By Alvin Powell, Harvard Staff Writer
The Intergovernmental Panel on Climate Change (IPCC) released a special report last week warning of the mounting effects of global warming on the seas, increasing temperatures and acidification, and on the world’s melting ice. It noted the potential dangers from sea level rise, water shortages in glacier-fed rivers, declining and shifting fish stocks, and increased frequency and severity of storms, among many other hazards. The release came during a week marked by climate-related activities, from youth protests around the world to a United Nations summit meeting of global leaders to consider the issue.
The Gazette spoke with John Holdren, the Teresa and John Heinz Professor of Environmental Policy at the Harvard Kennedy School, of environmental science and policy in the Department of Earth and Planetary Sciences, and affiliated professor in the John A. Paulson School of Engineering and Applied Science. Holdren was director of the White House Office of Science and Technology Policy during the Obama administration and now co-leads the Arctic Initiative at HKS’ Belfer Center for Science and International Affairs.
Surprisingly, while the situation seems urgent, Holdren suggested there may be something positive lurking under the gloom.
GAZETTE: These IPCC reports on climate seem to be getting more and more dire. Is there any good news in this latest report, the “Special Report on the Ocean and Cryosphere”?
HOLDREN: I don’t think there’s any good news in the report because it’s focused only on the science, and it’s been true for decades now that virtually all of the new news from climate science has been bad news. The current good news is on the public awareness side. It’s that the fraction of the American public and of publics around the world who understand that climate change is real, caused by humans, already doing significant damage, and that we need to act, has been going up. I actually think we could be close to a political tipping point, because of the combination of expanded grassroots conviction that more needs to be done and these authoritative reports underscoring how pervasive the impacts of climate change already are, even though we’re just at about 1 degree Celsius above the preindustrial temperature.
GAZETTE: It seemed like for many years the job was to convince people about the science of climate change. Are we at a point where that job has been mostly done, positions are more or less baked in on either side, and the question now is going to be decided at the ballot box?
HOLDREN: The polls now show that between 70 and 80 percent of the U.S. electorate is convinced about the realities of climate change. So, the challenge is not to persuade the last 20 or 30 percent. We don’t need them. Seventy or 80 percent support is more than we’ve had for almost any change in our political system over the life of the republic. What we need to do is to persuade those who are already convinced about the science to increase their sense of urgency, to decide that they need to work for and vote for candidates who understand this issue and are prepared to take serious action. Our problem now is that, although a high percentage of the American electorate understands that climate change is real and caused by humans, if you ask the same people, “What keeps you awake at night?” they’re worried about their jobs, getting their kids through college, their retirement, the health system, drugs, terrorism. Climate change tends to come in number eight or nine. But that’s progress. When I started talking to President [Barack] Obama about these matters in 2007, the percentage who believed in the reality of human-caused climate change was between 60 and 65 percent. And the priority ranking was 18 or 19.
GAZETTE: Did the climate protests last week — the fact that they were global in scope and youth-driven — move the needle a little bit?
HOLDREN: Absolutely. In my view, most of the major sociopolitical changes that have occurred in this country and elsewhere — Civil Rights, improving the status of women, and many others — have resulted from a combination of what you might call bottom-up and top-down influences. Consider how the Vietnam War ended. It ended because of the interaction of defections at the top — people like Daniel Ellsberg [who leaked the Pentagon Papers in 1971] on the inside, saying, “Wait a minute, the emperor has no clothes” — and the bottom-up withdrawal of public support that occurred after virtually every American had either a family member or a friend who had been killed or injured in Vietnam, and nobody could really explain why. I think we’re seeing that with climate change: from the top, with reports like those of the IPCC and the U.S. National Climate Assessment, which comes out roughly every four years, on the impacts of climate change on the United States. The last one was released on the day after Thanksgiving last year — Black Friday — and in spite of that it got big coverage in the mainstream media outlets. That in itself was a sign of positive change in concern about this issue.
GAZETTE: Is the “bottom-up” in this case driven by Texas, the Caribbean, the Carolinas getting hit again and again? Is that convincing people?
HOLDREN: I think there’s no question about it. People are experiencing more, longer, stronger heat waves; more and bigger torrential downpours producing more flooding; hotter wildfires burning larger areas and destroying more property; longer allergy seasons; worse pest outbreaks; and more.
If you look at the number of countries in which the highest temperatures ever recorded have occurred in just the last three or four years, it’s absolutely extraordinary. In almost every ocean basin in which hurricanes and typhoons occur, the largest and strongest ones ever recorded have occurred since 2012. One of the things the new IPCC ocean and cryosphere report emphasized very powerfully is that, in many parts of the world, previously once-per-century extreme sea level events are now going to occur every year by 2050. We’re going to have 100-year storms every year. This will happen in spite of a relatively modest change in the globally and annually average surface temperature of the Earth.
