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An assessment of bumblebee (Bombus spp) land use and floral preference in UK gardens and allotments cultivated for food


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There is increasing interest in the value of domestic gardens for supporting biodiversity. While it is well established that bumblebees exploit urban green spaces, this is the first study to explore the land use and floral preferences of the UK’s seven most common bumblebees in gardens and allotments cultivated for food. A citizen science survey was carried out at 38 sites, between 1st June and 30th September 2013. At the landscape scale, bumblebee abundance and species richness was not significantly correlated with surrounding land use characteristics (both p > 0.05). Bombus pratorum was the only species to show correlations with surrounding land use, demonstrating a positive relationship with built areas and gardens and allotments, and a negative correlation with greenspace and agriculture. At the local site-level scale, bumblebee abundance was negatively correlated with areas cultivated for vegetables and fruits, and positively correlated with areas cultivated for flowers, although neither correlation was statistically significant (p = 0.070 and p = 0.051 respectively). Bumblebee species richness was not correlated with either land use (p > 0.05). All bumblebee species were negatively correlated with areas cultivated for vegetables and fruit, bare ground and hard paving. Several flowering plants were visited by all bumblebee species, although relative preferences varied between bumblebee species. Results emphasise the importance of including floral resources within garden and allotment areas cultivated for food, and the need for a mosaic of different flowering plants to cater for varying floral preferences demonstrated by bumblebee species.
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An assessment of bumblebee (Bombus spp) land use and floral
preference in UK gardens and allotments cultivated for food
Gemma Foster
&James Bennett
&Tim Sparks
#Springer Science+Business Media New York 2016
Abstract There is increasing interest in the value of domestic
gardens for supporting biodiversity. While it is well
established that bumblebees exploit urban green spaces, this
is the first study to explore the land use and floral preferences
of the UKs seven most common bumblebees in gardens and
allotments cultivated for food. A citizen science survey was
carried out at 38 sites, between 1st June and 30th September
2013. At the landscape scale, bumblebee abundance and spe-
cies richness was not significantly correlated with surrounding
land use characteristics (both p>0.05).Bombus pratorum was
the only species to show correlations with surrounding land
use, demonstrating a positive relationship with built areas and
gardens and allotments, and a negative correlation with
greenspace and agriculture. At the local site-level scale, bum-
blebee abundance was negatively correlated with areas culti-
vated for vegetables and fruits, and positively correlated with
areas cultivated for flowers, although neither correlation was
statistically significant (p= 0.070 and p= 0.051 respectively).
Bumblebee species richness was not correlated with either
land use (p> 0.05). All bumblebee species were negatively
correlated with areas cultivated for vegetables and fruit, bare
ground and hard paving. Several flowering plants were visited
by all bumblebee species, although relative preferences varied
between bumblebee species. Results emphasise the impor-
tance of including floral resources within garden and allot-
ment areas cultivated for food, and the need for a mosaic of
different flowering plants to cater for varying floral prefer-
ences demonstrated by bumblebee species.
Keywords Garden .Allotment .Bombus .Bumblebee, land
use .Floral resources
There have been global declines in populations of insect pol-
linators, including the honeybee (Apis mellifera) and bumble-
bees (Bombus spp) a trend which has been well documented
across Europe and North America (FAO 2008; Goulson et al.
2008;UNEP2010; Potts et al. 2010). This is of concern be-
cause bees play an essential ecological role as pollinators of a
large number of wild flowers and crops (Klein et al. 2007),
including those that are commonly cultivated in domestic,
community and roof-top gardens and allotments (Matteson
and Langellotto 2009).
The main driver of insect pollinator decline is thought to be
habitat loss, as a result of agricultural intensification and in-
creasing urbanisation (Goulson et al. 2008; Winfree et al.
2009; Potts et al. 2010). Pollinator species richness has been
found to decline with increasing intensification of agricultural
practices (Kremen et al. 2002; Steffan-Dewenter 2003), and
levels of urbanisation (Hernandez et al. 2009; Bates et al.
2011). However, some studies have indicated that urban hab-
itats can actually support high bee species richness (Saure
*Gemma Foster
James Bennett
Tim Sparks
Centre for Agroecology, Water and Resilience, Coventry University,
Ryton Gardens, Wolston Lane, Coventry CV8 3LG, UK
Centre for Agroecology, Water and Resilience, Coventry University,
Ryton Gardens, Wolston Lane, Coventry CV8 3LG, UK
Faculty of Engineering, Environment and Computing, Coventry
University, Priory Street, Coventry CV8 3LG, UK
Urban Ecosyst
DOI 10.1007/s11252-016-0604-7
1996;Frankie et al. 2009;Baldock et al. 2015), and certain
taxa such as bumblebees have been found to demonstrate a
positive response to urbanisation (Carré et al. 2009; Bates
et al. 2011).
The value of well managed urban green spaces for native
biodiversity is therefore becoming increasingly recognised
(Goddard et al. 2010). Although the number of urban bee
studies has increased in recent years, urban areas remain
understudied (Baldock et al. 2015). Consequently, little is
known about the diversity and abundance of bees in domestic
gardens and allotments (Hernandez et al. 2009;Mattesonand
Langellotto 2009) or the variables that influence their pres-
ence and diversity (Shwartz et al. 2013).
Domestic gardens are private spaces surrounding dwell-
ings, which comprise a range of features such as lawns, flower
beds and vegetable patches. Allotments are areas reserved for
horticulture where plots are let to individuals for growing
vegetables and flowers. These spaces have high spatial het-
erogeneity as a result of varying land use, management and
plant cultivation at small spatial scales (Thompson et al.
2003). As a result they can provide bees with a wide diversity
of forage (Loram et al. 2007; Frankie et al. 2009). They have
also been found to support high densities of bumblebee
nests compared to agricultural land (Osborne et al.
2008b; Ahrné et al. 2009) and higher bumblebee abun-
dance and species richness than parks and cemeteries
because gardeners often employ techniques that enhance
pollinator habitats (Anderson et al. 2007).
There is great potential for domestic gardens, which ac-
count for between 21 and 27 % of the land in UK cities
(Loram et al. 2007), to be managed for conservation.
Despite this, many gardening recommendations in popular
literature are based on assumptions or informal observation
rather than empirical data (Garbuzov and Ratnieks 2013).
There is also a lack of understanding about how to support
and encourage bee populations in gardens and allotments
(Frankie et al. 2009). This is especially true of areas cultivated
for food, as the majority of advice about enhancing floral
provision focuses on the addition of flowers to ornamental
borders. As food cultivation is becoming an increasingly com-
mon practice in gardens and allotments in industrialised coun-
tries (Lawson 2005), the effect this has on the presence of bees
warrants investigation, especially as evidence suggests that
increasing intensity of garden management reduces bumble-
bee species richness (Smith et al. 2006).
The aim of this study was to explore the presence and
foraging activity of the UKs seven most common bumblebee
species in gardens and in allotments cultivated for food. We
hypothesised that bumblebee abundance, bumblebee species
richness and the individual bumblebee species would 1) be
positively correlated with built areas and gardens and allot-
ments in the surrounding landscape, 2) be positively correlat-
ed with the cultivation of flowers within allotment and garden
survey sites and that 3) bumblebees would demonstrate rela-
tive preferences in the flowering plants they visited both over-
all and between species.
Materials and methods
Study design
A citizen science approach was used to gather information
about the presence of the UKs seven most common bumble-
bee species in garden spaces and allotments used for food
cultivation. This enabled us to gather data from a wide variety
of locations across the UK (Fig. 1). A total of 121 participants
were contacted through Garden Organic, a UK charity pro-
moting organic growing. These participants were selected be-
cause they cultivated their gardens or allotments for food
(growing vegetables and/or fruits), and had experience of
bumblebee identification, having previously taken part in a
Garden Organic bumblebee survey. These participants were
therefore ideally placed for completing this survey as they
were confident in participating in citizen science projects,
and were familiar with the seven species of bumblebee we
asked them to monitor. Results were received from 38 partic-
ipants (representing 31 % of those contacted).
