Growing Solar, Protecting Nature

Transitioning to clean electric power in less than three decades is an absolute imperative for decarbonizing our economy, and a massive challenge. Massachusetts has made great initial strides in reducing greenhouse gas (GHG) emissions from electricity production, and has ambitious interim goals in place to complete the transition to nearly carbon-free electric power by 2050. Getting there will require a significant increase in the pace of clean energy deployment, including a growing role for solar of all types, and an unprecedented level of investment in electricity grid upgrades and transmission infrastructure.  

Urgency on climate action, however, does not justify the haphazard approach to solar deployment witnessed in the Commonwealth over the past decade. The current trajectory of deployment of large ground-mount solar is coming at too high a cost to nature. Concerns about impacts to nature are partly responsible for erosion of public support for solar, with many communities now seeking to slow or entirely stop new ground-mount solar systems.

 Growing Solar, Protecting Nature explores a different path forward for scaling up solar energy resources in the Commonwealth. In this vision, solar plays an essential and growing role in cleaning our power grid, while nature is also left intact to continue its irreplaceable role combating climate change, supporting biodiversity, and providing resilience to climate change’s worst impacts. This analysis shows that achieving the vision of growing solar while protecting nature is fully within our grasp. But, doing so requires a quick and intentional pivot from current siting practices, with immediate and purposeful changes to energy incentives and programs, enhanced and coordinated state and local planning efforts, and stronger incentives for keeping natural and working lands intact.

The challenge is formidable. By 2030, climate-polluting emissions in Massachusetts must be reduced by 50 percent relative to 1990 levels, and by 75 percent by 2040, on the way to net-zero emissions by 2050. Because it is not feasible to eliminate fossil fuel use across the entire economy by 2050, reaching our net-zero goal will also require removing carbon from the atmosphere, to counteract our remaining GHG emissions. Massachusetts’ forests are our primary and only means of carbon removal. ¹  As of yet, no other technology exists that can perform this function affordably. ²  Ensuring that nature continues this carbon removal service is among our lowest-cost strategies for meeting the net-zero goal. 

But forests can’t do it alone. Clean energy is foundational to unlocking reductions in GHG emissions needed across the economy. Massachusetts needs a massive build-out of clean electricity to support the electrification of the building and transportation sectors. In the Clean Energy and Climate Plan for 2050, the state estimates that the clean energy generation mix needed in Massachusetts could be 8 gigawatts (GW) of solar and 4 GW of wind (onshore and offshore) by 2030, and at least 27 GW of solar and 24 GW of wind by 2050. ³  Other New England states also need to expand clean power resources:  estimates are that the capacity of the New England electric grid will need to expand by 2 to 2.5 times by 2050, and more transmission must also be built to move clean power to where it’s needed.

Fortunately, Massachusetts and the New England region have abundant solar and wind resources. Massachusetts alone is planning for an estimated 5,600 megawatts (MW) of offshore wind energy by 2027. Both renewable technologies have recently undergone a massive market transformation. The National Renewable Energy Lab (NREL) estimates that, over the last decade, the price of solar photovoltaic modules has declined by 85 percent. ⁴ 

Mass Audubon and Harvard Forest believe that scaling up solar and other clean energy resources is an absolute imperative to meeting the state’s climate targets for 2030, 2040, and 2050. All types of solar will be needed, including ground-mount systems as well as “distributed” solar, i.e., rooftop solar that connects into the electricity distribution system, and solar on canopies erected on top of parking lots.

As we scale up our deployment of solar, we must also recognize the instrumental role that natural and working lands play in stabilizing our climate system. More than 60 percent of Massachusetts is covered by diverse forests, which are storehouses of carbon. Our trees alone contain the equivalent amount of carbon as in five years’ of statewide fossil fuel emissions. ⁵  Forest soils contain a similar amount. ⁶  Beyond storage, forests are also actively capturing carbon from the atmosphere at a rate equivalent to 10 percent of our current GHG emissions. ⁷  In addition, forests and natural ecosystems provide valuable, irreplaceable public goods: biodiversity, drinking water filtration, wildlife habitat, recreation, and resilience to impacts of climate change such as flooding and extreme heat.