GAZETTE: There are a lot of different projections in this report. Was there anything that surprised you?
HOLDREN: The climate scientists who have looked most broadly at the impacts of climate change are not surprised by this report. What you need to understand about the IPCC is that it is the nature of the beast that they only establish the floor on what we know, they are almost never on the cutting edge.
“I don’t think there’s any good news in the report because it’s focused only on the science, and it’s been true for decades now that virtually all of the new news from climate science has been bad news.”
There are scores of authors, and you’re never going to get all those authors to agree on what the top two or three understand in their own field. For example, they said in this new report that, by 2100, sea level might go up by a meter. That’s an increase on what the IPCC said before, but NOAA said in 2012 that the increase could be as much as two meters by 2100. This is typical.
The IPCC approach makes their results very respectable, because they got all these people to agree, but it certainly isn’t describing the worst that could happen. This report says some very sensible things about the influence of rapid climate change in the Arctic. One of these points is that, as the sea ice and the snow cover shrink, we’ll see impacts on the circulation patterns of the atmosphere over much of the Northern Hemisphere. The new report is more cautious than I would be on that particular issue. While the new IPCC report says, “It’s likely that there will be influences in this domain, but our confidence is low to medium,” in my view, I think expert confidence is already high. I think we’re already seeing effects and remaining disagreements among experts in this space are about how exactly it works, about the relative importance of different mechanisms that contribute to making the polar jet weaker and wavier. The waviness means that, in downward lobes, more cold, Arctic air penetrates in the midlatitudes, and, in the upward lobes, more warm midlatitude air penetrates into the far north.
GAZETTE: Is that the polar vortex we’ve seen?
HOLDREN: Yes, it’s what the media have called the polar vortex. Technically, the polar vortex has always been there. What’s changing is its speed and shape. I think the evidence for that [shifting circulation pattern] is stronger than the current IPCC report reflects. If you look at the history of IPCC reports going back to their inception in 1990, each one has reported increasing confidence, higher certainty, and bigger effects. The reality is that many of the effects of climate change are now manifesting more rapidly than was projected even 10 or 15 years ago.
GAZETTE: One thing mentioned during the news conference after the report was released was tipping points where a small change creates a cascade of changes from which there may not be any going back. Are there any of those that you see as particularly worrisome or likely?
HOLDREN: I think the most worrisome one is the possibility that we will get to the point where the thawing permafrost is emitting enormous quantities of both carbon dioxide and methane. We know the permafrost contains 2-and-a-half times as much carbon as is now in the atmosphere. It’s organic carbon that has been frozen undecomposed for millennia. As the permafrost thaws under the rapidly warming Arctic climate, that carbon becomes susceptible to bacterial decomposition. If the circumstances are anaerobic, the decomposition produces methane; if they’re aerobic — if oxygen is present — it produces CO2. Methane is worse in the short term. On a 100-year time scale, the methane is 30 times as potent a heat-trapping gas as CO2 per molecule. We don’t know yet at what point the permafrost will have thawed to a level at which these emissions become a really big deal. There’s already a lot of evidence that the permafrost is disgorging more CO2 and methane than it did before the human-caused warming raised the temperature. But, again, I think the evidence there is a little stronger than the IPCC report reflects.
In second place, but not by much, is the drying out of the tropical forests. If you look at what’s happening already in the Amazon and, to a lesser extent, in the tropics in Indonesia and central Africa, you see very strong drying tendencies already very evident.
GAZETTE: Is that causing the fires we’re seeing in the Amazon?
HOLDREN: Fire has been a longstanding phenomenon in the Amazon, but fires now are bigger, hotter, and get out of control more easily. You see this in Indonesia as well. Roughly a million people in that country are suffering acute air pollution because smoke from the fires is so widespread. We’ve seen that phenomenon in the United States, too. The wildfires in the Northwest — in Northern California, Oregon, and Washington State — have transmitted dangerous levels of fine particulates all the way to New England. These bigger, hotter fires generate a lot of smoke and transmit it farther.
GAZETTE: Climate change is characterized by these big problems and long-term effects. Are there things in the short term that can be reversed?
