Our planet in hot water

The waters off Florida and across the Caribbean are reaching record-breaking temperatures. As high as 100-plus degrees Fahrenheit.

If warm seawater is here to stay, what will it mean for all that lives in the ocean and on land?

“This year is unprecedented in terms of how early the bleaching started and the absolute temperature of the ocean that we’re recording, and that is well backed up by what I see every single day that I’m on the reefs this summer,” Katey Lesneski, geo-biologist, says.

Today, On Point: Our planet in hot water.

Guests

Katey Lesneski, marine biologist and Monitoring Coordinator for NOAA’s (National Oceanic and Atmospheric Administration) Mission: Iconic Reefs.

Peter de Menocal, oceanographer and paleoclimatologist and director of the Woods Hole Oceanographic Institution.

Also Featured

Ted Firkins, chief of Interpretation and Education at Biscayne National Park.

Transcript

Part I

MEGHNA CHAKRABARTI: On land in many parts of the world now, heat is shimmering off the pavement and forest fires are burning. So are the world’s oceans. More than 40% of the oceans are registering surface temperatures never seen in recorded history, and that figure is expected to pass 50% by September. One weather buoy in Florida’s shallow and enclosed Manatee Bay recently measured water temperatures at an astonishing 101.1% Fahrenheit.

Riley Kaminer, an On Point listener from Miami, says it’s not just a reading on a marine thermometer. You can feel the difference in the water.

RILEY KAMINER: I spent the day at the beach with my partner a couple weeks ago. The ocean is always a bit warmer in the summer, but for the first time this felt really quite different, that temperature plus the rampant sargassum made for an uncomfortable beach day. I’m no climate scientist, but it seems to me that that doesn’t bode very well for our planet.

CHAKRABARTI: Ted Firkins is the Chief of Interpretation and Education at Florida’s Biscayne National Park. He says Florida’s fate cannot be separated from the fate of the waters that surround it.

TED FIRKINS: So many livelihoods here in the state of Florida are based on the ocean, in one way or another. That could be that they’re in commercial fishing. That could be that they’re in the restaurant industry and that they serve fresh Florida seafood. There is a huge recreational fishing industry here. There’s a very big boat industry, and boat manufacturers and the sale of boats has really risen in the last couple of years.

We’ve got big ports that have billions of dollars’ worth of goods and merchandise coming through. Each year. We’ve got a big cruise industry that departs from Florida, that brings in lots and lots of visitors. We’ve got these amazing beaches where people plan their vacations to come to. So just so much of the Florida economy is based on our proximity to the ocean and use of the ocean.

CHAKRABARTI: Firkins says where he works, Biscayne National Park, is home to some of the most famous sea-based residents in all of Florida – its coral reefs.

FIRKINS: Biscayne National Park is 173,000 acres. 95% of that is ocean. So we do have some of the northernmost Florida Keys as land mass, and we do have some of the shoreline, but the vast majority of the acreage of Biscayne National Park is the ocean.

We’ve got the Florida Keys Coral reef track, which is the third largest living reef in the world, and it runs about 350 miles along part of the east coast of Florida and down the Florida Keys. You know, I would add that to another part of our economy. The Florida Keys like to call themselves the dive capital of the United States for people to come down and dive the wrecks and the reefs here.

CHAKRABARTI: Well, listener Manny Gilbert called us to sound the alarm about those same reefs.

MANNY GILBERT: I live in the middle of the Florida Keys. I’ve been a resident there for over 30 years, and I’ve never seen the watercolors change into a pea green as I have this last year. And now with the high temperatures of the water, I can just look out in the water and see the coral turning pink. And then white. We have a serious, beyond serious, issue now with this global warming.

CHAKRABARTI: As with any surprising environmental event, there’s always debate – are the measurements wrong? Is this an outlier year? Or is it another data point in the trend towards a hotter, less hospitable planet?

Listener Brian in Fort Lauderdale believes there’s no reason to worry.

BRIAN: We recorded a hundred-degree surface temperature, but if you go down maybe one foot or more, you’re going to see normal temperatures throughout the coast of Florida. It does not affect the reefs. It is at the surface, and we are avid fishermen and divers, and we don’t see how this can play into destruction of reefs when it is only at the surface.

