Project Report:
Urban Forests: Valuing and Protecting Their Many Services
- Investigates the causes of economic imbalances.
- Explores and develops market-based solutions.


The loss of mature canopy and valuable natural green space in urban and suburban areas risks undermining sustainability even in jurisdictions that are attempting to implement “smart growth” policies. The Urban Forests project of the Society for Conservation Biology in 2013 aligned local action to protect urban forests through new incentives in the Montgomery County, Maryland zoning code and other laws with a push to properly value natural capital and its many services in measures of economic performance. The County’s Planning Board has directed its staff to explore a “model” sustainability option for the Bethesda Sector Planning process being undertaken for 2014 and to work with the Project on the plan. At the 2013 International Congress for Conservation Biology in Baltimore, Maryland, the Project held a symposium on ecosystem valuation tools and measures of performance such as Maryland's Genuine Progress Indicator.


Aggressive development is causing the loss of mature canopy and valuable natural green space in urban and suburban areas of Maryland and beyond, and risks undermining sustainability even in jurisdictions that are attempting to implement “smart growth” policies.

With the support of the Alex C. Walker Foundation the “Urban Forests: Valuing and Protecting Their Many Services” project in 2013 seized the following six opportunities in Maryland to protect urban and suburban forests and to apply valuation of the many services of urban forests and other forms of natural capital in decision-making:

(1) Publicizing Maryland’s Genuine Progress Indicator and improved valuation tools at the International Congress for Conservation Biology and its audience of scientists, agency officials, and conservation practitioners.

At the International Congress for Conservation Biology (ICCB 2013), which convened over 1,500 scientists, conservation practitioners, and agency officials from the US and around the world to Baltimore, Maryland, SCB Urban Forests project leader Christine Real de Azua organized a symposium on “Valuing the Environment for Decision-Makers and Stakeholders: The Big Picture, from Maryland’s Genuine Progress Indicator to National Accounts.”

Featured speakers included:
o Kyle Gracey, Co-chair of SCB’s Treaties Task Force: “Are We Conveying the Big Picture to Decision-Makers? Implementing the Convention on Biological Diversity’s Strategic Plan and other international commitments on green national accounts and indicators.”
o Sean McGuire, Office for a Sustainable Future, Maryland Department of Natural Resources: “How has Maryland’s Genuine Progress Indicator been most valuable in supporting decision-making and what are the next steps for Maryland and other states with this and similar initiatives?”
o Joe Roman, Ph.D., Gund Institute Fellow, and prize-winning author, “Ecosystem-service valuation tools to inform environmental policy and decision making.”
o Robert Winthrop, SocioEconomics Program, Bureau of Land Management, US Department of Interior, ”Valuing the Environment: A Federal Agency Perspective.”

The symposium participants discussed the limitations of the existing System of National Accounts from which Gross Domestic Product (GDP) is derived, and potential applications for new measures like Maryland’s Genuine Progress Indicator (GPI). Maryland is the first state to have officially established a GPI. The panel also looked at current advances in ecosystem valuation tools and their use in cost-benefit analysis of proposed actions by federal agencies such as the Bureau of Land Management of the US Department of Interior.

The need for new measures of progress such as Maryland’s Genuine Progress Indicator (GPI) was also highlighted in the opening speech to ICCB by Maryland Secretary of Natural Resources Joe Gill. In his speech, Secretary Gill urged scientists to “advocate and engage for the resources they study and wish to protect.” He then reminded the audience of GDP’s shortcomings and of the GPI’s purpose: “The more we spend, GDP says, the more progress we are making. Yet gross domestic product, Robert Kennedy famously said in 1968, "measures everything… except that which makes life worthwhile.”

(2) Protection of Urban Tree Canopy in Montgomery County: Providing Montgomery County Council with options for strengthening Tree Canopy Bill 35-12.

In July 2013, after eight months of deliberations, Montgomery County moved to finalize and pass a Tree Canopy Bill (Bill 35-12). This proposed Bill offered an opportunity to stem the impact of runaway development on small lots under one acre in size, which are not covered under Montgomery County’s Forest Conservation Law or Maryland’s Forest Conservation Act.