Incentives under the Solar Massachusetts Renewable Target (SMART) program (and its predecessor programs for solar) have been very effective at driving development of ground-mount solar systems onto already-developed lands such as landfills and brownfields. As of 2020, over 50 percent of all landfills in the U.S. with large ground-mount solar projects were located in Massachusetts. ⁸  Massachusetts is also among the top 10 states in the U.S. in community and rooftop solar placed on buildings and parking lot canopies on a per capita basis. ⁹ 

However, our clean energy and land policies are still not doing enough to safeguard natural ecosystems and working lands. Under current siting practices, thousands of acres of forests, farms, and other carbon-rich landscapes are being converted to host large-scale solar. Mass Audubon’s 2020 Losing Ground analysis showed this recent shift: starting around 2010, clearing for ground-mount solar became one of the leading drivers of land-use change in Massachusetts. ¹⁰  A loophole in SMART provides state funding to ground-mount projects on high biodiversity lands as long as they are community solar. And with the state’s 2030 climate goals only seven years away, combined with new federal incentives for solar provided by the Biden Administration’s groundbreaking Inflation Reduction Act (IRA), the pace of ground-mount solar development is poised to accelerate. 

According to a recent state survey of public attitudes towards solar, over 85 percent of surveyed residents in Massachusetts believe that solar should be built on rooftops, parking lots, landfills, and other developed areas, rather than on cleared forests and on top of productive farmland.  

Massachusetts citizens strongly support expansion of solar and other clean energy resources. But local opposition to large ground-mount solar projects is growing, especially in places where the pace and scale of development has been significant, or done without sufficient input from communities. Public opinion is clear: Massachusetts residents expect a solar build-out that is balanced as much as possible with nature and agriculture. In fact, a recent Massachusetts Division of Energy Resources (DOER) ¹¹  survey found overwhelming support from the public for a more balanced approach to solar siting:

• Over 85 percent of surveyed residents in Massachusetts believe that solar should be built on rooftops, parking lots, landfills, and other developed areas, rather than on cleared forests and on top of productive farmland. 
• Over 70 percent of residents believe environmental impact is the most important trade-off to consider when siting new solar.

Our hypothesis is that there is ample space in Massachusetts to build economically viable solar on already-developed lands, buildings, and parking lots while minimizing solar that drives losses of terrestrial carbon, biodiversity, prime farmland, and lands that provide resilience to flooding, heat waves, and other climate impacts. 

We also believe that public opposition to ground-mount solar could grow unless policies are designed to ensure the best possible balance among clean energy, nature, and working lands. This will require adjustments to the status quo—that is, changing our current siting practices and incentives for large ground-mount solar projects, and deploying even more solar on our buildings and already-developed lands.

In Growing Solar, Protecting Nature, researchers from Mass Audubon, Harvard Forest, and Evolved Energy Research used the best geospatial data and energy-economic modeling available to answer the following questions:

• How have large ground-mount solar systems affected Massachusetts’ forests, habitats, and farms thus far? What would impacts be if roughly ten times as much ground-mount solar is sited in a similar way?
• Can Massachusetts deploy enough solar to meet the GHG emission reduction goals of the state’s Clean Energy and Climate Plan for 2050 while minimizing impacts on lands with the highest value for carbon, biodiversity, and food production, and reducing the impacts of climate change?  
• Which sites for ground-mount solar avoid additional losses to nature and farmlands? How much  solar can be economically sited in the built environment?
• What are the cost implications of deploying more solar with minimal impacts on highest value natural landscapes and farms? What is the cost of siting ground-mount solar on natural and working lands when the true value of carbon removal is included?
• What changes to policy and programs are needed to achieve better balance between ground-mount solar, nature, and working lands?

Solar installations in Massachusetts range from exemplary, nation-leading projects on landfills and brownfields to poorly designed and executed projects that harm unique ecosystems and natural assets. These Profiles of actual projects illuminate both the challenges and opportunities for all types of solar projects as we scale up this essential clean energy resource over the next few decades.

•  Forest Loss and Fragmentation 
•  Conversion of Prime Farmland to Solar 
•  Biodiversity Impacts 
•  Erosion and Runoff 

•  Landfills and Brownfields 
•  Solar Deployment on Commercial Rooftops and Parking Lots 
•  Redevelopment Opportunities for Solar 
•  Public Agencies and Non-Profit Institutions 

•  Agrivoltaics 

Importantly, each of these scenarios is projected to reach the GHG emissions targets set out in Massachusetts’ Clean Energy and Climate Plan for 2050,

though they may employ different levels of clean energy resources like solar, wind, and clean energy imports. ¹² 

Our analysis relies on the best available geospatial data, maps, and best-in-class energy modeling tools. This analytic approach involved three main steps, described below.  More detailed descriptions of our methods, data and assumptions, and modeling tools are available in  Appendix A .

Step 1.  Estimate technical potential of solar in Massachusetts, using different estimates of lands available for ground-mount solar.

