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Integrated Assessment Modeling

Integrated assessment modeling (IAM) is a tool that integrates knowledge from two or more domains into a single framework. In general, IAM brings a systems-based approach to decision-making that takes into account the three pillars of sustainability. Integration can occur at many different levels: some integrative models are limited to water quality or hydrology while other models integrate two or more environmental components (e.g., soil and water or water and biology). For example, the Framework for Risk Analysis in Multimedia Environmental Systems (FRAMES) represents a series of fate and transport models, which are integrated such that the outputs of one model feed seamlessly as inputs into one or more models in the framework. Still other IAMs integrate multiple decision criteria, which can permit stakeholders to consider all economic, social, and environmental criteria they can identify and obtain data for decision analysis. The integration of fate and transport (environmental) models with social and economic models and then the integration of these three components in multi-criteria decision approaches is yet another example of integration. The overarching goal of IAM is to ensure that policy decisions are informed by a thorough understanding of the interdependencies and interactions within a system’s economic, environmental and social spheres. Through IAM, policymakers and stakeholders can gain better insight into the suite of impacts of policy interventions, which is expected to lead to more sustainable outcomes. In a broader context, EPA defines integrated modeling as: [27] “…a systems analysis-based approach to environmental assessment. It includes a set of interdependent science based components (models, data, and assessment methods) that together form the basis for constructing an appropriate modeling system. The constructed modeling system is capable of simulating the environmental stressor-response relationships relevant to a well specified problem statement.”

Integrated Assessment Modeling

How can Integrated Assessment Modeling contribute to Sustainability?

Many subsystem IAMs exist--for example, water models that use point and non-point sources to predict water chemistry or air quality models that predict a suite of pollutant concentrations based on emissions inputs from point and non-point sources. However, system level IAMs that integrate across all media (air, water, and land) and then integrate with decision and uncertainty analyses capabilities are still being developed. IAM can play an important role in the scoping and options identification stage because it allows for the comparison of different scenarios by simulating their effects on social, economic, and environmental conditions.[192] In addition, the collaborative process used to develop the models assists in the identification and involvement of key stakeholders, and brings to light indicators that might otherwise have been overlooked or miss-valued. Finally, IAM can facilitate the stakeholder discussion in difficult tradeoff/synergy analysis and evaluation of outcomes of potential decision alternatives.

What are the main steps in Integrated Assessment Modeling?

There is no standard approach for conducting an integrated assessment model. Generally, an IAM would progress through the following steps:

  • Step 1—develop a qualitative, conceptual model that characterizes the system being modeled and outlines the key relationships between its physical, socioeconomic and institutional boundaries. This step should be done through close stakeholder engagement and collaboration so that the characteristics of the system are captured in the model;
  • Step 2—gather data to bound the system and assign quantitative values to the key relationships; and,
  • Step 3—develop the computational model reflecting these quantitative relationships. The model should allow users to explore the complexities of the system by running different scenarios, changing model inputs as new data and information become available, and analyzing tradeoffs and outcomes of specific interventions.[20]

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What are the strengths and limits of Integrated Assessment Modeling in a sustainability context?

IAM is a useful tool for supporting environmental decision-making. Although there are many possible levels of integration and it is not always clear at which level a particular IAM is being used, IAMs generally are not yet commonly used for policy analysis in the US. In a limited sense (i.e., entire economic, social, and environmental system is not being modeled), IAMs have been successfully applied internationally to address a variety of environmental issues, including climate change, air quality, water quality and biodiversity.[27] A significant barrier to the widespread implementation of IAM is that there are no agreed upon standards for how to approach and implement integrated assessment.[27] A major contributor to this barrier is that many of these models are designed with implicit contexts, which may not be obvious to stakeholders who themselves may not have had the opportunity to completely understand their own needs/contexts. As a result, opportunities for collaboration between modelers are limited, and it is difficult to build upon knowledge gained by past examples. A significant hurdle to integrated modeling into day-to-day practices has been stove-piping of research and modeling activities. Stove-piping is a systemic challenge that hinders effective and meaningful inter-office or inter-Agency collaboration.

