Green Infrastructure

Maryland's green infrastructure is a network of undeveloped lands that provide the bulk of the state's natural support system. Ecosystem services, such as cleaning the air, filtering water, storing and cycling nutrients, conserving soils, regulating climate, and maintaining hydrologic function, are all provided by the existing expanses of forests, wetlands, and other natural lands. These ecologically valuable lands also provide marketable goods and services, like forest products, fish and wildlife, and recreation. The Green Infrastructure serves as vital habitat for wild species and contributes in many ways to the health and quality of life for Maryland residents.

Hubs typically consist of large contiguous areas, separated by major roads and/or human land uses, that contain one or more of the following:

• Large blocks of contiguous interior forest (containing at least 250 acres, plus a transition zone of 300 feet)
• Large wetland complexes, with at least 250 acres of unmodified wetlands
• Important animal and plant habitats of at least 100 acres, including rare, threatened, and endangered species locations, unique ecological communities, and migratory bird habitats
• Relatively pristine stream and river segments (which, when considered with adjacent forests and wetlands, are at least 100 acres) that support trout, mussels, and other sensitive aquatic organisms
• Existing protected natural resource lands which contain one or more of the above (for example, state parks and forests, National Wildlife Refuges, locally owned reservoir properties, major stream valley parks, and Nature Conservancy preserves)

Corridors are linear features connecting hubs together to help animals to move between hubs. Corridors were identified using many sets of data, including land cover, roads, streams, slope, flood plains, aquatic resource data, and fish blockages. Generally speaking, corridors connect hubs of similar type (hubs containing forests are connected to one another; while those consisting primarily of wetlands are connected to others containing wetlands). Corridors generally follow the best ecological or "most natural" routes between hubs. Typically these are streams with wide riparian buffers and healthy fish communities. Other good wildlife corridors include ridge lines or forested valleys. Developed areas, major roads, and other unsuitable features were avoided.

Gaps are areas in which the absence of the characteristics that make up the surrounding green infrastructure causes discontinuities, thus severely limiting the advantage of the corridors and the ability of wildlife to move through it. The relatively narrow corridors seen on the map could be severely broken by what might appear locally to be a minor removal of the necessary habitat.

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