The Building Research Establishment (BRE) has published new biodiversity guidance to support developers in the siting and maintenance of solar farms. John Barwise summarises.

Biodiversity Management Plans (BMPs) help set out specific site objectives that include protection of existing species and habitats. They establish ways to enhance biodiversity and set out procedures for maintenance and monitoring. BMPs are particularly useful for businesses and factories that are considering introducing solar farms on brownfield sites or other available land.

Solar power projects have expanded across the UK in recent years. At the end of 2011 there were 230,000 solar power plants with an installed capacity of 750 megawatts (MW). By February 2014, just two months later, generating capacity had increased 25% reaching over 1000MW, increasing by a further 11% by the end of 2012. Over 1000MW of solar PV was installed across the UK in 2013, including 510MW of larger solar farms, each generating over 1MW. The rapid expansion of solar power is largely due to Feed-in-Tariff (FIT) rates, which offer attractive returns on investment for solar power developers.

Solar farms go through a rigorous planning process before approval is granted, taking into account the suitability of the site, any potential environmental impacts on the locality and UK renewable energy targets. But the rapid development of solar farms is causing concern in some communities about the detrimental impact of solar panels on the landscape and the negative impacts on the natural environment.

Revised planning guidance issued last year by the Department for Communities and Local Government (DCLG) gives local communities a greater say over the siting of solar farms in their areas. Other revised planning considerations include encouraging solar development on previously developed land and supporting sites that allow continued agricultural use as well as enhancing local biodiversity.

BRE’s National Solar Centre Biodiversity Guidance for Solar Developments explains how solar farms can enhance local biodiversity by improving habitats and green corridors that strengthen the overall network of spaces for wildlife. The guide is aimed at planners, developers, ecologists, clients and landowners and will be of particular interest to businesses that own redundant industrial sites or other available land suitable for solar farm development. This report covers some of the key considerations in biodiversity management plans.

Knowing which sites are not appropriate is the first consideration in BMPs. Special Protected Areas (SPAs), Sites of Special Scientific Interest (SSSI), Special Areas of Conservation (SAC), Ramsar sites and other designated sites recognised as having ecological importance should be avoided. Other areas that may be of local nature importance, but which are often undesignated, such as semi-natural grassland, should first be assessed by an ecologist to determine whether solar panel installations are likely to have serious impacts. Solar farms that seek to support agricultural development are outside the scope of the BMP guide, although maintaining land in good environmental and agricultural condition is explained.

Each potential solar farm site is unique. Soil characteristics, drainage, topography, elevation, aspect and proximity to neighbouring land all have an influence on the ecology of a site. Biodiversity enhancements should be selected to fit in with existing wildlife habitats and other physical attributes. The BMP should be written by a qualified ecologist and incorporate recommendations from the Phase 1 Habitat Survey or environmental impact assessment, where appropriate. Other key scoping elements of the BMP should:

  • identify existing biodiversity on site, including protected species and habitats of high conservation value

  • identify potential impacts from the proposed solar farm development being proposed

  • set specific biodiversity objectives for the site and the habitat enhancements these will achieve

  • improve connectivity between existing habitats, which will contribute to the wider local ecological network

  • indicate species for planting and other enhancements such as nesting and roosting boxes

  • set out a management and monitoring regime for habitats on site extending to the life of the site and explain how the site will be decommissioned.

As with onshore wind farms, engaging with local communities in solar farm developments is a key recommendation in the BMP. Basic requirements include publishing information about the site and the biodiversity plan, running open days, school trips, and setting up nature trails, where appropriate.

The initial scoping study sets out the requirements for enhancing biodiversity on a particular solar farm site. Each proposed site will have different environmental characteristics, and these will be reflected in the implementation plan.

There are a number of stages in solar farm construction and maintenance where habitat protection and enhancement must be considered. These are covered briefly below.