Participants were provided with instructions, recording
forms and a bumblebee identification field guide which
contained images and descriptions of the species that formed
part of the study. The species surveyed, which are often re-
ferred to as the big seven,wereB. terrestris and B. lucorum
(the Buff-tailed Bumblebee and White-tailed Bumblebee,
which were grouped because of the difficulty separating the
species in the field), B. hortorum (Garden Bumblebee),
B. pratorum (Early Bumblebee), B. pascuorum (Common
Carder Bee), B. lapidarius (Red-tailed Bumblebee), and
B. hypnorum (Tree Bumblebee). These species were selected
as they are the most common bumblebee species in the UK
and account for the majority of sightings (Goulson 2010).
With the exception of B. terrestris/lucorum, they are also dis-
tinct enough in appearance to be readily identified.
Bumblebee survey
The survey was undertaken from 1st June 2013 to 30th
September 2013. This period was selected to capture the peak
activity of the survey species (Prys-Jones and Corbet 2011).
Participants were instructed to select a survey site (3 m × 3 m,
rising to 3 m above the ground), which was representative of
the areas cultivated for food in their garden or allotment. They
were asked to make a note of, or mark out, its location so that
they could return to it each week during the survey period.
Participants were instructed to observe and record the bum-
blebees entering the survey site once a week, during a 10 min
Urban Ecosyst
period, when there was sunshine or scattered cloud, and the
temperature was above 15 °C.
Participants were asked to record the total number of each
species of bumblebee observed. In addition, they were asked
to record which flowering plant species each bumblebee vis-
ited and the number of visits made to flowers on that plant.
Participants were asked to record visits to all flowering plants,
including ornamental flowers, fruits, vegetables, herbs and
weeds. For each of the flowering plants visited, they were
asked to estimate the number of floral units of that species
within the survey site, using the following scale: 1 = 1 flower;
2=210 flowers; 3 = 1150 flowers; 4 = 51100 flowers;
5 = over 100 flowers. One floral unit was defined as a collec-
tion of flowers that a bumblebee could walk around when
foraging, without the need for flight. At the end of the season,
participants submitted their data either by mail or via an online
form. Since bumblebee tongue length affects floral prefer-
ences, the tongue lengths of the survey species were
characterised as long, medium or short, using descriptions in
Prys-Jones and Corbet (2011).
Landscape scale characteristics
The latitude of survey sites was determined from the garden
and allotment addresses provided by participants. The land
use characteristics within 2500 m of the midpoint of each
garden or allotment were categorised using digital data from
the Ordnance Survey MasterMap dataset (accessed through
Fig. 1 Locations of the 38 UK
gardens and allotments surveyed
for bumblebees
Urban Ecosyst
EDINA Digimap in February 2014), and analysed with the
ArcGIS 10.1 (ESRI Redlands, USA) geographical informa-
tion system (GIS). This radius was selected because bumble-
bee species may travel kilometres from their nest sites to for-
age within the surrounding landscape.For example, field stud-
ies have reported B. terrestris workers to forage at least 1.5 km
(Osborne et al. 2008a) and 2.2 km (Kreyer et al. 2004)from
their nests.
Based on previous work by Bates et al. (2011) and Ahrné
et al. (2009), five broad land use types were defined and attri-
butes from several OS MasterMap fields were grouped to
represent each category. The five categories (and their OS
MasterMap fields) were: Built (manmade buildings, glass-
houses, roads, rail, manmade tracks and paths), Gardens and
Allotments (multiple make general surface - which was com-
prised of lawns, vegetable/flower beds, trees, garages/sheds/
greenhouses, paving), Greenspace and Agriculture (natural
land, rough grassland, scrub, rock, boulders, natural tracks
and paths), Trees (coniferous trees, non-coniferous trees, or-
chards), and Water (tidal water, inland water, marsh reeds,
saltmarsh). A small percentage of the areas remained unclas-
sified (mean 0.4 % of the landscape) as the MasterMap data
included unclassified areas and minor gaps in the data.
Site-level characteristics
Participants were asked to provide details about site-level
characteristics by estimating the percentage ground cover ded-
icated to each of the following land use types within their
survey site: vegetable and fruit cultivation, cultivated flowers,
hard paving, lawn, trees, shrubs/hedges, waste ground/rough
habitat, water and bare soil. Participants were also asked to
score their gardening practices on a scale ranging from one to
five, with one representing frequent management with syn-
thetic chemicals, and five being exclusively organic.
Statistical analysis
For the purposes of analysis the B. terrestris/lucorum group
was treated as one species. Thus analyses considered six spe-
cies groups. Analysis was based on standard correlation and
regression techniques as described below, and carried out
using Minitab 17, Minitab Inc. Redundancy Analysis ordina-
tion was carried out in Canoco 5.
Weighted regression was conducted to investigate the ef-
fect of time on the abundance of each bumblebee species, total
bumblebee abundance and bumblebee species richness (the
number of bumblebee species) using mean values on week
number (weights in regression = number of recorders).
Correlation analysis was used to investigate the relation-
ships between latitude and the abundance of each bum-
blebee species, total bumblebee abundance and bumble-
bee species richness.
Redundancy Analysis ordination (RDA) was carried out to
compare the abundances of the six species groups with the
land use characteristics within 2500 m of the survey sites,
and with the land use characteristics within the 3 m × 3 m
survey sites. Total bumblebee abundance and species richness
were compared to the same land use characteristics at each
scale using Pearson correlations, data were checked for nor-
mality prior to analysis and no significant deviation was
To identify which flowering plants were preferred by bum-
blebees, flower abundance categories were converted to the
midpoint of their range and summed across each plant species.
Similarly, the total number of bumblebees feeding on each
plant species was summed. The log (x + 1) number of bum-
blebees was then regressed on log (x + 1) flower abundance
=64.2%,p< 0.001), using only those flower species/
cultivars (n= 94) with at least 3 records, and standardised
residuals stored. A cut-off of +1.645 (i.e. the expected 95th
percentile) for the standardised residuals was used to identify
plant species on which bumblebee feeding was greater than
expected given its flower abundance.
Preferences relative to overall feeding patterns were esti-
mated for individual bumblebee species. This involved
regressing the number of feeding records of the bumblebee
species on the total number of bumblebee feeding records
for each plant species. Again standardised residuals of
+1.645 were used as a cut-off point to identify relative prefer-
ences. This process was repeated for each bumblebee species
and was restricted to the same plant species as for total
Bumblebee surveys
The majority of participants (34, 89 %) surveyed gardens,
while the remaining four participants surveyed allotments.
Participantssurvey sites were located across the United
Kingdom the majority were located in England, two were
in Scotland and one was in Wales (Fig. 1). The 38 participants
submitted data from a total of 363 survey occasions undertak-
en between June and September 2013. The majority of survey
sites (57 %) were visited by five or six of the six bumblebee
species groups monitored (Fig. 2).
A total of 2621 individual bumblebees were observed
(Table 1). B. terrestris/lucorum was the mostly frequently ob-
served species group, accounting for 50 % of sightings and
was the only species group present at all 38 sites. All other
species were relatively common, being present at the majority
of survey sites, and accounting for 7 to 16 % of observations.
Between 3 and 16 (mean 9.6) weekly observations were made
by each participant. There were significant reductions in
Urban Ecosyst
species richness (p< 0.05), and in the number of both
B. pratorum (p<0.001)andB. hypnorum (p< 0.05) as the
season progressed (Fig. 3).
Landscape scale characteristics
Latitude was not found to have a significant effect on the
abundance of each bumblebee species, total bumblebee abun-
dance, or bumblebee species richness (all p>0.05).Landuse
characteristics within 2500 m of survey sites were not signif-
icantly correlated with total bumblebee abundance or bumble-
bee species richness (both p > 0.05).