HOLDREN: The difficulty in a problem like climate change is the time lag. By the time there are dead bodies in the street, you’re already way down the road. At any given time, we’re not experiencing everything that we’re already committed to. That causes policymakers and publics to underestimate how bad it is. If we could somehow freeze the atmospheric concentrations of heat-trapping gases and reflecting particles where they are today, the temperature would still rise to close to 1.5 degrees C above preindustrial times. If we actually want to stay below 1.5 — and the IPCC report from last fall argued that doing so would bring big benefits compared to going to 2 degrees or more — we really have to start reducing our emissions very rapidly. We’ll eventually have to be actually pulling more carbon dioxide out of the atmosphere than we’re adding in order to meet that extremely challenging goal.
The good news is it’s still up to us how bad the impacts of climate change get. It’s going to get worse, but it’ll get a lot less bad if we take action than if we don’t. If we do a lot, we can end up with a temperature increase of 2 or 2.5 degrees. If there are major breakthroughs, maybe we can get back to 1.5. And that will be a vastly better world than business as usual, where, by the turn of this century, you get to 4 or 4.5 degrees C.
Image: Stephanie Mitchell, Harvard Staff Photographer
By Alvin Powell, Harvard Staff Writer
As the only one in his family with a bent toward science, Jerry X. Mitrovica grew up spending more time discussing Renaissance history at the dinner table than the latest issue of Nature. But he always knew that science was compatible with creativity.
“Creativity comes from asking questions,” said Mitrovica, the Frank Baird Jr. Professor of Science in the Department of Earth and Planetary Sciences. “There is as much creative thinking that goes into great science as great art, looking at things and saying, ‘What’s a new way of understanding this and building on what’s gone before?’”
Mitrovica’s creative work in geophysics was recognized today by the John D. and Catherine T. MacArthur Foundation, which granted him a coveted “genius” fellowship.
The fellowships, which come with a stipend of $625,000, are awarded each year to 20-30 individuals who have displayed exceptional creativity in their field and have a history of accomplishment as well as potential for future success.
Mitrovica’s research group studies paleoclimate and modern sea-level change patterns across the globe, using statistics, measurements of sea levels taken from land and satellites, and geological records both ancient and modern. The research has implications for predictive modeling of sea-level rise and changes in land formation as a result of global warming.
“Studying paleoclimate provides us with a sense of [what] the natural rhythms of sea-level change should be, and we can also look to ancient geological records to look to other times when the planet was warmer than today or as warm as we are getting to,” he said.
Mitrovica, whose findings have been published in research journals including Science, Nature, and the Journal of Climate, developed ice sheet and glacier “fingerprint” models that support the claim that sea levels do not rise uniformly across the globe as ice sheets melt. His models trace the ways in which melted ice sheets affect sea levels across the planet, decreasing near the melting ice sheet due to gravitational shifts and rising land, and rising elsewhere, particularly in highly populated coastal regions.
“I’m always looking to answer questions about what sea levels were doing back in time, but we’re always cognizant of the lessons and tools that they give us to analyze modern sea levels,” Mitrovica said. “We’re faced with aggressively rising sea levels that are variable for many reasons, and we are going to face significant problems. The exact geometry of sea levels we’ll have by 2050 or 2100 are uncertain, but we know that the answer is not going to be pretty. That’s the next important step, to make accurate projections of sea-level rise, and greenhouse gas emissions as well.”
Mitrovica joined Harvard in 2009 as a professor of geophysics after working as a faculty member in the physics department at the University of Toronto, where he earned his doctoral degree. In 2015 he received the Arthur L. Day Medal from the Geological Society of America, and he gave the W.S. Jardetzky Lecture at Columbia University in 2014.
Pointing to the range of issues and questions studied in Mitrovica’s lab, Dean of Science Christopher Stubbs said the award is well deserved. “It’s wonderful to see such a creative and accomplished colleague be recognized with this generous and prestigious recognition,” he said.
“Harvard has been the perfect place to develop the close culture that we have in our group between researchers and students,” Mitrovica said. “I’ve been extremely fortunate to work with remarkable graduate students throughout my career.”
The students Mitrovica encounters in the lab and in the classroom will guide some of his decisions about his post-MacArthur activities. He has plans to develop more concrete diversity initiatives in the sciences.
“I was in shock when I got the call from the foundation,” said Mitrovica. “It’s an honor and a recognition of our whole research group. But we’ll probably keep going and doing our work. I don’t know if our workday will look too different.”
As part of its coverage of Climate Week (Sept. 23-29), the Gazette is running a series of stories on the issues involved, while spotlighting areas of University involvement, including research and programs designed to make a difference. For more information, visit the Tackling Climate Change site.
The pollution, acidification, and warming plaguing the world’s oceans are often seen as intractable as climate change and as important to resolve. But Jane Lubchenco, former administrator of the National Oceanic and Atmospheric Administration (NOAA), offers a new perspective, saying we should look to the seas for solutions, not problems.