Site construction

Construction work usually takes between 6 and 15 weeks, depending on the size of the solar array. The work can be very disruptive to local habitats during and even after construction. The BMP advises that disturbing or removing habitats during sensitive periods for protected species, such as the nesting and breeding season, should be avoided. Other negative impacts to avoid include light pollution and soil erosion or compaction from vehicle movement, especially during wet weather.

Habitat enhancements

As well as enhancing natural biodiversity for a particular site, there are opportunities for creating different habitats within a solar farm. These can include, for example, hedgerows, field margins, wildflower meadows and even winter bird crops, all of which can diversify local wildlife. Most of the rest of the BMP guide covers these and other options in detail and includes the following.

Site boundary features: These contribute to a wider network of connecting features in the wider environment, and have minimum impact on the solar array. Boundary features that have the potential to enhance biodiversity may include ditches, stone walls, hedge banks, field margins and scrub.

Grassland: This can be at the site boundary or under the solar array. Grassland helps prevent soil erosion and should be a priority after the construction phase. Grassland can also incorporate wild flower meadows and fine grasses which will support a range of invertebrates, small mammals, reptiles and birds. Alternatively, grassland can be developed as pasture (including wildflower species) to support a range of farm animals, as well as providing habitat for other species.

Woodland habitat: This provides screening for large solar farms, although to avoid shading, trees should not be planted close to the southern side of the array. Native tree planting, in keeping with local and national biodiversity targets, is encouraged. To support a wider range of wildlife, open glades or wood pasture should be included.

Ponds and water courses: These are beneficial to most animal species provided a high water quality is maintained. Artificial ponds should only be created on land with low wildlife value. Ditches are particularly attractive to wildlife, but if this involves substantial changes to local conditions it will be necessary to obtain a licence from the Environment Agency to undertake the work.

Artificial structures: Most man-made structures can be colonised by some form of wildlife. A variety of purpose-built structures for nesting, roosting and hibernation can also be incorporated on site. Hibernacula include logs, rocks and stone piles, which create suitable conditions for reptiles and amphibians to hibernate.

Site management

Incorporating enhanced biodiversity features into existing solar farm sites requires management to ensure the overall benefits for wildlife habitats are sustainable. For example, site management procedures would include setting appropriate times for cutting or grazing flower meadows and grassland. Hedgerows will also need managing, and the BMP guide recommends three-yearly cycles with two to five-year cycles for grass field margins to minimise disturbance and promote flowering and fruiting. Similarly, pesticide and fertiliser use should be kept to a minimum.

Low intensity grazing provides a low cost, productive option for managing grassland and can also help increase conservation value. Sheep grazing, within specific timeframes, is a preferred grazing choice for many solar farms as larger stock, such as cows and horses, can damage solar arrays.

Horticultural methodology, timing and frequency of interventions should be prescribed in the site management plan.

Site monitoring

Whichever biodiversity options and management regimes are chosen for enhancing local habitats, monitoring outcomes on a regular basis is essential. Key elements of the plan should be monitored against baseline indicators to ensure the BMP is performing as intended. For example, wildflower meadows should be monitored to determine whether they are developing to their full potential. The BMP guide provides a useful table describing the various monitoring activities for various habitats including frequency of monitoring indicator plant and animal species.

Case studies

The BMP guide provides various case studies of solar farms that have successfully incorporated best practice solutions to enhance and sustain biodiversity. The studies focus on a range of different habitat regimes including brownfield sites, grasslands, insect-rich habitats, and grasses to support nesting bird populations and wildflower meadows planted with native seed mixes designed to attract a diversity of wildlife and support bumble bees, which have been in serious decline in recent years. All the case studies show some involvement from wildlife organisations and local groups, which has helped to foster good relations between solar farm developers and local communities.

Further details

BRE National Solar Centre provides independent research-led information and best practice guidance on solar power in the UK. Its Biodiversity Guidance for Solar Development is available from BRE National Solar Centre.

Last reviewed 5 August 2014