow seas like the coral reefs. We're already seeing that the warming of the coral reefs is wreaking havoc on the ability of those keystone species, the corals themselves, to survive.

Brian Lehrer: Maybe this is a stupid question or a heartless one but why should humans care? Is it just because we don't want to do that to any other species of life, cause a mass extinction, or do humans have a self-interest here too?

Curtis Deutsch: No, it's a good question. It's a question that is as philosophical and ethical, and one might even say religious as it is scientific. I'll put on my citizen human hat for a moment, take off the science hat and just say that there are lots of reasons why people might care, and I would say ought to care. Earth has developed a rich biodiversity over hundreds of millions of years in a very connected way. That is, species rely on one another, even sometimes when they don't realize it.

We're all part of an ecosystem and ecosystems do all kinds of things that keep the whole system functioning. They recycle materials and animals provide carbon dioxide for plants and plants provide oxygen for animals. We're all really connected at some very deep level. There are more practical say, more immediate practical reasons why humans might care. Humanity gets something like a sixth of its global dietary protein from the ocean, so all the harvesting of animal life fisheries that sustains human beings at a very day-to-day level. In some parts of the world, the reliance on having sustainable populations for human consumption is even more important than that global average.

Plenty of places, and say the tropics, are very intimately tied to the fate of the oceans, the human populations are closely connected to the fate of the oceans. Then, of course, there are all kinds of, what you might call aesthetic, or just almost religious connections that people have to the ocean. There's a-- think about all of the art and poetry that have been written for the oceans that really move people. The vibrancy and the vitality of ocean ecosystems has obviously been incredibly moving to human beings throughout our history.

It's really sad to think about what would have happened if Pablo Neruda had showed up on the shores of Chile, and instead of riding his wonderful opus of odes to the ocean, he had instead encountered fish washed up dead on the shore because they ran out of oxygen, which is something that has just happened within the past year, or, for that matter, beaches covered in plastic or other forms of pollution that the ocean is experiencing. There's just a few reasons, and not everyone will care and that's fine, but for those of us who do care deeply about the integrity of Earth's ecosystems, not just in the ocean, but on land too, I think we have a responsibility to try to preserve that richness of life and on all of its diversity.

Brian Lehrer: A scientist does philosophy, religion, and literature, the scientist Princeton Professor Curtis Deutsch who's our guest in this week's climate story of the week here on the Brian Lehrer Show. We're talking about his study published in the journal Science last month, called Avoiding Ocean Mass Extinction From Climate Warming. Let's take a phone call. Frank in East Islip, you're on WNYC. Hi, Frank.

Frank: Oh, hi, Brian. How are you doing? I have a question about the acidity, the acid of the ocean. The ocean, you hear all these stories about how it's becoming more acidic. I go scuba diving every once in a while, I started back in the mid-'90s. Over the years, I have seen the coral get bleached and fish die-off. I just want to know the science behind the acidic nature of the ocean and how that affects the fish and how it becomes more acidic.

Brian Lehrer: Frank, thank you very much. Have you looked into that? Is that within your bailiwick, Professor?

Curtis Deutsch: Yes, thanks for that question, Frank. The oceans are indeed getting more acidic and it's something that we understand at a physical-chemical level very well. It's pretty basic chemistry, no pun intended. As you add, carbon dioxide into water, those carbon dioxide molecules react with water and they form a weak acid. We know that this happens, we understand the magnitude of that change, we have been observing it for quite some time. It's happening everywhere at the surface of the ocean, the upper ocean where it's absorbing Co2 from fossil fuel burning is getting more acidic.

The part where it gets a little bit more challenging is when we try to understand how does marine life react to that increasing acidity. There, you find all kinds of different impacts on life. Some things are relatively insensitive, some are harmed by it, and some do things a little bit better. It's harder to make generalizations about what happens when the oceans become more acidic than it is to make generalizations about what happens when the ocean loses its oxygen.