CHAKRABARTI: The surface temperatures are recording freakishly high numbers, and yes, the water cools as you go deeper. But our guests today say the relative difference in the thermocline isn’t what matters – the real numbers to focus on are the absolute increases we are seeing in ocean temperatures at every depth, year after year.

Park ranger Ted Firkins, at Biscayne National Park says not only should we try to understand what’s happening to the world’s oceans … we must. Warming waters are about more than commerce and recreation. It’s about understanding the marine ecosystems that support all life on Earth, ecosystems that humans are reliant on and drawn to, whether we realize it or not.

FIRKINS: We are a land-dwelling species, human beings, we don’t live in the ocean, yet we’re drawn to it, and we just have to go there. 50% of the U.S. population, half of us live within 50 miles of the ocean. That’s a small portion of the actual land mass of the United States. Yet that’s where we concentrate. So we’re just drawn to the ocean.

This is On Point. I’m Meghna Chakrabarti. And today, we’re going to try to better understand why so much of the world is, right now, literally, in hot water.

Joining me first from Key Largo, Florida is Katey Lesneski. She’s a marine biologist and Monitoring Coordinator for the so-called Mission: Iconic Reefs. That’s at NOAA, the National Oceanic and Atmospheric Administration. Katey, welcome to On Point.

KATEY LESNESKI: Hello Meghna. Thank you so much for having me on your show today.

CHAKRABARTI: So do you get to dive frequently in the waters that we’re talking about?

LESNESKI: I do, yes, I dive on a weekly basis as part of my position as a scientist here, but I’m also an avid recreational diver. I like to go out on the reefs here just to look at the beautiful ecosystem, as well as assist in things like debris removal, marine debris removal, to help protect these important ecosystems.

CHAKRABARTI: So then over the past, let’s say four to six weeks or so, what have you been seeing on your dives?

LESNESKI: So unfortunately, over this very short timeframe, myself, my colleagues, other recreational divers in the Florida Keys have seen a steep decline in the health of corals that are the actual organisms that make up the coral reefs here.

So in late June, we were starting to see corals undergoing paling, which is a precursor to coral bleaching. And since then, the bleaching has become more widespread, not only in very shallow reef areas where the water tends to be warmer, but as well as some of the deeper reef areas where we’re seeing that warm water essentially slowly creep into those areas.

CHAKRABARTI: What kind of depths are you talking about?

LESNESKI: So the very shallow reefs that have the most bleaching, so many different species are bleaching, many individuals are bleaching. Those are anywhere from about 20 feet to corals that get within a couple feet of the surface. The deeper reefs, 60 plus feet.

There’s definitely, at this point, some bleaching occurring in some of those areas, and we’ll be continuing to track this event at as many reefs as possible in the coming weeks.

CHAKRABARTI: Have you ever seen the kind of bleaching that you’re witnessing now occur at such a rapid pace in the waters around the Florida Keys or elsewhere near the Florida coastline?

LESNESKI: I have personally not witnessed this and many of the colleagues that I work with and others in this field who have spent more time than myself on reefs, have also never seen anything quite like this, where so early on in the season, we were already seeing such high-water temperatures, even water temperatures taken from data recorders that are at the bottom of the reef.

And that has been directly linked to a spike in widespread bleaching and unfortunately, the mortality of corals in reefs all across the Florida Keys. And it is now, we’re nearing mid-August and typically during warm years, we would see this level of bleaching later in August and into September.

But this has been something that we have been witnessing since July in some areas. So it is clearly coming into focus as an unprecedented event here.

CHAKRABARTI: Can you tell me a little bit more about the numbers that can describe how anomalous this year is. So for example, for those recordings that are taking place at the bottom of the reefs, what would you expect to be in the normal temperature around this time of year versus what you’re actually seeing?

LESNESKI: Yeah, so I’ll give you an example of Sombrero Reef, which is in the middle keys, and it’s one of the mission iconic reefs that we are actively restoring.

And typically, during July, at the bottom of the reef area, we would see temperatures of maybe around 87 degrees Fahrenheit. Back in July, we had recordings of 93, 94 degrees Fahrenheit over several days, which is a high enough temperature that it can actually affect the health of the coral. And shortly after that pulse of warm water, we had teams go out and do an assessment and saw that corals absolutely were affected by that, undergoing bleaching.

And unfortunately, we’ve recorded that a number of corals have died.

CHAKRABARTI: Wow. And so those high temperatures, again, were at 20, 30, 40, 50 feet even.

