THE EFFECTS OF SOLAR FARMS ON LOCAL
BIODIVERSITY: A COMPARATIVE STUDY
BY

HANNAH MONTAG, DR GUY PARKER & TOM CLARKSON

Joint Funded By:

APRIL 2016

THE EFFECTS OF SOLAR FARMS ON LOCAL
BIODIVERSITY: A COMPARATIVE STUDYAUTHORS:HANNAH MONTAG1, DR GUY PARKER2 & TOM CLARKSON1
1

2

Clarkson & Woods

hannah.montag@clarksonwoods.co.uk /Wychwood Biodiversity

guy@wychwoodbiodiversity.co.uk

tom.clarkson@clarksonwoods.co.uk

This document should be referenced as: H. Montag, G Parker & T. Clarkson. 2016. The Effects of Solar
Farms on Local Biodiversity; A Comparative Study. Clarkson and Woods and Wychwood Biodiversity.
Acknowledgements
This research follows on from a preliminary study conducted by Guy Parker and Charlie McQueen in2013. The same methodologies have been utilised for this project, with some expansion to include
further taxa.
This project was initiated by Kate Covill of Orta Solar, who also sourced the funding for the work. Kate
was instrumental in setting up the project and it would not have been possible without her enthusiasm
and perseverance.
We would like to thank those solar organisations who allowed us access to their sites, as well as thesite managers who met us on site (often early in the morning) and helped with setting up theequipment. Thank you also to the landowners who provided us with an adjacent control plot.
The fieldwork was undertaken by Hannah Montag, Harry Fox, Jo Donnelly and Mark Baker of Clarkson& Woods and by Charlie McQueen, Florence Parker-Jurd and Clare Halliday of Wychwood Biodiversity.
We would also like to thank Belinda Howell and Phil Bowater from Clarkson & Woods and Florence
Parker-Jurd of Wychwood Biodiversity who helped with analysis and number crunching.
Thank you to Dr. Jonathan Scurlock of the National Farmers’ Union and Dr John Feltwell for providing
comments on the draft report.
Several photographs used within this report should be credited as G Parker Westmill 2013. Pleasecontact the authors for further details if required.

Published by Clarkson & Woods and Wychwood Biodiversity
Copyright © Clarkson & Woods and Wychwood Biodiversity
ISBN: 978-1-5262-0223-9
The information, data and advice which has been prepared and provided is true, and has been prepared andprovided in accordance with the Chartered Institute of Ecology and Environmental Management’s (CIEEM) Code ofProfessional Conduct. We confirm that the opinions expressed are our true and professional bona fide opinions.

THE EFFECTS OF SOLAR FARMS ON LOCAL BIODIVERSITY: A COMPARATIVE STUDYCONTENTSNON-TECHNICAL SUMMARY ........................................................................................................................................ II1

INTRODUCTION ................................................................................................................................................... 1

2

OBJECTIVE AND AIMS ......................................................................................................................................... 2

3

APPROACH ........................................................................................................................................................... 3
3.1
3.2
3.3
3.4

4

SITE SELECTION AND SURVEY DESIGN ................................................................................................................... 3
SITE MANAGEMENT .............................................................................................................................................. 4
DATA COLLECTION ............................................................................................................................................... 7
STATISTICAL ANALYSIS ......................................................................................................................................... 7
LIMITATIONS ........................................................................................................................................................ 9

4.1
4.2
4.3
4.4
4.5
4.6
5

SITE SELECTION ................................................................................................................................................... 9
BOTANY ............................................................................................................................................................... 9
BIRDS .................................................................................................................................................................. 9
INVERTEBRATES ................................................................................................................................................... 9
BATS ................................................................................................................................................................... 9GENERAL ........................................................................................................................................................... 10
RESULTS ............................................................................................................................................................ 11

5.1
5.2
5.3
5.4
5.5
5.6

INTRODUCTION ................................................................................................................................................... 11
BOTANY ............................................................................................................................................................. 11
INVERTEBRATES ................................................................................................................................................. 15
BIRDS ................................................................................................................................................................ 19
BATS ................................................................................................................................................................. 24
OBSERVATIONS OF OTHER SPECIES.................................................................................................................... 26

6

RANKING OF SOLAR SITES .............................................................................................................................. 27

7

DISCUSSION....................................................................................................................................................... 30
DOES ACTIVE MANAGEMENT OF SOLAR FARMS LEAD TO GREATER BOTANICAL DIVERSITY? ............................................... 30
DO THE PHYSICAL STRUCTURES OF SOLAR FARMS ENCOURAGE A GREATER BOTANICAL DIVERSITY WHEN COMPARED WITHEQUIVALENT UNDEVELOPED AGRICULTURAL LAND ? ........................................................................................................ 32
CAN SOLAR FARMS ENCOURAGE GREATER INVERTEBRATE DIVERSITY? ........................................................................... 33
CAN SOLAR FARMS ENCOURAGE A GREATER DIVERSITY OF BIRDS? ................................................................................. 34
CAN SOLAR FARMS ENCOURAGE A GREATER DIVERSITY OF BATS? .................................................................................. 36
OTHER OBSERVATIONS ................................................................................................................................................ 38

8

CONCLUSIONS................................................................................................................................................... 39

AREAS OF POTENTIAL FUTURE RESEARCH ............................................................................................................ 40
9MANAGEMENT RECOMMENDATIONS ............................................................................................................. 41

10

REFERENCES .................................................................................................................................................... 42

APPENDIX A: SURVEY METHODOLOGIES ................................................................................................................ 43
APPENDIX B: STATISTICAL ANALYSIS....................................................................................................................... 45
APPENDIX C: GROUND NESTING BIRD TERRITORY MAPS ..................................................................................... 46i

NON-TECHNICAL SUMMARY
Very little research has been carried out on the impacts of solar farms on biodiversity, despite theproliferation of this industry within the UK.
This study investigates whether solar farms can lead to greater ecological diversity when compared withequivalent undeveloped sites. The research focussed on four key indicators; botany (both grasses andbroadleaved plants), invertebrates (specifically butterflies and bumblebees), birds (including notablespecies and ground nesting birds) and bats, assessing both species diversity and abundance in eachcase.
A total of 11 solar farms were identified across the southern UK for inclusion in this study. All sites had
been completed for at least one growing season. Approaches to land management varied from primarily
livestock grazing through to primarily wildlife-focused management. At each site the level of management
for wildlife was assessed as low, medium or high based upon activities such as re-seeding, grazing or
mowing regimes, use of herbicides and management of hedgerows and field margins.
To assess changes in biodiversity relating to the solar farm, we compared wildlife in the solar farm towildlife at a “control” plot nearby. The control plot was outside the solar array, but within the same farm.
Most importantly, the control plot was under the same management as the solar farm was prior to its
construction. The purpose of the control plot was to give an indication of wildlife levels before the solar
farm was constructed.
Botanical, invertebrate, bird and bat surveys were then carried out during 2015 on both the solar plot andthe adjacent matched control plot. The results of these surveys were compared statistically to identify any
changes in biodiversity the solar farm, and its land management, had brought about.
The results of the botanical surveys revealed that over all, solar farms had greater diversity than control
plots, and this was especially the case for broadleaved plants. This greater diversity was partly the resultof re-seeding of solar farms: where species-rich wild flower mixes had been sown this diversity was
greater, but even where agricultural grass mixes had been used diversity was greater as compared to thelargely arable control plots.
Management of grassland also influenced botanical diversity. At sites with conservation grazing (winterand spring sheep grazing with a pause through the summer for wild flowers to flower and set seed), plant
diversity had increased through natural processes as compared to the original seed mix.
The invertebrate surveys revealed that butterflies and bumblebees were in greater abundance on solar
farms than on control plots, and the greatest numbers occurred where botanical diversity was also high.
The number of species did not differ significantly between most solar farms and control plots. However,at several sites with higher botanical diversity, and where management for wildlife was considered to be‘high’, a greater diversity of bumblebee and butterfly species was observed.
The bird surveys revealed that over all, a greater diversity of birds was found within solar plots whencompared with control plots. On two of the sites, a greater abundance of birds was observed on the solar
farms when compared with control plots. The greater abundance and species of birds on these sites
suggests foraging opportunities within the solar farms are greater than on the adjacent undeveloped sites.

iiThis is likely to reflect the change from a homogenous arable environment to a diverse grassland habitatthat also contains structures for cover or perching.
When weighting bird species according to their conservation status, solar farms scored significantly higher
in terms of bird diversity and abundance, indicating their importance for declining bird species. The declineof many of these species has been attributed to intensification of agricultural practices. Solar farms witha focus on wildlife management tend towards limited use of pesticides, lower livestock stocking densities
and the re-establishment of field margins, which would benefit many of these bird species.
There was no overall difference in the numbers of skylark territories when comparing solar plots to control
plots, although one site showed a significantly higher number within the control plot. Nesting skylarks wereconfirmed within several of the control plots but at only one solar plot. The nest within the solar plot was
located within the security fencing surrounding the array, but outside of the actual footprint of the array.
The study shows that although skylarks may not nest beneath solar arrays, they do nest within solar farms
and they do incorporate solar farms into their territorial boundaries for foraging.
The results of the bat surveys revealed that there were significantly higher levels of bat activity at thecontrol plots when compared with the solar plots at three of the sites but no difference in bat diversity. The
lower levels of bat activity within the solar plots may reflect the problems bats have discerning artificiallysmooth surfaces such as solar panels. The results of the survey are, however, inconclusive due topotential issues with the survey methodology and warrant further research into this area.
Observations of other species during the surveys included the presence of owl pellets on the solar panels,
indicating that owls were utilising them for perching. Large numbers of brown hare were also noted within
the solar farms at several of the sites.
When sites were ranked for overall biodiversity value, it was revealed that the three sites with the greatest
management focus towards wildlife ranked highest for biodiversity overall.
In conclusion, the study revealed that solar farms can lead to an increase in the diversity and abundanceof broad leaved plants, grasses, butterflies, bumblebees and birds. The level of benefit to biodiversity ishighly dependent on the management of the site, with greater focus on wildlife management leading togreater biodiversity benefit. The sites with the highest wildlife value were seeded with a diverse seed mix
upon completion of construction, limited the use of herbicides, provided good marginal habitat for wildlife
and employed a conservation grazing or mowing regime.

iii

1

INTRODUCTION
Background to the Project1.1.1

Solar Photovoltaic (PV) technology is a relatively new industry within the UK, which has expanded greatly
over the last five years from a total capacity of around 32MW in 2010 to over 8GW in 20151.

1.1.2

PV technology can be utilised in many ways, however, the main area of growth has been large-scale solar
farms which are often constructed on agricultural land or brownfield sites. These can range in size from
1ha to 90ha and have varied greatly in terms of the management of the site post-construction, with somebeing managed specifically for wildlife and others continuing to be agriculturally worked, predominately
through sheep grazing.

1.1.3

During the planning process, a greater emphasis has been placed on seeking ecological enhancements
over the last few years as wildlife benefits are perceived to balance any negative effects relating to visual
impact as well as contributing to national and local conservation targets. Several guidance documents
have been produced to guide developers and local authorities, including Natural England’s “TIN 101: Solar
Parks: Maximising Environmental Benefits”2 and BRE / National Solar Centre’s “Biodiversity Guidance for
Solar Developers”3, which was produced with input from a number of solar development companies andenvironmental organisations.

1.1.4

Despite the growing emphasis on ecological enhancements within solar farms, very little research has
been undertaken on the effects of solar farms on wildlife in the UK and the effectiveness of theseenhancements. A literature review carried out by BSG in 20144 highlighted the limited availability of
research in this area and the difficulty in drawing conclusions on the potential impacts of solar farms on
wildlife. Much of the research has been carried out within other European countries, where solar farms
are often constructed within very different habitats, or in the United States, where concentrated solar
power technologyi is utilised in addition to PV.

1.1.5

A preliminary study was conducted in the UK in 2013 which measured biodiversity within four solar farms,
each with neighbouring control plots. The study focussed on grassland herbaceous plants, butterflies andbumblebees and concluded that under suitable management, solar farms can deliver measurable benefits
to biodiversity5. The study has been used as a basis for further research, as outlined within this report,with a widened scope to look at a larger number of sites and wider indicator taxa. A similar study carriedout in 2013 recorded greater biodiversity on a solar farm in West Sussex as compared to an adjoining
arable field6.

iThis system uses mirrors or lenses to focus sunlight onto a small fixed point where heat energy can be utilised and impacts on
wildlife are very different when compared with PV technology.
1

2

OBJECTIVE AND AIMS

2.1.1

The purpose of this study is to investigate whether solar farms are able to increase the ecological valueof the land they occupy. The over-arching objective, posed as a question, is: ‘Can solar farms and theirassociated management lead to a greater ecological diversity as compared to equivalent undeveloped
land?’ This objective can be broken down to the following questions:

2.1.2

Can solar farms create conditions for greater botanical diversity? There are likely to be changes inbotany resulting from the change of land management within the solar farm. The reduction in the intensityof agricultural activities including the application of herbicides and fertilizers may result in a greater floristic
diversity. Less intensive grazing may also encourage the establishment of broadleaved plants. Solar farms
may have management in place designed specifically to encourage wildlife, for example, diverse native
seed mixes established and with no grazing or cutting through the flowering season. The study exploredthe difference in plant diversity between a solar farm and control plot (land which is under the same
management as the solar farm was previously) in order to determine any changes in botany relating toland management. In addition to management, the solar farm structure may provide a variety of
microclimates with shaded and unshaded areas or wetter and drier environments resulting from thephysical effects of installing solar panels within the field. This study investigated whether there was adifference between the assemblage of plants directly beneath the solar panels with that between the rows,
where more sunlight and rainfall would be expected to reach.

