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Green infrastructure includes the connected natural systems and ecological processes that provide critical functions, such as habitat for wildlife, water storage and filtration, air quality, and healthful lifestyles. The Conservation Fund defines green infrastructure as a “strategically managed network.” What is meant by this is that habitats are linked and a systems approach is applied at the landscape scale.
Now more than ever, we need to take a green infrastructure approach. Evidence for declining resources abounds nationwide. Almost 2 million acres of farmland and half a million acres of private forest are developing each year, leading to loss of species, groundwater declines, climate change and lost recreation and open space. Loss of habitat not only degrades the quality of life and the environment, but it also has real economic consequences. Parks, protected rivers, scenic lands, wildlife habitat, and recreational open space support a U.S. tourism industry valued at $502 billion annually.
As we lose forests, we also lose our ability to have healthy and plentiful water. According to the Trust for Public Land, studies have documented that the larger the forest cover in a watershed, the lower the cost to treat drinking water (2007). Preserving and expanding our natural assets is thus also central to sound economic and heath policy.
A simple way to think about what constitutes a green infrastructure approach is that instead of considering a park, forest or wetland as individual sites, we consider how these resources are or could be tied together (travel for plants and animals, hydrology, etc.). Taking a green infrastructure approach requires identifying and understanding natural systems and protecting those systems first, before development begins, as well as seeking to restore connections and habitats in already-developed landscapes.
Many species need intact areas that are not bisected by roads, power lines, or other divisions. Often referred to as “hubs” or “cores,” or “patches” these intact zones are required by some species, such as the Louisiana water thrush, which prefers interior forest and requires clear, clean streams. When habitats are fragmented, other species can invade these areas and compete with native species. For example, brown headed cow birds invade fragmented areas and place their eggs in the nests of other birds, thus competing for food and resources.
Green Infrastructure Ecological Concepts
Green infrastructure planning seeks to protect and connect intact areas in order to avoid threats such as invasive species, while also seeking to maintain genetic diversity within the landscape. If species become extinct in one area, linkages between areas may allow plants and animals to repopulate over time.
Patch or Core: relatively homogeneous nonlinear area that differs from its surroundings. Consider that the greater the number of interior species present, the greater the diversity of habitat types, the degree to which they protect stream networks, and provide core habitat and escape cover for large animals, the more it is to conserve the intact patch or core.
Edge: outer portion of patch where the environment differs significantly from the interior. If there is greater structural diversity (different heights and types of vegetation) edges may also have greater diversity.
Corridor: strip of a particular type that differs from the adjacent land on both sides. Corridors may be used by wildlife to move between patches.
When a corridor is broken, a cluster of stepping stones (small patches) can provide connection and alternate routes for plants and animals – size and spacing is dependent on the species utilizing the corridor.
Streams are natural corridors and the width of the vegetative corridor should reflect the stream order (e.g. larger streams need wider forested buffers).
From a conservation perspective, it’s important to link areas together. Species that may decline in one area due to habitat loss can move over time to other areas and repopulate. In this way, both species diversity and individual species can be protected over larger areas. Mapping and protecting intact habitats and connections are critical to ensuring species diversity.
Steps to Green Infrastructure Planning
Green infrastructure planning entails inventorying green assets, identifying opportunities for their protection and/or restoration, and developing a coordinated strategy to channel development and redevelopment to the most appropriate locations. Green infrastructure planning is not anti-development. Rather it seeks to develop in the most appropriate places while conserving vital forests, farms, wildlife habitats and water resources that we all depend on for healthful lifestyles and strong economies.
Green infrastructure planning entails inventorying green assets, such as large forests, farms, dunes or wetlands, and identifying opportunities for their protection and/or restoration through a coordinated strategy to channel development and redevelopment to the most appropriate locations.
Green infrastructure planning is also linked to watershed planning, since land uses and development patterns are directly tied to water storage and quality. Waterways, bays, and wetlands are critical components of “blue” infrastructure; they provide habitat links for fish and wildlife and they are included in green infrastructure planning. Ground water resources are also part of green infrastructure. River corridors and stream valleys often provide the only remaining green connections for wildlife to move across landscapes. Wetlands provide areas for water storage and ground water recharge, while also hosting many unique and rare species of plants and animals. In coastal areas, wetlands provide shellfish grounds and nurseries for young fish.