We created three scenarios of technical solar potential, defined as where solar can be deployed based on technical and legal considerations only, from now until 2050. Estimates of technical potential do not include any economic considerations. All three scenarios use the same estimate of technical potential for solar on building rooftops and parking lot canopies. Of the ~119,160 acres ¹³  of available rooftops in the Commonwealth, NREL estimates that 40,772 acres are currently viable for hosting rooftop, with a technical solar potential of 20.6 GW. With over 55,000 acres of parking lots in the Commonwealth, we estimate that with set-backs, over 35,000 acres of these could viably host solar now, with technical solar potential of 9.9 GW. Combined together, the best rooftop and parking lot spaces in Massachusetts have over 30 GW of technical solar potential.

The key difference among the three scenarios is in how we depict the lands available to host ground-mount solar projects. This difference is created in order to estimate the range of impacts that ground-mount solar could have on natural and working lands over the next few decades, in particular to levels of forest carbon removal, biodiversity, climate resilience, and productive farmland. Specific assumptions used for the three scenarios are described below.

• The Current Siting scenario approximates the status quo in siting practices for ground-mount solar. In this scenario, ground-mount solar projects comply with existing legal and physical requirements for solar (e.g., relatively low slopes), but otherwise are not constrained by environmental or social goals or considerations.

In contrast with the Current Siting scenario, two Protecting Nature scenarios estimate the technical potential of solar if it is primarily limited to sites on already-developed lands, buildings, and parking lots in order to be highly protective of natural and working lands. By design, the supply of sites for ground-mount solar from now until 2050 is restricted in these scenarios as follows:

• The Protecting Nature—Mid-Impact scenario protects the majority of lands featuring high-carbon natural ecosystems, biodiversity, high climate resiliency, and productive farmland from the supply of sites modeled for hosting ground-mount solar.

• The Protecting Nature—Low-Impact scenario is even more protective of nature, farmlands, and other environmental attributes than the Mid-Impact scenario above.

Step 2.  Estimate how much technical potential for solar is most economically attractive.

As noted above, technical potential for solar only indicates where solar meets minimal legal and technical requirements (e.g., low slope). There is a subset of sites with technical potential that are the most economically attractive—these are the land parcels, buildings, and parking lots that are most likely to be first developed for solar, because they have lower costs compared to other sites. We refer to this portion of technical solar potential with lower relative costs as ‘economic’ or ‘economically attractive’ solar. Using a best-in-class energy-economic model, we evaluated the technical solar potential for each scenario to identify the portion of land parcels, rooftops, and parking lots of the technical potential that are the most economically attractive for hosting solar systems.

Many projects that rank as higher cost will still be developed by homeowners and business owners because of state policy incentives, preferences, and other reasons for installing solar.

Our economic analysis takes into account the effect of federal renewable energy incentives created by the Inflation Reduction Act on future solar capacity. Importantly, it does not include existing state-level incentives that impact the relative cost-effectiveness of solar. State incentives are a key policy tool available to encourage the types of renewable energy development that align with state priorities. By leaving the state-level incentives for solar out of the economic analysis, we are able to understand how changing them would impact future solar capacity. It is important to note that the solar identified as the most economic in our least-cost energy model is not a limit to how much solar can get built. Many projects that rank as higher cost will still be developed by homeowners and business owners because of state policy incentives, preferences, and other reasons for installing solar.

Step 3.  Estimate impacts of economic ground-mount solar on natural and working lands.

For each scenario, parcels identified as most economically attractive for ground-mount solar were then evaluated for the environmental impacts of converting the parcel for development, including changes in forest carbon, biodiversity, climate resiliency, and prime farmland. We used a statistical technique (i.e., Monte Carlo resampling; see  Appendix A ) to account for the uncertainty in exactly which sites are most likely to get built, then calculated differences among the scenarios to estimate the net impacts to nature and working lands.

KEY FINDING #1

As of 2023, Massachusetts has an estimated 4.2 GW of solar energy capacity, currently among the top 15 states in the U.S. ¹⁴  Most of this capacity—roughly 2.8 GW—is distributed solar on rooftops and canopies over parking lots. The remaining roughly 1.4 GW is estimated to be ground-mount solar. Starting around 2010, the build-out of ground-mount solar began to have a major impact on the state’s natural lands.

The impacts of over hundreds of ground-mount solar projects on our natural and working lands over the last decade have been broad and deep. Before these sites hosted ground-mount solar, 60 percent of the land was forested. We estimate that conversion of forests resulted in emissions of more than 500,000 metric tons of CO ₂ —equivalent to the annual GHG emissions from 112,000 passenger cars.   

