They buzz and swarm, hover and dart. In the process of gathering pollen and nectar for their hives, bees and other insects pollinate flowers, ensuring that plants reproduce and yield fruit and other products. They contribute to pollinating nearly 75% of all human food crops worldwide, and yet humans have put tremendous stress on insect pollinator habitats with pesticides, land development, altered hydrologic patterns, and other actions. As a result, insect species have declined significantly. Ultimate loss of these insect species could have global scale impacts — wiping out crops, elevating food production costs, and compromising human nutrition.
Researchers at the US Department of Energy’s (DOE) Argonne National Laboratory, however, are investigating ways to use pollinator-friendly solar power as a way to reinvigorate pollinator habitats. By studying solar energy facilities with pollinator habitats on site, researchers hope to rehabilitate pollinator populations that play a crucial role in national and global agricultural industries, plant species, and thriving pollinator numbers.
Concerns regarding the conservation of pollinators have risen to the global scale as countries have seen severe pollinator declines and have begun developing strategies to sustain pollinator species in the face of an ever-expanding human population. Although the total land area projected to be required for solar development through 2030 is less than 0.1% of the contiguous US surface area, a need exists to improve the landscape sustainability of large-scale solar developments to avoid or minimize potential impacts to local agriculture and cultural, ecological, and other natural resources.
With goals to conserve habitat, maintain ecosystem function, and support multiple ongoing human land uses in the landscape, researchers in Argonne’s Environmental Science (EVS) division have found that the area around solar panels could provide an ideal location for the plants that attract pollinators. This study outlines opportunities for investigating the environmental benefits of pollinator habitats, such as water conservation, land management, and carbon dioxide reduction.
Background about Rural Energy Development and Agricultural Intensification
Utility-scale solar energy (USSE) developments (≥1 megawatt [MW]) are increasing in agricultural landscapes, specifically on former agricultural fields. Driven variously by economics, rejection of fossil fuels, global climate change actions, air and water pollution, and energy security, USSE grew at an average rate of 72% per year between 2010 and 2016. By the end of 2016, USSE facilities accounted for approximately 22 GW of installed US electricity generation capacity, with an additional 13 GW of planned USSE construction. Interest in on-site vegetation management approaches to USSE farms is increasing, as it could restore ecosystem balance such as crop pollination that also maintains or even enhances agricultural production on nearby lands.
Recent emphasis has been placed on the creation and maintenance of pollinator habitats at USSE facilities. “Pollinator habitats” describes the practice of planting seed mixes of regional native plants such as milkweed and other wildflowers, within the solar infrastructure footprint after construction. Sowing could occur among solar panels or other reflective surfaces, or in off-site areas adjacent to the solar facility. Sowing has the intent to attract and support native insect pollinators by providing food sources, refuge, and nesting habitat.
Despite their ecological differences, all types of solar-pollinator habitats have the potential to improve biodiversity and ecosystem function as compared to conventional USSE vegetation management practices.
Conventional USSE management practices are intended to minimize or prohibit the growth of vegetation within the facility footprint:
- placement of gravel
- establishment and maintenance of turf grass
- herbicide application
Such practices provide little or no habitat suitable for pollinator species, especially if these vegetation management practices occur frequently during operation of the solar facility.
Solar-pollinator habitat and related activities provide ecological benefits for pollinators and non-pollinators alike:
- limited mowing
- no herbicide or pesticide applications
- planned seed sowing to attract pollinators
Reclaiming Pollinator Habitats through Cultivated Solar Farms
In response to the population decline of pollinating insects, such as wild bees and monarch butterflies, the Argonne researchers have examined the potential benefits of establishing pollinator habitats at USSE facilities to conserve pollinators and restore the ecosystem they provide. Examining over 2,800 existing and planned USSE facilities in the contiguous US, the researchers determined whether solar-sited pollinator habitat could benefit agriculture. They found over 3,500 square kilometers of agricultural land near existing and planned USSE facilities that could benefit from rehabilitation and which could help reinstate the declining pollinator population with few subsequent side effects.
For example, one team looked at 3 example crop types to measure the agricultural benefits of increased pollinator habitats. These crops – soybeans, almonds, and cranberries – depend on insect pollinators for their annual crop yields. If all existing and planned solar facilities near these crop types included pollinator habitat and increased yield by just 1%, crop values could rise $1.75 million, $4 million, and $233,000 for soybeans, almonds and cranberries, respectively.
Solar-sited pollinator habitats can help optimize the land-use efficiency of solar energy developments while not compromising solar panel efficiency. Often filled with gravel or turf grass, much of the land in a solar farm is untended. Research has shown that in many locations these grounds offer an ideal place to establish native plant species, such as prairie grass or wildflowers, which are prevalent pollinator habitats and can encourage steady insect population growth. There are economic benefits to pollinators, too — honey bee pollination alone adds more than $15 billion in value to agricultural crops each year in the US.
By increasing the ability of pollinators to pollinate adjacent agricultural fields, solar-sited pollinator habitat may boost farmers’ crop yields and create companion income revenues to neighboring agricultural farms. Rejuvenating local pollinator habitat is one way that local farmers can augment trends to lease land for solar arrays, as the practice has proven more lucrative to them at times than cash crops.
Studies in the UK support findings that solar panels enhance biodiversity and wildlife abundance — botanical diversity within solar farm landscaping is responding to favorable management practices.
Most UK sites studied point out that herbicide application to date at USSEs has been limited to spot treatment of weeds. They conclude that a reduction in the use of broad-spectrum herbicides will lead to greater diversity of broadleaved plants. High soil fertility of arable farmland favors a few dominant species of plants, but, as soil fertility reduces in the absence of fertilizer, diversity of both grasses and broad leaved plants is able to and is anticipated to increase. Where suitable USSE management exists, botanical diversity increases over time, with plants emerging from seed banks as well as airborne or animal-carried seed.
The symbiosis of solar farms and pollinator habitats may widen appreciation among community members and local governments for the pollinators’ role in agricultural production. It may persuade solar developers to rethink the landscape design around their installations.
Many US states are catching up to their European counterparts and acknowledging the need to address pollinator population declines through legislation. Solar facilities are beginning to respond by sowing in pollinator-friendly areas. Illinois recently passed a “Pollinator-Friendly Solar Energy Bill” in May, 2018. Other states like Maryland and Minnesota have made part of their legislative agendas to transition to USSEs that incorporate landscape compatible environs.