“Seventy-eight percent of countries border the ocean and, despite that, the oceans for the most part are not front and center when we think of mitigating climate change,” said Lubchenco.
The administrator of the NOAA during the Obama administration and now a professor at Oregon State University spoke at a Monday afternoon panel convened to honor the career of James McCarthy, the Alexander Agassiz Professor of Biological Oceanography who has been at Harvard for 45 years, conducting research on the oceans, and adding his voice to the environmental policy debate.
Despite the litany of problems facing the oceans, Lubchenco said, we should look to the opportunities they offer to solve both marine problems and those of global climate, opportunities which could help limit warming to 1.5 degrees Centigrade by 2100, the goal pursued by signatories to the 2015 Paris Agreement.
There are opportunities, Lubchenco said, to sequester carbon in coastal habitat by restoring mangrove forests, salt marshes, and sea grass beds, which, though disappearing, have the potential to store more carbon than land-based systems per unit area. That restoration, she said, will also make the seas healthier, boosting fisheries by protecting and creating habitat used as nurseries for juveniles of many species.
Similarly, she said, there are ways to reduce emissions from shipping and fishing activities, to take advantage of the ocean’s biological pump (which moves carbon to the sea floor as biological life dies and drifts downward), get renewable energy from the ocean itself, and to shift human diets toward seafood, which is less resource-intensive and healthier than land-based meat diets.
“The ocean, then, has a key role to play in both mitigation and adaptation,” Lubchenco said. “It is time to change our narrative around the ocean.”
“If I think about the future, I very much like the position that Jane advocates: We cannot ignore the ocean. It’s essential we think about the ocean in all these future plans,” McCarthy said. “I think the hopeful message is that it is something … that is absolutely essential.”
Daniel Schrag, Sturgis Hooper Professor of Geology and director of the Harvard University Center for the Environment, which sponsored the event, said one of the great benefits of working at Harvard is great colleagues, and McCarthy, who served as a mentor to him, was one of his first and foremost.
“There are many days when I feel like the luckiest person in the world, and the reason is I have spectacular colleagues,” Schrag said. “I am incredibly fortunate to be part of this community … but Jim McCarthy is dear and special to me. My entire time at Harvard he has been a mentor and a steady presence.”
Several of the speakers reflected on shared experiences and the impact McCarthy had on their careers, providing a nudge that landed one at the Massachusetts Institute of Technology and another in the top chair at the New England Aquarium. McCarthy, who sat on a panel during the event’s second half, said he was “extremely honored” by the gathering and said in reviewing the list of speakers, it was clear that each felt an obligation to not only conduct science, but a responsibility to communicate what they found to policymakers. McCarthy himself chaired a working group of the Intergovernmental Panel on Climate Change’s 2001 report and served in leadership positions, among others, for the Union of Concerned Scientists and the American Association for the Advancement of Science.
Other speakers addressed an array of ocean-centric topics, but in each case highlighted existing opportunities to engage with the problems of today. Overfishing, which is rampant in the world’s oceans, can be addressed by effective regulation. Aquaculture has the promise of boosting the availability of seafood even as free-swimming stocks decline. Even something as difficult as coral bleaching, a phenomenon prompted by warmer than normal water that has some predicting the doom of the world’s reefs, has been shown to be less deadly on reefs that are otherwise healthy and protected from pollution and overfishing, according to Jeremy Jackson of the Scripps Institution of Oceanography.
“There’s a really dangerous arrogance to the notion of hopelessness,” Jackson said. “Total hopelessness assumes that we know everything there is to know. … When we think we know everything, we preclude opportunity.”
All of us at the Harvard University Center for the Environment are deeply saddened by the loss of Martin L. Weitzman, recently retired professor of economics at Harvard University, who died unexpectedly on August 27, 2019. Weitzman’s contributions to environmental economics and policy are considered extraordinarily important, within both academia and the policy community. He published widely, was elected as a fellow of the Econometric Society and the American Academy of Arts and Sciences, was a longtime faculty associate and friend of HUCE, and for more than 25 years hosted with Robert Stavins the Harvard Seminar in Environmental Economics and Policy.
Marty Weitzman was a treasure—a gift that kept on giving to the research and policy worlds—for Harvard, for environmental economists around the world, and for the global intellectual community. His work as a theorist on environment, broadly, and climate change, in particular, was unparalleled and formed the basis of much empirical research carried out by many, many others, including myself. He was the first to develop strong arguments for why, when analyzing the benefits and costs of proposed climate policies, it is important—from an economic perspective—to take into account the possibility of catastrophic outcomes, despite the fact that their probability may be very small. That alone was a massive contribution, but it is only one of many.