2.1.3

Can solar farms encourage greater invertebrate diversity? The reduction in intensive agricultural
management and potential increase in botanical diversity would be likely to affect other taxonomic groups,
such as invertebrates, which rely on plants for food and shelter. This study investigated whether a greater
diversity and abundance of invertebrates was encountered within solar farms when compared to an
adjacent control plot.

2.1.4

Can solar farms encourage a greater diversity of birds? The increase in plant diversity and reduction
in agricultural pressure may provide suitable conditions for farmland birds, with a corresponding increasein bird diversity. This study investigated both number of species and their abundance, but also theconservation significance of the birds recorded. Bird diversity was compared between solar farm andcontrol plot. In addition, the pattern of use within the solar farm (within the array, site margins) wasinvestigated. There is a general consensus that ground-nesting birds which require unbroken sightlines,
such as skylarks Alauda arvensis, will be discouraged from nesting within solar farms due to the clutteredenvironment, however, no studies have been conducted to examine this theory. The study examined thepresence of ground nesting birds and how they utilise solar farms, including feeding and nesting sites, if
present.

2.1.5

Can solar farms encourage a greater diversity of bats? The study also investigates the usage of solar
farms by bats. Should solar farms offer a greater invertebrate abundance and diversity, this may result ina valuable foraging resource for bats and it has been theorised that the solar panels may even act asnavigational features for bats in the same way that linear habitats such as hedgerows and watercourses
do. Bat diversity was measured and compared between solar farms and their control plots.

2

3

APPROACH

3.1

Site Selection and survey design

3.1.1

A total of 11 solar farms were selected for this study. These ranged in geographical location acrossCambridgeshire, Cornwall, Dorset, Gloucestershire, Hampshire, Norfolk, Oxfordshire, Sussex and theVale of Glamorgan. The approximate locations of the sites surveyed are shown in Figure 3.1 below.
Figure 3.1: Map to Show Approximate Locations of Survey Sites (Red Stars) (Ordnance Survey Open Map)

3.1.2

The sites were selected using the following criteria:a good geographical spread (although the sites represent the higher prevalence of solar farms within
the southern half of the country);a range of management practices including those with no focus on biodiversity (but primarily used
for grazing) to those with a strong focus on management for biodiversity;

3.1.3



sites which had been completed and seeded for at least one growing season; and

a mixture of sites that were previously arable or pasture.

The selection of sites was somewhat limited by those operators that were willing to provide access as
there were health and safety considerations related to working within a solar farm. In most cases, thesurveyor had to be accompanied by the site manager outside of normal working hours in order to conduct
the bird surveys. Therefore, the desired mixture of previously arable and pasture sites could not be
obtained and there is a bias towards previously arable sites within the study.

3

3.1.4

A field within the solar farm was identified for survey. For some sites, this comprised the entire array andwith others it was one field within a larger solar farm. The surveyed field within the array (hereafter referredto the ‘solar plot’) was then matched with a field within the same land ownership, but outside the solar
farm (the ‘control plot’). Considerations when choosing the control plot included size, shape, similarity inadjacent vegetation, and distance from roads. The control plots were under the same management regime(i.e. arable crop production or intensive pasture) as the solar plot was prior to the construction of the array.

3.1.5

The purpose of the control plot was to provide an indication of the level of biodiversity occurring if the solar
farm had not been developed. Survey results from the solar plot and control plot were comparedstatistically to investigate any difference, so providing an indication of any biodiversity changes occurring
as a result of the solar development, and specifically, the land management associated with the solar
farm.

3.2

Site Management

3.2.1

The management of the solar and control plots at the time of the survey are outlined in Table 3.1, including
any seeding, grazing or mowing, use of herbicides and a description of boundary features such ashedgerows and field margins.

3.2.2

The final column of the table below shows a qualitative evaluation of the approach that the solar site
adopts with respect to wildlife. This has been calculated based upon a consideration of the approach
adopted by the manager of the array to a range of issues:

3.2.3



whether the site was seeded with a diverse seed mix;

if and how herbicides were used;

whether the site was subject to grazing or mowing and how this was managed; andwhether the field margins were managed in an ecologically sensitive manner.

Each site was scored according to the approach under each of these categories with an overall rankingof ‘high’, ‘medium’ or ‘low’ awarded to each site based upon the scores within the various categories. Thismethodology and the outcomes are therefore subjective. The outcomes were however cross-checkedwith the professional opinion of the field surveyors regarding the approach to habitat management within
the solar array and the outcomes were found to be similar and as such, this qualitative approach toassessment is considered to be robust.

4

Table 3.1: Description of the Management of the Solar and Control Plots
Site
No.

Site 1Site 2

Date Solar
Farm
Connected

Details of
Solar Farm
Seeding

Grazing/ Mowing
Regime on Solar
Plot

Seeded with arye-grassgrazing mix

Cutting and removalof arisings x 3 peryear.

Seeded with arye-grassgrazing mix

Sheep
in
a
permanent rotation–
approximately
100 sheep.

Location Context

Surveyed solar plot: 9.69ha
Entire solar site: 17.17ha
Size of control plot: 11.3ha
Distance between solar andcontrol plots: 280m

In a predominantly arable
setting, with occasional
woodland coppices, andadjacent a reservoir tothe east.

February 2013

Surveyed solar plot: 11.68ha
Entire solar site: 16ha
Size of control plot 11.71ha
Distance between solar andcontrol plots: 17m

Surrounded by a mix ofagricultural land, disused
quarries, and plantationandbroadleaved
woodlands.

March 2014

Surveyed solar plot: 5ha
Entire solar site: 30ha
Size of control plot: 3.5ha
Distance between solar andcontrol plots: 27m

Mixed landscape withpasture, coastal grazing,
rivers, lowland fens and arange of broadleaved
woodlands. Either side ofan A-road and north of ariver.

March 2014

Surveyed solar plot: 13.6ha
Entire solar site: 29ha
Size of control plot: 11.8ha
Distance between solar andcontrol plots: 10m

Surrounded by largely
arable farmland, a mix ofbroadleaved woodlands
and coastal grazing.
1.6km from the coast.

March 2014

Surveyed solar plot: 18ha (theentire solar site was surveyed)Size of control plot: 11.3ha
Distance between solar andcontrol plots: 20m

Mixed farmland withareasofancient
broadleaved woodlands
and lowland fens.

February 2015

Surveyed solar plot: 14ha (theentire solar site was surveyed)Size of control plot: 13.4ha
Distance between solar andcontrol plots: 6m

A
mix
of
ancient
woodland and conifer
plantation
woodland.
Less than 2km from thecoast.

March 2014

Site 3

Surveyed Areas (ha)Seeded with arye-grassgrazing mix

Seeded with arye-grassgrazing mix

Site 4Site 5

SeededwithKing’s Species
Rich Grass Mix(contains7
species of native
grasses) as well
as 13 species ofnative wildflower
Seeded with arye-grassgrazing mix

Use ofHerbicideon Solar
Site

Site 6

Description of Field
Boundaries on Solar Site

Description of Field
Boundaries on Control
Site

Mgmt ofControl
Plot

Spraying
beneathpanelstocontrol
vegetation.

Hedgerow on all edges with
newly planted infill (approx. 6
years ago). Diverse with goodstructure.
Trees
plantedalong
Nboundary.

East side, 30m wide band oftree/shrub planting.
Northern boundary is a private
railway line.
South
and
west
are
hedgerows.

Rape-seedcrop (nonorganicallyfarmed)N/A. No management
plan

Limited – spot
treatment.

Mix of mature and newly
plantedhedgerows
withgenerous grass strip (at least3m) between hedge andsecurity fence of solar farm.
This grass strip was managed
by a mechanical cut in latesummer.

Mature hedgerows with somelarge standards. Field seeded
tight to the hedgerow.

Silage(nonorganicallyfarmed)Mix of mature and newly
plantedhedgerows
withgenerous grass strip (2-4m)
between hedge and security
fence of solar farm. This grass
strip was managed by amechanical cut in late summer.
The hedge of the southernboundary of the solar farm runs
alongside a ditch.

Maturehedgerows
andwoodland at boundary. Field
planted tight to the boundarywith less than a 1m margin
between crops and the fieldboundary.

Barley(nonorganicallyfarmed)Hedges of varying age: somemature with standards, somenewly planted. On one
boundary between the hedge
and the security fence there isa grass margin of approx. 4m,
which is managed with twice
yearly cuts.
Wide field margins in places(over 30m) managed forwildlife. Mature hedgerows
with some tree planting.
Smallwoodlandcopsespresent at boundaries.

Hedges of varying age: somemature with standards, somenewly planted. The control site
was planted with crop tight tothe hedgerow.

Barley(nonorganicallyfarmed)Biodiversity
Management Plan –not fully adhered to:specified 3 different
seed mixes such as
EM5,
EM10
and
retained arable herbs
which
were
not
planted.
Biodiversity
Management Plan –not fully adhered to:specifiedplanting
speciesrich acidgrassland in 10 areas
beneath the arrays,
these
were
not
planted. Some bird
boxes installed andnewhedgerows
planted.
Biodiversity
Management Plan –not fully adhered to:specified sowing ofareas with a meadow
seed mix, which was
not done.

Narrow field margins. Mature
hedgerows with areas ofwoodland present.

Broad bean
crop (nonorganicallyfarmed)Site
Environmental
ManagementPlanfully adhered to.

Mature hedgerows with large
standards and woodland.
Generous grass strip (at least3m) between hedge andsecurity fence of solar farm.
This grass strip was managed
by a mechanical cut in latesummer.

Mature hedgerows with large
standards and woodland. Field
seeded tight to the hedgerow.

White
clover ley(nonorganicallyfarmed)Biodiversity
Management Plan –not fully adhered to:specifiedplanting
speciesrich acidgrassland in 10 areas
beneath the arrays
andtussockygrassland
strips,
these
were
not
planted.

Conservation
grazing from 2015,
with sheep taken off
during summer anda mechanical cut insummer 2015.

No

Sheep
in
a
permanent rotation–
approximately
100 sheep.

Spot sprayingof thistle &docks.
Blanketspraying
of
fence
line
areas
and
inverter areas.
Some mowing
tocontrol
weeds.

Conservation
grazing, with sheep
taken off during
summerforaflowering break.

Conservation
grazing from 2015,
with sheep taken off
during summer anda mechanical cut insummer 2015.

No

5

Mgmt Plan
Adhered to?

Mgmt focus
towards
wildlife

Medium

Low

Low

Med

High

Med

Site
No.

Site 7Site 8Site 9Site 10Site 11

Date Solar
Farm
Connected

Details of
Solar Farm
Seeding

Predominantly
mixed
agriculturallandscapewith mature hedgerows
and small patches ofwoodland, A-roads run
near the south and eastbounds of the site.

March 2013

OriginallyseededwithEmorsgate EM2
or EM6 but seed
did not establish.
Will be reseeded
April/May 2016.

Mowed

Surveyed solar plot: 5.12ha
Entire solar site: 16.1ha
Size of control plot: 5.72ha
Distance between solar andcontrol plots: 10m

Agriculturallandscapedominated by improved
grasslandwithoccasional small pockets
of woodland.

March 2014

Not seeded bysolar operator,
but likely to havebeen
seededwith
rye-grassgrazing mix byfarmer

Sheep grazed

Surveyed solar plot: 4ha
Entire solar site: 14.19ha
Size of control plot: 3.9ha
Distance between solar andcontrol plots: 130m

Predominantly
arablelandscape with patchesof broadleaved and someancient woodland, and ariver running 350m eastof the site.

March 2013

Seededyearlywithrye-grassgrazing mix

Hay cut and sheep
grazed at time ofsurveySurveyed solar plot: 12.14ha(the entire solar site wassurveyed)
Size of control plot: 16.18ha
Distance between solar andcontrol plots: 190m

Row of wind turbines
along
the
northernboundary. A-road tosouth. Mixed agriculturallandscape with patches
of woodland.

July 2011

Surveyed solar plot: 9.3ha (theentire solar site was surveyed)Size of control plot: 10.8ha
Distance between solar andcontrol plots: 22m

Ina
predominantly
agricultural (mixed arable
and pasture) landscapewith small patches ofwoodland and somemature hedgerows.

