The American Society of Landscape Architects (ASLA) has launched a new online guide that explains the many benefits of green infrastructure.
Green infrastructure includes green streets, park systems, urban forests, wildlife habitat and corridors, green roofs and green walls. These infrastructure systems help communities manage stormwater and reduce flooding, mitigate the urban heat island effect, and improve air and water quality, which underpin human and environmental health.
The idea that nature is also infrastructure isn't new, but it's now more widely understood to be true, according to Nancy Somerville, Hon. ASLA, executive vice president and CEO of ASLA. Researchers are amassing a body of evidence to prove that green infrastructure actually works. These systems are often more cost-effective than outmoded models of grey infrastructure—a term used for the concrete tunnels created to move water—and also provide far more benefits for both people and the environment.
“At all scales, green infrastructure provides real ecological, economic, and social benefits,” added Somerville. “Cities need as much green infrastructure as possible, and landscape architects are implementing it in communities across the country.”
The guide, part of ASLA’s series of sustainable design resource guides and toolkits, includes hundreds of research studies by leading scientists, news articles, and case studies on innovative uses of green infrastructure. Resources are organized into seven sections that go from large scale (the region, the city) to the small scale (constructed wetlands, green streets, and green roofs and walls).
The guide includes sections on forests and nature preserves; wildlife habitat and corridors; cities; constructed wetlands; green streets; and green roofs and walls. The guide also includes descriptions of the many types of green infrastructure, their quantifiable benefits, and the role of landscape architects in creating these systems.
Primary benefits of green infrastructure systems
- Absorbs and sequesters atmospheric carbon dioxide (C02)
- Filters air and water pollutants
- Stabilizes soil to prevent or reduce erosion
- Provides wildlife habitat
- Decreases solar heat gain
- Lowers the public cost of stormwater management infrastructure and provides flood control
- Reduces energy usage through passive heating and cooling
Grey infrastructure usually provides just a single benefit. In contrast, green infrastructure provides them all at once.
Two examples of green infrastructure in cities
In Philadelphia, a comprehensive green infrastructure approach is estimated to cost just $1.2 billion over the next 25 years, compared to over $6 billion for "grey" infrastructure. The city is expecting up to 1.5 billion pounds of carbon dioxide emission to be avoided or absorbed through green infrastructure each year, the equivalent of removing close to 3,400 vehicles from roadways. The city estimates 20 deaths due to asthma will be avoided, and 250 fewer work or school days will be missed. Lastly, the economic benefits are also outstanding: the new greenery will increase property values by $390 million over 45 years, also boosting the property taxes the city takes in.
New York City’s green infrastructure plan is projected to cost $1.5 billion less than a comparable grey infrastructure approach. Green stormwater management systems alone will save $1 billion, at a cost of about $0.15 less per gallon. Also, sustainability benefits in NYC range from $139 to $418 million over the 20-year life of the project, depending on measures implemented. The plan estimates that “every fully vegetated acre of green infrastructure would provide total annual benefits of $8.522 in reduced energy demand, $166 in reduced CO2 emissions, $1,044 in improved air quality, and $4,725 in increased property value.”
Landscape architects were deeply involved in the creation and management of these visionary plans. Many more contribute to making these plans a reality by planning and designing urban forests, parks, and green roofs and walls.