The trailblazing ecologist and co-founder of the Hubbard Brook Ecosystem Study sits down for a conversation about his life and career.
From humble beginnings growing up on a small farm in Indiana during the Great Depression, Gene E. Likens went on to build a storied career as one of the most pioneering ecologists of our time. Along with F. Herbert Bormann, Noye Johnson, and Robert Pierce, Dr. Likens co-founded the Hubbard Brook Ecosystem Study. He is now president emeritus of the Cary Institute of Ecosystem Studies—which he also founded—and holds faculty positions at the University of Connecticut, Yale, Cornell, Rutgers, and SUNY Albany.
Dr. Likens credits his success to “serendipity,” which he defines as “keeping your eyes, mind, and ears open, and when something interesting or important comes along you jump on it, grab it, and you run with it.”
The Hubbard Brook Research Foundation’s Clara Chaisson sat down with Dr. Likens in 2020 for a conversation about his life and career; how he transferred the skills he learned raising cattle and playing in the baseball rookie leagues to the scientific enterprise; and how the Hubbard Brook Ecosystem Study came to be. We released the interview in three parts during February 2021.
Listen to Dr. Likens in his own words by clicking here, or read a transcript of the interview below.
The four co-founders of the Hubbard Brook Ecosystem Study were you, two other Dartmouth scientists: Herb Bormann and Noye Johnson, and Forest Service scientist Bob Pierce. What do you think each of the four of you brought to the table? What made you work well together as a team?
First of all, we became friends.
I’ve actually written a couple of papers about teamwork. What I think is important in teamwork, and in my looking at the literature and my thinking hard about that topic, the single most important attribute is trust. Without trust, your team just doesn’t function well. By and large, the four of us had complete trust in each other. We worked as a team, we functioned as a team, but we also liked one another. That was important.
Scientifically, Herb was trained as a botanist—a plant ecologist. And Herb was a big thinker. He thought deeply about big problems.
Bob Pierce was trained as a soil scientist. But he had all the administration of the Hubbard Brook project to deal with. Bob took all the grief from the Washington office—from the Forest Service, and others. At that time, there was no great interest in having academic scientists like Noye, Herb, and me working with federal scientists like Bob, and at a federal location like Hubbard Brook. That wasn’t something that was thought highly about; it was thought negatively about. So Bob took all that grief. And he had the kind of personality that was always positive and he found ways to make it work.
Noye was a geologist turned limnologist. He was also very theoretically minded, thought deeply about problems, thought how systems worked and functioned, and was bringing that kind of expertise to our group.
I was trained as a biologist, or aquatic ecologist. But really, as an ecosystem ecologist. I really thought the ecosystem approach was so powerful, but also, largely from my time at the University of Wisconsin, thought about the critical importance of doing experiments at large scales. Experimentation is a very powerful tool in science, and I was convinced that it’s a powerful tool in larger systems—so to experimentally manipulate a stream, or a lake, or a forest, or in our case, a watershed. I was arguing with my colleagues that we really needed to experiment. And that’s what led to our first experiment: the Watershed 2 deforestation experiment.
I think those are the main things that we brought to the team, but I can’t overemphasize trust and friendship.
Since you mentioned the importance of large-scale experiments, let’s talk about the Watershed 2 experiment. It was the first large-scale experiment at Hubbard Brook and is also one of its best known. All of the trees were cut down on the watershed, and the remaining vegetation was treated with herbicide for a period of three years. Can you talk about what it was like to design and execute the experiment at the time? What was novel about it, and how unexpected were the results?
The experiment was discussed extensively by the four of us. Whether we had enough background information, pre-experiment, to evaluate what the experiment might show was a big question. So was the cost of doing the experiment, and the environmental impact. As I said, I aggressively pushed for doing the experiment. Not everybody thought we were ready to do it in our group, but I was successful in my arguments.
We expected that there would be more water coming out the stream, because the vegetation loses a lot of water through evapotranspiration, and transpiration water loss through the leaf surfaces is about 75 percent of evapotranspiration. So we knew that with transpiration being cut off, there was going to be a lot more liquid water because there wouldn’t be the water lost as water vapor. We expected that.
But we didn’t expect any change in chemistry. The forest was cut in the winter of 1965-66. But then when the following spring, and then summer, came, and the waters coming out of the deforested watershed had increasing concentrations of nitrate, we were just totally shocked. And puzzled. None of us were analytical chemists. We weren’t trained to be analytical chemists. We’d been doing a lot of chemistry, but that wasn’t what we were trained to do. So I thought we’d made some error, that we were not measuring something correctly. I attempted to measure the nitrate in every way that I possibly could, including one simple way using a Hach kit. It’s a simple way to measure chemistry in the field by adding reagents. And they all showed that yes, the nitrate was increasing and going to very high levels. So we became convinced that it was a real thing that was happening, but then why? And we didn’t know why.
There was a lot of effort, a lot of joint effort. It looked like—going back to our metaphor—okay, the stream water is changing, something’s wrong with our organism, we’re going to have to go inside and see what’s causing this. And it looked like the soil was where the changes were happening. So we had to go into the soil and do work that we hadn’t done before.