Ground-mount solar has resulted in losses to more than forest carbon. Sixteen percent of these sites were previously agricultural land. Almost 10 percent of solar acres built during this decade overlap with core wildlife habitat, and 11 percent overlap with critical natural landscapes identified by the state’s map of lands supporting high levels of biodiversity, called BioMap. ¹⁵  Moreover, approximately 15 percent of the affected areas are designated as “above average” for providing resilience to impacts of climate change, according to The Nature Conservancy. ¹⁶ 

If current trends of ground-mount solar construction continue, we stand to lose more than 20,000 additional acres of the most valuable wildlife habitat in the state, including 9,000 acres in the globally rare pine barrens habitat of southeastern Massachusetts and another 9,000 acres in largely forested areas of central and western Massachusetts. When left intact and connected, these areas are habitat for most of the Commonwealth's 432 endangered, threatened, and special concern species such as Blue-spotted Salamander, Northern Long-eared Bat, and Eastern Whip-poor-will. Connected forests also support our more common species and provide critical movement corridors for wide-ranging species such as bobcat, fisher, and black bear. Conversion to ground-mount solar, like other forms of development, drastically alters these natural communities, fragments the landscape, and interrupts wildlife movement patterns. These new forest openings also serve as entry points for invasive plants and provide favorable conditions for increased white-tailed deer density which has further negative impacts on the surrounding forest.

Beyond the direct impacts to wildlife, a fragmented landscape is a less resilient landscape, one that is less able to adapt as the climate continues to change. In Massachusetts, more than a quarter of the forest area is within 65 feet of a non-forest edge, ¹⁷  so it’s imperative that we keep our remaining forests intact. Connected and resilient landscapes allow for the slow range shifts of plants and animals in response to shifting temperature and precipitation patterns. They are better able to support our communities by absorbing and filtering stormwater, reducing flooding and protecting our rivers and drinking water supplies. By breaking up the landscape, we reduce resilience and put these precious ecosystem services at risk.

KEY FINDING #2

Results for the Protecting Nature scenarios show that Massachusetts has ample locations to site economically attractive solar, meeting the Commonwealth’s GHG emissions targets while being highly protective of nature. Under the first of these scenarios—the Protecting Nature—Mid-Impact scenario—solar deployment is at nearly 80 percent of the levels called for by the Clean Energy and Climate Plan for 2050. Reaching the solar levels described in the Clean Energy and Climate Plan can be achieved while protecting nature and working lands, but will require a shift in current state incentives to bring in even more distributed (i.e., rooftop and canopy) solar while also changing the type and location of new ground-mount solar.  

KEY FINDING #3

Ground-mount solar systems generally enjoy economies of scale over rooftop solar systems, which on average are smaller, and involve higher ‘soft costs’ (e.g., permitting, marketing). ¹⁹  Placing solar canopy systems over parking lots is very popular with the public, and the Commonwealth has supported deployment of many successful canopy systems on state-owned parking lots, state universities, and community colleges. However, canopies have higher average costs than most ground-mount and rooftop projects due to the additional materials and labor needed to elevate solar panels. These systems would benefit from additional incentives to be more attractive for developers.

If soft costs of rooftop and canopy systems can be reduced relative to the cost of ground-mount solar over the next few decades, the financial edge that large ground-mount systems currently have will be even lower. And our results project that solar will remain competitive with all other forms of electricity generation over the full timeframe to 2050.

Soft costs like permitting and marketing make up a large portion of rooftop solar costs. We see an opportunity to reduce those costs via policy interventions, which has been achieved in some international markets like Australia. To evaluate the impact of reducing soft costs for rooftops, we modeled potential reductions in these costs of 30 percent. ²¹ 

It is critical to note that the cost comparisons above apply to differences in costs in the energy system only—when the social costs of cumulative losses to nature and farmland by 2050 are included in the analysis, the costs of different approaches to siting ground-mount solar shifts to favor lower-impact siting, as described later in these Findings.

KEY FINDING #4

The Protecting Nature—Mid-Impact scenario estimates there are 41,000 acres of highly economic ground-mount solar, which is only 10,000 fewer acres than in the Current Siting scenario, and another 53,000 acres that could support slightly more costly ground-mount projects. Even though the total acres identified under Current Siting and Protecting Nature—Mid-Impact are only 10,000 acres apart, the land parcels identified in the Protecting Nature scenarios are very different from those indicated in the Current Siting scenario. On average, the Current Siting scenario features the largest parcels which are located primarily in forests and on other natural and working lands. Because the Protecting Nature scenarios are intentionally designed to avoid sites with high-carbon, high-biodiversity forests and farmland, it shifts both the location and size of ground-mount solar sites. Results also show these scenarios would also maintain much higher forest carbon sequestration capacity by 2050 relative to the Current Siting scenario, as described in greater depth in Finding #5 below. Gains in biodiversity, climate-resilient lands, and productive farmlands can also be achieved by shifting away from our Current Siting pathway.

