When many people think about nature, their minds turn to Africa’s vast savannahs, home to elephants and bounding gazelles – not a human around. But that view may be short-sighted, says Anna Shoemaker, a doctoral student in archaeology and ancient history at Uppsala University in Sweden. Humans have been an integral part of most of the world’s natural landscapes for thousands of years, shaping these ecosystems by growing crops, raising livestock and more.
“A lot of people don't realize that the African savannahs you might see in a David Attenborough documentary have been very much impacted by people,” Shoemaker says.
Such long-lasting relationships are the focus of historical ecology, an area of study that explores how humans have interacted with their environments over time. The field pulls together researchers and methods from a wide range of disciplines, including anthropology, archaeology, climatology and ecology. That diversity that can make historical ecology difficult, if not impossible, to define.
To get a better handle on this growing arena of study, Shoemaker and her colleagues set out to discover the issues that historical ecologists think are the most important for them to tackle in coming years. The researchers’ efforts resulted in a list of 50 questions that they published in February in the journal PLOS ONE. The queries range from “What roles have humans played in extinction events and what can we learn about these large and small-scale changes?” to “How has the construction of borders, boundaries, and frontiers affected land use practices?” Shoemaker says the list shows that historical ecologists are interested in solving modern problems like climate change or the loss of biodiversity worldwide.
“I think we’re constantly confronted with the question of what exactly is historical ecology,” she says. “We all agreed that that's OK. We don't need to say exactly what it is because it becomes reduced if you define it too narrowly. It seems like a better approach would be to bring together examples of what historical ecologists are doing and what they’re interested in doing in the future.”
And these researchers are doing a lot, even if their work is hard to define. Carole Crumley, Director of Integrated History and Future of People on Earth (IHOPE), a global research project of Future Earth, says that the strength of the field lies in its nimbleness. Historical ecology, she explains, uses a range of methods to probe the past. That can include techniques from the natural sciences – such as examining environmental records of climate conditions – to strategies taken from the social sciences – such as studying the oral histories of indigenous peoples.
“There’s no place on the planet where we can’t martial some information to be able to cross that human-environment boundary,” says Crumley, who is based at Uppsala University and is a co-author of the new study. The goal is to create “a narrative about what is happening in that particular place as humans have used different management strategies and as the environment has changed on its own and, perhaps, in concert with human activities.”
To capture the priorities of this nimble field, Shoemaker and study co-author Chelsey Armstrong of Simon Fraser University in Canada decided to assemble the questions that most intrigue historical ecologists. Over a two-year period, the students and their colleagues used in-person meetings and an online survey to collect more than 300 questions from researchers and non-researchers in 20 nations. They then whittled the submissions down to a slim 50.
The final list includes a diverse set of questions. Some address practical concerns: “What data standards should we develop to aggregate relevant information in a consolidated open-source database?” Others focus on bigger, philosophical issues: “When are ‘invasive’, ‘native’, and ‘introduced’ useful concepts? Should these terms be applied to humans as well as to other species?”
“I hope that everyone finds something they can completely agree with,” Shoemaker says. “But no doubt this exercise will also generate some controversy.”
Many questions – like “When did human activities begin to have significant impacts/effects on their environments?” – get to what Crumley calls the “baseline problem.” To understand how global challenges like climate change will affect natural landscapes, you first need to know what those landscapes looked like in the past, or what their previous states were. Human activities are a critical part of that baseline.
Shoemaker points to her own doctoral research. She studies the Maasai, a group of livestock herders who live in the Amboseli Basin in present-day Kenya and Tanzania. The Maasai, she says, have altered this savannah ecosystem over hundreds of years. Their cattle, for example, produce a lot of manure. That manure has shifted the distribution of nutrients like nitrogen in the Amboseli Basin, influencing how and where plants grow.
“If you’re looking at model of climate change in Africa, frequently those projections have been based on very little data about how humans have been modifying their landscapes for millennia,” Shoemaker says. “That has very real impact when we’re try to predict how the climate is going to change over the next few centuries if we don't have accurate baseline data.”
Crumley agrees. “One of the things that makes historical ecology so interesting is that it’s not just historical,” she says. “We wish to use the past to help guide ourselves into the future.”
That may be especially true for mitigating climate change, Crumley says. She notes that historical ecologists have made huge strides in understanding how humans have responded to past periods of shifting temperatures and rainfall.
Take the case of Mexico’s Yucatan Peninsula: Research by members of IHOPE’s Maya working group found that people abandoned several city-states in this region after a major drought in the ninth century. The shifting climate, however, was only one reason for the collapse. The researchers concluded that the drought likely would not have done as much damage if Mayan communities had not already over-taxed their surrounding environment, such as by cutting down forests.
When the climate shifts, “what we’re finding out is that there are certain kinds of things that semi- and sub-tropical cities need to be doing, and there are ways that they can make themselves resilient,” Crumley says.
And historical ecology may also help to protect a commodity that many people hold dear: wine. Crumley conducts research in the Burgundy region of France focusing on environmental and management changes over the past three millennia. Today, viticulture plays a strong economic role in the region, an area of rolling hills that is famous for producing Pinot noir and Chardonnay. But Burgundy also has the potential to become much drier in the future because of climate change. That could make it difficult for wine-makers to grow the same grapes they have cultivated over generations. Crumley says that vintners must now study how soil microbes and other organisms, along with farming tools and strategies, have evolved together in Burgundy for more than two thousand years – with an eye to finding ways that growers there can adapt to warmer and less predictable weather, perhaps by adopting new varieties of grapes.
The relationships among “the plants and other living things that are necessary for that very local environment, even if it's a production ecology like a vineyard,” Crumley says, “are going to have to be studied both separately and together to see how some of the things that we love best, like a good glass of wine, can be assured in the future."