Researchers are exploring the dynamic interrelationships between natural ecosystems and air quality—advancing our understanding of how air pollution can negatively impact forests, lakes, and other natural ecosystems and the benefits they provide.

A robust body of research links the negative impacts that air pollution can have on natural ecosystems. For example: pollutants such as sulfur can lead to excess levels of acid in lakes and streams, and damage trees and forest soils; atmospheric nitrogen can reduce the biodiversity of plant communities and harm fish and other aquatic life; ozone damages tree leaves and negatively affects scenic vistas in protected natural areas; mercury and other heavy metal compounds emitted as exhaust from fuel combustion can eventually accumulate in plants and animals, some of which are consumed by people.

EPA research on the environmental impacts of air quality supports the Secondary National Ambient Air Quality Standards (NAAQS), set under the Clean Air Act to protect animals, soil, crops, vegetation, water and buildings from the impacts of air pollution. (The Primary NAAQS protect public welfare.) To support the review of the NAAQS, EPA prepares Integrated Science Assessments (ISAs), which contain a concise evaluation and synthesis of the most policy-relevant science for reviewing the NAAQS.

The research improves the understanding of the pathways and magnitude of ecosystem exposure to nitrogen and sulfur; assesses the impacts of excessive atmospheric nitrogen deposition on ecosystems; identifies how wildfires impact ecosystems; and evaluates the environmental impacts of the nation’s mix of energy use, including air and water quality, among other activities.

Atmospheric Nitrogen and Sulfur Deposition and Impacts on Ecosystems

Atmospheric deposition of nitrogen and sulfur resulting from air pollution is a major stressor to natural ecosystems, often leading to acidification and eutrophication of both terrestrial and aquatic ecosystems. EPA, states and tribes need information on the impact of atmospheric deposition of nitrogen on the nation’s rivers, lakes, and estuaries to understand ecosystem exposure and response to nutrients and acidity, and manage resources impacted by deposition.

Although the U.S. has seen large improvements in air quality and reductions in deposition since the enactment of the Clean Air Act Amendments of 1990, there are still many regions where the critical load for a variety of ecological end points is exceeded. The critical load is the amount of deposition below which harmful effects do not occur, according to present knowledge.

As understanding of atmospheric deposition and critical loads evolves, measurement methods, models, and assessment tools must incorporate the most up to date science to support the NAAQS review and provide managers with the best available information for decision making. 

The research goals include:

• Advancing measurement and modeling capabilities to understand ecosystem exposure from deposition of nitrogen.
• Providing the science to improve estimates of critical loads and impacts from atmospheric deposition on ecosystems.
• Supporting the EPA’s Critical Loads Mapper web application and the National Critical Loads Database.

Related Resources:

• White Paper on Science needs for continued development of total nitrogen deposition budgets in the United States Exit

• Critical Loads Mapper Tool (CL Mapper)
  The CL Mapper is a joint project supported by EPA, the U.S. Department of Agriculture, the U.S. Forest Service, and the U.S. National Park Service to make information more accessible on effects from atmospheric nitrogen and sulfur deposition.

• Advances in Critical Load Science and the Impacts From Nitrogen Deposition and Climate Change on Forest Biodiversity and Ecosystem Services 

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Energy and the Impacts on Ecosystems and the Environment

The energy choices we make as a society influence our air and water quality and water supply, among other impacts. In an evolving energy landscape, how do we make sustainable energy decisions that balance environmental, economic, and societal objectives? Researchers are studying the potential health and environmental impacts of using different energy sources.

The research goals include the following:

• Evaluate the impacts of changes in the energy system to climate and air quality.
• Assess the impacts of air quality on biomass as an energy source.
• Identify and analyze models and approaches to assist with understanding impacts of emerging energy technologies and resources.

The research will improve our Nation’s ability to evaluate the potential costs, benefits and risks associated with production and use of emerging energy resources.

Related resourcce: Energy and the Environment Research

Science Tools 

• EPA EnviroAtlas Benefit Category: Clean Air
  EnviroAtlas provides geospatial data, easy-to-use tools, and other resources related to ecosystem services, including how they contribute to clean air.
• City-based Optimization Model for Energy Technologies (COMET)
  COMET provides local and regional authorities, especially in major cities, a way to systematically evaluate multiple potential strategies for achieving economic and environmental goals related to energy needs.
• GLIMPSE
  GLIMPSE is a computational framework for supporting state-level environmental and energy planning.
• EPAUS9rT
  An Energy Systems Database for use with the TIMES Model, EPAUS9rT is a fully transparent, publicly available database that represents greenhouse gas and air pollutant emissions. Researchers use the modeling platform to analyze the environmental impacts of potential changes in the way the U.S. produces and uses energy.
• SMaRT Search
  SMaRT Search is an inventory of freely available models, tools, and databases from EPA's Office of Research and Development.

Related Resources 

• Report on the Environment: Ecological Condition Topic
  The Report includes critical ecosystem characteristics that are affected simultaneously by stressors in multiple media.
• EPA Ecosystem Research 
• Climate Change Research
• Integrated Science Assessments (ISAs)
  Integrated Science Assessments (ISA) are reports that represent a concise evaluation and synthesis of the most policy-relevant science for reviewing the National Ambient Air Quality Standards (NAAQS).
• National Ambient Air Quality Standards (NAAQS)
  The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for wide-spread pollutants from numerous and diverse sources considered harmful to public health and the environment.
• EPA Science Matters: Wildfire Research 
• EPA Science Matters: Air Research