KEY FINDING #5

Nature’s prodigious benefits to society are not valued in markets, even though these are critical services that society needs and are not readily replaceable. Carbon removal by forests is just one ecosystem service that fares considerably worse under a continuation of current solar siting practices. The Current Siting scenario results in a significant loss of carbon from forests ranging from 5.7 to 5.9 MMTCO ₂ e. ²³  This is 4.7 to 4.9 MMTCO ₂ e higher than projected losses of forest carbon under the Protecting Nature—Mid-Impact and Low-Impact scenarios, respectively. To understand what would be needed to make up for this loss of carbon removal by forests and still meet the 2050 net-zero emissions, we calculated the costs of making up this decrement to forests’ carbon removal capacity by achieving other types of GHG emission reductions.

Using an estimate that achieving additional GHG reductions from the energy system in the latter part of this timeframe (2050) will cost approximately $200/ton CO ₂ e, replacing this quantity of natural carbon removal alone could cost up to $940M to $980M. The cost of replacing carbon removed by forests is actually greater than the difference in the energy costs (in present value terms) between the Current Siting and the Protecting Nature—Mid-Impact scenario. ²⁴  And because this estimate only reflects losses in carbon, and does not include the costs of losing other services when nature and working lands are converted, like flood protection, drinking water filtration, wildlife habitat, and local food production, it actually underestimates the costs to the public of further conversion and fragmentation of forests, other terrestrial ecosystems, and farms.

Adding together past and projected future effects of Current Siting, we estimate that by 2050, ground-mount solar will be responsible for the cumulative loss of 39,150 acres of forest, 9,397 acres of prime farmland and 22,794 acres of lands featuring high biodiversity.

In sum, the Protecting Nature scenarios result in markedly lower impacts to nature and the vast number of services it provides. Indeed, continuing along the Current Siting trajectory would not only result in the emissions of millions more tons of carbon than the Protecting Nature scenarios—it would also incur major additional losses to biodiversity, acres of productive farmland, and areas most important for resilience to climate change, on top of losses already incurred from the 2000s to the present.

KEY FINDING #6

This analysis shows that reducing losses of terrestrial carbon and other impacts to high-value natural lands will require a shift to siting ground-mount solar away from larger, forested parcels to smaller projects on lower-impact parcels. A solar build-out which features smaller ground-mount projects also means projects would likely be more evenly distributed around the state, rather than continuing to concentrate in a few counties where the largest, least expensive land parcels are available.

Ultimately, the economic viability of ground-mount solar projects depends on the availability and cost of connecting to transmission infrastructure. As of late 2022, approximately 6 GW of proposed solar projects in New England were waiting for approval to be interconnected to the grid; many of these will not get built due to high interconnection costs. ²⁵  In order to minimize impacts to natural and working lands, interconnection policies should favor smaller ground-mount projects located closer to electric load. Nationally, smaller solar projects (i.e., under 5 MW) are being interconnected about one year faster than large solar projects (i.e., 5-20 GW). ²⁶  Thus, policies focused on smaller ground-mount projects may also result in more solar being brought online more quickly compared to the current pathway of siting larger projects. 

KEY FINDING #7

Massachusetts is a national leader in community solar projects, which are a way for multiple households to buy and benefit from a single solar project. Community solar is a principal means to provide access to affordable solar to low- and moderate-income households in environmental justice communities and beyond, small businesses, and other electricity customers who otherwise cannot finance or host their own solar projects. Solar developers who specialize in residential and commercial rooftop systems state that the IRA’s specific provisions for community energy projects are already boosting their ability to finance these projects. Another component of IRA funding is the U.S. EPA’s new $8 billion Solar for All competitive grant program—this is designed to boost the ability of states, territories, Tribal governments, municipalities, and eligible non-profits to expand solar’s benefits more equitably to low-income ratepayers. ²⁷  Building partnerships among the state, cities, non-profit partners, and developers to make certain that Massachusetts takes full advantage of IRA funding for solar and secures a Solar for All grant should be a paramount priority for the state. These federal funds should be used strategically to secure community solar for low-income customers, and direct deployment towards opportunities on built environment and ground-mount projects on already-developed lands, not on natural and working lands.

The IRA provides tax credits to help home and building owners and renewable energy developers deploy more solar and other clean energy systems. ²⁸  These federal incentives will expire by 2035, which favors strong acceleration of new solar builds over the next decade. It is important to note that the IRA’s tax credits are structured in a way that could further widen the gap in cost competitiveness between new ground-mount systems and rooftop and canopy systems, even with the latter being supported by net metering policy. Massachusetts’ SMART incentives and net metering policy are levers that should be revisited to encourage development of rooftop and canopy systems.