We didn’t know quite how to prevent regrowth of vegetation. This wasn’t a forest timber harvest experiment. This was an experiment—a pure and simple scientific experiment—about deforestation.
We thought, we really need to keep the system from growing back. That first summer, we added an herbicide called bromacil by helicopter. There was a Yale graduate student, Peter Marks, who was beginning to look at pin cherry seeds, because when that first summer came about in the deforested situation, the whole watershed just shot up in pin cherries—kaboom! And then we came along with an herbicide, bromacil, and we killed them all back. And then the next summer, kaboom! Pin cherries again. Then we used a different herbicide, 2,4,5-T, called Agent Orange in Vietnam, and killed them all back. And then the third summer, kaboom! Just wall to wall pin cherries, and we killed them all back. And then in the fourth year, kaboom, all the pin cherries came back again.
Peter Marks’ work showed that there’s a huge population of buried pin cherry seeds in the soil. When there is disturbance, such as clearing the overstory of tree vegetation, some proportion of those pin cherry seeds germinate, but not all. So it’s a very good weedy species. From an evolutionary point of view, if they all germinated and then something came along—like humans with pesticides—then the population would be wiped out. But no, they’re smarter than that: only a proportion germinate. And then next year: another proportion. Then the next year: another proportion, and then the fourth year, another proportion…how long could that go on? And what was triggering just the proportion of that buried seed population, and not all of them?
So lots and lots of really interesting questions—about regeneration, about recovery, about species’ roles in ecosystem function…all of that really interesting stuff. That was the first experiment. And that is the one that is most cited in textbooks. It was a really, really interesting experiment.
It did cause a very large negative reaction from foresters who were thinking that we were doing a forest management experiment about timber harvests, which we were not. So they would say, “Oh no, no. We don’t use herbicides. It doesn’t work that way.” Bob Pierce was getting a lot of pressure to shut us down and throw “those academic scientists” out of there. I’m not exaggerating that. But he fended away that criticism.
It was a very controversial experiment. But a very important and interesting experiment, because we learned so much. With all the criticism about the experiment not being “normal” in terms of forestry practices, we then did other experiments—we strip cut Watershed 4 to try to see if we could do the cutting and have a minimal ecological impact, but still harvest the trees. Watershed 5 was whole tree harvested with large machines. They came in and cut all the vegetation with feller bunchers, and the entire trees were chipped and sent off to a paper factory. So there were experiments that followed that were relevant to normal forestry practices, or proposed forestry practices, but that wasn’t what we did in the first experiment.
It was truly very exciting. And I thought, given the value of experimentation, that doing it on this grand scale just was so important. And we learned so much and it led to so many questions that needed answers.
I think, in all humility, we handled it well. We just kind of kept our heads down and published scientific papers in high-quality peer reviewed journals, and then produced several monographs which allowed us to lay out the full story. I think doing that made the science come shining through.
It was also not long after the Hubbard Brook Ecosystem Study was founded that you discovered acid rain. Can you walk through the process of that discovery a little bit?
Well, actually, that was as it was founded. The very first sample of rainfall that we collected was about 100 times more acidic than we expected that it might be.
Let me back up just a moment. With this idea of using a watershed-ecosystem as a system, we needed to know what all the inputs and outputs for that system were in order to try to understand what was going on inside, and whether we needed to go inside and look.
We wanted to—very carefully, and as quantitatively as possible—measure all the inputs from the atmosphere and losses in stream water for the system. To do that, we needed to know how much rain and snow, all the impurities in rainwater and snow melt, any dry materials that might be coming into the system, and then materials lost in stream water, chemicals lost in stream water, solid eroded materials moved downstream…we had to measure all of that carefully and accurately, in great detail.
We set up this design where we were going to measure precipitation chemistry continuously. The very first sample of rainwater was very acid. We didn’t know why it was acid. We didn’t know how long it might have been acid. We didn’t know whether there was just something unusual about Hubbard Brook rainwater. We didn’t know where it was coming from. We didn’t know any of those answers. So we set about to try to gain those answers and did a lot of research. We didn’t publish the first paper on acid rain until nine years later. That first sample of rainwater was in the summer of 1963, when we started the Hubbard Brook Ecosystem Study, and the first paper came out in 1972. Nine years later.
Then in 1974, Herb and I published a paper in Science talking about how this was probably a regional phenomenon. By then, I had moved to Cornell University, and I’d set up precipitation collecting stations around the Finger Lakes— Cayuga Lake and Seneca Lake, in particular—and found that the acidity there was just about the same as it had been here at Hubbard Brook. That was our first clue—because I changed jobs, serendipity again—that this wasn’t just some unusual little thing in the White Mountains of New Hampshire.
We published that paper in Science, and the day before the paper came out the results appeared on the front page of the New York Times. My life has never been the same since.
I had calls from colleagues all over the world saying, “Likens, what is going on?” We were attributing, without much data, that the source was emissions from the large fossil fuel burning power plants in the Midwest that were used to produce electricity. And that the pollution was coming from the Midwest to the Northeast and falling on the Northeast as acid rain.