The first two axes of RDA explained 16.3 % (13.0 % and
3.3 % respectively) of the relationship between bumblebee
species abundances and surrounding land use characteristics
(Fig. 4). The more important first axis may be considered to be
a gradient from open green spaces to urban areas and gardens
and allotments; the second axis is difficult to interpret. Most
species had short vectors indicating the lack of a relationship
with surrounding land use characteristics, although the vector
for B. pratorum was close to (and hence positively correlated
with) vectors for built areas, and gardens and allotments, and
opposed to (and hence negatively correlated with) the vector
for greenspace and agriculture.
Site-level characteristics
The majority of participants (33, 87 %) rated their garden
management practices as organic (4 or 5 on the scale), and
so the range was not sufficient to allow further investigation
into the effects of management practices. The most common
land use within the survey sites was food growing (mean 42 %
of the area), followed by the cultivation of flowers (mean 26 %
of the area).
Total bumblebee abundance was positively correlated with
the percentage of the survey site used for cultivated flowers,
and negatively correlated with percentage of the survey site
used for food production, although neither correlation was
statistically significant (p= 0.051 and p= 0.070 respectively).
Correlations between bumblebee species richness and the per-
centage of the survey site used for flower cultivation and food
production were not significant (both p>0.05).
The first two axes of RDA explained 15.9 % (10.2 % and
5.7 % respectively) of the relationship between bumblebee
species abundances and site-level land use characteristics
(Fig. 5). The first axis can be interpreted as a gradient from
heavily managed sites to those containing more woody spe-
cies; the second axis as a gradient from flower rich gardens to
those dominated by lawns and vegetable production. Vectors
for all bumblebee species were opposed to (and hence nega-
tively correlated with) vectors for fruit and vegetable cultiva-
tion, bare ground and hard paving. Vectors for B. lapidarius
and B. pratorum were also close to (and hence positively
correlated with) vectors for flowers and waste ground.
Fig. 2 Frequency distribution of
bumblebee species richness
across the 38 UK survey sites
Tabl e 1 Presence of the bumblebees surveyed in 38 UK gardens and
allotments cultivated for food
Number (%) of sites with
species present (n=38)
Number (% of total) of
bumblebees recorded
B. terrestris/
38 (100 %) 1313 (50 %)
B. hortorum 25 (68 %) 300 (11 %)
B. pratorum 22 (58 %) 169 (6 %)
B. pascuorum 32 (84 %) 406 (16 %)
B. lapidarius 32 (84 %) 239 (9 %)
B. hypnorum 23 (61 %) 194 (7 %)
Urban Ecosyst
Floral preferences
There were 12,105 observations of bumblebees visiting 164
flowering plant species. The majority of bumblebee visits
were made to a relatively small proportion of the flowers
available, with 51 % of bumblebee visits being made to 37
plant species (24 % of the plants surveyed), which accounted
for 10 % of the floral units available. A small selection of plant
species were visited by all six bumblebee species groups, in-
cluding Meadow Cranesbill (Geranium pratense), Blackberry
(Rubus fruticosus), Borage (Borago officinalis) and Lavender
(Lavandula angustifolia).
Regression analysis identified 32 plant species where differ-
ences in feeding preferences could be detected (Table 2). The
plant species which were relatively preferred by bumblebees
overall were Meadow Cranesbill (Geranium pratense), Green
Alkanet (Pentaglottis sempervirens), Sage (Salvia officinalis),
Fig. 3 Plots between weeks 22
and 39 (1st June and 29th
September 2013) showing mean
numbers per location of each
bumblebee species, mean
bumblebee abundance and mean
number of species
Fig. 4 RDA biplot examining relationship between bumblebee
abundances and land use characteristics within 2500 m. Most species
had short vectors indicating the lack of a relationship with surrounding
land use characteristics, although B. pratorum was positively correlated
with built areas, and gardens and allotments, and negatively correlated
with greenspace and agriculture. Species abbreviations: B. terr/luco = B.
terrestris/lucorum group, B. hort = B. hortorum, B. prat = B. pratorum,
B. pasc = B. pascuorum, B. lap = B. lapidarius, B. hyp = B. hypnorum.
Land use abbreviations: Built = built areas, G & A = gardens and
allotments, Greenspace = greenspace and agriculture, Trees etc. = trees/
woodlands/ orchards, and Water = water
Fig. 5 RDA biplot examining relationship between bumblebee
abundances and land use characteristics within the 3 m × 3 m survey
sites in gardens and allotments. All species were negatively correlated
with fruit and vegetable cultivation, bare ground and hard paving, and
B. lapidarius and B. pratorum were positively correlated with cultivated
flowers and waste ground. Species abbreviations: B. terr/luco = B.
terrestris/lucorum group, B. hort = B. hortorum, B. prat = B. pratorum,
B. pasc = B. pascuorum, B. lap = B. lapidarius, B. hyp = B. hypnorum.
Land use abbreviations: Veg = vegetable and fruit cultivation, Flowers =
cultivated flowers, Hard paved = hard paved, Lawn = lawn, Trees = non-
crop trees, Shrubs = shrubs and hedges, Waste = waste ground/ rough
habitat, Water = water, and Bare soil = bare soil
Urban Ecosyst
Mallow (Lavatera spp), and Marjoram (Origanum vulgare).
Relative preferences varied between bumblebee species.
Our results indicate that the bumblebee species surveyed are
frequent visitors to spaces cultivated for food in UK gardens
and allotments. The majority of survey sites were visited by
five or six of the six bumblebee species groups surveyed,
indicating that these common species are fairly ubiquitous
within these spaces. The number of bumblebee sightings,
and the presence of each bumblebee species varied through
the season, probably as a result of phenological differences in
the bumblebee species studied.
In contrast to expectation, bumblebee abundance and spe-
cies richness were not correlated with surrounding land use
characteristics. A similar study of Swedish allotments also
reported landscape to have limited on bumblebee abundance,
but did find bumblebee species richness to be negatively cor-
related with increasing proportions of built areas/impervious
surfaces (Ahrné et al. 2009). If our study had surveyed all 25
UK bumblebee species a similar pattern may have emerged, as
evidence suggests that urban areas generally contain fewer
Tabl e 2 Standardised residuals for floral preferences of bumblebees relative to the overall mean. Standardised residuals of +1.645 were used as a cut-
off to identify relative preferences and these are shown in bold. Tongue length categories: Lt = Long tongue, Mt. = Medium tongue, St = Short tongue
Plant species All bumble-
B. terrestris/
B. hortorum B. pratorum B. pascuorum B. lapidarius B. hypnorum
(St) (Lt) (St) (Lt) (Mt) (St)
Meadow Cranesbill (Geranium pratense)3.08 0.01 0.18 2.47 2.72 3.05 0.21
Green Alkanet (Pentaglottis sempervirens)2.66 -0.55 -1.19 1.59 1.36 2.16 3.75
Sage (Salvia officinalis)2.49 -0.14 -1.12 -0.81 2.79 -1.00 -0.89
Mallow (Lavatera spp) 2.17 2.09 1.00 2.00 1.02 1.17 -0.32
Marjoram (Origanum vulgare)1.70 1.57 1.46 -0.87 1.26 0.18 2.48
Blackberry (Rubus fruticosus) 1.43 0.93 -0.26 2.55 0.66 0.46 2.32
Oriental Poppy (Papaver orientale)1.301.251.98 -0.07 -0.45 -0.39 -0.22
Opium Poppy (Papaver somniferum)1.241.68 1.06 -0.30 -0.29 0.65 -0.42
Borage (Borago officinalis) 1.04 0.5 4 0.74 2.13 1.61 1.82 1.47
Perennial Cornflower (Centaurea montana) 0.99 -0.81 -0.66 -0.38 0.80 2.11 -0.50
Cornflower (Centaurea cyanus) 0.92 0.5 2 0.29 2.21 -1.16 1.59 0.65
Russian Comfrey (Symphytum x uplandicum) 0.89 1.12 -1.02 2.37 -1.33 0.50 0.76
Foxglove (Digitalis purpurea)0.860.801.90 -1.14 1.35 -1.28 0.29
Common Bugle (Ajuga reptans)0.780.191.96 -0.77 0.92 1.13 -0.85
Geranium Rozeanne(Geranium Rozeanne
0.77 1.19 -0.98 1.51 -1.92 1.85 1.03
Small Globe Thistle (Echinops ritro) 0.73 1.20 -1.09 -0.78 -1.41 1.70 -0.34
Red Campion (Silene dioica)0.720.322.49 -1.04 -0.44 -1.19 -1.09
Common Snowberry (Symphoricarpos albus) 0.53 -0.20 -1.06 1.90 -1.36 -0.95 2.26