KEY FINDING #8

In addition to Mass Audubon and Harvard University, the Commonwealth and many cities and towns such as Boston, Cambridge, Amherst, Somerville, Plymouth, and Worcester, along with many non-profit institutions, have strong public commitments to significantly reduce their GHG emissions and to protect biodiversity. Many of these institutions also own and/or manage large campuses with many buildings, parking lots, and highly developed lands that could host low-impact solar.

Moreover, many of these entities have the ability to install solar projects which may have longer payback periods in comparison to the private sector, but would benefit from incentives for more costly low-impact solar opportunities such as canopies.  

Residential homeowners and commercial and industrial businesses also own significant acres of sites for ground-mount solar—ranging from nearly 15,000 on the low-end to 40,000 acres on the high end—which could be used to host economic low-impact solar. While many homeowners will prefer rooftop solar, those with large lots (e.g., >1 acre) are good candidates for creative small ground-mount systems. Some portion of the 5,000 to 10,000 acres of other already-developed open spaces that may be underutilized—such as shuttered golf courses—are also potential candidates for hosting ground-mount solar.

Solar’s impacts on forests and farms are part of what is undermining public support for this resource, with many communities now seeking to slow or block new ground-mount projects. The people of Massachusetts strongly support solar, but also highly value nature as a climate solution and an irreplaceable source of biodiversity and wildlife habitat, recreation, clean water and air, and public health benefits. 

Growing Solar, Protecting Nature results show that a more constructive path forward is possible, one that is both highly protective of nature AND scales up affordable solar to communities across the state.

To build and sustain long-term support for ground-mount solar, state policies, incentives, and plans must better align with the public’s strong desire for a better balance between clean energy resources, nature, biodiversity, and local food production. 

We identify three major areas where innovative new policies, as well as changes to current policies and programs, are needed: energy incentives and investments; state and local planning and community outreach; and policies specifically focused on protection of forest carbon, biodiversity, and productive farmlands. 

Solar incentives under SMART (and previous incentive programs) have played a major role in elevating Massachusetts to national leadership on solar, especially for distributed solar, community solar, and low-impact ground-mount solar on landfills and brownfields. Yet, by also supporting large ground-mount solar projects on natural and working lands, these incentives have also played a partial role in the loss of critical natural assets. Although the SMART program was adjusted in 2020 to shift incentives away from conversion of prime farmland towards solar integrated into farming activities (i.e., ‘agrivoltaics’), it still supports conversion of high biodiversity lands for community solar projects. Many of the community solar projects enrolled in the SMART program over the last five years, for example, have been built on converted forests and other valued landscapes. 

We strongly advocate for eliminating SMART incentives (including pass-through of federal funds) supporting large ground-mount solar projects on natural and working lands. Our results show that with just IRA funds alone, economic solar capacity of low-impact solar is nearly 80 percent of that projected under Current Siting. To boost building of low-impact solar, SMART should be further adjusted by increasing incentives for rooftop and canopy systems, especially for community solar. This will help to partially adjust for the fact that federal IRA credits are relatively more advantageous to large ground-mount systems, which are already more economically attractive than rooftop and canopy systems at the outset. Our specific recommendations include the following:

• Eliminate incentives under SMART for ground-mount solar systems on any natural and working lands and for ‘public entity’ solar located on BioMap Core and Priority Habitat lands. 
• Increase SMART incentives for canopy, rooftop, and ground-mount systems sited on already-developed, low-impact lands. 
• Create new SMART incentives for residential ground-mount and industrial and commercial rooftop projects with potential to avoid electric distribution upgrades. 
• Establish interconnection rules that support smaller, low-impact solar projects located close to electric loads. Allow distributed and low-impact ground-mount projects in the interconnection queue to connect first. 
• Require reporting of impacts to land use for SMART-funded projects, and produce annual SMART reports showing aggregate incentives, average cost for installed capacity, and land use impacts for all project categories.
• Set requirements for solar within the state’s Lead by Example and other programs that require rooftop and canopy solar on all new buildings and parking lots receiving state funding. 
• Delineate specific performance goals for rooftop, canopy, and low-impact solar within overall Clean Energy and Climate Plan goals for 2030, 2040, and 2050.
• Leverage existing programs focused on building efficiency and decarbonization to streamline enhance incentives for rooftop solar: o Require Mass Save program to evaluate rooftops for solar suitability during energy audits and discuss with customers.  o Direct Clean Energy Center to create grant program for roof evaluation, repair, and replacement, with priority for low- and moderate-income households and small businesses.
• Consider separate feed-in tariff for larger ground-mount systems outside SMART that utilize already-developed, low-impact sites.
• Require solar on new buildings, parking lots, and commercial and multi-family developments receiving state funding. 
• Prepare for end-of-life fate and establish recycling requirements of solar photovoltaics from all projects receiving state funding.

