Measuring the Anthropocene
At a time of human population explosion and globalized economies, major alterations to earth’s atmosphere, surface waters, land, and even the ground beneath our feet have led to a controversial proposal to rename our current geologic epoch the “Anthropocene,” for the “age of humans.” For researchers, a currently unresolved challenge to this proposal revolves around measurements: is there a measurable human imprint in the geologic record that warrants revising the geologic timeline? In addition to offering a good case study for understanding earth systems interactions, literature on the Anthropocene provides fodder for learning about the effectiveness of different approaches to capture environmental change at different spatial and temporal scales. In a course that I led during the spring of 2015, geography and ecology students at the University of Wisconsin-Madison explored methods for identifying and quantifying the human footprint in biogeochemical, geomorphic, and biophysical processes. Below, Chloe Wardropper and Eric Nost use one method—maps—to investigate some of the tensions in the debate around the Anthropocene.
Four maps to help us think about the “age of humans”
Eric Nost and Chloe Wardropper
As scholars tiptoeing the line between the social and ecological sciences, we believe data and metrics have an important role to play in understanding and communicating human and non-human contributions to global environmental change.1 In fact, maps and the metrics they depict can help strengthen some of the critical points Rob Nixon raises in his piece, “The Anthropocene: Promises and Pitfalls of an Epochal Idea.” In particular, Nixon notes that the Anthropocene cannot be linked to some fundamental feature of the human condition: it is only some societies—namely those which have burned massive quantities of fossil fuels for the past 200 years—which are driving environmental change on a global scale.
Maps have a special power in communicating science. Below, we present two sets of maps that distill new science on the Anthropocene, addressing the questions: Who is responsible? To what extent? And when did it all start? With maps’ power, however, comes their potential to mislead. The maps we present both conceal and reveal uneven or unexpected contributions to the Anthropocene.
First, we present a map that is typical of the standard conversation around the Anthropocene. The representation of data on the map suggests that all humanity is equally implicated.
The map, part of mapping software company ESRI’s Anthropocene Atlas and developed by the Wildlife Conservation Society, categorizes the extent of human modification of the landscape. Green indicates the least modification (e.g., by agriculture, deforestation, urbanization) and red the most. We see that some parts of Africa or Asia are colored similarly to the United States and Europe, suggesting comparable intensities of modification, and ultimately, similar negative environmental changes. The map intends to neutrally depict human modification of the landscape globally, but the use of red shading to indicate extensive management implies that such management is harmful.
We identify three problems here. First, human modification of the environment does not always equate to irreversible ecosystem damage or loss. In many parts of the world, management is not only necessary for ecosystems to exist, but may actually enhance biodiversity and forest protection (e.g., Naughton-Treves et al. 2005). Second, even when land management causes ecosystem degradation, these impacts may not be as spatially specific as the map suggests. Intensive coastal wetland management in places around the world may produce environmental changes that are seen as harmful—such as reductions in storm surge protection and fish habitat—but these may be relatively localized. On the other hand, effects of human activities can in fact have very long-distance consequences. Industrial agriculture in the American Midwest is a major source of nutrients to waters of the Gulf of Mexico, where they produce oxygen-depleted environments and decimate aquatic life. Third, the map does not include political boundaries (it is, after all, the “age of humans” and not the age of nations) yet many readers will associate management level in a space on the map with a particular nation, when the forces responsible for human land use—for example, rainforest loss in Brazil—may originate elsewhere.
How can we improve visualization of uneven anthropogenic contributions? CarbonMap.org shows which countries are most responsible for the release of CO2 from fossil fuel consumption and relates it to other factors such as wealth, population, and vulnerability. This map is interactive, so users are able to manipulate how variables are symbolized and to select new visualizations. The map also demonstrates different ways of accounting for national contributions to climate change. Users can look at current emissions from individual countries, but also “consumption,” a metric that determines overall carbon emissions based on where the goods and services that derive from carbon are actually consumed, rather than where they are produced. This approach differs from others where carbon emissions are usually assigned to where they come out of the smokestack—places like China that produce lots of consumer goods—rather than where the goods produced are actually consumed (U.S. and Europe). Users also can view total historical emissions by country, reminding us that because of the residence time of CO2 in the atmosphere, the Global North’s emissions 150 years ago contribute to the climate change we experience today. In addition to directly showing how different regions are connected, and showing historical trends, this map raises questions about who is responsible for recent climatic warming—often touted as the Anthropocene’s greatest indicator—and where they come from.
