The Anthropocene: Humanity’s age of change

A Thought Leader Series Piece

Nancy Grimm TLS

By Nancy Grimm

Note: Senior Sustainability Scientist Nancy Grimm recently guest edited and authored two articles in the November 2013 edition of the Ecological Society of America’s Frontiers in Ecology and the Environment, highlighting current and future implications of climate change for ecosystems. The issue includes work from over 50 scientists who contributed to this part of the U.S. National Climate Assessment.

In 2014, the United States will release its third National Climate Assessment (NCA) based on the efforts of hundreds of scientists and practitioners over a three-year period. During 2011-2012, I served as a senior scientist for the NCA in Washington, DC. I worked with teams who assessed the current and future impacts of human-caused climate change on biogeochemical cycles, ecosystems, and urban systems. These topics are highly interrelated and solutions to climate and global challenges must recognize their interdependence. A sustainable future depends on rethinking the extraction and recycling of Earth’s mineral resources, reducing impacts on ecosystems, and investing in building sustainable cities.

Why climate is changing: biogeochemical cycles

Human activities, especially since the Industrial Revolution, have changed our world so much that some scientists believe we are living in a new geologic era: the Anthropocene. Accelerating changes in all kinds of human activities—such as automobile use, fast food restaurants, direct foreign investments, and paper or wood consumption—are mirrored by ever-changing environmental conditions like increasing surface temperature, deforestation, and ozone depletion.

Among these environmental changes, the rise of carbon dioxide in the atmosphere, a direct consequence of our accelerating fossil fuel burning, is the most important driver of changes that we are already seeing in our climate system. Thus, it is essentially a major, human-caused disruption in the carbon cycle that has created one of our greatest challenges for sustainability.

Now in the Anthropocene, we also are mobilizing more nitrogen, phosphorus, and metals from the Earth’s crust and atmosphere, contributing not only to climate change but to other problems such as air, water, and soil pollution and excess fertilization of some land- and sea-based ecosystems. Alteration of these biogeochemical cycles feeds back to climate and paradoxically, can result in shortages through inequitable extraction and distributions of these nutrient and mineral resources worldwide.

Reduce impacts on ecosystems; reduce impacts on us

Ecosystems capture and transform energy and cycle materials. They provide the "stage" for individual plants, animals, and microorganisms to interact and go through their life stages. Some of the energy capture, material cycling, or life processes of individual species end up benefiting people, although that is not their so-called purpose. We call these benefits ecosystem services. The growth of commercially important fish is one example; water purification by rivers is another.

Major impacts on species from climate change and other stressors of the Anthropocene—including changes in the timing of major life events like flowering, insect emergence, shifts in ranges, and even extinctions—have already begun and are expected to continue unabated unless we reduce greenhouse gas emissions. When species’ loss and shifts are accompanied by physical changes in climate and increased extreme events, dramatic consequences in ecosystem services such as crop or forest products provisions, pollutant removal, and storm surge protection can occur.

Shifts and changes in species and ecosystems have obvious consequences for people, and experience is showing that promoting ecosystem integrity can reduce those impacts. Avoiding economic losses or food shortages as a result of reduced agricultural productivity and fisheries decline will require society to be nimble in management practices. The human and financial costs associated with the impacts of extreme weather events are well documented. Superstorm Sandy reminded us how intact oyster reefs and sand dunes provide ecosystem protection and reduced property loss.

Of course, causes are not always clearly assignable to climate change. In the Anthropocene, multiple interacting stressors are affecting people and ecosystems. One is of our own making: the massive human migration to cities that transformed the more developed world in the past century and that is now transforming the developing world even more rapidly.

Why cities?

How cities will be affected by and respond to a changing climate are questions of primary importance to society. But cities also are important drivers of environmental changes locally, nationally, and globally. As concentrated centers of human lives and activity, cities draw upon the non-urban world for resources to build infrastructure, support consumption, and drive production. Cities collectively influence global-scale climate trends by contributing up to 70 percent of annual global greenhouse gas emissions. So it is logical to suggest that we need a better understanding of how urban ecosystems interact with the carbon cycle in order to develop strategies that reduce emissions.

As the global population shifts to urban living, society’s ability to provide for basic human needs is an issue of utmost importance. When compounded with climate change, the urgent need to find solutions comes into greater focus.

For example, increasing frequency and severity of extreme events are an especially high risk for cities where housing, transportation, energy generation, and other sectors are often concentrated. Even the location of many cities—on coasts, along large rivers, and in the drought-prone interior U.S. West—increases their vulnerability. But so far, we have mostly relied on historical data to evaluate risk and a "hard" engineered infrastructure (like a levee or a sea wall) to "protect" us from climate-related extremes. In the changing conditions of the Anthropocene, a "new normal" demands a new approach.

City governments are keenly aware of these issues. Indeed, climate-change mitigation and adaptation actions, or at least planning, are taking place to a greater extent at this level of government than at state or national levels. After all, cities are places where people are concentrated, and with them, a great potential for innovation and solutions.

In my view, we need to stop thinking of our inventions and our built environment as a replacement for nature’s benefits or as a way to push nature out of our lives. Instead, when we design our cities, we must develop complementary ecological and engineered infrastructure that will not draw excessively on other ecosystems nor degrade the environment of downstream ecosystems or future generations.

In the Anthropocene, the new city for the new normal will be a flexible, resilient, diverse nesting place for humanity.

About the author: Nancy Grimm is a professor in the School of Life Sciences and has been director of the Institute’s NSF-funded Central Arizona-Phoenix Long-Term Ecological Research (CAP LTER) project since its inception in 1997. As the director of CAP LTER, Grimm collaborates with hydrologists, engineers, geologists, chemists, sociologists, and others to study the complex urban social-technological-ecological system of metro Phoenix. Her own research focuses on climate variability impacts on biogeochemical processes in urban, desert, and stream ecosystems. She received her doctoral and master’s degrees in zoology from Arizona State University and her bachelor’s degree in natural science from Hampshire College.