Siting of ground-mount solar on natural and working lands in Massachusetts has been significant but haphazard, with developers of larger ground-mount systems pursuing opportunities for the largest, least expensive parcels from landowners interested in leasing or selling. Our results show that absent changes to existing incentives and policies, a similar siting pattern will likely continue over the next few decades, with a notable acceleration from now until 2035 while IRA incentives are available. Moving to a deployment of solar that leaves nature largely intact, as portrayed by the Protecting Nature scenarios in this analysis, will require more intentional, forward-thinking planning and guidance. Because cities and towns in Massachusetts play an essential role in local land use, the state needs to provide resources and support for municipalities to shift solar to lower-impact sites and the built environment.

Inadequate transmission infrastructure and a need for distribution upgrades are limiting deployment of solar and other clean energy resources. Space for new transmission infrastructure is only one source of potential increased demand for land over the next 25 years. Two of the state’s current advisory processes—the Grid Modernization and Energy Infrastructure Siting and Permitting advisory groups—should leverage geospatial mapping from this and related analyses, and explicitly require that all recommendations for distribution and transmission system investments, respectively, must show consideration of options with lowest impact to natural and working lands.

Federal and state funds should be directed to help cities, towns, non-profits, and homeowners and businesses to capitalize on these opportunities for solar with low impacts to nature and working lands. For example, the state’s Green Communities program can leverage the IRA opportunity to increase incentives for cities and towns to plan for and support more low-impact solar and connect to landowners with low-impact sites for both ground-mount and distributed solar. The state’s plans for transportation and building decarbonization, promulgating a clean heat standard, and energy storage should be integrated in order to capture the best opportunities for distributed and low-impact solar with clean heat, EV charging, and energy storage.

Finally, the state should conduct a statewide land-use analysis and planning effort that evaluates transmission and distribution upgrades and new capacity needed to reach all clean energy goals, and plan for co-locating ground-mount solar projects close to locations where electric load will be highest under future electrification. This analysis should also anticipate land needs for new affordable housing and commercial developments. Increasingly, communities are encountering solar projects that incorporate battery storage into project design, and seek guidance on managing siting of new energy storage technologies. Our specific recommendation include the following:

• Require Grid Modernization and Energy Infrastructure Siting and Permitting advisory processes to evaluate and reflect options with lowest impacts for natural and working lands and consistency with state goals for forest carbon, biodiversity, Healthy Soils and Resilient Lands.
• Conduct a statewide planning effort to inform and identify zones for deployment of land-efficient, low-impact clean energy resources (including storage) and transmission.  These sites can also anticipate new affordable housing and commercial development, and transportation and water infrastructure.  Opportunities for redevelopment of commercial (e.g. shopping malls) and industrial sites should be prioritized.
• Provide update of 2014 model zoning by-laws for solar that align with state goals for natural and working lands and streamlining permitting for solar projects within developed lands.
• Provide municipalities with updated guidance on solar project decommissioning, battery storage siting and permitting, and related technical topics. Decommissioning should include plans for solar PV end-of-life as well as future land uses.
• Conduct direct outreach to industrial and commercial landowners with highest potential for ground-mount and rooftop solar that avoids electric distribution costs.
• Review UMass Clean Energy Extension and other recent empirical research to evaluate first tranche of agrivoltaics using SMART incentives, and update incentives and guidance on farming practices, local property tax assessments, projects in farmed wetlands and floodplains, and Agricultural Preservation Restrictions (APR). 
• Add requirements for municipal eligibility under Green Communities to assess potential for low-impact solar siting on municipally-owned buildings, schools, and parking lots.
• Increase Green Communities cap on municipal solar from $300K (may depend on success in securing EPA Solar for All grant).

Adjusting incentives within the SMART program to reduce support of projects with negative impacts on nature and working lands is necessary, but not sufficient to protect these lands: many large ground-mount solar projects are being financed with energy revenues and renewable energy credits alone, and thus do not rely on SMART incentives. We need stronger policies that redirect solar and other clean energy infrastructure towards already-developed lands and the built environment where feasible. Other jurisdictions with ambitious climate laws—including the European Union, Washington, and California—are advancing mandatory requirements and standards for carbon removal from natural and working lands. In response to the global biodiversity crisis, still others are setting biodiversity targets and goals to be joined with climate requirements.