Clover (Trifoliu m spp) 0.50 -0.13 -0.71 0.84 0.55 1.68 -0.54
BearsBreeches(Acanthus mollis) 0.43 -1.96 -0.45 -0.18 1.67 -0.48 -0.32
Sedum (Sedum spp) 0.37 0.92 0.06 0.39 -0.59 1.76 -1.20
White Campion (Silene latifolia subsp.Alba) 0.37 -2.00 1.98 0.66 -0.63 -0.50 -0.34
Poached Egg Plant (Limnanthes douglasii) 0.22 0.26 -1.42 2.02 -0.08 1.62 -1.14
Lavender (Lavandula angustifolia) 0.21 0.15 0.90 -0.39 1.27 0.16 1.72
Larkspur (Delphinium spp) 0.14 -2.05 1.85 -0.76 0.95 -0.96 -0.02
Raspberry (Rubus idaeus) 0.08 -0.69 0.30 1.93 -0.25 -1.43 2.50
Rock cranes-bill (Geranium phaeum) 0.04 0.53 -1.21 2.20 -1.56 -1.07 -0.96
Broad bean (Vicia faba) -0.13 -1.26 -1.52 1.69 1.24 -0.35 0.78
Hollyhock (Alcea rosea) -0.23 -1.79 1.88 -0.77 0.00 -0.21 -0.85
Field Scabious (Knautia arvensis) -0.41 -1.58 1.75 -0.77 0.15 -0.97 -0.85
Honeywort (Cerinthe major Purpurascens) -0.48 -0.79 -1.38 1.74 -0.28 1.38 -1.10
Montbretia (Crocosmia spp) -0.68 -0.96 -0.92 -0.62 -0.26 -0.85 1.70
Urban Ecosyst
floral specialists and rare species (Frankie et al. 2009;
Hernandez et al. 2009; Bates et al. 2011). In particular, the
rare species of bumblebee in the UK have been found to be
less generalist/polylectic than the common species which are
able to exploit the wide range of floral resources available in
gardens (Goulson et al. 2005).
Bombus pratorum was the only species to show correla-
tions with the surrounding land use characteristics, demonstrating
a positive relationship with built areas, gardens and allotments,
and a negative relationship with greenspace and agriculture. This
species appears to be becoming increasingly urbanised due to its
intolerance of agriculture (Benton 2000), and our results suggest
urban green spaces are important habitats for this species. This
could be because B. pratorum is a small species with a short
foraging distance. It also often nests in cavities and bird boxes
(Prys-Jones and Corbet 2011; Lye et al. 2012) and these features
are common in urban areas and gardens.
Many studies have suggested that local factors such as site
management, flower abundance and plant diversity have a
greater effect on bee presence than surrounding landscape
(Ahrné et al. 2009; Frankie et al. 2009; Pardee and Philpott
2014). Our results indicate that bumblebee abundance is neg-
atively correlated with increasing proportions of food cultiva-
tion, and all bumblebee species demonstrated a negative re-
sponse to this local land use. Bumblebee abundance was pos-
itively correlated with increasing flower cultivation. This is
supported by other studies which have reported bumblebee
abundance to be positively related to the proportion of
flowering plants (Ahrné et al. 2009), as well as floral abun-
dance and plant diversity (Hennig and Ghazoul 2012).
Bumblebee species richness however was not affected by
site-level land use, again possibly because the survey was
limited to the most common bumblebee species. Other studies
have reported an increase in bee species richness with increas-
ing floral diversity (Smith et al. 2006) and floral area
(Matteson and Langellotto 2010), and a reduction in bumble-
bee species richness with increasing intensity of garden man-
agement (Smith et al. 2006). This highlights the need for fur-
ther detailed assessments of garden management practices,
also called for by Shwartz et al. (2013).
Our results suggest the importance of including flowers in
areas cultivated for food, in order to maximise floral resource
availability within these areas. This message is likely to be-
come increasingly important if food production continues to
grow in popularity in domestic gardens and allotments. This
does not necessarily need to be at the expense of production in
vegetable patches or allotments, as bumblebees demonstrated
relative preferences for several herbs, fruits and
vegetables. The provision of floral resources may also
contribute to improved yields of insect pollinated crops.
Recent research by Potter and LeBuhn (2015) found
that tomato pollination in gardens was positively corre-
lated with floral resource density within survey gardens,
as an indirect effect of increased abundance of bees or
increased visitation rates.
Although 164 plant species were visited during this study, the
majority of visits were made to a relatively small number of
flowering plants. Half of all bumblebee visits were made to 37
plant species representing only 10 % of the available floral units.
Similar figures were reported by Ahrné et al. (2009), where al-
though 168 plant species were visited by bumblebees, half of the
visits were made to just 14 plant species. Some of the flowering
plant species monitored in this study were visited by all bumble-
bee species groups studied, including Meadow Cranesbill
(Geranium pratense), Blackberry (R. fruticosus), Borage
(B. officinalis)and Lavender (L. angustifolia). These plants can
therefore be recommended as useful species for supporting the
UKs common bumblebee species.
As expected, the relative preferences varied between bum-
blebee species, and the majority of the variation can be ex-
plained by the morphological differences in tongue length
(Prys-Jones and Corbet 2011). Meadow Cranesbill
(G. pratense), the most visited flower overall, was especially
popular with B. pratorum, B. lapidarius and B. pascorum
(short, medium and long-tongued species respectively), which
all showed a significant relative preference for the flower.
Many Geranium species are known to be popular with bees
because their open flowers enable a range of species with
varying morphology to access pollen and nectar resources
within the flower (Kirk and Howes 2012).
Few weed species were visited by bumblebees during this
study, and only four (Thistle (Cirsium spp), Red Deadnettle
(Lamium purpureum), Common Bugle (Ajuga reptans)and
Clover (Trifolium spp)) featured in the list of the 37 most visited
plant species. This is probably a result of the intensive weeding
practices commonly employed in spaces cultivated for food. As
native plants are an important source of forage in the wider
landscape, especially in the spring, gardeners may benefit from
education about the value of certain flowering weeds, which
could be removed after flowering but before seed set.
Although this study did not explore the huge variety of
plants available to gardeners, with over 75,000 being listed
in the RHS Plant Finder (Armitage 2016), it does highlight
some of the more commonly grown plants and how they are
used by bumblebees. Although plants such as Meadow
Cranesbill (G. pratense) had general appeal, many bumblebee
species demonstrated relative preferences for other flowers.
This emphasises the need for a mosaic of different flowering
plants that can cater for the needs of the various bumblebee
species in both space and time.
This is the first study to explore the land use and floral pref-
erences of bumblebees in gardens and allotments cultivated
Urban Ecosyst
for food across the UK. Although bumblebee abundance and
species richness was not significantly correlated with sur-
rounding land use characteristics, our results suggest that gar-
dens and allotments are important habitats for B. pratorum.
Our results also highlight the importance of local site-level
land use, as all bumblebee species were negatively correlated
with vegetable and fruit cultivation, while total bumblebee
abundance was positively correlated with flower cultivation.
This emphasises the importance of including flowers in areas
cultivated for food, in order to maximise floral resource avail-
ability within these areas.
Many gardeners are keen to support pollinators by growing
appropriate flowers and there are numerous lists available to
guide them in their plant choices. The preferred plants identi-
fied in this study generally compared well with popular lists of
plants designed to support pollinators (such as Royal
Horticultural Society 2016a;2016b). However, several plant
species that bumblebees demonstrated relative preferences for
in our study do not feature in the lists. This highlights the need
for expanding current lists or creating lists designed to support
pollinators in spaces cultivated for food, for which there is
limited information available.