Robert Stavins, A.J. Meyer Professor of Energy and Economic Development; Director of the Harvard Environmental Economics Program, Harvard Kennedy School
Marty Weitzman was a giant in the field of environmental economics. As a relative newcomer to the field, I was tremendously fortunate to be able to learn from him as a colleague. Marty cared deeply about tackling climate change; his research and thinking was driven by his desire that we must use all our tools as economists to solve this problem. In conversations as well as in his research, he had a way of looking at a problem from angles that are new, unexpected, and yield deep insights. This creativity—the ability to ask the right question, then answer it with beautiful simplicity—was a hallmark of his most influential research. That research included welfare comparisons of cap-and-trade vs. carbon taxes; discounting under uncertainty into the deep future; and why possible climate catastrophes provide a motivation for climate policy action today as a kind of climate insurance. Marty’s ideas have been foundational to environmental economics in general and to climate economics in particular. Speaking personally, I was inspired by how he merged his passion for climate action with hard-headed economics. There is so much more he could have taught me, indeed could have taught us all, and he will be sorely missed.
James Stock, Harold Hitchings Burbank Professor of Political Economy, Department of Economics, Harvard University
Nearly two decades ago, in my very first microeconomics lecture in graduate school, I became Marty Weitzman’s student. Ever since that day, I have been challenged, inspired, and enlightened by Marty and his work. As a graduate student and as a colleague on the Harvard faculty, I enjoyed his interventions in seminars. His comments and questions made you think, re-evaluate your assumptions, and cause you to consider a problem from another perspective. In his scholarship, Marty sought out questions whose answers could both advance the frontier of knowledge and lay the foundation for better public policy. In the classroom, when I am teaching from one of his papers, I see in our students the excitement when they begin to understand the insights from Marty’s work. And Marty was always generous with his time—and patient with me—when I solicited his feedback and guidance on my research. I will forever be Marty’s student and forever in debt to his generation of ideas and advancement of knowledge.
Joseph Aldy, Professor of the Practice of Public Policy, Harvard Kennedy School
By Peter Reuell, Harvard Staff Writer
For those who lived through the storms, their names — Katrina, Sandy, Harvey, Michael — are enough to trigger memories of homes, businesses, and loved ones lost in rising floodwaters. Other disasters elicited similar reactions, from the Midwest floods to the California wildfires, and droughts in the Great Plains.
The eventual response to catastrophes tended to be a defiant vow to rebuild, turn loss into lesson by making protective seawalls higher and stronger to hold back floods, or raising homes onto stilts to stay clear of the encroaching waves.
To this, A.R. Siders says, “Enough.” The time has come to consider a different path: retreat. Abandon areas prone to repeated disaster in favor of those that are safer and do so in a deliberate, thoughtful way.
Known as “managed retreat,” Siders, an Environmental Fellow at the Harvard University Center for the Environment who recently joined the faculty of the University of Delaware, said the strategy has the potential to save not only lives, but possibly billions of dollars in direct and indirect costs to cities and towns. The idea is described in an Aug. 23 paper published in Science with co-authors Miyuki Hino and Katharine Mach.
“Traditionally speaking, there are three ways people respond to floods or hurricanes,” Siders said. “There is protection — basically building a sea wall. There’s accommodation, which often means homes that are elevated, or there’s retreat.
“We see retreat listed as an option as early as 2001 by the [Intergovernmenal Panel on Climate Change], but retreat has been seen as largely theoretical — somewhere, sometime people might have to move. But what we’re seeing more and more is that it might be here and that it might be now. It’s no longer a theoretical last resort. It’s something we should talk about now as a realistic option.”
The purpose of the paper, Siders said, is to call attention to the need for a greater focus on the strategy as a way to avoid the fallout seen from earlier disasters.
“The point we’re trying to make is: Retreat will happen; people will move. Not managing retreat doesn’t stop people from moving,” Siders said. “After Hurricane Katrina, people had their homes destroyed, and they moved with no help and no support. They just left.”
For the neighborhoods they leave behind, the results can be corrosive.
“You have thousands of empty homes, and the city has to figure out who owns them,” she said. “They have to sell or demolish them, and maintain the lots. So it eats away at the community, because it’s dotted with vacant homes, and it eats away at the city’s resources.
“But if you do manage it and try to do this in a strategic way, then you have a better chance of avoiding those harms,” she continued.
The notion of managed retreat, however, is about more than what happens to the homes people leave behind when they flee.
“It touches on so many aspects of a city,” Siders said. “You have to think about things like where people are going — where they’re choosing to go and where you want to provide incentives for them to go.
