by Rick Pruetz, Vice President, Ecocity Builders
Communities with greenbelts conserve more open space and consequently sequester more carbon than communities without greenbelts. By concentrating urban growth, greenbelts also reduce greenhouse gas (GHG) emissions and promote diverse, compact neighborhoods served by planet-friendly infrastructure. In addition to GHG mitigation, greenbelts promote climate change adaptation by reducing development in places at higher risk from wildfires, floods, and sea level rise.
A 2021 study confirms that counties with greenbelts conserve more farmland, forests, grasslands, and wetlands than comparable counties without greenbelts (Han, Kim, and Daniels 2021). The study then quantifies the capacity of each county’s carbon sink in terms of carbon stock and carbon flux, meaning the exchange of carbon between the atmosphere and the land. As expected, the counties with greenbelts outperformed their non-greenbelted neighbors.
In addition to carbon sequestration, greenbelts mitigate GHG emissions concentrating growth in higher density urban centers where per capita energy consumption is lower than in sprawling auto-dependent suburbs. The 2021 study acknowledges but declines to quantify this mitigation effect. However, a 2018 study by the International Resource Panel of the United Nations Environmental Programme concluded that compact urban form, by itself, can cut resource and energy use in half compared with the sprawl produced by business-as-usual land use practices. And when applied in an integrated, mutually-supportive manner with three other key factors, compact urban form can decrease resource use by 80 to 90 percent (IRP 2018).
In addition to mitigating GHG emissions by sequestration and compact urban form, communities can use greenbelts to adapt to climate change. By protecting open space, greenbelts reduce development in places vulnerable to climate-change-exacerbated hazards including wildfires, floods, and sea level rise while safeguarding biodiversity and protecting water sources (Pruetz 2021).
Montgomery County, Maryland has permanently preserved 72,000 acres in its 92,000- acre greenbelt, which it calls the Agricultural Reserve. Montgomery County turned to permanent preservation after decades of seeing land converted to development because the countryside was only protected by zoning rather than permanent preservation. Montgomery County’s 1980 plan for the Agricultural Reserve observed that owners of land in metropolitan areas experience “impermanence syndrome”, the resignation that occurs when farmers fear that neighboring properties will ultimately be rezoned for residential subdivisions that make long-term agricultural activities difficult or impossible.
Preservation can be achieved by using tax revenues to compensate owners for voluntarily restricting the development of their land with a permanent conservation easement. Unfortunately, voters in many communities often oppose taxation for just about any reason including the creation of permanent greenbelts. However, Montgomery County and at least 282 other US communities pursue permanent preservation using transfer of development rights. TDR is a form of zoning in which developers of suitable places called receiving areas are allowed increased development potential when they compensate property owners who voluntarily preserve their land in places called sending areas. In the case of Montgomery County, sending site owners are granted one TDR for each five acres of land placed under permanent easement in the Agricultural Reserve. In receiving areas, developers who buy TDRs gain additional profit-generating density. Of the total 72,000 acres placed under easement in Montgomery County’s Agricultural Reserve, 52,000 acres were preserved by TDR.
In its 2009 Climate Protection Plan, Montgomery County recognized the success of TDR in reducing GHG emissions and added that: “The Agricultural Reserve should continue to be protected for food production, recreation and carbon sequestration” (Montgomery County 2009, ES-9).
In 2017, Montgomery County declared a climate emergency and committed to reducing GHG emissions by 80 percent by 2027 and 100 percent by 2035. In June 2021, the county unveiled a Climate Action Plan aimed at implementing ambitious goals using multiple strategies including one that relies on the Agricultural Reserve for improved carbon sequestration, biodiversity, water management, and natural ecosystems using regenerative agricultural practices incentivized by TDRs (Montgomery County 2021).
Not all TDR programs have had the success experienced by Montgomery County. However, as detailed in Smart Climate Action through Transfer of Development Rights, TDR works for jurisdictions that observe proven factors when developing and adopting their TDR programs. As frustration grows over inadequate responses to climate change at state and local levels, more local governments are likely to consider TDR as a way to create greenbelts and pursue other climate action strategies without relying entirely on tax revenues.
Han, A., C., Kim, and T. Daniels: 2021. Managing urban growth in the wake of climate change: Revisiting greenbelt policy in the US. Land Use Policy. December 2021. Accessed 12-3-21 at https://www.sciencedirect.com/science/article/pii/S0264837721005901.
IRP (International Resource Panel). 2018. The Weight of Cities: Resource Requirements of Future Cities. Paris: United Nations Environmental Programme.