Although the survey period covered the flight activity of all
the common bumblebee species, future studies would benefit
from an earlier start date to capture information about the
activity of emerging queens. There is also a need to study all
25 UK bumblebee species, as rarer species are in greater need
of conservation support than the common species, which tend
to be more generalist, with broader tolerances.
Acknowledgments We thank the Garden Organic members who kind-
ly volunteered their time to collect data for this project. We also thank
Stuart Gill for his work carrying out GIS analysis, as well as Barbara
Smith, Judith Conroy and two anonymous reviewers for their comments
which improved this manuscript. This study was funded by Coventry
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Urban Ecosyst
... Across the world, UA provides employment opportunities to urban residents in varying forms and degrees. In the global north, UA is usually practiced on a wide range of land areas, including allotments, private domestic gardens, community gardens, and commercial market gardens (Foster et al., 2017;Schmutz et al., 2018), producing predominantly fruits and vegetables (Orsini et al., 2013). Whereas, in the global south, urban food production is practiced on privately owned or rented land, vacant or open spaces, greenhouses, and as well as in rivers, ponds, and lakes (Ibitoye et al., 2016;Olumba et al., 2019). ...
Full-text available
Urban agriculture (UA) is promoted as a viable strategy to support the food demands of the increasing urban population in the global south. However, UA faces severe constraints that could undermine this potential. To sustain urban food production, there is a research need to identify the main factors deterring UA activities. This study, therefore, aims to examine the constraints faced by urban farmers in carrying out their UA production activities. Two hundred and eighty urban farmers selected through a multi-stage sampling technique were used for the study. Data were collected using a questionnaire/interview schedule and analysed using descriptive statistics and principal component analysis (PCA). The study shows that the urban farmers were engaged in four main types of agro-enterprises. They include crop production, livestock production, agro-processing, and the supply of farming inputs. The majority of the UA farmers indicated that they were into maize production (75%), poultry production (60%), and 25% were into fish farming. The PCA result suggests three key constraints to UA, namely infrastructural constraints, socio-economic/environmental constraints, and institutional constraints. For UA in southeast Nigeria to reach its full potential, the study recommends proactive policy responses in support of UA. Also required is infrastructural support in terms of good road networks and marketing facilities to best support UA activities.
... There is a good UK market for its seed oil, which is often marketed as the more attractively named 'Starflower oil' and the crop benefits biodiversity and is highly desirable to some pollinators (e.g. bumblebees; Foster et al., 2017). There is also a small local demand for its flowers, which are used as edible meal decorations by restaurants. ...
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Context Climate change will alter the global distribution of climatically suitable space for many species, including agricultural crops. In some locations, warmer temperatures may offer opportunities to grow novel, high value crops, but non-climatic factors also inform agricultural decision-making. These non-climatic factors can be difficult to quantify and incorporate into suitability assessments, particularly for uncertain futures. Objective To demonstrate how qualitative and quantitative techniques can be combined to assess crop suitability with consideration for climatic and non-climatic factors. Methods We carried out a horizon scanning exercise that used Delphi methodology to identify possible novel crops for a region in south-west England. We show how the results of the expert panel assessment could be combined with a crop suitability model that only considered climate to identify the best crops to grow in the region. Results and conclusions Whilst improving climate and crop models will enhance the ability to identify environmental constraints to growing novel crops, we propose horizon scanning as a useful tool to understand constraints on crop suitability that are beyond the parameterisation of these models and that may affect agricultural decisions. Significance A similar combination of qualitative and quantitative approaches to assessing crop suitability could be used to identify potential novel crops in other regions and to support more holistic assessments of crop suitability in a changing world.
... It is becoming increasingly recognized, that wellmanaged urban parks and other public green urban areas are highly valuable for insect pollinators (McFrederick and LeBuhn 2006;Frankie et al. 2009;Shwartz et al. 2013;Banaszak-Cibicka et al. 2018;Theodorou et al. 2020). There is also clear evidence that privately owned garden properties like allotments and domestic gardens can support a considerable diversity of pollinators (Ahrné et al. 2009;Foster et al. 2017;Baldock et al. 2019). Both, public parks as well as privately owned gardens, generally contain high plant species richness of native, exotic and ornamental plants, thus providing a large potential food resource for pollinators (Hope et al. 2003;Frankie et al. 2005;Hülsmann et al. 2015;Lowenstein et al. 2019). ...
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Urban landscapes are often characterized by a wide range of diverse flowering plants consisting of native and exotic plants. These flower-rich habitats have proven to be particularly valuable for urban pollinating insects. However, the ability of ornamental plants in supporting urban pollinator communities is still not well documented. For this study, we established flower beds at 13 different urban testing sites, which were planted with identical sets of ornamental garden plants. The pollinator visitation patterns were then observed throughout the summer seasons. Over a two-year period, a total of 10,565 pollinators were recorded with wild bees (> 50%, excluding bumblebees) being the most abundant pollinator group. Our results revealed that (I) the assortment of ornamental plants was visited by a high number of urban pollinators for collecting pollen and nectar, and (II) the pollinator abundance and composition varied significantly within the tested ornamental plants. These differences occurred not only among plant species but to the same extent among cultivars, whereby the number of pollinators was positively correlated with number of flowering units per plant. By using a generalized linear mixed model (GLMM) and redundancy analysis (RDA) we identified further significant impacts of the two variables year and location on the insect pollinator abundance and richness. Despite of the local and yearly variations, our approach provided a good and field-applicable method to evaluate the pollinator friendliness in ornamental plants. Such tools are urgently required to validate labels like ‘bee friendly’ or ‘pollinator friendly’ used by plant breeding companies.
... This biodiversity is also mainly positively correlated with the proximity to gardens and allotments (e.g. Foster et al. 2016;Baldock et al. 2019). In the tropics, in addition to these aspects, urban green spaces that present a high number of plant species that continuously offer floral resources may represent a refuge to many groups of pollinators, mainly bees (e.g. ...
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Urbanization has rapidly increased in recent decades and the negative effects on biodiversity have been widely reported. Urban green areas can contribute to improving human well-being, maintaining biodiversity, and ecosystem services (e.g. pollination). Here we examine the evolution of studies on plant–pollinator interactions in urban ecosystems worldwide, reviewing also research funding and policy actions. We documented a significant increase in the scientific production on the theme in recent years, especially in the temperate region; tropical urban ecosystems are still neglected. Plant–pollinator interactions are threatened by urbanization in complex ways, depending on the studied group (plant or pollinator [generalist or specialist]) and landscape characteristics. Several research opportunities emerge from our review. Research funding and policy actions to pollination/pollinator in urban ecosystems are still scarce and concentrated in developed countries/temperate regions. To make urban green spaces contribute to the maintenance of biodiversity and the provision of ecosystem services, transdisciplinary approaches (ecological–social–economic–cultural) are needed.
... Thymus longicaulis, Campolo et al. (2016)) and lavender flowers are also attractive to a wide range of insects (Herrera, 1988;Herrera, 1989). A recent UK wide citizen science project found that lavender (Lavandula angustifolia) was one of only a few plants that all six of their specified bumblebee groups visited, making it a highly recommended plant to support common native bumblebees (Foster et al., 2017). However, not all lavender varieties are equally attractive to pollinators; recent research from Garbuzov and Ratnieks (2014b) found that Lavandula x intermedia varieties (such as that used in this study) are more attractive than those of L. angustifolia and L. stoechas. ...