An important question in discussions of the Anthropocene is: When did it begin? When can we place “the Golden Spike” that marks the change to a human-dominated planet? Research on landscape change in the Amazon Basin offers an example of these contested questions: Which forces led to present-day conditions? How can we measure them? What role have people played?
The pair of maps below exemplify the disputed timeline and drivers of the Amazonian Anthropocene. Each attempts to situate humans in the historical rainforest, but what “counts” as a human marker is very different, with the result that the first map shows no “significant use” in the region in any historical period, while the second map shows an Amazon Basin littered with human-made mounds and other significant evidence of widespread occupation and modification of the landscape.
In the first map, Erle Ellis and his team used two global land-use models to calculate human ecosystem use over time. Their new model, KK10, was meant to improve upon HYDE, an older model, by incorporating more dynamic assumptions of the relationship between human population change and land use. “Significant” land use was defined as that which covered more than 20 percent of a model grid cell for a given time period. While KK10 results (in the bottom global map) do show more areas of significant historical land use than HYDE’s, both models’ maps show nothing significant in the Amazon basin.
The second map tells a very different story of Amazonian land use. This image, from anthropologist Anna Roosevelt, fills in some of the white space in the Ellis map. Roosevelt and others make the point that the historic forest in the Brazilian Amazon was “a dynamic anthropic formation, not a virgin, natural one.”2 Roosevelt has collected evidence of human impacts through diverse methods: ethnobotany suggests that groupings of trees throughout the forests were put there by humans; archaeological surveys have revealed large mounds and field systems, signs of human settlements and agriculture; and stratigraphy of soil sediments allows for dating of past land uses and the retrieval of artifacts. The environmental impacts of a long human history include the propagation of useful plants, the creation of mounds, the introduction of crops, the creation of trade routes, and the widespread altered soil composition, all of which have implications for how we measure today’s human influence on the Amazon landscape.
The authors of both maps converge on the conclusion that the past 500 years of increased population growth and globalized extractive economies have led to forest cover and biodiversity loss in the region and across the world. The first map, however, fails to acknowledge historic human alterations to the landscape and their legacies.
These examples illustrate how maps and metrics can be used to open up a space for dialogue around identifying and quantifying the “human imprint,” including uneven North-South contributions to the Anthropocene, and disputed measurements of and conceptions of “what counts” towards Anthropogenic global change.
Featured image: Visitors to CarbonMap.org can interactively engage with the map to visualize different measures of carbon emissions, one indicator of the Anthropocene.
Erika Marín-Spiotta is an Associate Professor of Geography and an affiliate of Soil Science and Forest and Wildlife Ecology, the Nelson Institute for Environmental Studies, and the Latin American, Caribbean and Iberian Studies program at UW-Madison. Her research group studies the ecological and biogeochemical effects of landscape disturbance and shifts in biodiversity due to changes in climate or human land use. Contact.
Eric Nost is a PhD student in Geography at UW-Madison. His research describes the tools environmental regulators, non-profit conservationists, and private sector entrepreneurs produce and utilize to confront the effects of climate change. He is currently looking at efforts to restore coastal marshes following the 2010 Deepwater Horizon oil spill in the Gulf of Mexico. Contact.
Chloe Wardropper is a PhD student in Environmental Studies at UW-Madison. Her research focuses on how agricultural conservationists in the American Upper Midwest produce and use measurements to track water quality. Prior to graduate school, she worked as a soil conservationist for the US Department of Agriculture’s Natural Resources Conservation Service. Contact.
We consider “metrics” to be systems of measurement created and used for the purpose of tracking and communicating some phenomenon of interest. In this sense, metrics differ from data; for example, GDP per person—a metric in the carbon map featured here—is a standard measure of economic wealth that can be populated with data from different countries. ↩
Anna C. Roosevelt, “The Amazon and the Anthropocene: 13,000 years of human influence in a tropical rainforest,” Anthropocene 4 (2013): 70. ↩