It took us that long. I think that’s really important. It took us that long to have enough information to have answered some of those questions before we could publish those first papers. Nine years, and then two years after that.
Some other colleagues, Jim Galloway and Bill Keane at the University of Virginia, and I set up monitoring stations in the most remote places we could find: the southern tip of Chile; the southern tip of Africa; an island in the middle of the Indian Ocean, called Amsterdam Island, it takes a month by ship to get there, there’s no landing strip, at least there wasn’t at that time; a remote site in Australia; a remote site in China, and so forth. We operated those sites for up to 10 years, in order to find out what the pH might have been before it was polluted by humans—because they were remote from human activity. We tried to look at glacial ice and ice cores, and that didn’t give us the answer. So we used those remote sites and collected precipitation to give us the answer that the precipitation pH prior to human activity was probably about 5.1. We didn’t know that; it took all that effort to get that one number. But we needed that number to know how much it had changed in terms of what we were measuring here at Hubbard Brook.
What was the pH of that first sample at Hubbard Brook?
The work that you did on acid rain was instrumental to the Clean Air Act Amendments of 1990. Do you have other examples of how Hubbard Brook research has influenced policy?
I think the deforestation experiment, and then the subsequent clear cutting experiments, did have major implications for policy. In fact, there’s almost no clear cutting done in the Northeast currently. I think no one expected to see the large loss in the vital nutrients from the soil. We were literally running down the system—we were depauperating the vital nutrients from the system by doing the cutting, and we didn’t know that. That was a factor that caught a lot of attention, and I think made people think really seriously all over the world about the effects of clear cutting. There are hydrologic effects, there are chemical effects, there are aesthetic effects…all of those need to be considered if you’re going to harvest. Now, some of the harvesting and cutting and burning is occurring in the Amazon, for example. And that still is relevant to those systems and is very important.
So I think there are two that had major policy implications: the discovery of acid rain and the forest harvesting and deforestation.
I think maybe as important, but more difficult to quantify, is the approach. The thinking at the system level about big systems. You can do very good science in the laboratory, or on small plots. But the large systems are often more relevant to what really is going on in terms of external impacts and the results of those impacts. I think the Hubbard Brook approach to thinking deeply about how those large systems respond to disturbance, that’s another major impact that we had.
There’s a series of pictures taken at the Cooperators’ Meetings at Hubbard Brook every summer, of all the scientists from different institutions and universities who participate in research here. It’s pretty remarkable to see how the community has changed and grown over the years. How would you compare the community now to the early days of the study?
Four of us started the project. And our team was, I think, very tight. There were some rifts now and then, of course. There always are, no matter whether you’re doing science, or sports, or performing arts, or whatever…there are always rifts, aren’t there? But, by and large, we were pretty tight. We all agreed that none of us would have started the Hubbard Brook Ecosystem Study by ourselves. It took the team to start it. It was just too big, and too difficult. But the four of us, and the team that we put together, and the attributes we brought to that team, allowed us to start it.
But there were only four of us. The first annual meeting that we had, I think there were probably six of us or seven of us…maybe 10, at most. So it was a very different kind of interaction, as you can imagine.
As we grew and became 50 of us, say, we always had an annual softball game—maybe that harkens back to my roots as a baseball player, I’m not sure. Herb and I felt that the social side of the project was very important, and you had to nurture that social side. You couldn’t just always do science, and our families needed to be involved. Our families used to all live up here in the summertime. That isn’t the case anymore, but we would rent a place somewhere nearby. That was a big part of the project. The graduate students all lived at what’s now called Pleasant View Farm. And the conversations around the lunch and dinner table were almost always about what you had found that day in your work in the lake, or the stream, or the forest, or wherever. And there were many projects that led to publications as a result of those discussions around the table. I’m very proud of that. I thought that was terrific. And there were some families that developed around the table as well.
Now, there’s maybe 200 at most that come to the Annual Cooperators’ Meeting. With growing into this much larger—and in many ways, more diversified—group, it makes it harder to have that real closeness. We’ve gone to having quarterly meetings of cooperating scientists as one way of trying to keep the communication and the closeness going.
I think it’s possible now with the much larger, more diversified group, more diversified tools that are available, scientific tools that are available, approaches that are available…to do some really good research. And I think that is what is happening. The competitiveness of proposals, like the recent LTER proposal, is a testament to that. There’s all kinds of new technology—just as an example, the technology that’s used by Matt Ayres to observe and follow bat populations over Mirror Lake. We couldn’t begin to think about doing that back in 1963. All of that leads to better opportunities for greater learning.
The Hubbard Brook Ecosystem Study began officially on June 1, 1963. And here we are in January of 2020. I think there’s every reason to expect that this Study will be here for a much longer time. The questions continue to be important and relevant.
And, there are many more stories, topics, and details that couldn’t be covered in this short interview—maybe another time!
This interview has been lightly edited and condensed for clarity.
Funding for this project was provided by a generous donation from Don and Gail Nelson.