Another major challenge inherent to IAM is the difficulty of integrating economic models with biophysical models.[193] Due to the complexity of economic, social, and environmental systems, the models inevitably contain a large degree of uncertainty; therefore, IAM should not be used to predict precise outputs of specific policies or actions, but rather to facilitate a better understanding of the directions and magnitudes of change that result from such interventions.[194] Learning how to use IAMs to teach stakeholders about the relative changes (rather than absolute predictions) in the economic, social, and environmental system will strengthen the acceptances of IAMs.

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How is Integrated Assessment Modeling used to support EPA decision-making?

Examples of integrated assessment models developed within the Agency span a variety of program offices and study areas. For example, in 1996, the Office of Solid Waste and Office of Research and Development partnered to develop an integrated modeling system known as FRAMES (Framework for Risk Analysis in Multi-media Environmental Systems) to serve the regulatory assessment needs of the Hazardous Waste Identification Rule. [27, 195] EPA Region 3 demonstrated how it could use an integrated assessment across multiple environmental media to ascertain regional environmental conditions, and inform program priorities and resource allocation for fiscal year 2010.[196] EPA’s Narragansett Bay Sustainability Pilot Project developed an integrated assessment model to assess environmental, economic, and social issues at a watershed scale.[197] The Chesapeake Bay Program (CBP) is an EPA-managed program that has produced a suite of sophisticated and highly respected integrated assessment models Exit EPA Disclaimer over the past 20 to 30 years. The result of collaboration with federal, state, academic and private partners, the current CBP models include models of airsheds, watersheds, and climate change impacts. For the CBP, one of the results of the integrated modeling process has been improved dialog among decision-makers and a better overall understanding of the concerns of stakeholders from across the six state region of the Chesapeake Bay watershed.[27, 198]

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Where can I find more about Integrated Assessment Modeling?

  • In 2000, EPA established a council of EPA senior managers, modelers and scientists, the Council for Regulatory Environmental Modeling (CREM) to “promote consistency and consensus among environmental model developers and users.”[199] The council’s website contains a wealth of information on integrated assessment modeling, including training and guidance documents, a database of the Agency’s models, as well as links to examples of models within the EPA community.
  • The EPA published a white paper (PDF) (69 pp, 3MB) on integrated assessment modeling. [27]
  • EPA uses a variety of economic models and analytical tools when conducting climate economic analyses; including integrated assessment models.
  • EPA’s Framework for Risk Analysis of Multi-Media Environmental Systems (FRAMES)

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Illustrative Approaches Applying Integrated Assessment Modeling

  • San Luis Basin Pilot: Regional Sustainable Environmental Management

    Source: EPA Office of Research and Development[259]
    Suite of sustainability tools: environmental footprint analysis; integrated assessment modeling
    EPA developed the San Luis Basin Pilot Project to measure the movement towards or away from sustainability at the regional level.[259] This sustainable environmental management effort sought to formulate and test effective long-term management strategies on a regional scale by measuring fundamental aspects of a system that characterize sustainability.

    In December 2006, EPA Region 8 in Denver, CO requested that EPA ORD provide assistance with sustainable land management in the San Luis Basin. This region, which includes the counties of Alamosa, Conejos, Costilla, Hinsdale, Mineral, Rio Grande, and Saguache, was growing in population, had scarce water resources, and was experiencing the effects of climate change. This project fostered collaboration between EPA ORD, EPA Region 8, National Park Service, US Department of Agriculture’s Forest Service, US Fish and Wildlife Service, Bureau of Land Management, local environmental organizations, and local communities.

    The multidisciplinary team was asked to establish and analyze a group of science-based metrics that would measure sustainability over a 26-year period using publicly available databases. Three fundamental aspects of a system that characterize sustainability were measured: its inherent order, the energy required to maintain that order, and the human impacts on the system. Four metrics were chosen to measure and characterize these aspects of the regional system:

    • Fisher Information, to estimate dynamic order or organization
    • Ecological Footprint, to characterize the environmental burden
    • Energy Budget, to compute the flow and conservation of energy resources through the system
    • Green Net Regional Product, to determine regional economic health.

    The results of the metrics reveal how each part of the system is moving toward or away from sustainability. This methodology can be used to monitor the overall stability of a system over time.

    This methodology proves to be an accessible and useful method for measuring regional sustainability. Since the initiation of the pilot, the project organizers have hosted a series of public meetings with local stakeholder groups and community members to actively involve them in the determination of the metric methodology. Such information will help planners and community members move toward a more sustainable path with their future decision-making efforts for their region.

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