Introduction

Because there are so many types of environmental problems, there are many projects designed to address these concerns and likewise many methods to assess them. Collectively, the methods for assessing environmental impacts and the uses of natural resources (both living and non-living) are called environmental performance indicators. Generally, performance indicators are used in fields ranging from marketing and economics to education and legal studies to measure a project’s progress and/or success. Some indicators can evaluate the actions of a single individual, while others are broad enough to reflect the efforts of entire nations or even the globe. Specifically, environmental performance indicators (EPIs) examine environmental issues such as pollution, biodiversity, climate, energy, erosion, ecosystem services, environmental education, and many others. Without these EPIs, the success or failure of even the most well-intentioned actions can remain hidden.

Because of the diversity of observational scales and topics, not all EPIs are useful in all scenarios. However, all EPIs should indicate whether the state of the environment is changed positively or negatively, and they should provide a measure of that change. An EPI is also more meaningful if it can quantify the results to facilitate comparison between different types of activities. But before an EPI is selected, targets and baselines must be clearly articulated. Vague targets are difficult to evaluate, and the results may be uninformative. The EPI selected must use indicators that are definitively linked to the targets, are reliable and repeatable, and can be generated in a cost and time efficient manner.

To evaluate an activity, an EPI needs to include information from up to four types of indicators: inputs, outputs, outcomes, and impacts. Inputs are the natural resources or ecosystem services being used. Outputs are the goods or services that result from that activity. While outputs can often be quantified, outcomes typically cannot be and instead represent environmental, social, and economic dimensions of well-being. In some cases it is useful to think of outcomes as why an output was sought; however, outcomes can also be unanticipated or unwanted effects of an output. Impacts refer to the longer-term and more extensive results of the outcomes and outputs, and can include the interaction of the latter two indicators.

For example, coal can be an input for an electricity-generating plant because we need the output (electricity) to turn on lights in our homes. Two outcomes would include the ability to read at night because of the electricity and the visible air pollution from the power plant smoke stacks. An impact of being able to read more can be a better-educated person, while an impact of the greenhouse gas emissions from burning coal is increased potential for global climate change. This is a simplistic example which does not include the majority of relevant indicators (inputs, outputs, outcomes, and impacts) for a complete and more meaningful analysis.

We can then evaluate each of the indicators. Is the input (coal) an appropriate choice? Is there enough for the practice of burning it to continue? Are there problems, such as political instability that could interrupt continued access? Does the output (electricity) sufficiently address the problem (in this case, energy for turning on lights)? Is the output produced and delivered in a timely manner? Is it provided to the appropriate consumers and in a quantity that is large enough? Does the output create the desired outcome (being able to read at night)? Does it also result in unwanted outcomes (air pollution)? Do the outcomes result in long-term impacts (such as life-long learning or decade-long climate change) that are widespread?

Note that outcomes and impacts can be either positive or negative. The strength of an EPI lies in its ability to look at the bigger picture and include multiple variables – particularly with regard to the impacts. However, whether an impact is considered meaningful depends on the values and perspectives of the individuals and groups involved. Judgment plays a role because of the difficulty in comparing completely different impacts. How do you compare life-long learning and climate change in the above example about the use of coal?

Uses

Monitoring the impacts of both short-term and long-term activities with EPIs allows decision makers to make changes that result in performance with lesser environmental impacts. In some cases, changes can be made to ongoing projects, or the results of an EPI can be used for publicity if the performance data indicate the activity is environmentally-sound. In other cases, the EPI establishes a performance benchmark against which other projects are measured, or the results are used in the strategic planning phase while projects are in development. In this way, past successes and failures can both be incorporated into future plans.

Use of EPIs requires production of multiple data points. A single application of an EPI does not mean much until placed into a larger context. For example, an EPI might evaluate the impact of your city’s recycling efforts (see Figure Municipal Solid Waste Recycling Rates), but that result can be difficult to interpret without additional data that can be presented in multiple ways:

• Absolute values: Is the impact greater or less than that of other cities? How does the total cost of the recycling program compare?
• Normalized values: How does the per person impact compare to another city, country, business, etc.? What is the amount of aluminum recycled per dollar spent on recycling?
• Trends: Is your city improving, or is the progress your city sees in recycling better than that that of other cities? This could be asked of either absolute or normalized data: Is the total amount of aluminum recycled in your city increasing? Is the per-person amount of aluminum recycled in your city increasing?

Municipal Solid Waste Recycling Rates Municipal solid waste recycling rates in the United States from 1960-2007. Source: EPA

Major EPI Areas

Most EPIs focus on one or a few categories of environmental problems and do not attempt to be all-inclusive methods of evaluating sustainability. A few of the more common categories are briefly described below.

