California has seen a rapid expansion of large-scale renewable energy development in the past decade, part of a state policy to lower pollution from power generation. Yet, our current power plant siting practices could dramatically alter our energy, agricultural and natural landscape. Can this be avoided or minimized?
Fortunately, more so than conventional energy sources, solar and wind have the potential to harness large amounts of energy without a severe impact on land, water, health or climate. This is in part because where sunlight is abundant, solar panels can be placed nearly anywhere, including cities and semi-urban spaces or land with degraded soil unsuitable for agriculture. Additionally, productive pasture or agricultural lands can simultaneously be productive wind farms, maximizing the land value and minimizing natural land conversion.
In light of these opportunities, we sought to better understand the environmental impact of solar energy development by exploring the trade-offs in the areas of energy, food, and conservation.
We conducted a study to explore patterns of land used for utility-scale solar energy installations in the state of California, a model for renewable energy development in other regions.
We found that the development of utility-scale solar power to date has caused changes to land use that threaten protected natural areas. However, there are many opportunities to site solar power plants that minimize its impacts.
‘Incompatible’ with the environment
California has a state mandate requiring utilities to procure 33% of their electricity from renewable sources by 2020, which has led to rapid development of utility-scale solar power plants. These plants use large arrays of solar photovoltaic (PV) panels or concentrating solar power (CSP) systems that use heat to generate electricity.
In examining the type of land cover impacted by California’s solar installations, we found that a large percentage of installed and planned solar photovoltaic and concentrating solar power capacity (36% and 48%, respectively) are sited in biologically rich shrubland and scrubland environments. Additionally, 28% of solar installations are located in croplands and pastures, creating potential conflicts between using the land for food or energy production.
By contrast, less than 12% of solar capacity is located in the “built environment” – rooftops, parking structures and buildings in urban areas where energy is being consumed. The built environment is the most desirable siting option from an ecological stand point.
Placing solar power in urban areas, rather than on natural land cover, means less habitat loss and landscape fragmentation. This is particularly important in sensitive and rare habitats, such as those found in the Mojave and Colorado deserts of Southern California.
In fact, we found that nearly 74% and 90% of all PV and CSP installations in California, respectively, are located within 10 kilometers (6.2 miles) of the nearest federally protected area, such as critical habitat for threatened and endangered species and Federal Roadless Areas.
Placing these large-scale solar farms close to protected areas may threaten their resilience and effectiveness.
The importance of “buffer” zones around and between protected areas that sustain the flow of organisms and natural resources has been well-demonstrated in previous research. Indeed, land and wildlife management practices today encompass land around protected areas up to a 75-kilometer buffer. Our study finds that the majority of solar installations are well within this buffer zone.
To further measure the ecological impacts of utility solar power, we also scored each installation as either compatible, potentially compatible or incompatible with technical criteria and environmental protection. Factors that affected suitability included the slope of the land, distance to the nearest transmission line and road, and the solar irradiance, or power intensity of sunlight, which is stronger in desert areas. (We excluded Inventoried Roadless Areas, Endangered and Threatened Species Habitat, and Federally Protected Areas.) A site was scored as “Compatible” by meeting these technical criteria as well as being located in the built environment.
We found that fewer than 15% of solar installations are sited in “Compatible” areas. The most common reason for incompatibility was the need for extending transmission lines to bring power from remote areas closer to populated areas.
Transmission line extensions are expensive and require lengthy planning and construction times due to siting difficulties. Thus, in addition to standing in the way of cost-efficient and rapid solar deployment, reducing transmission extensions raise ecological concerns because lengthy transmission lines may result in large-scale landscape fragmentation.
In two other studies released earlier this year, we demonstrated that California could meet renewable energy targets while avoiding land with conservation value.
The first study modeled different scenarios of future renewable energy growth and found that proactive electricity planning for conservation can prevent development on ecologically valuable land while still gaining access to high-quality solar and wind resources. However, this study also showed that without strategic and careful siting, many intact and sensitive habitats are at risk for development because they are particularly windy or sunny.
The second study showed that the technical potential of PV and CSP within the built environment alone could meet and exceed California’s total energy demand.
These studies together demonstrate that improved understanding of the environmental impacts of large-scale solar plants can lead to ecologically friendly and efficient renewable energy planning.
We recognize that siting solar power plants in remote areas is less expensive than distributed, smaller-scale development in built environments due to economies of scale. However, it’s worth noting there are additional costs to meet environmental regulations. For example, the developers of the giant Ivanpah concentrating solar plant in Southern California have spent US$22 million dealing with endangered desert tortoises and expect to spend up to $34 million to comply with federal and state mitigation obligations.
These studies, combined with future research quantifying the trade-offs between costs and conservation for renewable energy development, could arm policymakers and planners with the information to make smarter siting the new norm.