Since landscape conservation is often linked to the integrity and enjoyment of historic or cultural sites, assets such as battlefields or historic homes can also be included in the assessment inventory. In some states, such as Maryland and Virginia, there are state models available that can be used as a starting point for developing regional or local plans. See the GIC resources section for examples.
Simplified Steps for Green Infrastructure Planning.
Step 1: Set Goals – What does the community value?
- Forests for wildlife and timber?
- Recharge areas to protecting drinking water supplies?
- Conserving historic landscapes and battlefields?
- Protecting and promoting working farms?
Step 2: Data Review – What do we know and what do we need to know?
- Research existing studies – what are the findings and are they relevant? (e.g. watershed plans, wildlife plans, open space plans, ecological inventories, groundwater studies, air studies etc.)
- What data are needed? (If using Geographic Information Systems you may need digital layers – data arranged spatially that can be overlain and compared.
- Examples of data types include streams and watersheds, key agricultural soils, recreation routes, forested areas, wetlands, etc.
Step 3: Asset Mapping – Map the community’s ecological, cultural and economic assets. What is mapped is based on goals established in Step 1. Following are examples.
- Large intact forests or native meadows
- Large farms and farm communities
- Streams, rivers, wetlands and groundwater recharge areas
- Recreational areas (fishing, boating, hiking, biking, birding)
- Historic and cultural features (battlefields, historic landscapes)
- In urban areas, street trees, tree canopy and local parks, streams.
Step 4: Risk Assessment – Find out what’s at risk and what could be lost.
- Which areas are zoned for development and do they overlap key assets?
- Are there forests which have been fragmented by roads or subdivisions?
- Which steams are impaired (or might be in the future)?
- Where are new roads planned – do they fragment key assets?
Step 5: Opportunities – Based on assets and risks, assess what can or should be saved? What could be restored? What will be developed? Engage the community in ranking key areas of importance. Map these opportunities and draft strategies to conserve them.
- Where will future parks or recreational areas be located?
- Which forests can be conserved for forestry, recreation or wildlife habitats?
- Identify locations and routes for argitourism (local fruit, wines, honey, meat, vegetables, crafts).
- Identify areas where scenic views or routes for historic or cultural assets should be protected.
- Explore the extent to which current zoning adequately addresses the county’s or region’s land assets.
- Where should towns or developments be located in the future?
Step 6: Include strategies in local plans for parks, zoning, comprehensive planning, tourism development or recreational strategies.
Green infrastructure plans can be fitted into existing city and county planning efforts and can compliment already-identified conservation goals. Following are several examples of how green infrastructure assessments may be utilized:
- Environmental chapters in comprehensive plans and/or to implement existing comp plan goals for resource assessments and conservation
- Park, open space and recreational planning or strategic land acquisition
- Strategies for determining where to zone land for conservation or growth
- Lands for purchase of development rights or transfer of development rights
- Heritage tourism strategies and viewshed protection
- Urban tree canopy surveys and management
- Transportation planning for roads and mutli-modal planning
- Targeting land for conservation easement programs
- Protection of at risk or endangered species, such as the Delmarva Fox Squirrel
- New ordinance development (stream buffers, water protection, historic landscape overlays)
- Rezoning decision basis either for upzoning or downzoning
Of course, green infrastructure is not limited to “natural” or pristine areas. Green infrastructure planning is often needed because of the challenges in seeking to add grey infrastructure and buildings while not obliterating the green. In already developed areas, green assets can be reconnected through new corridors. Green infrastructure also can be restored by turning a brownfield into a forested site. For example, in 2007, GIC staff completed a green infrastructure strategy for Charlottesville VA; a city which is highly urbanized. Trails, stream buffers, tree canopy and park enhancements were mapped and evaluated and strategies were developed to conserve and enhance them.
Finally, individuals can take care of their own green infrastructure such as planting trees along streams and shade trees for homes and streets and using less pavement so water can infiltrate and recharge aquifers, planting native species and establishing non-mowed areas, as well installing bird boxes and bat houses. For larger properties, landowners can consider whether they want to apply for a conservation easement. Farmers can ensure their forests and farms have a management plan that conserve both natural and economic resources. For more ideas see the Resources section.
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