That's the reason why our study has focused on that second effect, the loss of oxygen and the warming because we have a good understanding of what that does to marine life, whereas the impacts of acidifying the ocean are less well understood. The understanding of that impact on life is still making advances and there'll be more to hear about that in the future.

Brian Lehrer: Tristan in Brooklyn, you're on WNYC. Hi, Tristan.

Tristan: Hi. I had a question for the guest about deep-sea ocean currents. I read recently that they've seen in the past, global warming that deep-sea ocean currents have sped up. I'm just curious what that means for the current system in the oceans as well as the life there and what it means for the poles because I've also seen that it's somehow tied into warming at the poles.

Curtis Deutsch: Yes, another great question. Thanks, Tristan. The currents in the ocean are a major factor in how the ocean loses its oxygen over time when it gets warmer, and how it redistributes the heat that it takes up from the surface climate. It's also a very rich area of research right now because, in general, what we think is that we're adding heat to the top of the ocean, and that makes the seawater at the surface get less dense or more buoyant if you want. When the water at the top gets more buoyant, it's harder to mix that water down into the more dense, cold, abyssal ocean.

Many of the oceans' currents that are important for oxygenating the deep ocean or bringing nutrients out of the deep ocean and back into the sunlight for phytoplankton, many of those currents actually get slower but there are some currents that could speed up. In particular, there are parts of the ocean around Antarctica where one might get a speeding up of those currents but that would be the exception and not the rule. In general, we expect the ocean's circulation by the collective action of all these currents to generally slow down.

Brian Lehrer: Thank you for your call, Tristan. Interesting. I want to ask you about some history in this context, and I don't mean history from a long time ago, like the 1950s or the Revolutionary War. According to your paper's language, biodiversity's evolutionary history amounts to 50 million years. What took 50 million years, like give us the 52nd version of 50 million years?

Curtis Deutsch: Sure. Well, there's an even deeper history of about 500 million years when the diversity of animal life forms in the ocean has been pretty much increasing. The number of species that the ocean has had has been generally increasing, but there are these periods when there's strong rapid setbacks for diversity of ocean life, they're called mass extinctions. The one that people are familiar with was about 65 million years ago, the end of the Cretaceous, when all the dinosaurs went away, that was a big extinction event on land that we all know, it was also a big extinction event in the ocean. It had a pretty massive reduction in the number of species living in the ocean.

What our results show is that over the next few centuries, if we were to stay on a very high emissions trajectory, not unlike what we have been on for the past 100 years, then the number of species that we would expect to disappear in the ocean would actually set the oceans' diversity back to something like it was at the end of the Cretaceous. That's the rebound from that earlier extinction that introduced many more species through evolution in the ocean, that would be basically undone. We would be reversing something like 50 million years of diversification of marine life in a very short time period, a few hundred years if we were to stay on the trajectory that we've been on in emitting Co2 at current rates.

Brian Lehrer: How do you get to the few hundred years' conclusion? I think sometimes one of the reasons that the media doesn't do more stories on studies like yours, and I have to say, I got your story from-- I've learned about your study from a story and other media so there's some coverage, but I think it just numbs people to hear terms like mass extinction and to hear what feel too many people like long and vague timelines like 100 to 300 years. What's your methodology? How do you come up with 100 to 300 years and how do you come up with mass extinction?

Curtis Deutsch: Yes, that's a great question. We actually looked at the future starting from now, actually, we started even a bit in the past, to look at how the persistence of species over time will change as we go out to the end of this century and then the end of the next century and the end of the century after that. That time horizon is basically dictated by how far into the future our models of the Earth system have projected the amount of warming that might happen under different scenarios of human behavior. It turns out that just by the time you get to that time horizon, that's where you can start to see extinctions that have accumulated to a level that places them on a geologic scale.

I also want to emphasize that you're absolutely right, it can be very disheartening to hear this kind of news. There was a flip side of our paper, which was that it's still within our grasp to avoid that kind of outcome. We have a lot of tools at our disposal to change our energy economy away from fossil fuels, toward renewable resources, renewable energy sources. If we do that and we do it now and we do it wholeheartedly and vigorously, there will be huge impacts on preserving marine diversity. In fact, we can basically avoid what anyone would consider a mass extinction if we were to reverse our emissions of CO2 now.