March 2014

Surveyed Areas (ha)Location Context

Surveyed solar plot: 13.33ha(the entire solar site wassurveyed)
Size of control plot: 20.4ha
Distance between solar andcontrol plots: 10m

Diversewildflower mix (8speciesofbroadleaved
plant)

Seeded with amixture of nativeand non-native
pollinator
attracting plants.
Not
seededdirectly beneathpanels.

Grazing/ Mowing
Regime on SolarPlot

Use ofHerbicideon Solar
Site
Spot spraying
of weeds

N/A - No weed
control has yettaken place.

Spot spraying
of weeds

Annual cut withsheep
grazing
through the winterandspring(conservation
grazing)

Selective spot
sprayingofproblemsp.
(thistle, dock,
nettle)Wildlife-sensitive
mowingregimeemployed (2 to 3
cuts per year).

N/A - no weed
controlbeyondmowing.

6

Description of Field
Boundaries on Control
Site

Mgmt ofControl
Plot

40-50m wildflower meadow
buffer present along south andsouthwest bounds comprisingfine grasses, red campion,
daisies, no dense thatch
formed yet. Control and solar
site share a woodland belt
along the western boundaries.
The remainder of the hedges
had been in-fill planted andhad varied structures.
Diverse field margins plantedwith clover mix, although notforming tussocky structure as
yet. Hedgerows mature withstandard trees with someevidence of poaching by
sheep.

Western boundary is awoodland belt, the northern Isa mature hedgerow, thesouthern boundary is a gappy
but developing hedgerow andthe eastern a line of scrub.

Arable crop
(nonorganicallyfarmed)Hedgerow around entire field.
Mature, with standard trees.

Maize crop
(springsown) (nonorganicallyfarmed)A max of 15m between the site
security fence and the hedge
which runs around ¾ of thesite, kept mown by the farmer.
The hedge to the west of thesite had failed to establish.
Shares a hedge with thecontrol site.

Earth bund covered by
wildflowers along lane to thesouth. Hedgerow along lane tothe east. Hedgerows alongwest and northern sides.

Barley crop
(nonorganicallyfarmed)Large grassland buffer aroundsite. Extensive open areas
within fenced area. Good
connectivity between seeded
grassland in array with othercorridors of seeded grassland
along tracks and beneathturbines. A hedgerow to thesouth and east but no otherboundaries. Wind turbines tothe north with grassy fieldmargin.
Site bounded by mixed
hedgerows.

South-west boundary has acourse grassland/scrub strip
with a large number ofpoppies. Scrub/field margin
along lane to the west. Wind
turbines to the north, below
whichisseededwithwildflower mix. No boundary to
the east.

Barley(nonorganicallyfarmed)Long grass left on part of thesite (possibly for skylarks).
Hedgerows present on threesides of boundary (E, N andW).
Grasslandandscrub
developing to the SW.

Newlyplantedgrass crop
cutforsilage (nonorganicallyfarmed)Description of Field
Boundaries on Solar Site

Mgmt Plan
Adhered to?
Biodiversity
Management
Planproduced – not fully
adhered to: bat andbird boxes have notbeen installed, andconifer trees wereplanted along thehedgerows instead ofherecommended
native trees.
N/A - No management
plan produced.

Mgmt focus
towards
wildlifeMed

Med

No management planthough the Planting
Plan was not adheredto.
The
nativehedgerow along thewest of the site had
failed to establish andEM1 seed mix was not
used.
N/A - No management
plan was produced.

Low

High

Habitat Management
Portfolio - bird boxes
have been installed,
as well as reptile
hibernacula and small
pond.

High

3.3

Data Collection

3.3.1

Four biodiversity indicators were selected: botany, birds, invertebrates (bumblebees and butterflies) andbats. The survey protocol for each discipline is provided within Appendix A. A brief description of theapproach to data collection is outlined below.

3.3.2

These indicators were selected for a variety of reasons including: the role and importance of the receptor
within an ecological community; whether the species group is used as a typical indicator of biodiversity
and ecosystem health7; the ease and practicality of collecting information within the available survey
period and budget; species groups for which questions remain regarding the impact of solar arrays; andspecies groups which are thought to be adversely affected by solar arrays.
Botany3.3.3

Quadrat surveys were used to compare the botany present within the solar array and the control plot. Ten
quadrats were surveyed within the solar plot (from between the panel rows) and 10 quadrats from thecontrol plot for this purpose. Within the solar plot, a further 10 quadrats were collected directly beneaththe solar panel rows. These quadrats were compared to those collected between the rows to assess theeffects of shading and water stress on plant communities. The locations of the quadrats were randomly
picked prior to visiting site in order to avoid surveyor bias.
Invertebrates

3.3.4

Invertebrate surveys focussed on bumblebees and butterflies within both the solar plot and control plot.
A total of ten, 100m transects were walked within the solar plot and within the control plot; these transects
were spaced evenly through the site. The species and number of individuals were recorded on eachtransect.
Birds

3.3.5

Three bird surveys were conducted both within the solar plot and within the control plot. Surveyors walkeda pre-defined transect route recording the species and abundance of all birds seen or heard. Additionally,
the behaviour of each bird was categorised into calling/singing, foraging or flying over site and the locationof the bird was marked as either within the field or the field boundary. This method is an adapted form of
the Breeding Bird Survey (BBS) method developed by the RSPB, BTO and JNCC8.

3.3.6

Ground nesting birds were mapped and behaviours recorded in order to assess the numbers of territories
and presence of active nests.
Bats

3.3.7

Static bat detectors were installed within both the solar plot and the control plot. Microphones were set
approximately 50m from the nearest field boundary at a height of approximately 3m. These were left
recording for around 10 nights and the data subsequently analysed using Kaleidoscope Pro software. Thismethodology allowed an assessment of the number of bat species using each site and the number ofpasses per night, giving an indication of activity levels.

3.4

Statistical Analysis

3.4.1

The data was subject to various statistical analyses in order to demonstrate whether any of therelationships and patterns observed were statistically significant. Chi-Squared Test was used to consider

7differences between the findings within the solar plot and the control plot and Mann Witney-U Test wasused to assess the significance of overall differences between the control and solar plots in the aggregatedfindings for all sites. Further details of the statistical analyses used are presented in Appendix B.

84

LIMITATIONS

4.1

Site Selection

4.1.1

Where possible, the control plot was selected to reflect the management of the solar plot immediately prior
to the construction of the array. However, one of the solar farms (Site 2) was constructed on land usedpreviously for arable crop production but was within a farm where arable and pasture rotation wasundertaken. At the time of survey it was only possible to select a control plot under intensive pasturemanagement. Given the regular rotation of this land between pasture and arable, this was not seen as amajor limitation.

4.1.2

It was not possible to obtain a good mixture of sites which were previously arable and pasture, due todifficulties in gaining access to sites. Therefore, the study shows a bias towards previously arable plots,with only two (Sites 6 and 11) on previously pasture land.

4.2

Botany4.2.1

Several of the sites had recently been cut or were grazed to a very short sward by sheep. It most cases,
plants could be identified to species level; however, it is possible that some species may have been missed
due to not being apparent during the survey.

4.3

Birds

4.3.1

Surveys were conducted between April and July; bird surveys become less effective later in the season
as males stop singing and defending territories when they are feeding young, therefore, surveys
conducted in June and July may have under-recorded singing birds. However, this bias will have beenequally introduced to all sites.

4.3.2

Ground nesting bird territory mapping was not carried out at one of the sites due to an error in the recording
methodology.

4.4

Invertebrates

4.4.1

Due to generally poor weather conditions during 2015, several bird and invertebrate surveys were
undertaken under suboptimal conditions. Although rain was avoided, several surveys were undertaken on
cloudy days with a light wind, which is suboptimal for butterfly and bumblebee surveys. Where possible,
survey dates were changed, however, in some cases this was not possible due to the long bouts ofsuboptimal weather in June/July 2015. As the surveys on the control and solar plots were conducted on
the same morning, this limitation would not affect the comparative analysis, but may have resulted in lower
numbers than expected for both solar and control plots.

4.5

Bats

4.5.1

Due to malfunctions in the recording equipment, only 8 of the 11 sites were successfully surveyed for bats.
The technical difficulties included static detectors failing to record, or on one of the sites the detector within
the solar plot recorded continuous noise, which appeared to have cancelled out any bat activity. It was
not clear whether this noise was emitted from electrical equipment associated with the array or if it was amalfunction within the bat detector. This resulted in the bat data being excluded from the ranking of overallbiodiversity value for each site.
9

4.6

General

4.6.1

Later in the season, it became difficult to navigate through the control sites which were planted withrapeseed due to the density and height of the crop. Therefore, the transects and quadrats had to bemodified to follow existing tramlines. However, due to the monoculture nature of the crop it is not thoughtthat this would affect the results of the survey.

10

5

RESULTS

5.1

Introduction

5.1.1

The results of the surveys are set out within this section with statistical information shown in table form.
All highly significant differences (where the probability that the results show a non-random difference ismore than 99%, or P=<0.01) are shown as “HSD” and highlighted in dark green. All significant differences(where the probability that the results show a non-random difference is more than 95%, or P=<0.05) are
shown as “SD” and highlighted in light green. Where an inverse relationship is found (i.e. where the results
show significantly higher numbers on the control plot when compared with the solar plot), significant results
are highlighted in orange.

5.1.2

The term “Diversity” has been used to express species richness, i.e. the number of different species
present within a sample. The term “Abundance” has been used to express the number of individuals
present within a sample (of all species).

5.2

Botany5.2.1

The botanical data was analysed to compare the diversity between control/solar plots and between sites.
The diversity within solar plots was also explored to investigate whether there was a difference in thesward directly beneath the panels compared withsummarised below.

5.2.2

Overall, when looking at the number of plant
species found on all solar plots combined (144)compared with control plots (70), there weresignificantly more species on solar plots (Chi-160

Total No. Plant Species

between the rows of panels. The results are

140
120
100
80
60
40
20
0

Squared P=<0.001), as shown in Figure 5.1.

solar

Comparing Botanical Diversity Between Solar

control

Figure 5.1: Overall Comparison of Solar and Control
Plot Botanical Diversity

and Control Plots
5.2.3

Solar plots contained between 15 and 41 species of plant. By contrast, control plots contained between 2
and 18 species of plant.

5.2.4

The analysis below encompasses “broadleaved plants”, which includes all species with wide leaves rather
than narrow leaves. Narrow leaved plants which grow from the base (graminoids) have been given aseparate group (“grasses”) and includes grasses, rushes and sedges.

5.2.5

Total plant diversity (i.e. the combined totals of broadleaved plants and grasses) was significantly higher
within the solar plots when compared with the control plots and this difference was found to be highly
significant (P=0.0001). For individual sites plant diversity was significantly greater in solar plots at ninesites (highly significant difference; P<0.01) and at two sites there was no significant difference (Table 5.1).

11

Table 5.1: Diversity of Plants Compared between Solar Plots (S) and Control Plots (C) for Each Site using Chi-Square
Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
Total Species
SiteSignificanceS
C
Site 125

2

HSD (P=0.000)

Site 223

7

HSD (P=0.003)

Site 328

5

HSD (P=0.000)

Site 415

7NS (P=0.08)

Site 522

8

HSD (P=<0.01)

Site 622

18

NS (P=0.52)

Site 731

6HSD (P=0.000)

Site 821

6HSD (P=0.003)

Site 925

4HSD (P=0.000)

Site 1024

9HSD (P=0.009)

Site 1141

18

HSD (P=0.002)

Overall comparison of solar plots and control plots

5.2.6

HSD (P=0.0001)

When comparing grass diversity between solar plot and control plot for all sites, grass species diversity
was greater in solar plots and this difference was highly significant (P=0.0005). When comparing individualsites, in two sites the solar plot displayed greater diversity which was highly significant (P<0.01), and in
two plots which was significant (P<0.05). In seven plots, there was no significant difference in the diversityof grasses between solar plot and control plot. The statistical results are shown in Table 5.2.

Table 5.2: Grass Species Diversity Compared Between Solar Plots (S) and Control Plots (C) for Each Site using ChiSquare Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom
Row
Total species
SiteSignificanceS
C
Site 111

1

HSD (P=<0.004)

Site 25

3

NS (P=0.48)

Site 3

7

1

SD (P=<0.03)

Site 443

NS (P=0.71)

Site 580

HSD (P=0.005)

Site 67

7

NS (P=1.0)

Site 77

1

SD (P=0.03)

Site 861

NS (P=0.06)

Site 973

NS (P=0.21)

Site 10105NS (P=0.19)

Site 11104NS (P=0.11)

Overall comparison of solar plots and control plots

HSD (P=0.0005)

125.2.7For broadleaved plants, diversity was greatest in solar plots as compared to control plots and thisdifference was highly significant (P=0.0002). For individual sites, the diversity was greater in eight solar
plots as compared to their control plots. This difference was highly significant (P<0.01) in five sites, andsignificant (P<0.05) in three sites. In three sites, there was no difference in broadleaved plant diversity
between the solar plot and control plot (Table 5.3).

