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Influence of the reduction of urban lawn mowing on wild bee diversity (Hymenoptera, Apoidea)

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  • Dr. Unterweger Biodiversitätsplanung

Abstract and Figures

To analyse the effects of reduced green space management in urban areas on the biodiversity of insects, we compared intensely mowed lawns (mowed 12 times per year) with meadows under reduced maintenance (mowed only twice per year) in the city of Tübingen (Baden-Württemberg, Germany). Over the entire field season, 177 wild bee individuals representing 43 species were caught using sweep nets. Areas with reduced maintenance showed significantly higher total species numbers and biodiversity indices. Our research supports the initiative "Bunte Wiese (Colourful Meadow) - Species Diversity in Public Greenspaces" of the University of Tübingen, which is campaigning for the enhancement of species diversity in public urban Greenland areas by reorganising intensive mowing into a "twice a year" programme.
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Inuence of the reduction of urban lawn mowing on wild bee diversity... 51
Influence of the reduction of urban lawn mowing on
wild bee diversity (Hymenoptera, Apoidea)
Laura Wastian1, Philipp Andreas Unterweger1, Oliver Betz1
1 Eberhard-Karls-Universität Tübingen. Institute of Evolution and Ecology. Evolutionary Biology of Inverte-
brates. Auf der Morgenstelle 28. D-72076 Tübingen, Germany
Corresponding author: Philipp Andreas Unterweger (philipp.unterweger@uni-tuebingen.de)
Academic editor: Jack Ne |Received 26 January 2016 | Accepted 31 March 2016| Published 28 April2016
http://zoobank.org/C55E0AB0-99A7-4272-B064-F8E7DA02A0D2
Citation: Wastian L, Unterweger PA, Betz O (2016) Inuence of the reduction of urban lawn mowing on wild bee
diversity (Hymenoptera, Apoidea). Journal of Hymenoptera Research 49: 51–63. doi: 10.3897/JHR.49.7929
Abstract
To analyse the eects of reduced green space management in urban areas on the biodiversity of insects, we
compared intensely mowed lawns (mowed 12 times per year) with meadows under reduced maintenance
(mowed only twice per year) in the city of Tübingen (Baden-Württemberg, Germany). Over the entire
eld season, 177 wild bee individuals representing 43 species were caught using sweep nets. Areas with
reduced maintenance showed signicantly higher total species numbers and biodiversity indices. Our
research supports the initiative “Bunte Wiese (Colourful Meadow) - Species Diversity in Public Greens-
paces” of the University of Tübingen, which is campaigning for the enhancement of species diversity in
public urban greenland areas by reorganising intensive mowing into a “twice a year” programme.
Keywords
Colourful meadow, conservation, grassland, meadow, mowing, urban ecology, urban green space, wild bees
Introduction
Urbanisation is one of the major environmentally relevant phenomena of our time.
e expansion of urban areas is rapidly increasing. In western Germany, the areas
settled by humans has increased by about 140% in the past fty years (Kompakt
2011, Russel 2005). 13.6% of the area of Germany is covered by settlements and
JHR 49: 51–63 (2016)
doi: 10.3897/JHR.49.7929
http://jhr.pensoft.net
Copyright Laura Wastian et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC
BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
RESEARCH ARTICLE
Laura Wastian et al. / Journal of Hymenoptera Research 49: 51–63 (2016)
52
infrastructure (Bundesamt 2016). Fragmentation and destruction of natural areas
occurs as a result of these developments (BMU 2008). Even in the countryside,
intense agricultural use leads to monocultures and the loss of biological diversity
(Landschaften 2006). Green spaces usually have a wide range of owering aspects
and oer a large number of niches for animals (Briemle and Fink 1993). e loss
of natural grassland endangers these functions (García 1992). e intensication of
grasslands (fertilization, high mowing intensity, ploughing) has a negative inuence
on the diversity of owering plants and the animals depending on these resources
(Haufe et al. 2015, Schuch et al. 2012).
Urban areas can oer classic nature, providing a wide range of dierent small
habitats with positive impacts on, for instance, ower-visiting insects (Matteson et
al. 2013). is explains the current focus of conservationists on these easily intro-
duced replacement biotopes (Bischo 1996). According to Westrich (1989), half of
the German wild bee species can be found in urban areas. For example, 258 bee species
have been recorded in Stuttgart (Schwenninger 1999). Although urban natural spaces
cannot provide the same functions, continuity, and habitat qualities as natural areas
(Müller 2005), the protection of urban nature must form an important part of all bio-
diversity projects (Müller 2005).
We have investigated the inuence of maintenance reduction on public grasslands
in the city of Tübingen (Germany, Baden-Württemberg) on the occurrence of ower-
visiting wild bees. We assume that the simple reduction of the lawn mowing frequency
compared with an intense monthly mowing regime in cities can make an important
contribution to the international eorts to reduce the loss of biodiversity (Ade et al.
2012, Hiller and Betz 2014, Kricke et al. 2014, Unterweger et al. 2012, Unterweger
and Betz 2014).
If mowing events occur too frequently and at inappropriate times, they can cause