“What are the effects on the community they’re moving to? Do they have enough services? Do they have enough hospitals and schools to take in the people they’re receiving? For the people who stay behind, do they suddenly have no sense of community because of all these vacant lots, or do they have something like a new public park or feature to maintain a sense of community?”
Those questions only deepen, Siders said, when retreat crosses national and cultural borders.
Robot builds erosion barriers from interlocking metal sheets, while robot swarms could protect threatened areas
“That coordination can happen when people leave New Orleans and go to Houston,” she said. “But what happens when you’re crossing national borders? How do you handle that? So far much of the focus has been on making people safer … but there’s not a lot of focus on if they’re better off holistically, on the emotional or cultural or social aspects. And those are important issues.”
For some communities, retreat could mean leaving behind centuries of cultural and religious connection to a particular land, something people are often unwilling to do.
“There are examples where people have overcome these problems in creative ways,” Siders said. “There is a community in Indonesia where people moved away from a volcano, but they were allowed to return to visit, and they were given rights to provide tourism in the area, so now they have an economic benefit they didn’t before.
“So the problems are not insurmountable,” she continued. “They’re challenging, but they’re not insurmountable, and they can be much more easily overcome if people start thinking about retreat as a real option, and how it ties in to these other issues.”
Though it remains an uphill battle to convince communities to consider ideas like managed retreat, Siders said, the tide is slowly turning.
“It’s still a very difficult topic to talk about, but in the last few years we’ve seen such drastic wildfires and floods just in the U.S. … there’s a major push for people to start thinking of retreat as an option,” she said. “Just in the time since Sandy there’s been a shift in our thinking. I was in New York during the storm and wrote a paper about the legal strategies that could be used to help communities undertake managed retreat, and no one wanted to talk about it. But fast-forward to this spring, and Columbia University had a conference on managed retreat with 150 presentations. I think people are starting to see the effects of climate change and realize that extreme changes require extreme adaptation.”
This research was supported with funding from the Harvard University Center for the Environment, Stanford Woods Institute for the Environment, and the Sykes Family Fellowship in Stanford University’s Emmett Interdisciplinary Program in Environment and Resources.
Image: Jerry Coli/Pixabay
By Leah Burrows, SEAS Communications
Add another item to the ever-growing list of the dangerous impacts of global climate change: Warming oceans are leading to an increase in the harmful neurotoxicant methylmercury in popular seafood, including cod, Atlantic bluefin tuna and swordfish, according to research led by the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Harvard T. H. Chan School of Public Health (HSPH).
Researchers developed a first-of-its-kind, comprehensive model that simulates how environmental factors, including increasing sea temperatures and overfishing, impact levels of methylmercury in fish. The researchers found that while the regulation of mercury emissions have successfully reduced methylmercury levels in fish, spiking temperatures are driving those levels back up and will play a major role in the methylmercury levels of marine life in the future.82% of U.S. population-wide exposure to methylmercury comes from the consumption of marine seafood
The research is published in Nature.
“This research is a major advance in understanding how and why ocean predators, such as tuna and swordfish, are accumulating mercury,” said Elsie Sunderland, the Gordon McKay Professor of Environmental Chemistry at SEAS and HSPH, and senior author of the paper.
“Being able to predict the future of mercury levels in fish is the holy grail of mercury research,” said Amina Schartup, former research associate at SEAS and HSPH and first author of the paper. “That question has been so difficult to answer because, until now, we didn’t have a good understanding of why methylmercury levels were so high in big fish.”
It’s been long understood that methylmercury, a type of organic mercury, bioaccumulates in food webs, meaning organisms at the top of the food chain have higher levels of methylmercury than those at the bottom. But to understand all the factors that influence the process, you have to understand how fish live.
If you’ve ever owned a goldfish, you know that fish do pretty much two things: eat and swim. What they eat, how much they eat, and how much they swim all affect how much methylmercury fish will accumulate in the wild.
Let’s start with what fish eat.
The researchers analyzed 30 years of ecosystem data from the Gulf of Maine, including an extensive analysis of the stomach contents of two marine predators, Atlantic cod and spiny dogfish from the 1970s to 2000s.
The researchers modeled methylmercury levels in cod based on their diet and results indicated levels were 6 to 20 percent lower in 1970 than they were in 2000. Modeled concentrations of methylmercury in spiny dogfish, however, were 33 to 61 percent higher in 1970 compared to 2000 despite living in the same ecosystem and occupying a similar place in the food web. What accounts for these differences?
In the 1970s, the Gulf of Maine was experiencing a dramatic loss in herring population due to overfishing. Both cod and spiny dogfish eat herring. Without it, each turned to a different substitute. Cod ate other small fish such as shads and sardines (small herring), which are low in methylmercury. Spiny dogfish however, substituted herring with higher in methylmercury food such as squid and other cephalopods.
When the herring population bounced back in 2000, cod reverted to a diet higher in methylmercury while spiny dogfish reverted to a diet lower in methylmercury.
There’s another factor that impacts what fish eat: mouth size.
Unlike humans, fish can’t chew – so most fish can only eat what fits in their mouth whole. However, there are a few exceptions. Swordfish, for example, use their titular bills to knock down large prey so they can eat it without resistance. Cephalopods catch prey with their tentacles and use their sharp beaks to rip off mouthfuls.40% of U.S. population-wide exposure to methylmercury comes from fresh and canned tuna
“There’s always been a problem modeling methylmercury levels in organisms like cephalopods and swordfish because they don’t follow typical bioaccumulation patterns based on their size,” said Sunderland. “Their unique feeding patterns means they can eat bigger prey, which means they’re eating things that have bioaccumulated more methylmercury. We were able to represent that in our model.”
But what fish eat isn’t the only thing that impacts their methylmercury levels.
When Schartup was developing the model, she was having trouble accounting for the methylmercury levels in tuna, which are among the highest of all marine fish. Its place on the top of the food web accounts for part of this but doesn’t fully explain just how high its levels are. Schartup solved that mystery with inspiration from an unlikely source: swimmer Michael Phelps.
“I was watching the Olympics and the TV commentators were talking about how Michael Phelps consumes 12,000 calories a day during the competition,” Schartup remembered. “I thought, that’s six times more calories than I consume. If we were fish, he would be exposed to six times more methylmercury than me.”
As it turns out, high-speed hunters and migratory fish use a lot more energy than scavengers and other fish, which requires they consume more calories.
“These Michael Phelps-style fish eat a lot more for their size but, because they swim so much, they don’t have compensatory growth that dilutes their body burden. So, you can model that as a function,” said Schartup.
Another factor that comes into play is water temperature; as waters get warmer, fish use more energy to swim, which requires more calories.
The Gulf of Maine is one of the fastest warming bodies of water in the world. The researchers found that between 2012 and 2017, methylmercury levels in Atlantic bluefin tuna increased by 3.5 percent per year despite decreasing emissions of mercury.
Based on their model, the researchers predict that an increase of 1 degree Celsius in seawater temperature relative to the year 2000 would lead to a 32 percent increase in methylmercury levels in cod and a 70-percent increase in spiny dogfish.
The model allows the researchers to simulate different scenarios at once. For example:
“This model allows us to look at all these different parameters at the same time, just as it happens in the real world,” said Schartup.
“We have shown that the benefits of reducing mercury emissions holds, irrespective of what else is happening in the ecosystem. But if we want to continue the trend of reducing methylmercury exposure in the future, we need a two-pronged approach,” said Sunderland. “Climate change is going to exacerbate human exposure to methylmercury through seafood, so to protect ecosystems and human health, we need to regulate both mercury emissions and greenhouse gases. It is important also to remember that fish are a very healthy food overall and when people switch away from fish in their diet they generally pick less healthy alternatives. We can all agree less methylmercury in these fish in the future would be a good thing.”
This study was co-authored by Colin P. Thackray and Clifton Dassuncao, of SEAS and HSPH; Asif Qureshi, of the Department of Civil Engineering, Indian Institute of Technology Hyderabad, Kandi, India; and Kyle Gillespie and Alex Hanke of Fisheries and Oceans Canada. This research was supported in part by the US Environmental Protection Agency, the US National Science Foundation and the Nereus Program sponsored by the Nippon Foundation.
Nate Herpich, Harvard Correspondent
If a tree could talk, what might it say?
Would it plead for rain in a drought? Fawn over a neighbor’s foliage? Crack jokes about how fast another tree loses its leaves in fall?
It seems unlikely anyone will ever come across a loquacious linden. But for the arbor-curious, a red oak at the Harvard Forest in Petersham has been tweeting as @awitnesstree since July 17. Outfitted with sensors and cameras, and programmed with code that allows it to string together posts with prewritten bits of text, the Harvard Forest Witness Tree has been sharing on-the-ground insights into its own environmental life and that of its forest.
Already renowned in certain circles as the subject of the popular climate-change book “Witness Tree” by Lynda Mapes, the century-old oak’s social-media debut was the brainchild of Harvard Forest postdoctoral fellow Tim Rademacher and is now a team effort with Clarisse Hart, who heads outreach and education for the forest. Its online presence is modeled after similar “twittering” trees that chronicle their life experiences as part of a tree-water and carbon-monitoring network based in Europe called TreeWatch.net.
