Healthy and Attractive Environmental Assets

Degree of Compliance with National Ambient Air Quality Standards

Since the mid 1990’s, air quality has been steadily improving in Southeast Michigan. However, national pollutant standards are continually being strengthened. Attaining and maintaining these more stringent standards pose an increasing challenge for the region.

Overall air quality continues to improve

There are six pollutants that are tracked to comply with National Ambient Air Quality Standards:

• Ozone (O3): Levels have declined significantly, but the new standard is a challenge to maintain
  
• Fine Particulate Matter (PM_2.5): Annual levels continue to decline
  
• Sulfur Dioxide (SO₂): Levels have declined but one monitor is still above the standard
  
• Carbon Monoxide (CO): The entire region has been in compliance with standards for this pollutant since 1995
• Nitrogen Oxides (NOx): Southeast Michigan has always been in compliance with standards for this pollutant
• Lead (Pb): Southeast Michigan has always been in compliance with standards for this pollutant

Under the federal Clean Air Act, the U.S. Environmental Protection Agency (EPA) is responsible for establishing air quality standards (NAAQS) at levels that protect public health and welfare. These standards are set for pollutants considered harmful to public health and the environment. Areas not meeting these standards are required to develop and implement a corrective air pollution control strategy and reach compliance with the standard by the deadline set by the EPA.

Why it matters: Good air quality is a healthy, environmental asset and is an essential to the development of desirable communities. It also impacts Southeast Michigan’s economic prosperity. Under the Clean Air Act, areas not meeting the NAAQS are subject to additional federal regulations that make it more difficult for certain types of economic development to occur. Failure to meet the standards can also result in a loss of federal transportation funding.

Percent of Tree Canopy

In 2010, tree canopy covered 33% of southeast Michigan’s total acreage. The percentage of tree canopy varies from over 40% to 20% in the counties due to differences in land uses that do not conventionally feature tree canopy, such as agriculture or industrial. In order to realize the multiple benefits of tree canopy (e.g., air quality benefits, improved sense of place, habitat connection, reduced stormwater into our rivers and lakes), a 40 percent target is recommended.

With one third of the region covered by tree canopy, there is a good foundation to build towards 40% coverage through Green Infrastructure practices

SEMCOG used advancements in aerial imagery to measure tree canopy coverage across southeast Michigan. This was the first time tree canopy cover data was collected in this manner. The 2010 tree canopy data will be used as a benchmark used in the development of the Green Infrastructure Vision for Southeast Michigan.

Why this matters: Tree canopy provides multiple benefits to the region and to communities. It enhances quality of life and improves aesthetics of the area. It also reduces air pollution and can be used to reduce the impacts of dust in highly industrial areas. Tree canopy also provides habitat and connections for wildlife and shades streams to provide cooler water for area fish. Tree canopies improve water quality by interrupting rainfall during storms and slowing the rate of flow of rainwater into storm sewers, rivers, and streams. This allows more rainwater to infiltrate the ground, reduces erosion, and reduces the amount of pollution carried by rain into water bodies.