Dessert apple orchards in the UK have successfully intensified their growing systems to enable a higher yield output per unit area. This agricultural intensification has allowed for more efficient crop management. However, this intensification has come at the detriment to space for non-crop vegetation in the orchards, attributed to sustaining invertebrate populations of pollinators and natural pest enemies with alternative resources and refuge. Therefore, the remaining populations of beneficial invertebrates in these systems might not be able to deliver sufficient or stable regulating ecosystem services such as pollination and pest control to the crop system. To address this concern, I firstly carried out a survey with a select group of top-fruit growers in my study region to understand the practices and perceptions surrounding existing non-crop vegetation in orchards. Non-crop trees were already in place on farms as hedgerow or windbreak structures; however, these had rarely been designed to support beneficial invertebrates. Furthermore, various blockers for annual wildflower adoption were identified. Therefore, this knowledge contributed to the design of a novel ecological experiment to enhance apple orchard edges with perennial lavender and thyme plants. The aim was for these plants to provide successional floral resources in close vicinity to the crops to sustain pollinator populations after the mass apple bloom, whilst not deterring natural enemy populations to thrive on-site during the apple-growing season. Orchard edges with either a mixed lavender and thyme treatment, or a lavender treatment, successfully sustained wild pollinators, such as bumblebees, in the orchards over the late summer months. The wild bee visitation rate to apple flowers in the spring also increased in orchards with a mixed orchard edge treatment. Although no repellent effects of lavender and thymes on natural enemies were found; the effects on ground or tree dwelling natural enemy populations remain uncertain due to sampling methods and agrochemical use. Aerial hoverfly abundances were higher in the orchards with a mixed lavender and thyme edge however, it would need to be confirmed that these were aphidophagous species before concluding that natural enemies with an aerial life stage, which relies on floral nectar or pollen provision, could benefit from this orchard edge enhancement. Apple yield and quality were both unaffected by orchard edge treatments in the first two years after establishment. However, pollinator exclusion experiments confirmed the necessity of pollinators to the apples to achieve good yields and quality. Therefore, any increase to wild bee abundances from the orchard edge treatments could potentially contribute stability to the pollination service delivery by buffering the natural fluctuations in pollinator populations and the potentially inconsistent pollination services from managed honeybees. This research shows how collaborating with the select group of growers that are responsible for non-crop habitat provision and management on farms in the study region can enable the development of novel alternatives to ensure that floral resource provision is available on-site for beneficial invertebrate populations.
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Aktuell ist weltweit eine zunehmende Ausdehnung der städtischen Gebiete zu beobachten, was ein Verlust von natürlichen Lebensräumen bedeutet. Soll die derzeitige Biodiversität jedoch erhalten bleiben, müssen vermehrt Anstrengungen unternommen werden, um heimischer Flora und Fauna auch im urbanen Gebiet Ersatzlebensräume bieten zu können. Hinsichtlich der Artenvielfalt und der Bewertung des Lebensraums „Stadt“ kommen wissenschaftliche Studien zu stark unterschiedlichen Ergebnissen, wenngleich sie jedoch alle betonen, dass urbane Grünflächen einen wertvollen Beitrag zur Förderung eines städtischen Artenreichtums leisten können. Während vielfach darauf hingewiesen wird, dass ausreichende und geeignete Nahrungsressourcen für die Bestäuberinsekten bereitgestellt werden müssen, wurde in den seltensten Fällen untersucht, ob Zierpflanzen von den urbanen Bestäubern überhaupt als Nahrungsquelle genutzt werden. Dies war für lange Zeit umstritten, wird aber inzwischen zunehmend durch Publikationen belegt, wobei die ökologische Bedeutung der Zierpflanzen nach wie vor kontrovers diskutiert wird. So gibt es offenbar große Attraktivitätsunterschiede innerhalb der Zierpflanzen und darüber hinaus können wohl nicht alle Bestäubergruppen gleichermaßen von den zumeist exotischen Zierpflanzen als Nahrungsressource profitieren. Da zum jetzigen Zeitpunkt nicht zu jeder Zierpflanze wissenschaftlich erhobene Daten vorliegen, war es zunächst ein Ziel dieser Arbeit, belastbare Daten hinsichtlich der Bestäuberfreundlichkeit bestimmter Zierpflanzen, insbesondere solche mit einem hohen Markanteil, zu gewinnen. Für solche Versuche sollten darüber hinaus entsprechende Erfassungsmethoden beurteilt und weiterentwickelt werden. Ein weiterer und bisher kaum untersuchter Schwerpunkt der Arbeit war die Frage, welche Faktoren sich in welcher Form auf die Zusammensetzung und Abundanz der urbanen Bestäuber auswirken. Um diese Fragestellungen bearbeiten zu können, wurden in den Jahren 2017 – 2019 in Freiland- und Semifreilandversuchen Zählungen, Beobachtungen sowie Kescherfänge zur Bestäuberattraktivität bestimmter Zierpflanzen durchgeführt. Im ersten Versuchsansatz wurde an 13 verschiedenen Standorten im Stadtgebiet Stuttgart jeweils ein Hochbeet aufgestellt, welches mit einer identischen Auswahl an Zierpflanzen bepflanzt wurde. In den Jahren 2017 und 2018 wurden alle Standorte während der Sommermonate wöchentlich besucht und die Hochbeete 20 Minuten lang beobachtet. In dieser Zeit wurde die Anzahl der Bestäuberinsekten sowie deren Zugehörigkeit zu bestimmten Insektengruppen erfasst. Es konnten im Rahmen dieser Erfassungen insgesamt 10.565 pollen- und/oder nektarsammelnde Blütenbesucher gezählt werden. Dies bestätigt zunächst einmal, dass unsere Auswahl an Zierpflanzen von Bestäuberinsekten als Nahrungsquelle genutzt wurde. Die Attraktivität der getesteten Zierpflanzen unterschied sich jedoch in erheblichem Maße innerhalb der Pflanzenarten und reichte von durchschnittlich 1,2 Blütenbesuche pro 20 Minuten bei Bracteantha bracteata (Garten-Strohblume) bis zu 5,3 Besuche bei Bidens (Goldmarie). Die Attraktivität variierte jedoch auch – und dies teilweise in stärkerem Maße – zwischen den Sorten einer Art. Statistische Modelle zeigten darüber hinaus signifikante Einflüsse von Untersuchungsjahr und Standort. Dies unterstreicht die Notwendigkeit einer kontinuierlichen Testung aller Zierpflanzen hinsichtlich der Bestäuberfreundlichkeit, wofür die hier beschriebenen Methoden sich als gut geeignet erwiesen haben. Bemerkenswert ist, dass sich nicht nur die Abundanz, sondern auch die Zusammensetzung der Bestäuber signifikant zwischen getesteten Zierpflanzen unterschied (Publikation I). Bei ihrer Nahrungssuche und zur Entscheidungsfindung, ob sich eine Ressource als Nahrungsquelle eignet, ziehen Bestäuberinsekten die charakteristischen und oftmals gattungs-, art- oder gar sortenspezifischen Merkmale der Blüten heran. Während diese bei vielen heimischen Blühpflanzen gut untersucht sind, ist sehr wenig über die Rolle der Blütenmerkmale wie Farbe, morphologische Ausprägungen oder Blütenduft bei den Zierpflanzen bekannt. Da die einzigen diesbezüglichen Untersuchungen bei Astern keine klaren Ergebnisse erbrachten, wurden in dieser Arbeit erstmals anhand der Beispielkultur Calibrachoa und dem Modellbestäuber Bombus terrestris untersucht, welche Blütenmerkmale mit der Attraktivität für Bestäuber korreliert sind. Wie im oben angeführten Stadtversuch zeigte sich, dass die Attraktivität zwischen den getesteten Calibrachoa Sorten stark variierte. Während der Blütenduft die beobachteten Attraktivitätsunterschiede nur in geringem Maße erklären konnte, hatte die Blütenfarbe einen signifikanten Einfluss auf die Attraktivität bei B. terrestris. Für die Frage, ob und welche spezifische Blütenmerkmale bei Calibrachoa und anderen Zierpflanzen die Attraktivität für Bestäuberinsekten beeinflussen, sind aber weitere Untersuchungen notwendig (Publikation II).