Table 5.3: Diversity of Broadleaved Plants Compared between Solar Plots (S) and Control Plots (C) for Each Site using
Chi-Square Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the
Bottom Row
Total species
SiteSignificanceS
C
Site 114

1HSD (P=0.001)

Site 218

4

HSD (P=0.002)

Site 321

4

HSD (P=0.001)

Site 411

4NS (P=0.07)

Site 514

8NS (P=0.2)

Site 615

11

NS (P=0.43)

Site 724

5

HSD (P=<0.001)

Site 815

5

SD (P=0.03)

Site 918

1

HSD (P=<0.001)

Site 1014

4

SD (P=0.018)

Site 1131

14

SD (P=0.011)

Overall comparison of solar plots and control plots

HSD (P=0.0002)

Comparing Botanical Diversity Within Solar Farms
5.2.8

An analysis of the data collected from within the solar plots was conducted, looking at those samples
collected in the middle of the rows (i.e. in the open) and those collected from beneath the panels (i.e.
shaded). There was no significant difference in plant diversity beneath the panels as compared to between
the rows when comparing all plots together (P=0.08; Table 5.4)

5.2.9

Comparing plant diversity in the middle and under the rows, at nine solar plots there was no significant
difference, at one plot there was significantly higher diversity in the middle of the rows and in another plot
there was significantly higher diversity of plants beneath the panels (Table 5.4).

13

Table 5.4: Diversity of Plants in Solar Farms Compared Between Panel Rows (M) and Beneath Panels (U) for Each Siteusing Chi-Square Test. An Overall Comparison between the Two Locations using Mann-Whitney U Test is Shown in
the Bottom Row
Total species
SiteSignificanceM
U
Site 122

11

NS (P=0.055)

Site 218

17

NS (P=0.87)

Site 324

17

NS (P=0.27)

Site 41213

NS (P=0.87)

Site 520

17

NS (P=0.62)

Site 622

16

NS (P=0.33)

Site 722

17

NS (P=0.42)

Site 818

7

SD (P=<0.02)

Site 9920

SD (P=0.04)

Site 101924

NS (P=0.44)

Site 1128

20

NS (P=0.25)

Overall comparison of between panel rows and beneath panels

5.2.10

NS P=0.08

Comparing the diversity of grasses within solar plots, no significant difference was found beneath thepanels as compared to between the rows in all eleven plots (P=0.07) and there was no significant
difference found at the site level (Table 5.5).

Table 5.5: Diversity of Grasses in Solar Farms Compared Between Panel Rows (M) and Beneath Panels (U) for Each
Plot using Chi-Square Test. An Overall Comparison between the Two Locations using Mann-Whitney U Test is Shownin the Bottom Row
Total species
SiteSignificanceM
U
Site 1105NS (P=0.19)

Site 25

3

NS (P=0.48)

Site 37

5

NS (P=0.53)

Site 42

4

NS (P=0.41)

Site 58

6NS (P=0.59)

Site 67

6

NS (P=0.78)

Site 75

2

SD (P=0.25)

Site 863

NS (P=<0.32)

Site 955NS (P=1.00)

Site 10910NS (P=0.81)

Site 117

5

NS (P=0.56)

Overall comparison of between panel rows and beneath panels

14

NS (P=0.07)

5.2.11Comparing the diversity of broad-leaved plants between the rows vs underneath the panels, there was no
significant difference for all sites together (P=0.44). Looking at individual sites, two sites displayed greaterbotanical diversity between the rows than under the panels, with the difference being highly significant(P=0.01) in one site and significant (P=0.045) at the other. At one further site, broadleaved plant diversity
was greater beneath the panels than between the rows, this difference being significant (P=0.018). At theremaining eight sites there was no significant difference in diversity between rows and beneath (Table
5.6).

Table 5.6: Diversity of Broadleaved Plants in Solar Farms Compared Between Panel Rows (M) and Beneath Panels (U)for each site using Chi-Square Test. An Overall Comparison between the Two Locations using Mann-Whitney U Test isShown in the Bottom Row
Total species
SiteSignificanceM
U
Site 112

6

NS (P=0.16)

Site 213

14

NS (P=0.84)

Site 317

12

HSD (P<0.01)

Site 4109NS (P=0.81)

Site 51211

NS (P=0.83)

Site 615

10

NS (P=0.32)

Site 717

15

NS (P=0.72)

Site 812

4

SD (P=0.045)

Site 94

15

SD (P=0.018)

Site 101014NS (P=0.41)

Site 1121

15

NS (P=0.32)

Overall comparison of between panel rows and beneath panels

NS (P=0.44)

5.3

Invertebrates

5.3.1

The invertebrate transect data was analysed to compare species diversity and abundance between solar
and control plots for each site and as an
overall measure. This section has been split

100

into an analysis of butterflies and bumblebees.
5.3.2

Abundance

80

Diversity

Overall, when looking at the number of both70

butterfly and bumblebee species found on all

60

solar plots combined (29) compared with50

control plots (21), there was no significant

40

difference (Chi-Squared P=0.26). There was,30

however, a significantly higher abundance of20
10

invertebrates on solar plots (Chi-Squared0

P=<0.001), as shown in Figure 5.2.

solar

control

Figure 5.2: Overall Comparison of Solar and Control
Plot Invertebrate Diversity and Abundance

Butterflies
5.3.3

90

The number of species of butterfly observed in solar plots ranged from 2 to 5, with a mean of 3.4. For
control plots, the range was 0 to 3 with a mean value of 1.8. There was a highly significant difference15

between the numbers of butterfly species recorded within solar plot and control plot when all sites wereconsidered together (P=0.008).
5.3.4

In terms of individual sites, the number of butterfly species observed was significantly higher in the solar
plot than the control plot at a single site (P=0.045), as shown in Table 5.7.

Table 5.7: Diversity of Butterflies Compared between Solar Plot (S) and Control Plots (C) for Each Site using ChiSquare Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom
Row
Total Species
SiteSignificanceS
C
Site 13

2

NS (P=0.65)

Site 220

NS (P=>0.05)

Site 34

2

NS (P=0.41)

Site 42

2

NS (P=1.00)

Site 543

NS (P=0.70)

Site 62

3

NS (P=0.65)

Site 742

NS (P=0.41)

Site 83

3

NS (P=1.00)

Site 942

NS (P=0.41)

Site 1040

SD (P=0.045)

Site 115

1

NS (P=0.10)

Overall comparison of solar plots and control plots

5.3.5

HSD (P=0.008)

In terms of numbers of individual butterflies observed, for solar plots the number ranged from 3 to 99 witha mean of 19.9, and for control plots, 0 to 68 with a mean of 8.3. The number of butterflies observed per
survey in all solar plots was statistically higher than in all control plots (P=0.005), with the difference being
highly significant (Table 5.8).

5.3.6

Looking at individual site surveys, the number of butterflies observed was greater in the solar plot thanthe control plot for surveys at six sites. This difference was statistically highly significant at four sites, andsignificant at a further two sites. However, in one site the reverse was true, with significantly greaternumbers of butterflies being observed in the control plot, which was highly significantly different(P=<0.001), as shown in Table 5.8.

16

Table 5.8: Butterfly Abundance Compared between Solar Plot (S) and Control Plots (C) for Each Site using Chi-Square
Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
Mean Abundance Across All Surveys
Site
SignificanceS
C
Site 111

3

SD (P= 0.03)

Site 230

NS (P=>0.05)

Site 315

3HSD (P=0.004)

Site 442

NS (P= 0.41)

Site 599

7

HSD (P=<0.001)

Site 613

68

HSD (P=<0.001)

Site 710

2

SD (P=0.02)

Site 83

3

NS (P= 1.00)

Site 962

NS (P=0.15)

Site 10160

HSD (P=<0.001)

Site 1139

1

HSD (P=<0.01)

Overall comparison of solar plots and control plots

HSD (P=0.005)

Bumblebees
5.3.7

The number of species of bumblebee per survey observed in solar plots ranged from 0 to 10, with a mean
per survey of 3.6. For control plots, the range was 0 to 5 with a mean value per survey of 1.7. However,overall, the number of bumblebee species observed per survey in solar plots was not statistically different
from control plots (P=0.06).

5.3.8

Comparing bumblebees at individual sites, the number of species observed was significantly higher in thesolar plot than the control plot at one site (P=0.01), as shown in Table 5.9.

17

Table 5.9: Diversity of Bumblebees Compared between Solar Plot (S) and Control Plots (C) for Each Site using ChiSquare Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom
Row
Total Species
SiteSignificanceS
C
Site 130

NS (P=0.08)

Site 22

2

NS (P=>0.05)

Site 34

2

NS (P=0.41)

Site 42

2

NS (P=1.00)

Site 560

SD (P=0.01)

Site 63

3

NS (P=0.65)

Site 7105NS (P=0.19)

Site 81

1

NS (P=1.00)

Site 91

1

NS (P=1.00)

Site 1022

NS (P=1.00)

Site 115

1

NS (P=0.10)

Overall comparison of solar plots and control plots

5.3.9

NS (P=0.06)

Considering the number of individual bumblebees observed per survey, for solar plots the number ranged
from 1 to 196 with a mean of 43.8, and for control plots, 0 to 36 with a mean of 6.8. The number ofbumblebees observed per survey in all solar plots was statistically higher than in all control plots (P=0.02).

5.3.10

Looking at individual sites, the number of bumblebees observed was significantly higher in the solar plot
than the control plot for seven sites and the results were highly significantly different (see Table 5.10).

Table 5.10: Bumblebee Abundance Compared between Solar Plots (S) and Control Plots (C) for Each Site using ChiSquare Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom
Row
Mean Abundance Across All Surveys
Site
SignificanceS
C
Site 180

HSD (P=<0.001)

Site 235

6

HSD (P=<0.01)

Site 34

2

NS (P=0.41)

Site 4196

36

HSD (P=<0.001)

Site 554

0

HSD (P=<0.001)

Site 613

6

NS (P=>0.05)

Site 782

16

HSD (P=<0.001)

Site 81

1

NS (P=1.00)

Site 91

1

NS (P=1.00)

Site 1049

6HSD (P=<0.001)

Site 1139

1

HSD (P=<0.001)

Overall comparison of solar plots and control plots

SD (P=0.02)

18

5.4

Birds

5.4.1

The data collected from the bird surveys was analysed in various ways in order to investigate differences
between the solar and control plots and160

Abundance

between sites. This included looking atdiversity and abundance as well as behaviour,

5.4.2

140

conservation status and territory mapping for120

any ground nesting birds recorded. The

100

results of the analysis are outlined below.

80

Overall, when comparing the number of bird

60

species found on all solar plots combined (60)Diversity

40

compared with control plots (51), there was no20

significant difference (Chi-Squared P=0.39).

0There was, however, a significantly higher

solar

abundance of birds on solar plots (Chi-control

Figure 5.3: Overall Comparison of Solar and Control
Plot Bird Diversity and Abundance

Squared P=0.02), as shown in Figure 5.3.

Comparing Species Diversity Between Solar and Control Plots
5.4.3

The number of species of birds observed per survey within the solar plots ranged from 6 to 23 with a meanof 15.2. The number of species within the control plots ranged from 4 to 21 with a mean of 12.8.

5.4.4

When all surveys carried out on solar plots were compared with control plots, there was a significantly
higher diversity of birds found within the solar plots (P=0.04).

5.4.5

When looking at the total number of bird species recorded over all three surveys for each site, there wasno significant difference between solar plots and control plots, as can be seen within Table 5.11. However,in 10 of the 11 sites the species diversity was higher on the solar plot although this was not statisticallysignificant.

Table 5.11: Diversity of Birds Compared between Solar Plots (S) and Control Plots (C) for Each Site using Chi-Square
Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
Total Species
SiteSignificanceS
C
Site 130

23

NS (P=0.34)

Site 229

21

NS (P=0.26)

Site 320

21

NS (P=0.88)

Site 428

20

NS (P=0.25)

Site 524

20

NS (P=0.55)

Site 628

27

NS (P=0.89)

Site 718

18

NS (P=1.00)

Site 819

18

NS (P=0.87)

Site 921

18

NS (P=0.63)

Site 1024

15

NS (P=0.15)

Site 1123

22

NS (P=0.88)

Overall comparison of solar plots and control plots

SD (P=0.04)

19

Comparing Bird Abundance Between Solar and Control Plots
5.4.6

The total numbers of birds observed during each survey was examined. The abundance on solar plots
ranged from 13 to 135 individual birds observed during a single survey, with a mean of 47.8 individuals.
The number of birds observed on the control plots ranged from 12 to 77 with a mean of 38.8 individuals.

5.4.7

When looking at the difference between bird abundance on all solar plots compared with all control plots,
there was no statistically significant difference (P=0.06).However, it is worth noting that bird abundance
was higher on the solar plot at 8 of the 11 sites, indicating a trend, albeit not statistically significant.

5.4.8

When comparing bird abundance between solar plots and control plots for individual sites, in two sites
there were significant higher numbers of birds recorded within the solar plot when compared with thecontrol plot (this was statistically highly significantly different). In the remaining nine sites, no significant
difference was found, as shown in Table 5.12.