Biodiversity is the number and variety of forms of life, and can be calculated for a particular tree, an ecosystem, a nation, or even the planet. Food, fuel, recreation, and other ecosystem services are dependent on maintaining biodiversity. However, biodiversity is threatened by overuse and habitat destruction (see Figure Endangered Animals). Because the actual number of species alive is not known, biodiversity indicators often use proxy data. These include patterns of habitat preservation and resource use, because they are the primary factors influencing biodiversity. The better-known groups of organisms, such as birds and mammals, are also monitored for a direct count of biodiversity, but vertebrates are a tiny proportion of life and cannot accurately reflect changes in all species.

Endangered Animals Illustration shows the number of endangered animals in each country of the world. Source: World Atlas of Biodiversity

Wood is harvested for timber and fuel, but forests are also cleared for agricultural fields and housing developments. Such deforestation frequently leads to rapid soil erosion and extinctions. Cutting of forests also results in changes to the water cycle, altering precipitation patterns and rates, and nutrient cycles, such as the release of carbon dioxide into the atmosphere. At the same time as deforestation takes its toll in places, trees are being planted elsewhere. Developed countries are increasing their forested areas, but this is commonly being done at the expense of developing countries, which are exporting their wood (see Figure Deforestation at the Haiti/Dominican Republic Border). Forestry indicators in EPIs include the annual change in forested areas, but can be broken down into the types of forests because each has different environmental impacts. Another indicator is the use of non-sustainable wood resources. Tree farms and some harvesting methods provide renewable supplies of wood, while clear-cutting tropical forests does not. Irresponsible wood harvesting produces negative results for ecosystem health.

Deforestation at the Haiti/Dominican Republic Border Satellite photograph show deforestation of Haiti (on the left) at the border with the Dominican Republic (on the right). Deforestation on the Haitian side of the border is much more severe. Source: NASA

Air, water, and land pollution directly, and adversely, impacts human and ecosystem health. It also has economic consequences from the damage of natural resources and human structures. In many cases the level of pollutants can be measured either in the environment or at the point of emissions. Additional indicators include whether pollution monitoring even occurs, to what extent legal maximum levels are enforced, and whether regulations are in place to clean up the damage. Visit the EPA’s MyEnvironment application to learn more about environmental issues in your area.

Greenhouse gas emissions and ozone depletion are results of air pollution, but are frequently placed in a separate category because they have global impacts regardless of the source of the problem. Levels of greenhouse gases and ozone-depleting substances in the atmosphere can be measured directly, or their impacts can be measured by looking at temperature change and the size of the ozone hole. However, those methods are rarely part of EPIs because they do not assign a particular source. Instead, EPIs include the actual emissions by a particular process or area.

Examples of EPIs

There are dozens of EPIs that can be used to evaluate sustainability. Below are two examples of multi-component methods that allow comparisons at a national level, which is necessary for promoting many types of systemic change.

Comparisons

There are no perfect measures of sustainability, and different indicators can sometimes give conflicting results. In particular this happens when perspectives on the most important components of sustainability, and the methods to address them, differ. Therefore, it is often useful to examine the main characteristics of several Environmental Performance Indicators to find the one most appropriate for a particular study. As an example, ESIs, EMPIs, and ecological footprinting (discussed in a previous section) are compared below.

Ecological footprinting (EF) has units that are the easiest to understand – area of land. Both EF and EMPI employ only a single type of unit, allowing for use of absolute variables and permitting quantitative comparisons. However, EF does not use multiple indicators to allow for focused attention on impacts. EMPI can also be used as scaled values (such as the proportion of emergy from renewable sources), in the same manner as ESI. However, ESI combines multiple units of measurements, which can provide a more holistic perspective, but at the same time leads to concerns about combining those data.

Of the three, ESI and EMPI take into account wastefulness and recycling, and only ESI includes the effects of all emissions. But while ESI includes the most variables, it is the most complex to calculate; the simplest to calculate is EF.

Because ESI includes social and economic indicators, it can only compare nations (or in some cases, states or other levels of governments). EF and EMPI are effective at comparing countries, but can also be used at scales from global down to individual products.

All three of the EPIs compared here can be useful, but each has their limitations. Additionally, there are scenarios where none of these are useful. Specific environmental education projects, for example, would require different types of performance indicators.

Additional Resources

Environmental Sustainability Index (http://sedac.ciesin.columbia.edu/es/esi/)

EPA MyEnvironment (http://www.epa.gov/myenvironment/)