signicant harm on the biodiversity of both plants and insects (Landschaften 2006).
In particular wild bees (Hymenoptera, Apoidea) are highly sensitive to mowing
(Buri et al. 2014, Schweitzer et al. 2012). e fast and highly engineered mowing
of a owering meadow at a warm day can kill about 50% of an entire insect popula-
tion (Hemmann et al. 1987, Oppermann and Claßen 1998) and, for example, kill
up to 90,000 honeybees per hectare (Fluri et al. 2000). is is possible as highly
engineered mowing entails huge machines, high mowing speeds mowing and a high
ground coverage per hour.so the whole foraging ground of a bee population can be
cut within a few hours. Mowing aects the life on a meadow by (1) the mowing
process itself, (2) the preparation for loading (swathing) and (3) the loading process
(Di Giulio et al. 2001). Moreover, (4) the change of the microclimate including
humidity (Albrecht et al. 2010) after mowing also contributes to the loss of faunistic
biomass on meadows.
Unimproved ower-rich grassland is one of the most important habitats for bum-
ble bees. However, in western Europe, it has been largely lost to agriculture (Goulson
et al. 2008). Its restoration can boost bumble bee populations (Carvell 2002, Carvell
et al. 2007). In addition, the loss of food sources leads to a decline of wild bees as they
Inuence of the reduction of urban lawn mowing on wild bee diversity... 53
are no longer able to feed their ospring eciently (Buri et al. 2014). Albrecht et al.
(2010) have shown the positive eect on wild bees resulting from ecological improve-
ments in meadows (transformation into two times/year mown hay meadows) that
support species richness and ecological functions. Even in private gardens, more nature
and less care provide more biodiversity by oering nesting sites for bees (Lindemann-
Matthies and Marty 2013).
In 2010, both students and employees of the University of Tübingen founded
a pressure group to support national and international aims to protect biodiversity
(Unterweger et al. 2012). is group called “Initiative Bunte Wiese” (“e colourful
meadow initiative”) has been instrumental in persuading decision makers to improve
the maintenance of inner urban green areas with respect to conservation issues. is
improvement involves (1) the reduction of mowing events towards only twice a year,
(2) the use of bar mowers and (3) the removal of the mown grass from the surface
(Unterweger et al. 2013, Unterweger and Braun 2015). e results of this manage-
ment reduction have been evaluated in several research projects. We have investigated
grasshoppers (Hiller and Betz 2014), true bugs (Unterweger 2013), beetles (Ade et
al. 2012) and butteries (Kricke et al. 2014). All these investigations have revealed a
signicant positive impact of reduced grassland maintenance towards species diversity
and the occurrence of rare or endangered species.
In the present work, we investigate the inuence of a reduced mowing regime on
the diversity of ower-visiting wild bees in urban green spaces. We hypothesize that (1)
endangered species are strongly linked to areas with reduced maintenance and (2) the
number of both species and individuals is signicantly higher in these areas.
Methods
Presentation of sampling areas
e locations of the ve sampling areas in the city of Tübingen (Baden-Württemberg,
Germany) are shown in Figure 1. ese sampling sites were carefully selected and rep-
resent typical urban green spaces. We think that eects caused by mowing and found
on these areas are representative for other areas. Each sampling site was divided into
two equal study sites (200–500m2), i.e. one was treated as a lawn (mowed 12 times
per year, a common maintenance practice performed by many public garden depart-
ments), whereas the other was mowed twice a year (rst cut at the end of May, second
cut at the end of September).
Climate
e climatic conditions in 2010 did not signicantly dier from those of the past six
years. e average annual temperature was about 8.7 °C. In July, the average tempera-
Laura Wastian et al. / Journal of Hymenoptera Research 49: 51–63 (2016)
54
Figure 1. Map of the sampling sites in the urban area of Tübingen. A = Europastraße, B = Sand Süd,
C= Sand Courtyard, D = university institute of political science, E = Julius-Wurster-Straße and X the city
centre. Each area was divided into an intensely mowed lawn and an area with reduced maintenance (two
cuts per year). Provided by OpenStreetMap contributors.
0500 1000 1500 m
N
ture was 19.9 °C. Rainfall was rare at the beginning of the year. However, this changed
in May (99 mm m-2). In June and July, the weather conditions were wetter than usual
but returned to normal in September.
Sampling methods
We followed the sampling methods of Schwenninger (1992). Sweep nets were used to
catch the individuals from the owering plants and the whole area. Collecting time
per study site amounted to one hour per date, and management type (honeybees were
Inuence of the reduction of urban lawn mowing on wild bee diversity... 55
not collected as the parent species of the domesticated honeybee is extinct in Europe
(Amiet and Krebs 2012).) e sampling period was between April and September
2010 with collections performed on a monthly basis. e sampling dates corresponded
to warm and sunny weather.
Preparation and determination
Bees that could not be determined to species in the eld were killed with ethyl ac-
etate and carefully prepared. