Jacquelyn Gill, paleobiologist

We can learn a lot about our environmental fate by looking back at the era of mammoths and warm forests, says this socially active scientist. Interview by Sarah Derouin

May 01, 2017

Jacquelyn Gill. Credit: Jeremy Parker

What do you study when everything interests you? Jacquelyn Gill, an assistant professor at the University of Maine, found that her love of the environment, history and anthropology were a perfect fit for studying paleobiology.

Gill is a true interdisciplinary scientist, researching how ecosystems have changed over the last 2 million years using the fossil record and modern field experiments. She concentrates on the Quaternary Period, which is a time period of alternating ice ages and subsequent warm spells. Gill compares ancient, relatively fast shifts in climate to what we are currently experiencing with climate change.

Gill wants to better understand what happens to ecosystems when the climate swings from an ice age to a warm period—what paleobiologists call biotic upheavals. In particular, she wants to know how climate change and the extinction of megafauna—think mammoths and mastodons—affected "novel" forests unique to that specific time and climate. She uses her research about ancient changes to help inform modern ecology and conservation management practices for the next 100 years.

An advocate for women and diversity in STEM, she is active on social media, blogging at The Contemplative Mammoth and co-hosting on Our Warm Regards, a podcast about our warming planet.

In a talk at the February 2017 meeting of the American Association for the Advancement of Science in Boston, Gill presented her research on what happens to forests after the extinction of mammoths. She met afterwards with SciCom’s Sarah Derouin to take a look back in time at the surprising interconnectedness of species and how mammoth poop can help reconstruct an ecosystem.

How can we use the past 2 million years, the Quaternary Period, as an analog of what might be coming with climate change?

I like to call them natural experiments: events that happened in nature that are recorded in the geologic record. We can look to those as good analogs for what’s coming—for example, climate change, especially really rapid climate change like the end of the last Ice Age. We’re looking at the same degree of warming that we’re going to experience in the next century. The starting and ending point [temperatures] will just be different.

Can you give some examples of what problems climate change might cause? Or how it caused problems in the past?

I mostly focus on how climate change affects biodiversity. One good question is, when does climate change cause extinction? Is it just that things get too hot in the landscape and die? Or is it that their food or water goes away?

When we think about how species respond to climate change, we usually say they move, they adapt, or they die. We see examples of death and extinction in the fossil record and have an understanding when that happens and why. With adaptation, there’s a question about how quickly can organisms adapt or evolve. That’s not something we can answer easily in the fossil record on these time scales. The question in my field is: How quickly can species move on a landscape? And I’m not just talking about how quickly can a bison run across the plains.

Given how much warming we expect in the next 100 years, are there any analogs from the past that can tell us how well trees can disperse across the landscape?

I never really thought about how losing megafauna can cause ripples of ecosystem collapse. Can you explain what you’re seeing when you have megafauna extinctions?

This is a new field of research. For decades, people spent time arguing about why they went extinct, and nobody paid attention to what happened after. For me, the question of why they went extinct is not as interesting. What I want to know is: What happens when you lose big animals?

We like to call these big herbivores “keystone species.” It comes from the idea of an arch—you build an arch out of stones and that block at the top is called the keystone. If you take it out, the whole system falls apart. Similarly, if you take the keystone species out of an ecosystem, that ecosystem falls apart. They are creating habitat by eating plants, by knocking trees down, by eating so much vegetation that fires don’t get too strong, which turns out to be really important in African savannas today.

You ultimately get a lot of biodiversity when you have big herbivores, which isn’t intuitive because you think big animals eat a lot and there’s going be [fewer] plants. We’re just starting to understand what megafauna losses mean for plants. There’s been some really exciting research that’s starting to suggest just how important these animals are and just how much we lost when we lost them.

"The idea of saving a million species in the next century that could be threatened because of climate change is so daunting."

What was your original research question?

These novel forests [unique forest ecosystems with no modern comparison]—we’ve known about them for decades in the paleorecord. People had always thought they were just a response to climate, with different temperature and precipitation than we have now.