However, at the 11th hour, less than a week before the Council’s scheduled vote on Monday July 23, 2013, the few provisions to conserve canopy (as opposed to cut and plant), were gutted from the bill as it moved out of committee. After reviewing the final bill, and acting as individuals due to the late notice, the project drafted an analysis regarding the lost conservation provisions, sounded the alarm with County Council members and with conservation groups, and provided options for strengthening amendments to protect existing canopy (COMMENT on Tree Bill 35-12 – Planting is not enough: Request for amendments to also conserve tree canopy).

The comments and options sent to Council members and shared with conservation groups active on the Tree Bill built on the principles set out in the Society for Conservation Biology’s Forest Declaration (International_Year_of_the_Forest_1.pdf) and other policy statements and publications (, and emphasized the value of trees and of mature tree canopy and the availability of tools such as the i-tree tool developed by the US Forest Service and the US EPA to estimate the value of the ecosystem services, such as stormwater management, which trees provide. The comments also mentioned the value of mature canopy and green space in fostering biodiversity, such as birds, other wildlife and plants. The comments noted that, increasingly, research at the city/county scale as well as at the landscape scale reveals that urban areas, as well as suburban and rural areas can contain relatively high levels of biodiversity, depending on the management practices used.

(3) Valuation and Protection of Urban Tree Canopy in Baltimore.

Baltimore has adopted a Sustainability Plan and a Climate Action Plan, and, to track progress, is considering the development of a Genuine Progress Indicator (GPI) for the City. The development of a GPI for Baltimore offers several opportunities to highlight the value of urban forests and of policies that the City could consider to protect them.

We coordinated with the Genuine Progress project of the Institute for Policy Studies (IPS) and Center for Sustainable Economy (CSE) regarding enhancements to the GPI that CSE is developing for Baltimore, including the valuation of urban forest canopy as part of a Baltimore-specific GPI. The preliminary analysis of Baltimore's Climate Action Plan using the GPI's panoply of economic, environmental and social indicators, suggests that investments in green infrastructure, including urban forests, would efficiently boost the City's GPI. We also reached out to local organizations regarding potential spaces to be protected or restored and the benefits for Baltimore of using the GPI once it is developed.

(4) Montgomery County Zoning Rewrite and market-based mechanisms to protect urban forests.

The Urban Forests project identified and leveraged the Montgomery County, Maryland’s “Rewrite”—the first revision to its zoning code in 35 years – as an opportunity to propose mechanisms to value and protect urban forests.

The Project's comments on the proposed Zoning Code, which were submitted as formal comments of the Society for Conservation Biology North America Section, included the following recommendations:

o Increase the amount of open space and environmental services required under the Optional Method and under any other method for new commercial development, not eliminate or reduce that requirement.

o Create a Green Infrastructure Reserve (GIR) zoning category that expands or is modeled on the existing Agricultural Reserve (AR) zoning category, and includes green spaces and corridors in urban areas, public parks, and private green space in residential zones that meet certain eligibility standards. Green infrastructure qualifying as Green Infrastructure Reserve would include “micro” units such as urban community gardens, certain residential green backyards, and linear parks, which, in the aggregate, can constitute an effective and resilient green infrastructure network.

o Extend the existing Tradable Development Rights mechanism to include the Green Infrastructure Reserve so that it incentivizes protection of and investment in green infrastructure. To this effect, enable property owners including residential, commercial, government and otherwise who have green space or would like to convert an area to green space and green infrastructure to make that space voluntarily available for conservation easement and designation as a Protected Overlay Area or Green Infrastructure Reserve zone that becomes qualified for Points Under the Optional Method, provided that green space meets certain green infrastructure qualifications. Such a designation would make it possible for those property owners to benefit from incentives generated through Tradable Development Rights.

o Facilitate the establishment and valuation of green infrastructure, through easement programs and land acquisition for urban forests, parks and corridors, including but not limited to the programs described above.

o Emphasize protection of urban forests in planning and zoning and in doing so, establish a Tree Canopy Goal for the County that includes urban forests in conjunction with the County’s implementation of the County’s new Tree Canopy Bills, including Bill 35-12, which calls for the establishment of such a goal.

o This Tree Canopy goal and other provisions listed above could begin with the principle of no net loss of tree canopy, and of native biological diversity, rewarding and conserving contiguous or connected green spaces, and identifying measures for rewarding spaces as small as "backyard habitats" that host an array of birds and wildlife, and especially those that avoid the use of pesticides, herbicides and invasive ornamentals.

o Tighten and strengthen the public amenity process to ensure that, in return for high density, public benefits reflect the views of the communities who are supposed to benefit from them, and accrue locally.