Table 5.12: Bird Abundance Compared between Solar Plots (S) and Control Plots (C) for Each Site using Chi-Square
Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
Mean
Site
SignificanceS
C
Site 15034

NS (P=0.09)

Site 2

66

50

NS (P=0.15)

Site 326

26

NS (P=0.96)

Site 4110

67

HSD (P=0.0013)

Site 54630

NS (P=0.07)

Site 666

57

NS (P=0.42)

Site 729

29

NS (P=0.93)

Site 821

19

NS (P=0.75)

Site 920

20

NS (P=0.92)

Site 1050

24

HSD (P=0.002)

Site 1141

38

NS (P=0.71)

Overall comparison of solar plots and control plots

NS (P=0.06)

Bird Behaviour
5.4.9

Information on bird behaviour was collected during the surveys. An analysis has been carried out on thisdata, however, very few significant differences were observed when comparing behaviour at solar andcontrol plots.

5.4.10At Site 2, a significantly lower diversity of birds was observed foraging within the field boundaries on thesolar plot when compared with the control (Chi-squared test P=0.02), however, a significantly higher
abundance of birds was recorded foraging within the field on the solar plot when compared with the control.

5.4.11

At Site 4, a significantly higher diversity and abundance of birds was observed foraging within the field at
the solar plots when compared with the control plots (Chi-squared test P=0.02 and P=0.0001 respectively).

20

Similarly, at Site 10 a significantly higher diversity and abundance of birds was observed foraging within
the field at the solar plot (Chi-squared test P=0.01 and P=0.00004 respectively).
5.4.12

At Site 5, a significantly higher diversity of birds was observed singing within the field at the solar plotwhen compared with the control plot (Chi-squared test P=0.03).

5.4.13Overall, when comparing bird behaviours between all solar and control plots, no statistically significant
difference was observed.
Comparing Notable Bird Species Between Solar and Control Plots

5.4.14The bird species recorded within each site was weighted depending on its conservation status (Red or
Amber listed Bird of Conservation Concern). When comparing solar and control plots overall, the solar
plots scored significantly higher than control plots (P=0.04) indicating that they are more important forbirds of conservation concern.

5.4.15

When looking at the results on a site by site basis, the results show no statistical difference between solar
and control plots when looking at bird diversity, as shown in Table 5.13.

Table 5.13: Weighted Scoring of Bird Species Compared Between Solar Plots (S) and Control Plots (C) for Each Siteusing Chi-Square Test (Scoring: Red Listed=3; Amber Listed=2; Non-Notable=1). An Overall Comparison between
Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
Total Score Across All Surveys
Site
SignificanceS
C
Site 1

44

34

NS (P=0.26)

Site 24530

NS (P=0.08)

Site 33130

NS (P=0.90)

Site 44130

NS (P=0.19)

Site 53330

NS (P=0.71)

Site 641

41

NS (P=1.00)

Site 728

24

NS (P=0.58)

Site 830

28

NS (P=0.79)

Site 930

23

NS (P=0.34)

Site 1038

23

NS (P=0.055)

Site 1133

34

NS (P=0.90)

Overall comparison of solar plots and control plots

5.4.16

SD (P=0.04)

When looking at abundance of birds of conservation concern, with species recorded weighted dependingon their conservation interest, overall, solar plots scored significantly higher when compared with control
plots (P=0.04).

5.4.17

When looking at the results on a site-by-site basis, a statistically highly significant difference can be seen
within four sites, where the score for the solar plot was significantly greater than that for the control plot,
as shown in Table 5.14.

21

Table 5.14: Weighted Scoring of Abundance of Birds Compared Between Solar Plots (S) and Control Plots (C) for Each
Site using Chi-Square Test (Scoring: Red Listed=3; Amber Listed=2; Non-Notable=1). An Overall Comparison between
Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
Mean Score Across All Surveys
Site
SignificanceS
C
Site 164

48

NS (P=0.12)

Site 2

115

69

HSD (P=<0.001)

Site 337

35

NS (P=0.84)

Site 4140

97

HSD (P=0.005)

Site 561

35

HSD (P=0.006)

Site 692

79

NS (P=0.31)

Site 747

44

NS (P=0.78)

Site 83735

NS (P=0.78)

Site 927

26

NS (P=0.86)

Site 1088

51

HSD (P=0.0014)

Site 1155

64

NS (P=0.39)

Overall comparison of solar plots and control plots

SD (P=0.04)

Ground Nesting Birds
5.4.18Where ground nesting birds were identified, behaviour and movements were mapped in order to ascertain
the likely number of territories and active nests within each plot.

5.4.19The only species of ground-nesting bird consistently recorded across all but one site was skylark. The
only other ground-nesting bird species recorded was one juvenile meadow pipit Anthus pratensis; callingwithin the boundary of the control plot at Site 9.
Skylark Territories

5.4.20

The results of the territory mapping are shown in Appendix C. Mapping of ground nesting birds was not
carried out at Site 5.

5.4.21

The total number of territories recorded for control and solar plots were 29 and 26 respectively. Table 5.15
below provides the number of territories recorded for each site in solar and control plots; with the resultsof a Chi-Square test on this data also being presented. The sites varied greatly, with several solar plots
accommodating more territories and some control sites accommodating more territories, however, only
Site 11 had significantly more skylark territories on the control plot when compared with the solar plot
(P=0.014). The overall comparison of solar and control plots was also not significant.

22

Table 5.15: Number of Ground Nesting Bird Territories Compared between Solar Plots (S) and Control Plots (C) for
Each Site using Chi-Square Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test isShown in the Bottom Row
No. Territories
Site
SignificanceS
C
Site 14

7

NS (P=0.37)

Site 23

2

NS (P=0.65)

Site 320

NS (P=0.16)

Site 43

3

NS (P=1.00)

Site 620

NS (P=0.16)

Site 71

1

NS (P=1.00)

Site 82

4

NS (P=0.41)

Site 92

1

NS (P=0.56)

Site 1075NS (P=0.56)

Site 110

6

SD (P=0.014)

Site 5 (no data)

Overall comparison of solar plots and control plots

NS (P=0.97)

Skylark Nesting
Skylark nesting was confirmed through observing adults carrying food to a site repeatedly. The actual
nests were not searched for in order to avoid disturbance and prevent accidental damage to the nest
through trampling.
5.4.22

Skylark nesting was confirmed by surveyors at Site 10 within the solar plot, but outside of the footprint of
the array itself (Appendix C refers). This was the only instance of a confirmed nest within any of the solar
plots surveyed.

5.4.23

Skylark nesting behaviour was recorded within several of the control plots. Surveyors noted that possible
nesting within tramlines of the control plot at Site 10 was occurring, but could not be confirmed due to thedense arable crop. Site 11 had an unconfirmed skylark nest recorded adjacent the western boundary of(but outside of) the control plot. Unconfirmed numbers of skylark nesting were recorded at Site 7, withskylark noted as nesting within the centre of the control plot.
Skylark Foraging

5.4.24

Skylark foraging was observed across all but two of the sites included in the study. Table 5.16 below
details the numbers of skylark recorded foraging across solar and control plots.

5.4.25

There were significantly more skylarks recorded foraging within the solar plots when compared with thecontrol plots at two of the sites, however, the overall comparison between solar and control was not
significant.

23

Table 5.16: Number of Instances of Skylark Foraging Compared between Solar Plots (S) and Control Plots (C) for Each
Site using Chi-Square Test. An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shownin the Bottom Row
No. Foraging Instances
SiteSignificanceS
C
Site 10

1

NS (P=0.32)

Site 211

1

HSD (P=<0.01)

Site 32

2

NS (P=1.00)

Site 48

0

HSD (P=<0.01)

Site 500

N/A

Site 61

1

NS (P=1.00)

Site 701

NS (P=0.32)

Site 830

NS (P=0.08)

Site 900

N/A

Site 1039NS (P=0.08)

Site 1103

NS (P=0.08)

Overall comparison of solar plots and control plots

NS (P=0.81)

5.5

Bats

5.5.1

Both the numbers of bats recorded and the species diversity were examined for solar plots and control
plots. Due to equipment failure, only
eight of the eleven sites weresurveyed.

180
Abundance

160

Diversity

140

5.5.2

Overall, when looking at the number

120

of bat species found on all solar plots

100

combined (8) compared with control

80

plots (8), there was no difference.

60

There was, however, a significantly

40

higher total number of bat passes on20

the control plots when compared with0

solar (Chi-Squared P=<0.001), as
shown in Figure 5.4.

solar

control

Figure 5.4: Overall Comparison of Solar and Control Plot
Bat Diversity and Activity

Comparing Bat Activity Between Solar and Control Plots
5.5.3

The number of bat passes per night ranged from 1.78 to 24.44 on solar plots and 7.22 to 71.5 on control
plots. When considering all sites combined, there was no significant difference between the numbers ofbat passes between solar and control plots (P=0.08), as shown in Table 5.17.

5.5.4

When comparing the number of bat passes per night between solar plots and control plots, three of thesites showed significantly higher numbers of bat passes within the control plots when compared with thesolar plots (and this was a highly significant difference). The five remaining sites showed no significant

24difference when comparing solar to control plots, although it should be noted bat activity was higher incontrol than solar plots in four out of the five sites.

Table 5.17: Bat Activity Compared between Solar Plots (S) and Control Plots (C) for Each Site using Chi-Square Test.
An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
Mean Passes per Night
Site
SignificanceS
C
Site 1109NS (P=0.81)

Site 32

14

HSD (P=0.003)

Site 47

13

NS (P=0.20)

Site 539NS (P=0.053)

Site 66

11

NS (P=0.23)

Site 924

50

HSD (P=0.003)

Site 102

7NS (P=0.07)

Site 1127

72

HSD (P=<0.001)

Overall comparison of solar plots and control plots

NS (P=0.09)

Comparing Bat Diversity Between Solar and Control Plots
5.5.5

The number of species recorded by the static detectors on the solar plots ranged from 4 to 7, while on thecontrol plots the number of species ranged from 3 to 8. When assessing all of the survey sites combined,
there was no statistically significant difference between the number of species recorded within the solar
plots when compared with the control plots (P=0.55).

5.5.6

When comparing the species diversity of bats recorded within the solar and control plots on a site-by-sitebasis, it can be seen that no statistically significant difference was found when comparing solar to control
plots across any sites, as shown in Table 5.18.

Table 5.18: Bat Diversity Compared between Solar Plots (S) and Control Plots (C) for Each Site using Chi-Square Test.
An Overall Comparison between Solar and Control using Mann-Whitney U Test is Shown in the Bottom Row
No. Species Recorded
SiteSignificanceS
C
Site 175NS (P=0.56)

Site 358

NS (P=0.41)

Site 487NS (P=0.80)

Site 557NS (P=0.56)

Site 67

8

NS (P=0.80)

Site 956NS (P=0.76)

Site 1045NS (P=0.74)

Site 1153

NS (P=0.48)

Overall comparison of solar plots and control plots

NS (P=0.55)

25

5.6

Observations of Other Species

5.6.1

Beehives were present within the solar plot on Site 11 and large numbers of honeybees Apis mellifera
were noted during the invertebrate surveys. This site is being managed for pollinating invertebrates witha specific seed mix being sown to benefit these species.

5.6.2

Owl pellets were observed on the solar panels at Site 8 on the southern row (although they could not bereached in order to identify to species), which was adjacent to a field margin comprising rough grassland.
Anecdotal evidence of owls using the solar array was also obtained from the site manager at Site 9. A
tawny owl Strix alucowas was observed during one of the bird surveys on Site 4. It is likely that thepresence of a more diverse habitat along with rough grassland within field boundaries provides good
habitat for small mammals, which owls prey on. The panels are also likely to provide suitable perching
opportunities for hunting. Similarly, large numbers of raptors were observed within solar plots, particularly
on Site 10 where kestrels Falco tinnunculus and a red kite Milvus milvus were observed hunting within thearray.

5.6.3

Brown hare Lepus europaeus was found to be particularly abundant within solar plots, with counts ranging
from 3 to 12 on a single survey. Hares were less abundant on control plots, with counts ranging from 1 to
3 on a single survey. The hares were seen to form scrapes beneath the panels and appeared to be utilisingthem for shelter. Natural gaps beneath the security fencing and gates were used to access the site. The
highest number of hares were observed within Site 1.

5.6.4

Fox Vulpes vulpes scat was observed within the solar plot on Site 1. No evidence of badgers Meles meles
was observed within the solar plots, although a sett was found within the control plot on Site 7 and badger
latrines within the control plot on Site 9.

26

6

RANKING OF SOLAR SITES

6.1.1

An overall score has been calculated for each site reflecting its rank for each biodiversity indicator.

6.1.2

The rank has been calculated by comparing the difference in the score of the solar plot to its corresponding
control plot. This way any variation in diversity and abundance of species which might be explained by
the geographic location of the site or its surrounding landscape can be largely eliminated. The rank
therefore illustrates how successful or otherwise the solar plot has been at creating a positive change indiversity when compared with the adjacent control plot.

