panels is not usually accessible to mechanical mowers).iiiThis management approach may have led to greater plant diversity beneath the panels.
7.1.14 It is worth noting that in some instances the vegetation directly under the panels was more vigorous in growth than between the panels and it may be that there is an effect, often observed in shaded habitats such as woodland, where shade can lead to increased humidity and reduced drying out of soils, particularly when the site is relatively wet to begin with. Over time, it may be that shade tolerant species such as woodland specialist plants, may colonise the areas beneath the panels, as has been seen in sites outside of this study (Hannah Montag pers. obs. of ferns growing under panels).
7.1.15 It was noted that at Site 1 spraying of herbicide on vegetation beneath the panels was likely to rapidly reduce the diversity of broadleaved plants. At this site the diversity of both grasses and broadleaved plants was lower beneath the panels than between the rows, but this difference was on the cusp of being significant (P=0.055). It is anticipated that in time, such a management approach will lead to a marked reduction in botanical diversity.
7.1.16 It should be noted that a number of indirect effects of the presence of solar panels might influence botany under and between the panel rows. Where sheep graze sites, their grazing and resting patterns will vary across the site, with the area beneath panels being used for shelter during adverse weather. Where sites are mowed, the area beneath the panels cannot be accessed by tractor-towed mowers and so a different method (usually hand held strimmers) is used. These variations in management convey differing selective pressures upon the grassland sward and may lead to differences in plant assemblages.
Can solar farms encourage greater invertebrate diversity?
7.1.17 Over all, the abundance of butterflies and bumblebees was greater on solar plots than at control plots. The sites which had the highest butterfly abundance were those that had management in place considered to be ‘high’ in terms of its focus upon wildlife (Sites 5, 10 and 11). Those with the highest bumblebee abundance (Sites 4, 5 and 7) had ‘medium’ to ‘high’ management focus on wildlife. Sites 5, 10 and 11 were sown with a species-rich seed mix including wild flowers which are likely to include suitable foraging plants for both butterflies and bumblebees (although they appear to be benefitting butterflies more significantly). This high botanical diversity is likely the principal reason for the greater abundance of invertebrates on these sites.
7.1.18 The exception to the above was Site 4, where botanical diversity was low. Here, a bloom of white clover occurred during the survey period which attracted a large abundance of bumblebees (196), but of just 2 common species.
7.1.19 Invertebrate species diversity at solar farms, as in the wider environment, will be heavily influenced by botanical diversity, as plants provide essential forage, habitat and structure for nesting and egg laying. The suitability of a plant as a food source depends upon its floral structure, with bees and butterflies being adapted for different structures. In addition, several butterflies rely on a single or very few plant species for laying eggs and larval stages and can only breed on a site if this species is present. Therefore, to attract a wide range of bumblebees and butterflies, it is necessary to have a high diversity of plants.
7.1.20 At two sites invertebrate species richness was significantly greater within the solar plots as compared to the control plots. At Site 10, significantly higher numbers of butterfly species were observed, and at Site 5