I went into my graduate work thinking, well, something else happens around there at this time. I approached my graduate advisor and said, “Hey, have you ever thought about looking at megafauna?” and he said, “We can’t, because it’s too hard to compare fossil bones to fossil plants: they’re not found in the same places, there’s not a lot of the bones…”

I read this paper, and instead of using fossil bones, scientists looked at spores from a fungus that has to go through herbivores and ends up in their poop. The spores end up in the lakes along with pollen, so they should be in the pollen cores. Then we can say, “Here’s where the megafauna are. Let’s see what the vegetation does.”

So it was really the spores in herbivores’ poop that gave you the clue?

Yes. We can’t measure the plants and animals [directly], so we use something that can approximate for them—in this case, the pollens from the plants and the fungus that relies on these animals’ poop to survive. We’re looking at two different proxies. It’s like an apples-to-apples comparison. When we lose the animals, we lose the poop and we lose the habitat for the fungus.

What did you find?

The order of events was the opposite of what I expected. I thought we’d have megafauna and these unusual forests, and then when one left we’d lose the other one. And it turns out, we had megafauna, they died, and then the forests went wonky.

How are you hoping your research will get used?

I would like to see people look at the paleorecord to constrain our worry. There’s value in learning from history, or even pre-history. We can better protect our contemporary biodiversity if we pay a little attention to the recent past. We can give good action items for conservation. We can say, “We know from this record that losing big animals makes plants less resilient to climate change, so let’s protect our musk oxen.” It gives us something to do—and it’s not just because we like musk oxen or they’re cute, but they’re actually going to help a lot of other species. They’re functional. Or we know this species of tree is actually really resilient to climate change. This high alpine forest has not done anything in 10,000 years, it’s exactly the same—it’s a nice story of resilience dealing with 500-year droughts. So that’s a success story, and we don’t have to worry about it.

One of the things that came up in your session at AAAS is the fine line between paralyzing fear and using science to move forward. People are depressed when they hear about climate change and extinctions and don’t know what to do. What’s your take on that?

The idea of saving a million species in the next century that could be threatened because of climate change—and that’s a number that gets thrown around—is so daunting. What’s nice about conservation paleobiology is that, in our case, the casualty lists were already written. So we’re not adding to them.

If we can use the past to inform us, it’s a sort of triage question. But instead of triage in terms of, “We’re just going to let you go,” it’s triage in terms of, “You’re going to be fine so we’re going to focus our effort over here.” I would like people to adopt that idea a little more. We can give good action items for conservation.

Can you give an example?

This is going to be super controversial, but when it comes to climate change, people are really worried about a concept called phenological mismatch: As they respond uniquely to climate change, will pollinator and plant relationships be disrupted?

I have a hard time getting worried about that when we know that probably happened in the paleorecord a lot. As species responded in their own unique way to climate change—and we know species moved across the landscape after the ice melted, often pretty rapidly—we didn’t necessarily see this lock-step relationship. There was probably a lot of switching between a pollinator and its host. I just have a hard time thinking that’s going to cause a lot of extinctions, based on the paleorecord.

You mentioned in your talk that everything that’s alive in the environment today has made it through at least one climate transition.

Right. But having said that, we’re kicking the earth out of that range of change they’ve gone through. Things can adapt quickly, but when we start reaching the limits of what these species have experienced, in terms of recent evolution history, we might start getting worried.

For example, we often worry about the tundra because it’s warming really fast, but maybe we should be worrying more about the tropics because they’re already close to their maximum limits in terms of temperature. It can’t get much hotter. So it might cause us to reframe where we put our efforts. I’d like to see more people using that long-term perspective to make conservation decisions.

Instead of decadal? Or yearly?

Yeah, like, “Here’s my three-year study on a warming grassland and I’m going to extrapolate from there.”

There’s value in learning from history, or even pre-history. And whether we’re looking at the losses or the ice age survivors, they have lessons for us. We can better protect our contemporary biodiversity if we pay a little attention to the recent past.


© 2017 Sarah Derouin. A complete record of Sarah’s stories exists at www.sarahderouin.com.