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The following principles are criti-
<br />cal to the success of green infrastruc-
<br />ture initiatives. They provide a strate-
<br />gic approach and a framework for con-
<br />servation that can advance sustainable
<br />use of land while benefiting people,
<br />wildlife and the economy.
<br />This approach includes design, plan-
<br />ning, acquisition and decision-making
<br />guidance for agencies and organiza-
<br />tions. It is our hope that public offi-
<br />cials and private citizens will use these
<br />principles as benchmarks for incorpo-
<br />rating agreen infrastructure approach
<br />into land use and economic develop-
<br />ment plans and policies.
<br />Principle l: Green infrastructure
<br />should function as the framework
<br />far conservation and development.
<br />Most of our nation's land conserva-
<br />tion programs have focused on pro[ect-
<br />ingindividual pazks, preserves, or other
<br />isolated areas with important natural
<br />or cultural resources. Yet, conservation
<br />biology teaches us that, because wild-
<br />life populations cannot flourish and
<br />ecological processes cannot function if
<br />natural connections aze severed, these
<br />"islands" are unlikely to meet their
<br />conservation objectives. By contrast,
<br />the roads and highways upon which
<br />America depends-and which provide
<br />a framework for future growth and de-
<br />velopment-are planned, built, and
<br />maintained as a system of intercon-
<br />nected parts.
<br />By making green infrastructure the
<br />framework for conservation, commu-
<br />nities can plan for interconnected,
<br />green space systems. Where isolated
<br />"islands" of nature exist, green infra-
<br />structure planning can help identify
<br />opportunities to restore the vital eco-
<br />logical connections that will maintain
<br />those protected areas. Green int}astruc-
<br />ture planning also minimizes the ad-
<br />verse impacts of rapid growth on eco-
<br />system functions and services, such as
<br />the disruption of wildlife migration
<br />corridors or the loss of riparian areas
<br />that absorb nutrients, recharge ground
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<br />water supplies and reduce stotmwater
<br />runoff.
<br />Principle 2: Design and plan green
<br />infrastructure before development.
<br />Restoring natural systems is far more
<br />expensive than protecting undeveloped
<br />land, and man-made wetlands and
<br />other restoration projects often fail to
<br />function as well as their natural coun-
<br />terparts over the long term. Because
<br />green infrastructure provides commu-
<br />nities with an ecological framework,
<br />it is essential to identify and protect
<br />critical ecological hubs and linkages
<br />in advance of development. Central
<br />Park could not be created today nor
<br />could Cook County, Illinois', Forest
<br />Preserve System or many other of the
<br />nation's best parks and preserves. Pro-
<br />tecting green infrastructure up front
<br />ensures [hat existing open spaces and
<br />working lands are seen as essential
<br />community assets and not left vulner-
<br />able to development.
<br />In situations where development has
<br />already occurred, it is still important
<br />to assess where restoring green infra-
<br />structure would beneSt people and na-
<br />ture. Green infrastructure plans should
<br />set acquisition and restoration priori-
<br />ties and help communities identify op-
<br />portunities to reconnect isolated habi-
<br />tat islands as redevelopment opportu-
<br />nities occur.
<br />Principle 3: Linkage is key.
<br />The desired outcome for all green
<br />infrastructure initiatives is a green
<br />space "network" that functions as an
<br />ecological whole. A strategic connec-
<br />tion of system components-parks,
<br />preserves, riparian areas, wetlands, and
<br />other green spaces-is critical to main-
<br />taining vital ecological processes and
<br />services (e.g., stormwater runoff,
<br />cleaning fresh water, etc.) and to main-
<br />taining the health of wildlife popula-
<br />tions. In addition, green infrastructure
<br />requires linkages between different
<br />agencies, nongovernmental organiza-
<br />tions, and the private sector.
<br />The nation's federal, state, and ]o-
<br />cal highway networks holistically cre-
<br />ate afunctional transponation system
<br />funded and supported by different lev-
<br />els of government. Why not design
<br />green infrastructure in the same way,
<br />taking advantage of natural stream net-
<br />works and terrain features to create
<br />physicaliy connected green space sys-
<br />tems that protect and restore vital eco-
<br />logical functions and linkages?
<br />Principle 4: Green infrastructure
<br />functions across jurisdictions and at
<br />different scales.
<br />We need to design green infrastruc-
<br />ture systems to connect across urban,
<br />suburban, rural and wilderness land-
<br />scapes and to incorporate green space
<br />elements at the state, regional, com-
<br />munity and parcel scales. Green infra-
<br />structure strategies can be used for ini-
<br />tiatives of any size or scale, including:
<br />• Individual parcels of land or within
<br />single real estate developments;
<br />• The community and regional
<br />scale, including park, recreation
<br />and other open-space projects;
<br />• The landscape scale, encompass-
<br />ing statewide and national conser-
<br />vation and open space resources.
<br />Green infrastructure may be most
<br />successful when it functions at multiple
<br />scales in concert. For example,
<br />Toronto's "Greening the Portlands"
<br />project focuses on regional parks,
<br />neighborhood parks, wide habitat
<br />corridors, narrow trail corridors, and
<br />greenspace within developments.
<br />It is important to note that green in-
<br />frastructure systems do not require, or
<br />even imply, public ownership of al]
<br />land in the system. Clearly, privately
<br />owned land, particularly working farms
<br />and forests, can play an important role
<br />in any green space system.
<br />Principle 5: Green infrastructure is
<br />grounded in sound science and land-
<br />use planning theories and practices
<br />Conservation biology, landscape
<br />ecology, urban and regional planning
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