What Is Green Infrastructure?
Vol. 22 Issue 2, Summer 2017
by Cheri Conca
We hear a lot about green infrastructure lately. What exactly is it, and why is it so important? Now is a great time to learn, as Loudoun’s current green infrastructure blueprint is at risk of falling on the cutting room floor during the County’s new comprehensive plan draft process.
Forests, floodplains, wetlands, meadows and open space comprise the “green” in green infrastructure. When interconnected, these geographic features function as a natural infrastructure, providing valuable health, economic, and recreational services, as well as critical habitat for breeding and migrating wildlife. While rain gardens, bioswales and green rooftops are also components of green infrastructure, it is our large-scale geographic features that are at immediate risk, and that each one of us has an opportunity to preserve.
The ecological functions of green infrastructure cannot be replaced. It absorbs floodwaters, mitigates drought damage, lowers surface temperatures and energy use, and filters contaminants that flow into the public water supply. For those on well water, preserved stands of forest and meadows allow rainwater to slowly filter and seep into the ground to replenish the drinking supply.
What would we rely on in the absence of green infrastructure? Gray infrastructure. In other words, pipes-and-ponds to manage stormwater runoff. However, stormwater management is the only function of gray infrastructure. Green infrastructure, on the other hand, is multi-functional. It not only manages stormwater in a natural, cost-effective manner, it also provides valuable services such as clean drinking water, good air quality, carbon sequestration, recreation, an outlet for well-being, and biodiversity. Gray infrastructure stormwater systems are capital intensive and require periodic upgrades. Plus, they collect and carry runoff rainwater from streets, roofs and parking lots, which leads to erosion, and the draining of chemicals straight into drinking water supplies.
Green infrastructure saves money and reduces future spending. For example, a survey by the American Water Works Association found that a 10 percent increase in forest cover reduced chemical and treatment costs of drinking water by 20 percent.
For green infrastructure to function effectively, geographic features must be purpose-built and interconnected, not just a patch of grass or a dog park. Fragmentation is the enemy of green infrastructure. Fragmented ecological areas are vulnerable to invasive species and disease, and do not provide the necessary habitat for many of our native wildlife species. On an administrative level, fragmentation of oversight poses another threat to green infrastructure. County agencies must coordinate and communicate with each other, and with state and federal agencies and nonprofit organizations, to protect and connect critical land and water. The key to successful green infrastructure is to identify and preserve ecological hubs, and connect them via corridors that allow for the movement of wildlife and people. This can be accomplished on a small scale in neighborhoods, and on a large scale in stream valleys, on farms, and throughout large portions of entire counties and regions.
How much forest, wetland or meadow needs to be protected to qualify as an ecological hub? The Green Infrastructure Center in Charlottesville, Virginia, recommends that ecological hubs be comprised of habitats that have adequate interior area that is unfragmented by intrusions such as roads or power lines that create edges that facilitate encroachment from invasive species or predators. In the eastern U.S., 100 acres of green infrastructure with proper conditions (that does not include the necessary 300-foot buffer from surrounding land use) is a minimum size to accommodate a diversity of native forest-dwelling animals, birds and plants.
Many species need more habitat than the minimum requirements listed above. Let’s take the cerulean warbler as an example. These dazzling birds are considered area-sensitive because they prefer breeding in large, deciduous hardwood forest tracts that have tall, large-diameter trees of diverse heights. Cerulean warblers are sensitive to forest fragmentation. One study found a 50% decrease in occurrence when forest patch size dropped from 7,410 acres to 1,729 acres. No birds were detected on patches of less than 341 acres.
Our Board of Supervisors and county staff are under enormous pressure from the building industry to add more housing developments, and the accompanying schools and services that come along with development. As the population grows, so does our deficit of parkland, the demand for abundant, clean water and open space, and the need to preserve wildlife habitat. A strong green infrastructure delivers solutions for all of these needs, reduces demand for gray infrastructure and contributes to economic development by conserving the unique landscape that draws so many people to Loudoun to enjoy the natural, historic and agricultural gems that define our community.
How do we preserve and enhance Loudoun’s green infrastructure? Through the county’s comprehensive plan, a document that guides our community’s future actions through long-range goals and objectives. The current plan includes a Green Infrastructure Policy that we want to keep, and fortify with measurable standards of success. Now is the time to voice our support for inclusion of green infrastructure policy in the new comprehensive plan, while land is still available or relatively affordable. We must tell our County Supervisors that we want them to protect and preserve our natural habitats now and in the future. It would behoove each of the supervisors to leave a legacy of a protected, connected Loudoun, in the form of a strong green infrastructure plan. It was none other than Ronald Reagan who said, “Preservation of our environment is not a liberal or conservative challenge, it’s common sense.”
Visit Loudoun Wildlife Conservancy’s “Current Campaigns” page for conservation advocacy updates.
• Barton & Ernst, Land Conservation and Watershed Management for Source Protection (AWWA Journal, April 2004) https://www.awwa.org/publications/journal-awwa/abstract/articleid/15007.aspx