Moreover, Massachusetts has major goals for natural and working lands. Under the state’s Resilient Lands Initiative, the Commonwealth has goals to achieve ‘No Net Loss’ of forests and farmlands, and to increase carbon storage and climate resiliency capacity of natural and working lands. Over the next few years, we need policy drivers working on nature’s behalf that go beyond changes to clean energy incentives alone. This requires imagining innovative policies focused on protecting forests, farms, and other natural ecosystems for long-term provision of carbon removal, biodiversity, climate resilience, and food production. Policies for financially compensating forest landowners and farmers for the carbon and ecosystem services these lands currently provide, as well as any additions or enhancements to these natural assets over time, will incentivize keeping these as forest and farms. 

We advocate for an integrated policy approach that begins to internalize the non-market values of benefits provided by natural and working lands: carbon removal, biodiversity, flood protection, climate resilience, clean drinking water, local food production, and recreation, among others. The cost of replacing carbon removal services lost from forests calculated in this analysis—$200/ton CO ₂ e—is a solid point of departure for such a valuation but should be considered a floor value, given that it only reflects the carbon benefits of natural lands. Our specific recommendations include the following:.  

• Establish a statewide goal for biodiversity that sets clear, measurable goals at timelines aligned with climate planning intervals (e.g., 2030, 2040, and 2050).
• Establish permanent statewide funding source, at annual levels that are commensurate with goals to protect lands featuring highest carbon removal, biodiversity, and resilience to climate change.
• Develop and promulgate a performance standard for natural and working lands that embeds long-term carbon removal, biodiversity, water resource protection, climate resilience, and food productivity goals.
• Require developers to pay fees for losses of forest carbon, biodiversity, and other ecosystem services from conversion of natural and working lands, and use proceeds to establish a revolving fund for protection of at-risk nature and farms.
• Scope the parameters of a state-level carbon and biodiversity market to draw in private capital by establishing credits that can be applied to mandatory carbon and biodiversity performance standards.

Mass Audubon and Harvard Forest have many people to thank in the development of Growing Solar, Protecting Nature. Evolved Energy Research experts (Katie Pickrell, Ryan Jones, and Gabe Kwok) led the energy systems modeling to identify least-cost, emissions policy-compliant solar development trajectories under each land-impact scenario. The Evolved Energy Research team also performed the energy systems modeling behind the Massachusetts Decarbonization Roadmap ²⁹  and the 2025/2030 and 2050 Clean Energy and Climate Plans. ³⁰  Mass Audubon staff leading this research project include: Heidi Ricci, Jeff Collins, Sam Anderson, Drew Powell, Will Rhatigan, and Michelle Manion; Christina Wiseman provided vital project management and coordination, Pat Farrar was our project intern from the Woodwell Climate Institute, and David O’Neill provided invaluable strategic direction and guidance. Harvard Forest was led by Dr. Jonathan Thompson, with Lucy Lee and Josh Plisinski providing expert geospatial and forest carbon analysis. Our Marketing and Communications team supported the production and communication of this work, and our design consultant Nancy Crowley skillfully designed the StoryMap. We would also like to recognize The Nature Conservancy’s groundbreaking Power of Place series on renewable energy siting as a key inspiration and roadmap for this work. 

We would like to thank the members of our Technical Advisory Group, who volunteered their time and provided key insights and feedback on methods approach, results, and communication strategies:  Doug Albertson (Town of Belchertown), Fred Beddall (Farmer), Buzz Constable (MLTC Board), Brian Donahue (Brandeis University), Dr. Neenah Estrella-Luna (Star-Luna Consulting), Andy Finton (TNC Massachusetts), Dottie Fulginiti (Old Colony Planning Council), Jessie Partridge Guerrero (MAPC), Lucy Hutyra (Boston University), Scott Jackson (UMass), Steve Long (TNC Massachusetts), Scott Millar (Grow Smart RI), David Publicover (AMC), Jessica Rempel (Cape Cod Commission), Ben Underwood (Resonant Energy), Jessica Wilkinson (TNC), Henry Woolsey (Mass Audubon Board), and Dr. Grace Wu (University of California Santa Barbara). Ann Berwick and Bill Ferguson generously provided insights and data from their experiences leading solar deployment for the City of Newton. Many other experts from the solar industry, clean energy policy experts, local and regional governments, advocacy groups, and planning organizations generously provided data and real-world insights. 

Participation in our Technical Advisory Group and external peer review does not reflect endorsement of our findings or recommendations. Any and all errors or misstatements are our own.

Financial support for this study came from Mass Audubon’s generous donors and supporters.

Michelle Manion, Jonathan R. Thompson, Katie Pickrell, Lucy Lee, Heidi Ricci, Jeff Collins, Joshua Plisinski, Ryan Jones, Gabe Kwok, Drew Powell, & Will Rhatigan (2023). Growing Solar, Protecting Nature. Mass Audubon and Harvard Forest. DOI:10.5281/zenodo.8403839

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