Green building finally has some traction within the commercial and residential design and construction professions, and throughout the current recession and housing downturn green building has appeared to be the best-performing segment of the industry. Voluntary, market-driven rating systems for sustainable homes, office buildings, and facilities are both widely available and being implemented with greater frequency. But while these rating systems provide ambitious green benchmarks for buildings, they give only cursory attention to site and landscape sustainability.

Stepping in to fill the void is a new set of voluntary guidelines addressing the sustainable design, construction, and maintenance of sites and landscapes: the Sustainable Sites Initiative Rating System. The system is designed to be applied to all types of designed landscapes independent of any building, including the site of a commercial structure, a state park, a public garden, a new-home development common area, or a private home's backyard. Sites may be urban or rural, previously developed or undeveloped.

The Sustainable Sites Initiative (SSI) is a partnership between the American Society of Landscape Architects (ASLA), the Lady Bird Johnson Wildflower Center at The University of Texas at Austin, and the U.S. Botanic Garden. In development for the past four years, the rating system has been influenced by several stakeholder organizations, as well as by professionals in a variety of fields, including civil engineers, horticulturalists, and economists. Representatives from the U.S. Environmental Protection Agency, the National Association of County and City Health Officials, The Nature Conservancy, the National Recreation and Park Association, and the U.S. Green Building Council served on the initiative's steering committee and contributed to the development of the rating system.

The guidelines of the Sustainable Sites Initiative Rating System, based on 10 principles, are designed to create self-sustaining, regenerative landscapes that function as nature intended, performing the same "services" provided by any healthy environment—among them cleaning air, filtering and storing water, sequestering carbon, supporting wildlife, regulating local climates and contributing to a balanced global climate, and preventing soil erosion. It also requires project teams pursuing certification to develop long-term maintenance plans for the landscape, to ensure continuing performance as it matures and evolves, and rewards teams that monitor and evaluate a site's performance over time and use innovative sustainable practices and strategies.

Air and water pollution and carbon emissions are issues that every community in the United States faces, but they can be mitigated through sustainable land development and management, according to Nancy Somerville, executive vice president and CEO of ASLA. "A lot of the [environmental issues] come from what were very well-intended practices that actually took a huge toll on the environment," she says. "In a naturally functioning landscape, the plants and soil are constantly performing these services for us. But when the plants or landscape are removed and replaced with an impervious surface or ... a green lawn over a compacted surface, you lose that benefit."

In addition to addressing ecological factors, the rating system also considers a landscape's impact on humans. "The core of the rating system is all about the landscape design, and the impact on the land, and what design practices might lead to changes in the ecosystem services, but it was understood that there had to be a human factor component to this as well," says Rich Dolesh, chief of public policy for the National Recreation and Park Association, who served on the initiative's steering committee. "A lot of that is related to aesthetics, but also to the potential for education, public use, and public access to sustainable sites."

Implementing the sustainable sites guidelines offers a range of benefits, not just to the owners and operators of landscapes, but to the greater community. Not only will sustainably designed and managed sites require less energy for maintenance and save money, the ecosystem services that have been disrupted by development and construction will be restored as well, contributing to a healthier and safer environment.

Those who have been working with the USGBC's LEED rating system will find the Sustainable Sites Initiative Rating System very familiar, as its structure complements LEED's and, in fact, was developed with the idea that it be merged with LEED at some point. Under the 250-point rating system, the process of site development is organized into nine sections, each of which sets out prerequisites that must be met and outlines additional credits that may be earned. The certification levels are:

One Star (minimum 100 points)
Two Stars (minimum 125 points)
Three Stars (minimum 150 points)
Four Stars (minimum 200 points)

Dolesh points out that while many of the guidelines and practices outlined in the rating system take a different approach to landscape development and management than most practitioners, operators, and maintenance personnel are used to implementing, they will be very familiar to those who are already oriented toward low-impact design. "It's a very innovative system that has a lot of flexibility in it that will allow for a lot of adaptability, but it will require a very forward-looking view, not 'business as usual,'" Dolesh says.

SSI launched the rating system pilot phase on November 5 with the publication of two reports: "The Case for Sustainable Landscapes" and "The Sustainable Sites Initiative: Guidelines and Performance Benchmarks 2009." The organization has issued an open call for pilot projects, and interested parties may submit projects for consideration until Feb. 15, 2010, at Although the rating system addresses sites of all sizes, SSI is seeking sites of at least 2,000 square feet for the purposes of the pilot phase. Somerville says the pilot testing phase will conclude in 2012 and that the organization hopes to publish the first working version of the rating system by the end of 2012 or early 2013.

Both reports and the guidelines (as well as several project case studies) are available for download at