LESNESKI: Sombrero Reef the temperatures that were taken there are 15 to 20 feet.

CHAKRABARTI: 15 to 20, okay.

LESNESKI: Yes. Yeah, it really has been so far these very shallow reefs that have hit the hardest, but we’re expecting continually elevated.

Not only air temperatures, but ocean temperatures, which over the course of time, until late August and September, could very much affect those deeper regions more.

CHAKRABARTI: Okay, so when we come back from the break, Katey, I want to hear a little bit more about the health and prospect of the reefs that you’re studying, trying to preserve and dive in.

Part II

CHAKRABARTI: This is On Point. I’m Magna Chakrabarti, and today we’re trying to understand what’s driving the unusually high-water temperatures that we’re seeing in 40% and soon to be 50% of the world’s oceans. I’m joined today by Katey Lesneski. She is a marine biologist and monitoring coordinator at the National Oceanic and Atmospheric Administration’s project called Mission Iconic Reefs.

Now Katey, actually, could you just help us take a step back and describe as vividly as you can, the reefs that you dive in, what do they look like? How much life is on them, what colors do you see when they’re in a healthy state?

LESNESKI: Yeah, so healthy reefs that are very important, not only ecologically, but also economically to Florida are, as you said, very vibrant, full of life and actually very noisy.

So earlier this year, working on these reefs throughout the Florida Keys region, any reef that you pop onto, you put your scuba gear on and you descend through the water, and as you get closer to the reef, you’re seeing all of these colors pop out. So the corals themselves, these rich greens and browns and oranges, and the sea fans bright purple.

With colorful fish, blues, greens, and yellows. Essentially every color of the rainbow you can find on reefs. There’s sea turtles here, there’s sharks, there are all sorts of different game fish that swim through the reefs that people love to come here to fish. It’s very noisy. You can hear fish eating, you can hear groupers grunting.

You can sometimes hear sharks sifting through rocks, especially the nurse sharks who are trying to get around. So it’s really a lively place that awakens all your senses when we have a healthy reef.

CHAKRABARTI: Wow. Groupers grunting. What does that sound like?

LESNESKI: It sounds a low boom, other people describe it as a barking noise.

CHAKRABARTI: Okay, fantastic. So it, it awakens all your senses. So then when we start seeing these temperature driven bleaching events happen in those same reefs, does it have an immediate, so first of all, the bleaching is actually the loss of what the bacteria that create the color on the coral, is that right?

LESNESKI: Yeah, so this is a very important concept to understand how bleaching occurs. So corals themselves are actually an animal, and within their tissues, they host a single cell algae. They also have bacteria, fungi, viruses, that are all part of a healthy coral in the rest of their tissue and their mucus.

But during coral bleaching, which is a stress response, and it can be caused by warm temperatures, among other things, that single cell algae that provides the coral with its color as well as most of its food, will actually leave the tissue. And what’s left behind is the clear coral tissue and that white limestone skeleton underneath.

So the coral essentially looks like it has been bleached.

CHAKRABARTI: I see. Okay. But importantly, as you said, the algae is providing the coral with its food. So how long can the coral survive then in this bleach state? So during periods of mild bleaching or a mild increase in temperature, corals can survive in that state for several weeks.

Unfortunately, at some of the reefs that we have seen here, that period of death is occurring within a matter of days, just because the water is so hot. But it is definitely important to remember that just because a coral bleaches doesn’t automatically mean it will die. If environmental conditions do improve, they can indeed recover.

CHAKRABARTI: So that’s hopeful and good news. On the other hand though, I’m seeing some predictions that ocean temperatures may continue to rise, or at the very least, stay high through September. So that’s a total of many weeks of potential bleaching in some of these reefs.

LESNESKI: Yes, exactly. So the NOAA Coral Reef Watch program generates predictions about bleaching based on satellite data collected on sea surface temperatures, as well as real-time data transmitted from buoys or other instrumentation.

And right now, the forecast shows that we can expect to see ongoing widespread bleaching and subsequent mortality for the next nine to 12 weeks. So we are continually bracing to continue to witness that. And we will be collecting as much data as possible about the effects on the reef here.

I will say that there are corals that we have seen on these deeply affected reefs that are still healthy. It’s very few, but that does provide us hope and those are the individuals that we will absolutely be tracking, and studying and trying to understand why they are resilient in the face of this bleaching event.

CHAKRABARTI: Okay. Coral though are, they’re not just these beautiful reef dwelling organisms that sparkle the eyes of divers. The reefs themselves are what, I think you’ve said in the past they’re less than 1% of the ocean, but 25% of all marine life rely on coral reefs at some point in time. And also, they provide a physical barrier for wave energy as well.

So what impact would losing these reefs have on the broader ecosystem that rely on them?

LESNESKI: Yeah. So you did a great job of summing up some of those ecological benefits that reefs provide. Recently down here in Florida, we had lobster season, and now lobster season is open. And coral reefs provide essential habitat for lobsters that people enjoy fishing, enjoy eating.

Folks come down here to scuba dive on these reefs. And really healthy reefs definitely could draw more people who want to learn how to scuba dive and enjoy these reefs. And so that is directly tied into the economy, as well. You mentioned the fact that they provide a natural barrier during storms for wave energy, so they’re reducing coastal erosion and flooding during storms.

Which directly, in turn, benefits the taxpayer in providing that extra protection. So with the loss of corals from bleaching, what essentially happens is if they do die, they will start to disintegrate over time and the reef framework and the habitat itself will essentially crumble.

And so all the different animals that rely on that habitat will have to find somewhere else, if they can. But that collapse in the framework is also directly tied to potential economic losses. So it’s really important to consider it from both sides, both the ecology and the economic impact.

CHAKRABARTI: Okay. I’ve just got a couple more questions about the coral reefs specifically, and then we’re going to broaden our analysis to oceans around the world.

But you heard a bit earlier at the top of the show, Katie, a caller, an On Point listener who called in and said he’s not noticing any differences in deeper waters and is also a diver. What do you, what’s your response to that? How can you explain what he’s seeing versus what you’re seeing in the places you dive?

LESNESKI: My understanding is that caller was diving and fishing off of Fort Lauderdale. Is about 50 miles north of any of the reefs that we work on here. And while that might not seem very far, it is a different offshore reef structure system. There are different currents and water exchanges that come into play.

That lead to different environmental conditions, off Fort Lauderdale versus the Keys. And those different environmental conditions will drive differences in ecology and the ecological response. So we, as I mentioned, we have temperature loggers and other environmental loggers that are deployed at the bottom of these reefs, all throughout the Keys.

And we’re pulling that data and those temperatures. And that data we have, very, a lot of confidence in how accurate and precise they are. The reefs here, there’s, on almost every shallow reef, you will absolutely see bleaching that is undeniable. Folks around here who I know in the community who are not scientists, they’re able to see it with their own eyes.

And I would take it as a sign of hope that off of Fort Lauderdale, there isn’t this significant amount of impact right now. And hopefully those reefs continue to stay healthy and continue to escape the heat and the effects that are happening down here.

CHAKRABARTI: I appreciate your very clear explanation of the difference that 50 miles can make, because I think it’s really important to emphasize that we also at the top of the show, played a little bit of tape from another caller in Key West who was speaking with the sound of shock in his voice, almost.

LESNESKI: Yes.

CHAKRABARTI: What he was seeing where around where he is. So one of the goals that we hope to achieve with this hour is to really have people think beyond sort of their immediate realm of experience into the broader global systems, the broader global changes we’re seeing in marine environments around the world, and how that’s all going to impact us.

So Katey Lesneski in Key Largo. Just hang on for one minute, because I want to hear from some more listeners and then bring in again, a global Marine expert. So first of all, we got a call from Tallahassee, Florida, On Point listener Melissa told us that she is not feeling any changes in the waters where she swims.

MELISSA: I was in Panama City Beach literally this morning and did get in the Gulf, and I did not notice that the temperature was too warm. It was quite refreshing, and the water was beautiful. However, I don’t know what it’s like in any other part of the state. I have been traveling to this particular timeshare since 1980, the same week every year.

So to me it is definitely comfortable. So I didn’t notice any warming.

CHAKRABARTI: On the other hand, we got a call from Tom who lives in Seattle, Washington. He left us a VoxPop to say warm is a relative term when it comes to the world’s oceans. It depends on where you’re getting your feet wet. But still, he thinks the problems of increasing water temperature is real and getting worse.

TOM: As a former Floridian who lived in Florida in the 1990s, I do want to make folks aware that the ocean water in Miami where I lived got very warm every summer. So it is maybe not as alarming as it may sound if you are consistently used to ocean water in Washington State, or Massachusetts, where it will always be colder.