6.1.3

Bats have not been included within the ranking as unfortunately, an incomplete data set was held for thisgroup and as such, it was not possible to ascribe a ranking to a number of the sites. It should be notedthat a general trend observed within the bat data was for an inverse relationship between the abundanceof bats in the solar plots when compared to the control plots. As such it may have been difficult to scorebats in the same manner as other sites have been scored. This is not to say that the findings with respectof bats are not considered important; however, there may be explanations behind the findings of the batmonitoring. This is discussed further in Chapter 7.

6.1.4

It is acknowledged that, as both abundance and diversity have been included for invertebrates and birds,
there is some degree of bias. However, the final scoring combines both of these measures and so can beseen as a reflection of biological diversity (a combination of species diversity and abundance).

27

Table 6.1: Sites Ranked According to Overall Biodiversity Value (based on each indicator), with Higher Ranking Sites Coloured Darker Green and Lower Ranking Sites Coloured
Lighter Green. The Final Column Shows the Grade of each Site in Terms of its Management Focus Towards Wildlife.

Grass Diversity
Rank

Broad-Leaved
Plant Diversity
Rank

Butterfly Diversity
Rank

Butterfly
Abundance Rank

Bumblebee
Diversity Rank

Bumblebee
Abundance Rank

Bird Abundance
Rank

Bird Diversity
Rank

Sum of Ranks

FINAL RANKManagement
Focus Towards
Wildlife

Site 10

6

7

1

3

6

4

2

1

30

1

High

Site 11

3

2

1

2

3

5

7

7

30

1

High

Site 5

2

10

7

1

1

3

3

5

32

3

High

Site 7

3

1

3

5

2

2

9

10

35

4

Med

Site 1

1

6

7

5

4

7

3

4

37

5

Med

Site 2

9

5

3

8

6

6

3

2

42

6

Low

Site 3

3

2

3

4

5

9

9

11

46

7

Low

Site 4

10

9

9

9

6

1

1

2

47

8

Med

Site 9

8

2

3

7

6

10

9

6

51

9

Low

Site 8

6

7

9

10

6

10

8

7

63

10

Med

Site 6

11

11

11

11

6

8

6

7

71

11

Med

Site

28

6.1.6

The three highest ranking sites were Sites 10 and 11 (joint first) and 5 (second), which were also graded ashaving a ‘high’ management focus towards wildlife. All three of these sites were seeded with a diverse mix,
although, interestingly, Site 5 scored lowly in terms of broadleaved plant diversity, but highly for grasses, andSite 10 displayed moderate plant diversity.

6.1.7

Site 11 was previously grassland and the control plot comprised a grassland field, although the solar farm had
been reseeded post construction, therefore, the higher plant diversity is not surprising.

6.1.8

The three top sites all have relatively high butterfly and bumblebee rankings as well as birds for sites 10 and 5.

6.1.9

Site 7 is ranked fourth overall due to high broadleaved species diversity and a high diversity of invertebrates,
particularly bumblebees. This is possibly due to the failure of the sown seed mix to establish, which has resulted
in an abundance of early colonising plants such as arable weeds. The marginal habitat (a wide wildflower
meadow buffer) may also attract invertebrate species.

6.1.10Sites 1 and 2 are ranked fifth and sixth overall due to strong bird assemblages and high grass diversity at Site
1. Site 2 was previously arable, however, was compared with a grassland control plot due to the current rotationof the farm at the time. Although this site was low ranking in terms of grass diversity, it had a moderatebroadleaved plant rank.

6.1.11Site 3, which ranked seventh overall, had relatively high botanical diversity but moderate invertebrate scoringand poor bird diversity. Site 4 is ranked eighth overall, which exhibits some of the lowest botanical diversity, butscores highly in terms of bird diversity and bumblebee abundance. Site 9 ranked ninth, but had a high diversityof broadleaved plants and butterflies.

6.1.12The lowest ranking sites were Site 8 and 6 which generally had low scores for all indicators, but were classed
as having a ‘medium’ management focus towards wildlife due to diverse field margins at site 8 and aconservation grazing regime at Site 6 (although this was initiated in the same year that the survey was conducted
so the full effects may not yet be realised). The control plot at Site 6 had also been managed as a ley and so
exhibited a high plant diversity compared with a grazed pasture site. Site 6 was one of the two sites that werepreviously grassland.

29

7

DISCUSSION

7.1.1

This study was designed to address the following over-arching question: Can solar farms and their associatedmanagement lead to a greater ecological diversity as compared to equivalent undeveloped land? In tackling thisquestion, several areas of investigation were followed.
Does active management of solar farms lead to greater botanical diversity?

7.1.2This study demonstrates that solar farms were significantly more botanically diverse overall for grasses andbroadleaved plants. This result is expected given that control plots were either arable fields or intensive pastureand therefore botanical diversity was restricted to a monoculture crop and a low diversity of arable weeds, or
pasture composed of one or two agricultural grasses. All solar farms had been seeded with grass mixes
including a minimum of several species of grass and on three sites including wild flowers. This initial seeding
provided equal or greater botanical diversity than the site’s arable or pasture origins.

7.1.3

As well as the initial seed mix, it isConservation Grassland Management

likely that botanical diversity within
solar

farms

is

respondingtofavourable management practices.
All solar farms in this study wereconstructed on arable or intensive
pasture, and therefore had been
subjected to intensive agricultural
management

includingregularherbicidetreatments

andapplication of chemical fertilizers,
as the control plots still were.
7.1.4

For the solar farms included in thisstudy, the intensity of management
has been significantly reduced in terms of agricultural inputs. On one site, herbicide has been widely applied(beneath the panels), but on most sites herbicide application is limited to spot treatment of weeds. It is logicalthat a reduction in the use of broad-spectrum herbicides would lead to greater diversity of broadleaved plants.
No sites were known to be spreading fertilizer. The high soil fertility of arable farmland favours a few dominant
species of plant, but as soil fertility reduces in the absence of fertilizer, so the diversity of both grasses andbroadleaved plants is able to, and indeed is anticipated to, increase.

7.1.5

Sheep grazing is known to be a good mechanism for grassland diversification where sheep are at lower stocking
densities, and especially where grazing is stopped during the flowering season (April to July), as occurs on
several sites. However, where sheep grazing is undertaken at higher stocking density, and without a pause forflowering there is little opportunity for the grassland to diversify.

7.1.6

Evidence for the effects of management can be found in sites 10 and 5. Both sites had been sown with diverse
grasses and wild flowers, which provided an initial step change in the number of plants. However, both sites too
have been grazed with sheep at low stocking density and with a pause for flowering in the spring and summer,

30

and with minimal application of herbicides. This management approach encourages wild flowers, as evidenced
by an increase in plant diversity: at Site 10, the number of species of broadleaved plants recorded was greaterthan the original seed mix (8 sown as compared to 14 observed). Likewise, at Site 5, the number of species has
increased by one grass species (from 7 to 8) and one broadleaved plant (from 13 to 14) from those originallysown. At Site 10, the rapid colonisation of broadleaved plant species is likely to have been facilitated by wild
flower headlands occurring close to the solar farm.
7.1.7

By contrast, at Site 6, Site 2 and Site 4ii, intensive sheep grazing at higher stocking density and with no pause
for flowering, has led to a relatively low
botanical diversity: these sites ranked
lowest of all in terms of botany. For
Sites 6 and 4, there was no significant
difference in plant diversity between
solar and control plots.

7.1.8

The sites within this study ranged frombeing 1-4 years old, therefore, adetailed analysis of how plant diversity
if affected by the age of the site could
not be conducted. Further study may
focus on a larger number of sites witha greater age range in order todetermine whether more established

Ryegrass Seed Mix with Year Round Grazingsites have a greater diversity of plant
species. It should be noted that solar farms often have planning permission which lasts around 25 years,
although in the UK solar farms are in the early stages of their operational lifetime. The botanical benefits may
become more pronounced once the farms have been established for a decade or more.
7.1.9

It is worth specifically discussing the three sites which were compared with grassland control plots; Sites 6 and
11 were previously grassland and had grassland control plots. Site 2 was previously arable, but the control plot
comprised grassland due to a lack of a suitable arable control site. These sites varied in terms of their ecologicalassessments. Sites 2 and 11 had a significantly higher diversity of plant species on the solar plots, which was
related to broadleaved plants rather than grasses. On Site 11, this is likely due to the fact that the solar array
had been re-seeded with a diverse mix post construction, however, Site 2 was seeded with a rye-grass mix
similar to that of the control plot, therefore, the increase in broadleaved diversity is more likely to be a result of
the cessation of intensive agricultural farming. The solar plot at Site 6 had slightly more broadleaved plants,
however, this was not statistically higher than the control plot.

7.1.10The difference between botanical diversity on sites which were previously arable or previously pasture would
make an interesting basis for future research, but would require a greater number of sites of each type to bestatistically robust. Previously arable sites which are converted to solar farms are predominately low grade
agricultural sites; poorer soils are likely to provide a better habitat for a wider diversity of plants.

ii

It should be noted that conservation grazing has been instated at Sites 3 and 6 in 2015 but that this is too recent to have influenced
the botanical results herein.

31

7.1.11

Therefore, where suitable management

Management of pernicious weeds

exists, botanical diversity is expected toincrease over time, with some plants
emerging from the seed bank in response
to favourable conditions, and otherscolonising from airborne or animal-carried
seed.

The Weeds Act 1959 specifies five injurious weeds: Common
Ragwort, Spear Thistle, Creeping or Field Thistle, Broad Leaved
Dock and Curled Dock. Under this Act the Secretary of State may
serve an enforcement notice on the occupier of land on which
injurious weeds are growing, requiring the occupier to take action

Do the physical structures of solar

to prevent their spread.

farms encourage a greater botanical

Recognising that certain pernicious weeds must be controlled bydiversitywithlaw, and tall weeds also present a risk of over-shadowing solar

equivalent undeveloped agricultural

panels, some form of weed management is usually required onland?

solar farms. From observations during this survey, and indeed,when

comparedfrom wider survey work on solar farms, it has been noted that

7.1.12

Botanical diversity on solar farms may be
influenced by the diversity of ecologicalIn one site weeds were being controlled by regular spraying ofconditions provided by the solar panels

broad-spectrum herbicide which kills off the majority of grasses

themselves. In several sites, greaterand broadleaved plants. In the authors’ experience this strategy

broadleaved plant diversity was observed

may be effective in the short term, but also invites repeat

between the rows as compared to beneathproblems with pernicious weeds. Spraying creates bare groundthe panels. This difference is likely to bewhich is ideal for weeds to colonise. Weeds such as ragwort anddue to the effects of shading and drying

thistle produce large quantities of wind-borne seed designed forbeneath the panels, where more extreme

colonising bare ground.

ecological conditions are likely to occur. It

To reduce the risk of weed colonisation, it is recommended all

is likely that more ‘natural’ field conditions

bare areas be sown with a seed mix of some description to coverexist between rows, where shading is lessand rainfall is not impeded by the panels.
Therefore, in the more extreme conditions

7.1.13

pernicious weeds tend to proliferate beneath solar panels.

the ground in vegetation. Before re-sowing it is recommended that
all existing weeds are spot treated. A wild flower and fine grassmix is recommended as it a) provides a stable mat of vegetation
which once established will outcompete weed species, and b)

beneath the panels, one might expect only

provides forage and habitat for wildlife. A suitable mix of shade

more specialist plants tolerant to thesetolerant and low growing species can be selected for beneath theconditions to grow. This may be a focus ofsolar panels.

further analysis work of the current data,

In recognition of the need for some weed control spot treatment

however, it was not under the remit of thiswith a non-residual translocated herbicide is considered the moststudy.

ecologically sensitive option.

However, the reverse was also found at

As the grassland becomes

established beneath the panels the requirements for regulartreatment should decline, as weeds tend to be early colonisers.

one site, where diversity of broadleaved
plants was greater beneath the panels
than between the rows. On this site (Site9), the effects of regular cutting may have
reduced the botanical diversity of the area

Re-sowing bare areas beneath the panels rather than spraying
should provide a long-term solution to the weed problem. Thisapproach is expected to substantially decrease management
costs over the life of the solar farm by minimising spraying of
herbicide, which also has benefits for biodiversity.

between the rows (the area beneath the32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 growththan 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 thesite 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).

7.1.15It was noted that at Site 1 spraying of herbicide on vegetation beneath the panels was likely to rapidly reducethe 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.

7.1.16It should be noted that a number of indirect effects of the presence of solar panels might influence botany underand between the panel rows. Where sheep graze sites, their grazing and resting patterns will vary across thesite, with the area beneath panels being used for shelter during adverse weather. Where sites are mowed, thearea 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 thegrassland 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’ interms 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-richseed mix including wild flowers which are likely to include suitable foraging plants for both butterflies andbumblebees (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.

7.1.18The 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.

7.1.19Invertebrate species diversity at solar farms, as in the wider environment, will be heavily influenced by botanicaldiversity, as plants provide essential forage, habitat and structure for nesting and egg laying. The suitability ofa 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 larvalstages 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.