The project shared the Urban Forests Project comments on the “Zoning Rewrite” with the Maryland’s Department of Natural Resources, with the Town of Chevy Chase and the influential citizen’s association WeAreMoCo, which are engaged in the “Zoning Rewrite,” with the local chapter of the Sierra Club and other environmental groups, and with the two main local newspapers covering the issue (the Bethesda Gazette and the Washington Post);

After a lengthy process the Zoning Rewrite was adopted by the County Council in March 2014 in spite of objections by a range of public interest groups and at least one Council member. While neither the provisions recommended by the Urban Forests project nor several other provisions to strengthen public benefit options advocated by civic associations and public interest groups were included in the final draft, the Urban Forests project nonetheless laid the groundwork for subsequent improvements both in the Code and in accompanying Sector Plans.

Because Montgomery County Zoning will be carried out in conjunction with updates to Sector Plans, the Urban Forests project has identified opportunities to weigh in on planning decisions coming up in 2014, including the Sector Plan for Downtown Bethesda. The County's Planning Board has directed its staff to explore a "model" sustainability option and work with the project on the plan.

(5) Cumulative impacts of poorly planned high density development and loss of urban canopy and endangered species habitat.

Can rapidly urbanizing areas of Montgomery County, Maryland, such as downtown Bethesda, become a model of sustainability and accommodate high-density development while also protecting its natural areas and a local endangered species? Can abutting communities successfully preserve networks of biodiverse backyards and canopied green space, which provide valuable stormwater management, water regulation, climate resilience and other ecosystem services?

The Urban Forests project staff focused on urban forests in the Bethesda area where these questions are coming to a head because of the cumulative impacts of accelerated residential and commercial development and the direct and cumulative impacts from the proposed Purple Line, a light-rail transit line that would originate in downtown Bethesda and cause the felling of a total of 47 acres of urban forest along its path, much of it in its western section near Bethesda. Moreover, a Maryland endangered species, the amphipod Stygobromus kenki, has been found in a canopied riparian buffer along Coquelin Run, a tributary to Rock Creek whose headwaters originate in Bethesda. The species' location and habitat, and threats to the species, were acknowledged in a local Sector Plan environmental appendix, but no plans or mechanisms are in place to ensure protection of the species, its habitat, and the recharging of the hillside water seeps that it inhabits. Amphipods are freshwater shrimp-like creature that live in seeps and cannot swim far away from where they located, and are indicators of water quality and forested ecosystem health.

The loss of tree canopy and green space from the line would result in loss of ecosystem services such as stormwater management, replenishment of groundwater and seeps, air and water pollution filtering services, wind and temperature regulation, and climate resilience. These losses are compounded by the losses of green space occurring on private residential lots. After seeking information and feedback on their findings from experts, Urban Forests counsel John Fitzgerald, project leader Christine Real de Azua, as individuals, and John Talberth, Ph.D., and President of Center for Sustainable Economy, developed and submitted comments on the Purple Line Final Environmental Impact Statement, which are part of the public record, to highlight these impacts. The comments incorporate the research advanced by Urban Forests but were not submitted as official comments of the project. In addition, two memos prepared for the project by biologists with expertise on these species, David Culver, Ph.D. and David Berg, Ph.D., describe the amphipods and the ecosystems for which they serve as indicators, the threats to these species and ecosystems, and recommendations for species recovery. The memos will enable the project, decision-makers, and others to apply to specific areas tools that highlight and reflect in market and other values, the benefits of green space and natural systems. The memos will support steps for preserving those spaces, from ensuring compliance with existing law to helping to shape options for improving existing zoning, land use plans and other tools.

In next steps, the project proposes to advance mechanisms and incentives for conservation easements for the valuable canopied urban and suburban corridor along Coquelin Run.

(6) Town of Chevy Chase Tree Ordinance: A potentially powerful Ordinance.

The Town of Chevy Chase has in place a Tree Ordinance that could be a model for other jurisdictions. The ordinance forbids the felling of a canopy tree without a permit and requires a tree protection plan for new home construction or significant construction activity. Based on the strength of its ordinance, the Town weighed in at the County level to urge the County to strengthen the Tree Canopy Bill under its consideration. The Town has also enacted a voluntary conservation easement program. Even so, the Town is losing valuable mature canopy and green space. To incentivize and strengthen the implementation of the Town Ordinance and better protect of the Town’s abundant mature trees Urban Forests counsel John Fitzgerald drafted proposed improvements to the ordinance. These have been referred to the Town's Environment Committee, which will take up these up in 2014.