It’s just clearly getting worse.

CHAKRABARTI: Tom, I have to say I appreciate your call. As a native Pacific North Westerner, I know how cold the Pacific is off the coast of Oregon and Washington. It’s way colder than it is off the coast of Massachusetts, but down in Florida, as we’ve been talking about, 101-degree temperature recorded in at least one weather buoy.

CHAKRABARTI: Joining us now is Peter de Menocal. He’s an oceanographer and paleoclimatologist, and also director of the Woods Hole Oceanographic Institution. Peter, welcome to On Point.

PETER DE MENOCAL: Thank you very much for having me on your show, Meghna.

CHAKRABARTI: Now. I understand you’re in Nantucket today, so surrounded by water as well. When you first saw the data coming in from the waters, around Florida, Southern Florida especially.

And let’s just focus on that 101-degree temperature mark that that buoy recorded in Manatee Bay. What was your first response?

DE MENOCAL: It was alarming to many of us indeed. Indeed, the people living there and also those of us who are climate scientists. But it’s important to recognize, too, that it is an enclosed bay.

It’s not an entire section of the ocean. So I think understanding it within the context of a limited embayment area, it’s understandable that it can get warmer like that, but it is, 101 degrees is exceptional.

CHAKRABARTI: We heard Katie though just now say that in the places that she’s trying to preserve and study, that there’s unusually, been unusually high-water temperatures even at 20, 30, 40, 50 feet below the surface.

So how pervasive right now is this high-water temperature problem? Where else in the world are we seeing it?

DE MENOCAL: We’re seeing it almost all over the world, but certainly in specific parts of the world. For example, the region in the Gulf of Mexico and off of Florida has warmed up a great deal.

One of the most concerning trends is actually the North Atlantic. The North Atlantic is now the warmest it has ever been in recorded history. We’ve been measuring ocean temperatures for about 100 years, actually going to be extended back for 150 years. This is the warmest we’ve ever seen the entire North Atlantic basin.

CHAKRABARTI: How much warmer than usual.

DE MENOCAL: Right. So it’s about one and a half degrees centigrade warmer than the historical period. And that’s more than twice as warm as it has been in the past. And just to give our listeners some context. It’s over 15 degrees centigrade warmer off of Nova Scotia and off of Newfoundland right now.

CHAKRABARTI: More than 15 degrees C. Wow.

DE MENOCAL: No, 15 degrees Fahrenheit. Warmer.

CHAKRABARTI: Oh, I thought you said degrees centigrade.

DE MENOCAL: No. 15 degrees Fahrenheit.

CHAKRABARTI: Okay. That’s a lot. Either way. Now I want to get right to something that I know a lot of people may be wondering. Because there’s some claims or analysis out there that are saying that this is simply maybe an outlier year.

It’s not necessarily due to overall and continuous warming of the world’s oceans, driven by human caused climate change. But rather what we’re seeing is just a really vigorous El Nino, right now. Peter, what do you think about that?

DE MENOCAL: Yeah, no, I’m happy to take that on. So the warming of the global oceans is in fact the single best indicator of global warming that we have for the planet.

The oceans have absorbed more than 93% of the excess heating that we get from the buildup of greenhouse gases in the atmosphere. And so the oceans are doing us a big favor right now by absorbing all that heat. Remember the ocean or water has 3,000 times the heat capacity of air. And so as the ocean’s warm, they can take up this heat that would otherwise be in the atmosphere.

So we can thank the oceans for really protecting us from really extreme heat. But tell me a little bit more then about how you would scientifically differentiate the global warming caused effects on ocean warming versus what’s driven by El Nino.

DE MENOCAL: So that’s a great question. So we have 4,000 autonomous robots in the ocean that are basically pogo sticking up and down in the ocean, from the surface, to a depth of about a half a mile, and then they surface again. And as they go up and down in the ocean, remember these are all over in all the world’s oceans right now.

They measure temperature and salinity and pressure, and they basically show that the oceans are warming, not only at the surface, but at depth, as well.

Part III

CHAKRABARTI: Peter, before the break, you were describing how we can tell the difference between global warming caused ocean temperature rises, versus El Nino caused temperature rises.

Keep describing that to me because I’m still not quite clear how we can differentiate the two.