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Background The world's growing population and growing need for food have increased attention to urban agriculture around the world. Most crops grown in urban environments need bees for pollination. However, little is known about bee populations in urban areas and little attention has been paid to the function of these pollinators in cities. Therefore, studying the ecology of pollinating bees in urban gardens and green roofs contributes greatly to urban agriculture. In this study, the results of 87 articles related to the presence of bees in gardens and urban farms were summarized in three general sections. The first part deals with issues, such as the diversity of bees in urban gardens, dominant species in these areas, their nesting type, origin, specialty, and sociality. The second part examines the attractiveness of host plants in urban gardens and farms and their origin for bees. The third section examines the effects of landscape and local variables effects on the presence of bees in urban farms and gardens. Results Our data showed that urban environments, especially urban gardens, contain a high diversity of bees, which honeybees and bumblebees are the most dominant species in these environments. The results of the second part showed that native plants were more attractive to bees than non-native plants. In the third section, most studies have shown the negative role of urbanization on the presence of bees. On the other hand, many studies have shown that the presence of green spaces or other farms and gardens around the studied gardens have a positive effect on the presence of pollinators. Conclusion Urban environments have a high diversity of plants and bees that provides a good opportunity to increase agricultural production in these environments. Planting native plants and creating artificial nests for solitary bees and bumblebees can help attract more bees to urban environments. Converting lawns into floral resources or carrying out agricultural activities around green spaces can also effectively help to increase agricultural production in the city.
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Cities are emerging as refugia for pollinators, among which bees play a pivotal role for maintaining ecosystem functioning in agricultural and urban settings. While measures to promote bees have been investigated predominantly in the agricultural or rural context, a wide knowledge gap persists with regard to the effectiveness of such measures within urban landscapes. In order to guide research addressing this lack of knowledge, the aim of this perspective paper is to give an overview of the recent research activities based on the published peer-reviewed literature. While research on flower seed mixtures in general focuses on nutritional aspects, studies on plantings of perennial herbs are relatively limited to few plant taxa. Implementation of comparable case studies investigating the effects of tree plantings on bee populations is hampered by a lack of methodological standardization. The conservation value of providing nesting sites in cities needs to be further investigated, in particular concerning ground-nesting bee species. While several case studies indicate a nutritional supporting function of green roofs for urban bee populations, findings with regard to vertical isolation remain equivocal. Various factors driving bee diversity and population structure in the urban context at the local and landscape scale have been identified, the reported relevant landscape scale being represented by radii between 500 and 1000 m in most cases. Future study designs reflecting a continuous and complete gradient of urbanization will be helpful in comparing results on bee promoting measures in agricultural landscapes (which are numerous) to urban settings (which are still encountered much less frequently). Studies looking into the genetic structure of bee populations with regard to urbanization so far represent only a tiny fraction of bee diversity, and the further development of molecular methods could yield novel tools for assessing the success of bee promoting measures in terms of habitat connectivity in the near future.
Urban agriculture contributes to food security and human wellbeing and is associated with a wide range of environmental benefits. In the United Kingdom, a substantial proportion of urban agriculture occurs in allotment gardens, and these are a historically significant part of the landscape. However, allotment land provision has declined significantly since its mid-twentieth century peak. Here, we examine the magnitude and nature of this decline using a GIS analysis of historic Ordnance Survey maps covering ten British urban areas from the beginning of the twentieth century to the present. We find there has been a 65% decline in allotment land from its peak to 2016, a pattern also reflected in per capita provision, which declined by 62%, demonstrating a long-term trend across the case study areas, and the loss of food provisioning land for an average of 6% of the urban population. We also show that the most at-risk areas for food insecurity have faced eight times the level of allotment closures than the least deprived areas. Assessing subsequent land-use of former allotments, we show that 47% of allotment land is now part of the urban built infrastructure, and 25% is other forms of urban greenspace. Restoration of these greenspace sites to allotments has the potential to meet up to 100% of the current levels of demand for new allotments by residents of our case study areas. Our results demonstrate that whilst a significant amount of urban agricultural land has been lost, opportunities for restoration exist on a substantial scale.
Urban areas are growing worldwide and alter landscapes in a persistent fashion, thereby affecting biodiversity and ecosystem services such as pollination in a little understood way. Here we present a systematic review of the peer-reviewed literature to identify the drivers of urban pollinator populations and pollination. A total of 141 studies were reviewed and qualitatively analyzed. Pollinator responses to urbanization were contrasting. We contend that positive responses were often associated with urban sprawl, i.e. moderate levels of urbanization of rural, mostly agricultural land below 50% impervious surface, whereas high levels of densification with high percentages of sealed and built-up area (above 50%), largely led to pollinator declines and loss of pollination services. Further, urbanization generally reduced pollinator diversity when compared to natural or semi-natural areas, but enhanced it when compared to intensified agricultural landscapes. In addition, pollinator responses were commonly highly trait-and scale-specic. Cavity nesters and generalist species usually profited more from urbanization than ground nesters and specialists. Overall, urban pollinator communities still seem to provide sufficient pollination services to wild vegetation and crops. Pollinator diversity generally increased with the amount of urban green spaces at the landscape scale, and locally with availability of nesting resources and flowering plants. Positive effects of floral additions were largely independent of the plant's origin, whether native or non-native. Only a few studies included landscape configuration. Likewise, abiotic urban drivers, e.g. heat island effects and air and light pollution, remain little studied. Tropical and developing regions, most heavily impacted by current and future urbanization, are strongly underrepresented. We conclude that biodiversity friendly urbanization can make a valuable contribution to pollinator conservation, in particular in face of the continued intensification of rural agriculture.
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Insect pollinators provide a crucial ecosystem service, but are under threat. Urban areas could be important for pollinators, though their value relative to other habitats is poorly known. We compared pollinator communities using quantified flower-visitation networks in 36 sites (each 1 km²) in three landscapes: urban, farmland and nature reserves. Overall, flower-visitor abundance and species richness did not differ significantly between the three landscape types. Bee abundance did not differ between landscapes, but bee species richness was higher in urban areas than farmland. Hoverfly abundance was higher in farmland and nature reserves than urban sites, but species richness did not differ significantly. While urban pollinator assemblages were more homogeneous across space than those in farmland or nature reserves, there was no significant difference in the numbers of rarer species between the three landscapes. Network-level specialization was higher in farmland than urban sites. Relative to other habitats, urban visitors foraged from a greater number of plant species (higher generality) but also visited a lower proportion of available plant species (higher specialization), both possibly driven by higher urban plant richness. Urban areas are growing, and improving their value for pollinators should be part of any national strategy to conserve and restore pollinators.
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Insect pollinators provide a crucial ecosystem service, but are under threat. Urban areas could be important for pollinators, though their value relative to other habitats is poorly known. We compared pollinator communities using quantified flower-visitation networks in 36 sites (each 1 km2) in three landscapes: urban, farmland and nature reserves. Overall, flower-visitor abundance and species richness did not differ significantly between the three landscape types. Bee abundance did not differ between landscapes, but bee species richness was higher in urban areas than farmland. Hoverfly abundance was higher in farmland and nature reserves than urban sites, but species richness did not differ significantly. While urban pollinator assemblages were more homogeneous across space than those in farmland or nature reserves, there was no significant difference in the numbers of rarer species between the three landscapes. Network-level specialization was higher in farmland than urban sites. Relative to other habitats, urban visitors foraged from a greater number of plant species (higher generality) but also visited a lower proportion of available plant species (higher specialization), both possibly driven by higher urban plant richness. Urban areas are growing, and improving their value for pollinators should be part of any national strategy to conserve and restore pollinators.
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Urban agriculture can increase the sustainability of cities by reducing their ecological footprint, conserving biodiversity, and improving quality of life in a city. Given the environmental, economic and social value of urban agriculture, it is important to understand the ecosystem services that sustain it. We experimentally investigated how pollination by wild bees affects tomato production on 16 urban agriculture sites in San Francisco, CA. By comparing four pollination service indicators (fruit set, fruit mass, yield, and seed set) in four pollination treatments (open, artificial-self, artificial-cross, control), we were able to determine that tomatoes pollinated by wild bees significantly outperform the control in terms of all four pollination service indicators measured. Furthermore, the results of this study indicate that urban areas can support adequate pollination service to urban agriculture, regardless of garden size, garden age, or proportion of impervious surface in the surrounding matrix, and that floral resource density is a major factor influencing pollination service.