There is no room to be complacent about the future, but there's no reason to be fatalistic about it. We've got a choice, and if we exercise it well, we can really act still to preserve the diversity that has accumulated in the ocean over the past many millions of years.

Brian Lehrer: Julia, in Manhattan, you're on WNYC with Professor Curtis Deutsch. Hi, Julia.

Julia: Hi. How are you? I feel like we can't have a conversation like this without also addressing the impact of industrial fishing and microplastics because that's also eroding our oceans. I feel like we need to do more as consumers and people and be willing to make sacrifices and lifestyle changes with our overconsumption of fish, with the way we fish, also all of our plastics are polyester fibers that are contributing microplastics to the oceans. I just wonder how much that plays into this as well, and what actionable things we can do to change the way we function.

Brian Lehrer: Julia, thank you. Do these overlap? I think when we talk about any kind of pollution, whether it's ground-level air pollution from cars or power plants, or other sources that might be causing asthma or other health conditions on the ground, and we talk about climate, some of the sources are the same but they're really different conversations. Do they overlap in the case of the oceans, whether it's plastic pollution as the caller references or industrial fishing as the caller references? Those aren't climate stories per se, or climate functions per se, but where do they merge if at all?

Curtis Deutsch: It's a really great point. It's one that was not the main focus of our paper, but we do address the relative impacts of climate change, strictly speaking, that is the change in the global temperature and all that goes with it. Those can be compared to the other kinds of more direct immediate impacts that humans are visiting on the ocean. The caller is exactly right, that in naming the overfishing, overconsumption of marine resources, various forms of pollution, including plastics, there's introduction of invasive species that has a big impact on food webs, there's transportation that has a big impact.

All of these things are happening at once in the ocean, and it's quite likely that climate is not at this moment, the most profound impact because we are harvesting fish at extremely high rates, trolling the seafloor, being very disruptive to the ecological communities that live on the seafloor. All of these things are having really profound impacts already right now. Our paper was focused on what happens in the future if climate continues to add to those impacts.

We don't know exactly whether how these two things interact, that is, does the presence of both of these kinds of perturbations, do they add together, or do they multiply together. These are quantitative questions that science hasn't quite provided good answers for. What we do know is that each individually is having a pretty big impact on the ocean, and they're each worth taking much greater care.

They do, as you say, Brian, stem from fundamentally similar human processes, that is, a population that is consuming natural resources at really accelerating rates and finding ways of satisfying basic human needs without it coming at the expense of intact ecosystems around the world is an incredibly important project. People can eat lower on the food chain, they can find ways of, of transporting themselves that don't require highly in fossil fuel-intensive methods.

There are lots of things that individuals can do right where they are in their own lives, but also that institutions can do, from corporations to governments, to various kinds of private institutions. Everyone needs to be doing their part to figure out ways that we can reduce our ecological footprint. That's not just climate, it's plastics, it's overfishing, it's all of the things that are treating the ocean as an inexhaustible resource supply and dumping ground. We can't go on that way and expect the ocean to just absorb all of that.

Brian Lehrer: Let me take one more phone call for you because it's not every day that somebody calls in from an aquarium at the exact moment that we're talking about ocean life. I think Jason from Maritime Aquarium in where, Jason? You're on WNYC. Hi there.

Jason: Hi, Brian. It's Maritime Aquarium at Norwalk, Connecticut.

Brian Lehrer: Cool. First of all, do you want to shout out your aquarium? Is this something that the public can go and observe marine life in?

Jason: Oh, absolutely. The Maritime Aquarium at Norwalk is an hour outside of Midtown, Manhattan, 60 minutes on Metro-North. In fact, Metro-North gives a discount if you're coming up to the aquarium and we give a discount on any MTA users. We've got 7,000 animals, 320 species, and 75 exhibits. Pre-pandemic, we get about half a million visitors, mostly from Connecticut and Westchester. I'd love to see more folks from Manhattan and Queens come on up.