The local implementation of this tree ordinance is also highlighting unintended consequences in the implementation of the County’s new water runoff regulations, which can result in the digging of drainage drywells to manage runoff from new impervious building surfaces… but also can cause fatal harm to tree roots when those drainage drywells are located in root areas—ironically harming some of the best stormwater management tools that exist, which are mature trees. In next steps the project will explore how to make these ordinances (tree protection and stormwater runoff) work in synergy in terms of their requirements and incentives.

The tools and options recommended by the project advance the transition to sustainability.


This project of the Society for Conservation Biology shines the light on the failure of market signals and conventional measures of economic progress to fully value the ecosystem services such as stormwater protection, air and water purification, and carbon capture that urban forests and other forms of natural capital provide to our economy.

The project also advances market-based solutions based on such valuation, such as improved easement and tradable development rights programs to fund protection of urban forests.


The options to value and protect urban forests, and the broader macroeconomic cost-benefit analysis tools and measures of economic progress to demonstrate the value of natural capital to decision-makers, are relevant not only at the local level within Maryland, but are replicable and can be scaled at the state, national and international level.

Information Dissemination

In this project period, the project communicated with its target audiences in the following ways:

-Filings, comments, testimony, and in-person communications with local and county-level and state decision-makers, including government agency officials and non-profits active in the decision-making process, on the value of sub/urban forests, and on options for improving and implementing policies and practices to protect such forests;

-Presentations at the ICCB Congress about valuation options and about Maryland’s Genuine Progress Indicator and its potential applications.

--Coordination with research institutes and nonprofits, such as the Institute for Policy Studies, Center for Sustainable Economy, and members of the Gund Institute, and outreach to organizations active in Montgomery County, Maryland.

Project Link

Amount Approved
$20,000.00 on 7/1/2013 (Check sent: 7/9/2013)

Urban Canopy-Capital Crescent Trail, Bethesda MD
Urban Canopy-Capital Crescent Trail, Bethesda MD.

Urban Canopy along Coquelin Run.jpg
Urban canopy along Coquelin Run, with high rise residential and commercial buildings in background. This and other private, deep "riparian buffer" backyards have been inventoried and recognized as eligible for conservation easements, but landowners are concerned about loss of property value and lack effective incentives to place them under easement.

County Planning Board meeting.png
Montgomery County, Maryland Planning Board meeting. Following testimony, Urban Forests project leader and Planning Board staff discuss Downtown Bethesda Scope of Work with Planning Board meeting.

Dr. Culver, Ph.D., expert in the biology of amphipods and subterranean animals, at Coquelin Run
Dr. Culver, Ph.D., expert in the biology of amphipods and subterranean animals, at Coquelin Run. Dr. Culver described the Kenk's and other amphipods, the ecosystems for which they serve as indicators, and the threats to these species and ecosystems in a memo that will support steps for valuing and protecting such spaces.

DNR Secretary Joe Gill copy.jpg
Maryland Department of Natural Resources Joe Gill at ICCB 2013. Secretary Gill noted: “The Genuine Progress Indicator, or GPI, is an alternative way of looking at our progress. GPI considers not only economic indicators in measuring progress, but environmental and social factors. It considers the cost of water pollution, air pollution and noise pollution, the loss of forest cover, and the impact of climate change. It considers the loss of leisure time - remember leisure time? - the cost of commuting and the value of volunteer work. It is a far more comprehensive look at assessing whether we, as a society, are genuinely making progress.”

ICCB 2013 Symposium
ICCB 2013 Symposium on Valuing the Environment for Decision-Makers and Stakeholders. Participants discussed advances in ecosystem valuation tools and potential applications for new measures like Maryland's Genuine Progress Indicator.

iTree .jpg
i-Tree: The Urban Forests project publicizes the availability of online tools like i-Tree, developed by the US Forest Service to provide urban forestry analysis and benefits assessment tools.

Coquelin Run-Riparian buffer.jpg
Coquelin Run: This stream and its forested riparian buffer is under stress and at risk from cumulative development impacts. Can rapidly urbanizing areas of Montgomery County, Maryland, become a model of sustainability and protect valuable natural areas and their ecosystem services?

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