“We’ve done the work as a team to equip the tree with a voice, which we decided made the most sense in the first person, and even with a personality, in order to make it relatable to a larger audience,” said Rademacher. “But most importantly, our Witness Tree is an objectively data-driven account, which I expect will amplify messages of climate change. But we don’t decide what gets posted, the tree does.”
By Samuel Myers
Image: Narendra Shrestha/EPA-EFE/REX/Shutterstock
Samuel Myers is a principal research scientist at the Harvard Chan School of Public Health and director of the Planetary Health Alliance.
Feeding a planet inhabited by 10 billion people by mid-century — already a daunting task — is getting harder due to a little-known impact of global warming: the decline of essential nutrients in the world’s staple foods that exist in almost every single person’s diet around the world.
The mechanism by which rising carbon dioxide saps nutrients from our food crops remains somewhat unclear, but the effect is consistent across most plant types from trees to grasses to edible crops: It is reducing the availability of zinc, iron, protein and key vitamins in wheat, rice and several other fundamental grains and legumes.
The implications are huge: By 2050, hundreds of millions of people could slip below the minimum thresholds of these nutrients needed for good health, and more than 2 billion already deficient could see their conditions worsen. And it extends well beyond human nutrition as every animal in the biosphere depends, directly or indirectly, on plant consumption for nutrients.
These findings, which will appear this week as part of the most comprehensive review ever compiled on the two-way relationship between global warming and land use, highlight the urgent need to slash the greenhouse gas emissions that drive climate change. Human activity has increased atmospheric carbon more than 40 percent since the mid-19th century, enough to unleash a deadly onslaught of extreme weather made more destructive by rising seas. Without a drastic drop in emissions, those levels will climb even more quickly over the coming decades.
Scientists from the United Nations' Intergovernmental Panel on Climate Change are meeting in Geneva this week to validate a 30-page summary for policymakers of a 1,000-page underlying report. Food security is high on the agenda.
Nutritional deficiencies continue to take a heavy toll. Zinc deficiency affects the immune system and increases vulnerability to malaria, lung infections and deadly diarrheal diseases, claiming the lives of some 30,000 children younger than 5 each year. Protein deficiency causes stunting and increases infant mortality. Iron deficiency is linked to nearly 60,000 deaths and 34 million “life years” lost to disability or premature death every year, and can also result in decreased work capacity, reduced IQ and anemia.
Humans are deeply vulnerable to reductions in the nutrient content of staple food crops. We get 60 percent of dietary protein, 80 percent of iron and 70 percent of zinc requirements from plants, most of which are losing these nutrients in response to rising carbon dioxide levels.
Research I have co-written indicates that as a result of these emissions, nearly 2 percent of the global population — an extra 175 million people — could become zinc-deficient, and 122 million would no longer get enough protein. Some 1.4 billion women and children younger than 5 would find their iron intake reduced by 4 percent or more. Half a billion in this group risk developing iron-deficiency-related disease.
By 2050, the vitamin B content of rice is expected to drop 17 to 30 percent, upping the risk of deficiencies in folate (B9), thiamine (B1) and riboflavin (B2) for tens of millions of people, especially in regions dependent on rice. All these vitamins are crucial for normal and healthy development.
The reason for this is still a bit of a mystery. There are theories, such as that more carbon dioxide causes plants to produce more starch, which could have a diluting effect whereby plants become carbohydrate-rich and nutrient-poor. But that’s not the case for all nutrients; the science has a long way to go before we have sound answers.
We do know, however, that when the carbon dioxide effect is combined with the impact of climate change on crop yields, we see even larger reductions in the availability of nutrients in the global diet. Compared with a world without these effects, we anticipate a 14 to 20 percentreduction in the global availability of iron, zinc and protein by 2050, which would threaten large segments of the global population with nutrient deficiencies.
Supplements and vitamins could temporarily alleviate some of the health consequences, but these options have existed for decades and have not protected the billions of people who already suffer from nutrient deficiencies, in part because they are difficult to distribute and do not address the underlying cause of malnutrition.
The countries hit hardest are primarily those that have contributed the least to global carbon emissions, particularly nations in South Asia, the Middle East, sub-Saharan Africa and North Africa, and the former Soviet Union. India would also be hit especially hard, and there would be dramatic increases in zinc and protein deficiencies in China, Indonesia, Bangladesh, Brazil, Kenya and other emerging economies.
The bottom line is frighteningly clear: Unless governments dramatically step up their emissions-reduction efforts, nutritional deficiencies and their associated burdens are set to become even more severe and widespread. We cannot wait to act any longer.