Summary Since bumblebees are a group associated with cool climates, Britain supports a large proportion (~10%) of the world's bumblebee fauna. However, three of our 25 species have become extinct, and seven species are Biodiversity Action Plan (BAP) listed, a higher proportion than for any other insect group. Declines are primarily driven by habitat loss and declines in floral abundance resulting from agricultural intensification, notably the loss of ~97% of all species-rich grasslands (haymeadows, calcareous grasslands) in the last 60 years. The decline in the abundance of Red Clover, once a common fodder and ley crop and a major source of pollen and nectar for many bumblebee species, is likely to have had a significant impact. Effects of habitat degradation and fragmentation are compounded by the social nature of bumblebees and by their largely monogamous breeding system, which means that they have a very low effective population size (most bumblebees are sterile workers). Hence, populations are susceptible to chance extinction events and inbreeding. Given the importance of bumblebees as pollinators of crops and wildflowers, their declines have broad ecological and economic significance. Suggested measures for their conservation include tight regulation of commercial bumblebee use and targeted use of agri-environment schemes to enhance floristic diversity in agricultural landscapes. Introduction The drone of bumblebees busily collecting nectar and pollen is, for me, the sound of summer: I have fond memories of childhood days spent in our garden in Shropshire catching bumblebees and imprisoning them temporarily in jam jars.
Urban gardens may support bees by providing resources in otherwise resource-poor environments. However, it is unclear whether urban, backyard gardens with native plants will support more bees than gardens without native plants. We examined backyard gardens in northwestern Ohio to ask: 1) Does bee diversity, abundance, and community composition differ in backyard gardens with and without native plants? 2) What characteristics of backyard gardens and land cover in the surrounding landscape correlate with changes in the bee community? 3) Do bees in backyard gardens respond more strongly to local or landscape factors? We sampled bees with pan trapping, netting, and direct observation. We examined vegetation characteristics and land cover in 500 m, 1 km, and 2 km buffers surrounding each garden. Abundance of all bees, native bees, and cavity-nesting bees (but not ground-nesting bees) was greater in native plant gardens but only richness of cavity-nesting bees differed in gardens with and without native plants. Bee community composition differed in gardens with and without native plants. Overall, bee richness and abundance were positively correlated with local characteristics of backyard gardens, such as increased floral abundance, taller vegetation, more cover by woody plants, less cover by grass, and larger vegetable gardens. Differences in the amount of forest, open space, and wetlands surrounding gardens influenced abundance of cavity- and ground-nesting bees, but at different spatial scales. Thus, presence of native plants, and local and landscape characteristics might play important roles in maintaining bee diversity within urban areas.
Pollinating insects are globally declining, with one of the main causes being the loss of flowers. With the value of countryside reducing, urban areas, particularly gardens, are increasingly recognized as of benefit to wildlife, including flower-visiting insects.Many gardeners specifically select plant varieties attractive to wildlife. Given the wide public interest, many lists of recommended varieties have been produced by both amateurs and professional organizations, but appear not to be well grounded in empirical data. These lists, however, are not without merit and are an obvious starting point. There is clearly a need to put the process onto a firmer footing based more on data and less on opinion and general experience.We collected data over two summers by counting flower-visiting insects as they foraged on 32 popular summer-flowering garden plant varieties in a specially planted experimental garden, with two smaller additional gardens set up in year two to check the generality of the results. With many thousands of plant varieties available to gardeners in the United Kingdom, and other countries or regions, it would have been an impossible task to make a comprehensive survey resulting in a complete and authoritative list.Our results are valuable and encouraging. Garden flowers attractive to the human eye vary enormously, approximately 100-fold, in their attractiveness to insects. Insects, especially bees and hover flies, can be attracted in large numbers with clear differences in the distribution of types attracted by different varieties.Our results clearly show that there is a great scope for making gardens and parks more bee- and insect-friendly by plant selection. Horticulturally modified plant varieties created by plant breeding, including hybrids, are not necessarily less attractive to insects and in some cases are more attractive than their wild-type counterparts. Importantly, all the plants we compared were considered highly attractive to humans, given that they are widely sold as ornamental garden plants.Helping insect pollinators in gardens does not involve extra cost or gardening effort, or loss of aesthetic attractiveness. Furthermore, the methods of quantifying insect-friendliness of plant varieties trialled in this study are relatively simple and can form the basis of further research, including ‘citizen science’.
Citizen science can provide a valuable tool for collecting large quantities of ecological data over a larger geographic area than would otherwise be possible. Here, data were collected on 1,022 bumblebee nests by means of a public survey in which participants were asked to record attributes of bumblebee nests discovered in their gardens. All commonly reported species appeared to be generalist in their nest site selection and though species-specific differences in nest site choice were evident, there was a high degree of overlap in nesting habitat between most species. There was little evidence supporting the hypothesis that bumblebees tend to nest in the same site in consecutive years. A comparison of the contributions made by different species to the total nests reported in this and previous similar surveys suggests that the common bumblebee species Bombus pascuorum may have declined over the past 20 years relative to other species, comprising ~21% of colonies discovered in a survey conducted in 1989–1991, but just 8–9% of colonies in 2007–2009. This was accompanied by a reduction in the proportion of nests on the ground surface (the preferred position of this species). This is the first quantitative evidence of potential declines in the one of the UK’s ‘big six’ common bumblebee species.
As part of a larger survey of biodiversity in gardens in Sheffield, UK, we examined the composition and diversity of the flora in two 1-m 2 quadrats in each of 60 gardens, and compared this with floristic data from semi-natural habitats in central England and derelict urban land in Birmingham, UK. Garden quadrats contained more than twice as many taxa as those from any other habitat type. Ca. 33 % of garden plants were natives and 67 % aliens, mainly from Europe and Asia. A higher proportion of garden aliens originated from Asia and New Zealand than in the UK alien flora as a whole; 18 of the 20 most frequent plants in garden quadrats were natives, mostly common weeds. Garden quadrats showed no evidence of 'nestedness', i.e. a tendency for scarce species to be confined to the highest diversity quadrats. Conversely, species in all semi-natural and derelict land data sets were significantly nested. Compared to a range of semi-natural habitats, species richness of garden quadrats was intermediate, and strikingly similar to the richness of derelict land quadrats. Although species accumulation curves for all other habitats showed signs of saturation at 120 quadrats, gardens did not. Correlations between Sørensen similarity index and physical distance were insignificant for all habitat types, i.e. there was little evidence that physical distance played any part in structuring the composition of the quadrats in any of the data sets. However, garden quadrats were much less similar to each other than quadrats from semi-natural habitats or derelict land.
I investigated how habitat area, habitat connectivity, and landscape context affect the species richness and abundance of trap-nesting bees, wasps, and their natural enemies. The research was done on 45 orchard meadows ranging in size from 0.08 to 5.8 ha and differing in habitat connectivity and the surrounding landscape matrix. Effects of the surrounding landscape matrix were restricted to circles with a radius of 250 m. Only the species richness of natural enemies increased with landscape diversity in the surrounding matrix. Population densities of bees increased with habitat connectivity. Total species richness and species richness of bees, eumenid wasps, and natural enemies significantly increased with habitat area. Significant species-area relationships existed for insect groups but not for plants, thereby confirming the hypothesis that higher trophic levels are more affected by habitat fragmentation than lower trophic levels. The slope of species-area relationships was steeper for mutualistic bees than for predatory wasps and natural enemies. In contrast to expectations, the rate of parasitism did not depend on habitat area but only on the local and regional abundance of hosts. My results suggest that the area and connectivity of habitat fragments is most important for the conservation of habitat specialists, whereas generalists may profit from a diverse surrounding landscape matrix.