DE MENOCAL: So I’m happy to clarify that. So from these robots and basically ship measurements in the ocean, we can document that the oceans are indeed warming all around the world. In fact, they reached the warmest ocean temperatures ever measured globally.

Just this year. In fact, July was an absolute record of the oceans having warmed up about one degree centigrade around the world. Now that’s just the average planetary warming. Now, El Nino is this four-to-six-year natural oscillation of waters in the tropical Pacific, and basically it oscillates between two extremes.

One is called La Nina, and that is an amplification of the current situation in the Equatorial Pacific where the waters are warmer off of Australia and they’re colder off of Peru. Now what we’re experiencing this year is called El Nino, and I think many of our listeners are probably familiar with that.

That is a warming in the tropical Eastern Pacific and a relative cooling off of Australia. So it’s the opposite pattern. What happens during El Nino, it’s a release of tremendous ocean heat back to the atmosphere. Now, remember we said that the ocean has about 3,000 times the heat content of the atmosphere.

In past years, the ocean has been accumulating all that heat and now’s it’s a time for that to burp itself out, if you will, or release that heat back to the atmosphere. So if we look back over really the last century or so of temperature changes, we find that the warmest years in any decade, were in fact El Nino years, and we are headed right now into a strong El Nino period, which will develop in the wintertime later this year and into 2024.

CHAKRABARTI: I see. So what you’re saying is that baseline water temperatures have been rising and now what we have is an inline effect on top of that. So that’s why you’re saying it’s undeniable that human caused climate change is the baseline driver here.

DE MENOCAL: And then, one of the other sort of indicators of the fact that the whole planet is warming is that when you actually measure ocean warming. It’s not just the skin of the ocean, it’s not just in one place. It actually extends all the way through the water column as far as we can measure. And we can measure now down to a mile or two miles into the ocean, so we can actually trace this warming to the bottom of the sea floor.

CHAKRABARTI: Meaning that your paleoclimatologists expertise is coming in here, are there patterns of similar warming in the deep past?

DE MENOCAL: (LAUGHS) Well, we have to go back quite far in time to find a time when the earth has been as warm as it is today. It’s certainly the warmest that it’s been throughout what’s called the Holocene, which is the time of human civilization spending the last 10,000 or 12,000 years.

But we believe we have to actually reach back further in time. Back to at least a hundred thousand years, perhaps even earlier than that, to get to a time that was as warm as today. And then where it’s headed in the decades ahead is basically, we haven’t seen this for many millions, even tens of millions of years.

CHAKRABARTI: Oh gosh. Okay. Katey, I really appreciate your patience in listening to the analysis that Peter’s offering there. I want to tie your two areas of research together here, because it suddenly occurred to me that the bleaching of the coral reefs are devastating. It’s terrible, and part of the reason why is because the coral can’t move.

But are you seeing other evidence of long-term impact regard when it comes to these warmer waters on other forms of marine life? Are they moving, are they changing their location? What’s happening sort of year by year in terms of marine life around where you are, as the waters get warmer?

LESNESKI: That’s a great question and it’s definitely important for us to consider how other marine life is affected just because these ecosystems are so diverse. Here in the Florida Keys, we have what we call the oceanside, which is out towards the east where the coral reefs are. And then we have the bay side, which is to the west of the Florida Keys where Florida Bay is.

And Florida Bay is a very shallow environment and it’s full of sea grass and sponges and many different types of fish that people come here to fish for, like game fish. And those fish will, some of them migrate between both sides. So the ocean side and the bay side. Unfortunately, we’re already hearing reports of large areas of sea grass die off, as well as sponges that are dying.

From the unusually high-water temperatures. Sponges are critical for water filtration. And we also have been hearing reports of fish kills. A number of fish that are floating on the surface or washing up onto the shoreline, and those are all indicators of a decreasing, a decrease in health of the environment here.

Exactly as you mentioned, corals can’t move. Once they choose a place to settle and they grow, that’s where they are. And corals are very constrained by not only the water temperature that they live in, they can’t live in cold waters and still continue to build their skeletons. They also require an adequate amount of sunlight.

So that’s why we don’t see corals growing, much far north beyond Port St. Lucie in Florida, which is a couple hundred miles north of where I am today. And that sort of migration, if it ever were to happen, would take hundreds if not thousands of years.

This article was originally published on WBUR.org. [Copyright 2023 NPR]