The big challenge that we have is getting folks who want to escape a rainy day, or a hot summer day to actually read the signs and come away learning more and becoming more of an environmental steward than when they came in a couple hours earlier. Everything that you are discussing here are themes and messages that we try to convey. We try to do it from not so much the academic perspective for the scientist or even your listeners, Brian, but for a much broader audience.

I'm curious what the professor suggests to translate these very difficult concepts, and as you said, trying to pay attention to what goes on on geological time is difficult for a lot of folks, even more so for younger audiences but that's our goal. I'm curious what the professor suggests in terms of translating these scientific themes, these really important messages to a younger, broader audience.

Curtis Deutsch: That's a wonderful question. Thanks for that. It's something is not directly part of my training, but I do take a great interest in it as someone who has two children myself and likes to go to their schools and see the bright lights of curiosity turn on when you talk about the oceans and about nature, and about climate. I think that there are lots of really wonderful, small demonstrations that can be done in an educational setting with pretty minimal resources.

All the things that I've been talking about here, the loss of gases like oxygen from water when you heat it up, or the formation of acidity when you add carbon dioxide to water, these are all things that people can do in their own home, but better still, do it in a group at an aquarium. Take a beaker of water and heat it up and just watch the bubbles come out. It's a more extreme version of what's happening in the ocean, but it's exactly the same concept. It can really-- I've seen students, just their eyes get big with curiosity, and then that leads to the desire to understand. Of course, understanding leads to, I think, a desire to protect and preserve.

Similarly, you can just pull out a standard, seltzer water maker and a soda stream, just inject some carbon dioxide into water. Take a glass and fill it with that carbonated water and take a glass with regular tap water. Just take a standard piece of school, Blackboard chalk and drop a chunk into each glass and watch which one dissolves faster. You're seeing the signs of ocean acidification on shells, of animals right there in front of your eyes.

These are things that can be done virtually anywhere and they are, I think curiosity is just stimulating. Curiosity is especially among young people, so important. Relatively easy, much easier than for us old folks, and is really a first step toward a desire to engage and protect and conserve. I applaud what you're doing at the aquarium there.

Brian Lehrer: That's a great answer. A watched pot never boils, but it can inspire.

Curtis Deutsch: Indeed.

Brian Lehrer: Jason, before you go, what's your most popular exhibit there at the Maritime Aquarium in Norwalk?

Jason: Well we have a number and I'm always asking our kids who come and visit what their favorite animals are, what their favorite exhibits. We have a brand new habitat for our harbor seals. We've got five harbor seals that's really amazing. We've got a touch tank, the stingrays, and sharks, and that's always popular. We've got a number of exhibits on jellies, which are very popular. Then we've got some terrestrial animals. We've got meerkats and we've got tamarins. There, the signage is all about what connects the land to the ocean and how the ocean influences even the Namibian Desert, which is home to meerkats, and our meerkats are really just a show stopper as well.

It's a lot of fun, and yes, building those fun types of engagements and interactions for our young kids is exactly what we try to do in our education programs. It's getting our guests to get those experiences as they walk through the exhibits but thank you. It's a wonderful discussion and very important. Really appreciate it.

Brian Lehrer: Thank you, Jason. Thank you for your wonderful call. Little affirmation, by the way, Jason. My producer says to what you just referenced. "Oh, we've done the stingray touch tank at the Atlantic City Aquarium. My kids loved that. Ha." There we leave it, our climate story of the week for this week on the Brian Lehrer Show with Curtis Deutsch, Geosciences professor at Princeton and co-author of the paper published in the journal Science last month, titled Avoiding Ocean Mass Extinction From Climate Warming. Thank you so much for all your clarity and for sharing it with us. I really enjoyed it.

Curtis Deutsch: Thanks for your interest, Brian.

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