7.1.20At two sites invertebrate species richness was significantly greater within the solar plots as compared to thecontrol plots. At Site 10, significantly higher numbers of butterfly species were observed, and at Site 5

iiiThe Weeds Act 1959 specifies five injurious weeds: Common Ragwort, Spear Thistle, Creeping or Field Thistle, Broad Leaved Doc k andCurled Dock. Under this Act the Secretary of State may serve an enforcement notice on the occupier of land on which injurious weeds are
growing, requiring the occupier to take action to prevent their spread.

33

significantly higher bumblebee species were observed within the solar plots. This result reflects the sowing ofthese solar plots with wild flower mixes providing suitable forage for a wide range of invertebrates. Further, atSite 10, the relative longevity of the site (4 years) is likely to influence this result. At Site 7, the highest bumblebee
diversity of all solar plots was observed (10 species), even though this was not significantly higher than its
control plot. For this site, too, botanical diversity is the reason for high invertebrate diversity: Site 7 displays thesecond highest plant diversity of all the solar plots.
7.1.21On the majority of solar farms

Small Copper Butterfly on Thistle

included in this survey, invertebrate
species richness was generally notsignificantly different between solar
plot and control plot on a site-by-sitebasis (although overall, butterfly
diversity was higher on solar plots).
This is because the botanicaldiversity on many of the solar plots
is still quite low and based upon an
agricultural seed mix. However, as
botany improves

overtime in

responsetofavourable

management,soinvertebrate

diversity would be expected to
improve. In addition, the solar farms
are relatively new features of the landscape, and so even where there is higher botanical diversity it will takesome time for species to discover and utilise the sites.
7.1.22Agricultural flowers such as white clover or crops such as oil seed rape may attract an abundance of bees, but
this is likely to be short lived (3-4 weeks of the year) and benefit only a few species. To benefit a high diversityof invertebrate species in larger numbers, it is necessary to sow a meadow with a range of grass and wild flower
species. Higher plant diversity will have the added benefit of providing early and late season flowering which inturn will provide nectar sources at times of year when food sources for bumblebees are in short supply.

7.1.23

The results of the surveys indicate that solar farms can have a part to play in ecosystem services, throughincreasing the abundance and diversity of pollinator species. They may act as an important reservoir ofpollinating invertebrates, particularly within intensively farmed landscapes where other suitable habitats are
scarce. The fact that generally solar farms are constructed on land of poor agricultural value may mean that theeconomic benefits of providing a pollinating invertebrate resource (and thus benefitting adjacent agriculturalland) may outweigh that of planting crops within the site. Additional indirect ecosystem services may be throughthe reduction in agricultural inputs leading to cleaner groundwater or adjacent waterbodies. Further study may
look at calculating the economic value of solar farms in terms of their ecosystem services.
Can solar farms encourage a greater diversity of birds?

7.1.24The conclusions reached so far indicate that solar farms can support a greater diversity of plants as well as
greater numbers of butterflies and bumblebees, particularly under management which focuses on optimising34

biodiversity. This increase in plant and invertebrate availability may lead to more opportunities for foraging birds
in terms of invertebrate prey and seed availability.
7.1.25Overall, a higher diversity of birds was found within solar plots when compared with control plots (although noneof the results were significant on a site-by-site basis). This may reflect the change from a homogenous arable
environment to one with more foraging opportunities as well as structures for cover or perching.

7.1.26

The abundance of birds was not significantly different between solar and control plots, however, the results
indicate a trend towards higher numbers of birds using solar farms when compared with control plots (the Pvalue was close to the threshold of significant at 0.06). There were significantly more birds on the solar plot
compared with the control plot at two sites. Again, this higher number of birds observed is likely to reflect theincrease in foraging opportunities available. Interestingly, the two sites where significantly more birds wereobserved within the solar plot (Sites 4 and 10) comprised sites of medium to high management focus on wildlife,
although Site 4 ranked low in terms of both plants and butterflies. As mentioned previously, Site 4 had anabundance of flowering clover at the time of the survey and this had led to an increase in bee abundance which
could in turn attract foraging birds.

7.1.27

The reduction in intensive agricultural activities and provision of permanent foraging habitat for birds may
encourage declining farmland birds into the solar array. Many of these species are declining due to the recentchanges in farming practices including the use of pesticides, reduction in field margins, higher stocking densitiesetc.

7.1.28The study shows that overall, both a higher
diversityandabundance

of

birds

of

conservation concern utilise solar arrays whencomparedwith

controlplots.

This

has

implications for bird conservation and indicatesthat solar farms may be able to provide animportant resource for declining species. The
results of the analysis of bird behaviours showsthat four sites are important for birds foraging
within the fields and, interestingly, these are thesame four sites that are important for notablebird abundance.
7.1.29Those notable species which were only foundon solar plots and not on control plots were:
kestrel, tawny owl, stock dove Columba oenas,
willow warbler Phylloscopus trochilus andmallard Anas platyrhynchos. Only reed bunting

Low Intensity Sheep Grazing Outside Flowering Season

Emberiza schoeniclus was observed on control
plots and not on solar sites. It is interesting thattwo of the five species found on solar sites only were raptors and at Site 10, kestrels were observed frequently
hunting within the array, as well as a foraging red kite. Additionally, owl pellets were found on the solar panels
at one of the sites. It may be that the less intensively managed grassland and tussocky field margins at thosesites managed specifically for wildlife has led to an increase in small mammals, which are prey for these raptor

35species. Future research may focus on the use of solar sites by raptors (which would also include nocturnal
surveys) or an investigation into the abundance and diversity of small mammals through Longworth trappingand footprint tunnel surveys.
7.1.30

Another aim of the study was to investigate the usage of solar sites by ground nesting birds, as it is generally
assumed that these species will be dissuaded from utilising these sites due to the cluttered nature of theenvironment. Skylark was the only ground nesting bird which was regularly recorded and the analysis showsthat at only one site was the number of skylark territories within the control plot significantly higher than at thesolar plot. Overall, there was no significant difference between solar and control plots. This shows that skylarks
are utilising solar farms within their territorial boundaries. However, only one confirmed nest was identified withina solar plot (at Site 10, the highest overall ranking site when looking at all indicators). The nest was situatedoutside of the footprint of the array but within the security fencing surrounding the site in an area of grassland
measuring approximately 40x90m. This has implications for assessing impacts on skylarks and mitigation forthis species within other solar farm sites, as quite often within the layout of solar farms large areas remain
outside of the footprint of the array due to various factors (underground services, public rights of way, visual
impacts etc.). If these areas can be managed specifically for ground nesting birds, they may contribute towards
mitigation for these species. It should be noted, however, that Site 10 was situated in an area with very few
hedgerows and trees and so where these features are present, a larger open area may be required to encourage
ground nesting.

7.1.31

Although the study shows that skylarks do not nest within the footprint of the array, it does show that this species
will forage within solar farms. Indeed, within two of the Sites (2 and 4), significantly higher numbers of foraging
skylarks were observed within the solar plots when compared to the control plots.

7.1.32

In conclusion, although skylarks were not found to utilise solar sites for nesting, they do incorporate them into
their territorial boundaries and some of the sites may represent a valuable foraging resource for this species.
An interesting focus for future research would be to assess the productivity of skylarks utilising solar and control
plots. A proposed hypothesis may be that skylarks nesting adjacent to solar farms would be more productive
than those on control plots due to the increase in foraging resources.
Can solar farms encourage a greater diversity of bats?

7.1.33

The findings of the study generally suggest that fewer bats are recorded within the solar array than within thecontrol plot, although the differences in abundance of bats was only significant on a small number of sites andthe overall comparison of solar and control plots was not significantly different. It also appears clear that bats
do not entirely avoid solar arrays with regular activity by bats recorded at all sites.

7.1.34The bat activity at both solar and control plots was generally very low when compared with other static surveysof this type, although this is likely to reflect the placement of the microphones in the middle of the fields, as most
species of bat utilise hedgerow habitats or other linear features for navigation.

7.1.35Interestingly, although the bat activity was low, the number of species was relatively high, although there wasno significant difference between solar and control plots. A peak number of eight species were recorded atseveral sites and this includes the pooling of the Myotis genus, which cannot be separated to species by callalone. It should be noted, however, that the distribution of bat species is limited within the UK and several of thesites were located in areas where more species of bats are present, therefore, a direct comparison betweensites cannot be made.

36

7.1.36

It is unclear if the general reduced levels of activity recorded within the solar plots when compared with thecontrol plots is a real relationship or whether this is an artefact of the survey methodology.

7.1.37The detectors employed during the surveys were fitted with high-gain microphones which are able to pick up
calls, in particular loud calls, at substantial distance. Microphones were therefore placed at least 50m from fieldboundaries, where possible.
Placement of Static Bat Detector and Microphone

7.1.38As such, whilst the microphones were placed atleast 50m from the field boundaries within both thearrays and the control plots it is unclear if the batsrecorded by the detectors were recorded within thefields or at the field boundaries. Furthermore, due
to the presence of the solar panels within the array
it is likely that calls would attenuate more quickly
within this cluttered environment than within thecontrol sites which had a more uniform and lowlying structure. Vegetation heights were on every
control site lower than the height of the panels.

7.1.39In

retrospect,

therefore,themethodology

employed to assess the diversity and abundanceof bats foraging within the array and control sites
had certain limitations.
7.1.40

Nevertheless, it remains possible that there is areduced level of bat activity within solar array sites.
This may be explained by the interaction of thebats with the solar panels. Research suggests bats may be confused by artificially smooth surfaces. Bats havebeen observed trying to drink from flat panels within laboratory settings9 and it has been suggested that they
may have difficulty in perceiving glassy surfaces as they do not reflect the echolocation calls in the same way
as a natural (and rough) surface. Instead, bats perceive smooth surfaces as holes and may even collide withthese surfaces (pers. com. Stefan Greif). Whilst it seems likely in a natural setting confusion would not be asignificant risk, as bats will learn to navigate these objects, the presence of smooth surfaces may bedisconcerting to bats who consequently avoid these areas in favour of typical natural environments which they
are familiar with.

7.1.41It should also be noted that if the evidence of the invertebrate studies translates through to night-timeinvertebrates (midges, moths etc.) it would suggest that the solar arrays will provide a better foraging resourcefor bats than the control areas.

As such the solar arrays and panels whilst having disadvantages andrepresenting unfamiliar, difficult to perceive structures, may ultimately become adopted by bats as they provide
excellent foraging opportunities. As bats are particularly long-lived animals it may be several years before theeffects of habituation become apparent. It may be that providing wide, diversely seeded field margins would
benefit bat species more than enhancing the grassland within the array itself.
7.1.42

The findings of the study suggest that a variety of species of bats do use solar arrays but possibly at a lower
level than within the control plots. If this pattern is true then the proliferation of solar arrays across the UK could
be having a small but nevertheless, adverse effect upon foraging and commuting bats. Clearly further study of37

the relationship between bats and solar arrays are required. We would recommend that such further surveys
include the use of both manned and static detectors and that a survey methodology is devised which avoids thepossibility of high gain microphones recording bats at some distance from the location of the microphone.
Infrared cameras may be employed in order to investigate the behaviour of bats around the solar panels.
Other Observations
7.1.43

Whilst conducting the surveys for the selected biological indicators, anecdotal observations on other species
observed were also recorded.

7.1.44

One notable observation was that large numbers of brown hare were recorded within the solar farms comparedwith surrounding land. This is a species of conservation concern due to declines in numbers in many parts ofthe country. During the surveys, these animals were often flushed from beneath the strings of panels where
they had formed scrapes. It appears that solar arrays provide preferential habitat for hares, which would usuallyform scrapes in the middle of large arable fields or long grassland during the summer months. It may be thatthe panels offer shelter from sun/rain as well as protection from aerial predators. The animals are also likely tohave a good horizontal field of view under the panels to be able to detect ground predators. Therefore, thisartificial habitat may lead to increased hare survival or productivity, although further research would be requiredin order to investigate this further.

38

8

CONCLUSIONS

8.1

Summary of ConclusionsThe over-arching finding of this study is that where solar farms implement management that is focused uponwildlife, an increase in biodiversity can be detected across a number of different species groups.

In this study, wildlife focused management included the seeding of a site with a diverse seed mix, limited use ofherbicides, conservation grazing or mowing and management of marginal habitats for wildlife. In sites wherethese elements were implemented, greater increases in biodiversity were recorded.

Botanical diversity was found to be greater in solar farms than equivalent agricultural land. This partly reflects
sowing of new grassland, including species-rich meadow mixes, but also reflects less intensive management
typical of a solar farm.

Where botanical diversity is greater, this leads to a greater abundance of butterflies and bumblebees, and inseveral cases, an increase in species diversity too.

The increase in botanical diversity and consequently the availability of invertebrates also results in a higher
diversity of bird species and in some cases, abundance. The study revealed that solar sites are particularly
important for birds of conservation concern.



