Coupled Human and Natural Systems

Coupled human and natural systems (CHANS) are integrated systems in which human activities interact reciprocally with natural systems. As a species, humans’ most successful adaptation has been the ability to manipulate our environment to suit our needs. Though people have always interacted with their environment, the scope of interactions has expanded significantly since the Industrial Revolution, as population, technology, and resource use have increased. Though the term CHANS is new in the 21st century, elements of this approach have been part of geography since its inception. In particular, a focus on humanenvironment relations has been a major theme in geography since at least the 19th century. However, physical geographers have tended to focus on biophysical systems, and human geographers have tended to focus on social systems. CHANS adds several foci to the discussion of humanenvironment relations, including a systems approach, a focus on complexity, and a focus on the reciprocal nature of the relationship between humans and their environment. The interdisciplinary nature of geography has kept itself well poised to address questions regarding the interaction between humans and their environment. Unfortunately, the backlash following the rise and fall of environmental determinism caused geographers to focus on the effects of humans on the environment (environmental geography), at the expense of complex, two-way interactions that may reach from local to global scales. As a result, the varied responses of human societies to environmental change have received less attention, with the exception of hazards research. Recent projects supported by the National Science Foundation, the National Oceanic and Atmospheric Administration, and the National Institutes of Health have focused funding and attention on CHANS, not just in geography but across the sciences, making it an extremely relevant and timely topic.

Since the development of CHANS as an area of study, human-environment relations have been studied in a more holistic and reciprocal fashion to address pressing environmental challenges such as global climate change, land use and cover change, rapid urbanization, exotic species invasions, and population studies. These environmental and associated societal changes have necessitated a sophisticated and complex approach to understanding humans and their environment. Research approaches must be capable of measuring biophysical variables (land cover change, acid rain, greenhouse gases, biodiversity, and forest fragmentation), human variables (socioeconomic processes, qualitative and quantitative aspects of culture and societies, agents, policies, and governments), linkages across human and environmental spheres (resource use, natural hazards, and pollution), and complexity (nonlinearities, thresholds, feedbacks, nested scales, discontinuities, unintended consequences, emergent properties, ecological surprises). In addition, many interactions [Page 600]between humans and their environment transcend single scales, so approaches must be capable of viewing problems from the scale of a single human actor up to the global scale.

The remainder of this entry is devoted to defining the major characteristics of CHANS, an exploration of climate change as a CHANS, and a review of methods and approaches used to study CHANS. The entry concludes with a discussion of recent gains in knowledge from studies of CHANS as well as limitations of CHANS for understanding environmental problems.

...