Coupled human–environment system

A coupled human–environment system (known also as a coupled human and natural system, or CHANS) characterizes the dynamical two-way interactions between human systems (e.g., economic, social, cultural) and natural (e.g., hydrologic, atmospheric, biological, geological) systems.^[1][2] This coupling expresses the idea that the evolution of humans and environmental systems may no longer be treated as individual isolated systems.^[3] The complexity that CHANS research reveals is useful to inform policy decisions regarding environmental sustainability.^[2]

CHANS research is a broad field. Some research programs draw from, and build on, the perspectives developed in trans-disciplinary fields such as human ecology, ecological anthropology, environmental geography, economics, as well as others. In contrast, other research programs, such as Critical Zone^[4] science, aim to develop a more quantitative theoretic framework focusing on the development of analytical and numerical models, by building on theoretical advances in complex adaptive systems, complexity economics, dynamical systems theory, and the earth sciences. To some extent, all CHANS programs recognize the need to move beyond traditional research methods developed in the social and natural sciences, as these are not sufficient to quantify the highly nonlinear dynamics often present in CHANS. Some research into CHANS emulates the more traditional research programs that tended to separate the social from the ecological sciences.^[5][6]

Research

Common Patterns

When social science and natural science research is integrated within CHANS research, some common and distinct patterns emerge that would otherwise be hidden.^[6]

• Reciprocal Effects: These effects provide a similar benefit to both subsystems (both natural and human). ^[6]
• Feedback Loops: A feedback loop emerges when one subsystem (either natural or human) effects and is also affected by the other subsystem. An impact flow is going in and out of both subsystems.^[6]
• Nonlinearity: There can be a nonlinear relationship between two variables within a coupled system. This describes a dynamic whose rate of change does not consistently match the rate of change of the variables.
  • A concept that supports nonlinearity is a threshold. This describes a point of shifting between different states of being. This shift can happen through time or space.^[6]
• Surprises: This pattern describes a literal surprise to researchers. This occurs when something unintended emerges.^[6]
• Legacy Effects: A legacy effect is an impact from a previously coupled system that becomes apparent or influential after some time. Time lags are an important factor here as they describe the time it takes for a coupling to produce an impact.^[6]
• Resilience: Resilience is the ability of a system to continue after a disruption. CHANS research can reveal the different resilience degrees that different systems have.^[6]
• Heterogeneity: This pattern describes the way that different systems vary in their composition and behavior. Even the same system can operate differently in a different time period or space.^[6]

Conceptual Framework

In order to connect location specific CHANS research and accumulate knowledge on coupled systems, multiple research frameworks were created with different scales and complexities in mind.^[7]

1. Intracoupling is for research within one coupled system^[7]
2. Pericoupling is used to analyze two coupled systems that are geographically adjacent from each other.^[7]
3. Telecoupling provides guidance for research on two systems that are spatially distant from each other.^[7]
4. Metacoupling uses all three previous frameworks (intracoupling, pericoupling, and telecoupling) at the same time.^[7]

Framework Elements

CHANS research frameworks use central elements to reveal complex relationships and dynamics within and between systems.^[7]

• Flows: a flow is a transfer between elements within a focal system or from a system to another system. The transfer can include “information, energy, material, organisms, people, and/or capital” (Liu 2017).^[7]
• Agents: an agent is someone or thing, involved with the system, whose decisions affect the strength of interactions within the system or between systems.^[7]
• Causes: The causes are the circumstances that lead to the coupled dynamic either within a system or between systems.^[7]
• Effects: The effects are outcomes of the coupled interactions. Effects integrate socioeconomic with environmental repercussions and can be complex.^[7]
• Spillover: A spillover system is a separate system affected by the interactions within the focal system. Even though there is one focal system for the intracoupling framework, a spillover system might be present.^[7]
• Sending system: a sending system is a system that sends a flow to another system, either adjacent or distant.^[7]
• Receiving system: a receiving system is a system that receives a flow to another system, either adjacent or distant.^[7]

It's important to note that a system can be both sending and receiving in different contexts for different research questions.^[7]

Research Examples

CHANS research is broad and the frameworks can be applied to many different contexts and research questions. Below are a few examples to demonstrate some uses of the CHANS concepts.

Sarkar, Debnath, and Reang (2021) used a coupled human and environmental systems framework to understand the complex dynamic between the socioeconomic and environmental impacts from government responses to the Covid-19 Pandemic. Due to the scale of the pandemic, the entire world system was affected. The authors argued that understanding the shifts within the larger system would help inform policy decisions in local and regionally specific systems. Conducting a literature review, the researchers analyzed the effects of lockdown on the following: economic recession, poverty, transportation, waste generation, social activities, workplaces, environmental noise, biodiversity, and education. They created a model (below) to demonstrate how these factors were influenced in a positive or negative way including flow directions and feedback loops.^[8]

Paudel et al. (2025) conducted a CHANS study to understand the nexus between farmland abandonment, migration and wildlife encroachment in three mountain regions in Karnali River Basin, Nepal. Agriculture in Nepal’s highlands regions provide multiple measures of environmental health, an income and livelihood for residents, and resources (food) for the county. Despite this, farmland abandonment is increasing. The purpose of this paper is to investigate the influence of migration and wildlife encroachment on farmland abandonment to inform Nepalese policy and provide a reference point for other areas experiencing similar issues. Questionnaire data was taken from 169 households and combined with known geographic farmland abandonment data. It was concluded that migration and wildlife encroachment are significant triggering factors that lead to farmland abandonment. Other factors that contribute are ones known to make agriculture difficult such as access to resources including water and labor.^[9]

History

The phrase "coupled human–environment systems" appears in the earlier literature (dating back to 1999) noting that social and natural systems are inseparable.^[10][11] "In 2007 a formal standing program in Dynamics of Coupled Natural and Human Systems was created by the U.S. National Science Foundation."^[2]: 218 Research into CHANS is increasing in frequency in scientific literature concerning the sustainability and conservation of ecosystems and society.^[12]

Funding by the National Science Foundation to study "Dynamics of Coupled Natural and Human Systems" occurred from 2001-2005 as a part of a "special competition" within the "Biocomplexity in the environment" program, and in 2007 gained formal standing.^[13][14]

Bibliography

• W.C. Clark, B. L. Turner, R. W. Kates, J. Richards, J. T. Mathews, and W. Meyer, eds. The Earth as Transformed by Human Action. (Cambridge, UK: Cambridge University Press, 1990).
• Turner, B. L; Matson, Pamela A; McCarthy, James J; Corell, Robert W; Christensen, Lindsey; Eckley, Noelle; Hovelsrud-Broda, Grete K; Kasperson, Jeanne X; Kasperson, Roger E; Luers, Amy; Martello, Marybeth L; Mathiesen, Svein; Naylor, Rosamond; Polsky, Colin; Pulsipher, Alexander; Schiller, Andrew; Selin, Henrik; Tyler, Nicholas (2003). "Illustrating the coupled human–environment system for vulnerability analysis: Three case studies". Proceedings of the National Academy of Sciences. 100 (14): 8080–5. Bibcode:2003PNAS..100.8080T. doi:10.1073/pnas.1231334100. JSTOR 3139883. PMC 166185. PMID 12815106.
• Eric Sheppard and Robert B. McMaster, eds. Scale and Geographic Inquiry: Nature, Society, and Method (see especially "Crossing the Divide: Linking Global and Local Scales in Human–Environment Systems" by William E. Easterling and Colin Polsky) (Blackwell Publishing, January 1, 2004)

See also

• Human ecology
• Conservation medicine
• Deep ecology
• Environmental factor – examples of coupled systems