While greater botanical diversity is somewhat expected, especially where diverse seed mixes have been sown,
the importance of this finding should not be under-estimated. Botanical diversity provides the basic building
blocks from which greater biological diversity can be achieved (as demonstrated by the increases recorded forother species groups).



Wild flower meadows have declined by 97% in the UK since the 1950’s. The establishment of wildflower
meadows within the UK’s intensively farmed landscape would significantly contribute to the UKs biodiversity
targets. This study shows that a diverse meadow also has a knock-on positive effect on wider species, including
birds of conservation concern.

Furthermore, by providing diverse meadow habitat, solar farms will contribute a mosaic of habitat types which
is important foraging habitat for a wide range of species, especially in a farmed landscape. This is likely tobenefit species which occur in a wide range of habitats such as bumblebees as well as species requiring diverse
landscapes such as hares. A mosaic habitat will also benefit specific bird species, with a low sward height
benefitting some species and a longer sward benefitting others.



By encouraging high abundances of bees and butterflies, solar farms can become net producers of pollinatinginsects. These insects perform a vital task of pollinating crops (including cereal crops, vegetables, soft fruits andorchard fruits) and are in decline across the UK. Solar farms are likely to benefit surrounding farmland byincreasing the local abundance of pollinators.

Solar farms are likely to provide further benefits to humanity (such benefits are termed ecosystem services)
including carbon storage, water cycling, erosion control and provision of pest controlling species such as solitary
wasps and farmland birds. The provision of ecosystem services by solar farms should be the subject of future
research.

Solar farms are unique in the farmed landscape in that they provide a high value crop (solar power) while leaving
the majority of the land area free for wildlife management. There are very few other ways that farmers can earna sustainable amount of money by creating large areas of conservation habitat.

39

AREAS OF POTENTIAL FUTURE RESEARCH

Further study including sites of a greater range of ages in order to examine how the age of a solar farm
affects plant diversity.

Comparison of solar sites that were previously pasture compared with those which were previously arable
to examine plant diversity.



Analysis of species found beneath solar panels and whether there is a bias towards more specialist,
shade tolerant plants.



Economic analysis of solar farms and their contribution to ecosystem services.



Examination of the use of solar farms by raptor species (including nocturnal surveys for owls).

Study of the diversity/abundance of small mammals within solar farms (as linked to the presence of raptor
species) which may include Longworth trapping (potentially with mark and recapture) and footprint tunnel
surveys.



Investigation into the productivity of skylarks in the local landscape of a solar farm in order to investigate
the hypothesis that skylark productivity is higher adjacent to solar farms due to the increase in foraging
opportunities.



Further research into the impacts of solar arrays on bats. This should include manned surveys as well as
further static surveys potentially utilising a different methodology (such as reducing microphone gain).
Infrared cameras may also be utilised to investigate bat behaviour around solar panels.



Investigation into the usage of solar farms by brown hare.

Further research into other taxa including amphibians and reptiles as well as other invertebrate species.

40

9MANAGEMENT RECOMMENDATIONS

9.1.1

Given the results of the surveys, the following management practices would be recommended in order to
optimise the benefits of a solar farm for biodiversity:

To enhance biodiversity, it is recommended that all or part of a solar farm is re-sown with a diverse wild flower
and fine grass mix.

The best approach would be to re-seed most or all of the site, and to incorporate as many native species ofgrass and wild flower as possible. However, it should be noted that even including a few species of grass andherb should have positive benefits.

An experienced ecologist should advise on the seed mix to ensure it includes suitable forage plants for bothbutterflies and bumblebees, and to avoid tall species which may overshadow the panels.



Fine grasses should be used in place of typical agricultural grasses, e.g. rye-grass, which is aggressive anddoes not encourage diversity.

In all sites where re-seeding has been done it is recommended that monitoring is undertaken to ensure thevegetation develops as planned.

All plantings (seed mixes and woody plants) must be native species and should be of local provenance.

Solar farms should be managed through conservation grazing, with sheep grazing from September – Marchand a pause from April – August to allow wild flowers to flower and set seed. If mowing is the management
option, then a similar approach should be adopted, with a pause in cutting from April – September.

Where solar sites comprise multiple fields, implementing different management regimes would benefit a wider
range of species. For example, one field may be grazed year-round in order to encourage species that requirea short sward height, while the main site area should be managed as above. If mowing is the management
option, the date of cutting may be varied across the site or between years in order to encourage plant species
that may flower and seed at different times.

All bare areas of a solar farm should be re-seeded as soon as possible with an appropriate meadow mix to a)cover bare ground and reduce the risk of weeds, and b) increase the botanical diversity of the site.

Use of herbicide should be restricted to spot treating of pernicious weeds (docks, thistles and ragwort) wherever
possible. Herbicides reduce wild flower diversity and create conditions suitable for weeds.

Open areas within the solar farm (wayleaves or voids) should be managed specifically for ground nesting birds
by grazing at low stocking density through the winter and allowing the grasses to grow up through the bird
breeding season (March – July inclusive).

41

10

REFERENCES
1

Solar Photovoltaic Deployment in the UK. September 2015. Department of Energy and Climate Change

2

Solar Parks: Maximising Environmental Benefits. TIN101. September 2011. Natural England

3

BRE (2014) Biodiversity Guidance for Solar Developers. Eds G E Parker and L Greene

4Taylor R (2014) Potential Ecological Impacts of Ground-Mounted Photovoltaic Solar Panels in the UK. An

Introduction and Literature Review. BSG Ecology
5Parker G and McQueen C (2013) Can Solar Farms Deliver Measurable Benefits for Biodiversity? Wychwood

Biodiversity and Rowsell & McQueen
6

Feltwell, J. (2013) A Comparative Biodiversity Study of a Working Solar Farm and a Wheat Field in West

Sussex, July- November 2013. (Unpublished Report, dated 7 December 2013)
7

JNCC (2013) UK Biodiversity Indicators in your Pocket

8Gilbert et al. (1998) Bird Monitoring Methods – A Manual of Techniques for Key UK Species. RSPB,

Bedfordshire
9

Greif, S & B. M. Siemers (2010) Innate Recognition of Water Bodies in Echolocating Bats. Nature

Communications 1. Article 107

42

APPENDIX A: SURVEY METHODOLOGIES
BotanyAll botanical visits were conducted from mid-June to late July (16/06/15 to 21/07/15) in order to standardise
surveys.
The surveys comprised the assessment of the grassland sward utilising 50cm² quadrats. Percentage cover of
each plant species within the quadrat was recorded using the Domin Scale:% Cover

Domin Score

91–100%10

76–90%

9

51–75%

8

34–50%

7

26–33%

6

11–25%

5

4–10%

4

<4% (>10 individual plants)

3<4% (5-10 individual plants)

2<4% (<5 individual plants)

1

A total of 30 quadrats were recorded at each site, comprising:

10 quadrats within the treatment plot - unshaded, between strings of panels

10 quadrats within the treatment plot – directly beneath panels, adjacent to the above

10 quadrats within control plot
The quadrat locations were selected using random points generated within qGISiv mapping software and werelocated on the ground using a GPS device.
Birds
A total of three bird surveys were conducted at each site during late April to early July. The treatment andcontrol plot surveys were carried out on the same day between 06:00am and 10:00am.
The bird surveys followed a fixed transect designed in a ‘zig zag’ pattern, with the transect being started on
the northern field boundary, then crossing the plot every 100m until the southern field boundary is reached.
The length of the transect therefore varied from site to site, but was roughly the same distance between thepaired treatment and control plots.

iv

Quantum GIS Development Team (2014). Quantum GIS Geographic Information System. Open Source Geospatial Foundation
Project.http://qgis.osgeo.org

43All bird species within 50m of the transect route were recorded, including the behaviour (calling/singing,
foraging, flying over site) and location (within field or within field boundary). As far as possible, birds were notdouble-counted, however, this methodology allows for some double counting.
Where ground nesting birds were observed, the location and behaviour was mapped on a separate survey
sheet using the BTO common bird census territory mapping methodologyv. These were then utilised to assess
the numbers of ground nesting bird territories and potential location of nests.
Invertebrates
Invertebrate surveys concentrated on two taxa; bumblebees and butterflies. A total of ten 100m transects
were carried out within the treatment plot and ten within the control plot.
Invertebrate surveys were conducted during June, with five sites being revisited for a second survey in midJune to early July.
Transects were spaced evenly throughout the field, positioned in an east/west arrangement, with one transect
at the northern field boundary and one at the southern.
The transects were were walked at a slow pace, with all bumblebee and butterfly species within 2.5m of eachside of the transect line recorded. The ground ahead was also scanned, with binoculars used where required.
Bats
Automated bat surveys were conducted at both the treatment and control plot using Song Meter 2 Acoustic
Monitoring systems. The detectors were placed in the centre of the fields, at a height determined by the sizeof the solar panels within the treatment plot; both microphones were positioned 150mm above the height ofthe solar panels. Detectors were deployed from early June to early July and collected two weeks later.
Microphones were attached to extendable poles within the control plots or batons attached to the solar panel
frames and left to record for a period of at least 10 days. The batteries lasted for varying amounts of time oneach site, depending on the amount of bat passes or noise recorded.
Upon collection, the data was subsequently analysed using Kaleidoscope software. This computer programautomatically analyses bat calls using a stored library of comparison calls. Any less widespread bats whichwere automatically identified by the software were also manually checked to verify the species recorded.

v Marchant, J.H. 1983. Common Birds Census instructions. BTO, Tring. 12pp

44

APPENDIX B: STATISTICAL ANALYSIS
The majority of data collected on site consisted of frequencies, that is the number of species or individuals
observed. In most cases the comparison of solar plot and control plot surveys involved comparing the numberof species found in each, e.g. 7 species of butterfly observed in the solar plot vs. 3 observed in the control
plot. In such cases, the Chi Square statistical testvi was used to determine if the difference between the solar
plot and control plot was significant. It is possible to directly compare these results because the same survey
methods and effort were used in the solar plot and control plot.
While Chi Square works for individual sites, it was necessary to compare all butterfly survey results on solar
plots with control plots. In these cases, the 17 surveysvii for solar plots were compared with the 17 for control
plots using the Mann Whitney U testviii.
To explore botanical diversity, the results of individual quadrats within the solar plot were compared to thosewithin the control plot, so 10 solar quadrats were compared to 10 control quadrats (only the ‘between panels’
quadrats were used in this analysis) for each site. The Mann-Whitney U test was used to compare botanicalresults.
Within the solar plot, we investigated whether there was any difference in botany between the panels vs.
beneath the panels. As above, the Mann-Whitney U test was used to compare the results.
Where notable birds were identified during bird surveys, this was explored further. Birds were categorised
depending on their conservation status, based on those listed within the British Trust for Ornithology Birds ofConservation Concernix. This list contains red and amber designated birds which are showing declines in
population and so are of particular conservation concern. A weighted scoring system was utilised within theanalysis of the data where non-notable birds (those not on the Birds of Conservation Concern list) were givena score of 1, amber listed birds were given a score of 2 and red listed a score of 3. An overall score could thenbe obtained in order to carry out the statistical analysis.
An over-arching analysis of all 11 solar plots was conducted where the results for all solar plots were pooled
and compared to the 11 control plots. This approach was designed to investigate what patterns existed overall
between solar and control plots. It was possible to pool data for all sites because the same survey methods
and effort had been applied at each site.

vi

This non-parametric statistical test is designed to compare individual numbers and is able to deal with count data.
There were 17 invertebrate surveys in total spread across 11 solar farms. On 6 solar farms 2 surveys were conducted while on 5
solar farms a single survey was conducted.
viii
The Mann-Whitney U test is a non-parametric statistical test that compares two data sets and is able to deal with count data.
ix
Eaton MA, Aebischer NJ, Brown AF, Hearn RD, Lock L, Musgrove AJ, Noble DG, Stroud DA and Gregory RD (2015) Birds ofConservation Concern 4: the population status of birds in the United Kingdom, Channel Islands and Isle of Man. British Birds 108,708–746.
vii

45

APPENDIX C: GROUND NESTING BIRD TERRITORY MAPS

1

Solar Photovoltaic Deployment in the UK. September 2015. Department of Energy and Climate Change
Solar Parks: Maximising Environmental Benefits. TIN101. September 2011. Natural England
3
BRE (2014) Biodiversity Guidance for Solar Developers. Eds G E Parker and L Greene
4Taylor R (2014) Potential Ecological Impacts of Ground-Mounted Photovoltaic Solar Panels in the UK. An Introduction and
Literature Review. BSG Ecology
5Parker G and McQueen C (2013) Can solar farms deliver measurable benefits for biodiversity? Wychwood Biodiversity andRowsell & McQueen.
27
8

JNCC (2013) UK Biodiversity Indicators in your Pocket.
Gilbert et al. (1998) Bird Monitoring Methods – a manual of techniques for key UK species. RSPB, Bedfordshire.
9 Greif, S & B. M. Siemers. 2010. Innate Recognition of Wa
ter Bodies in Echolocating

Bats. Nature Communications 1. Art

icle 107.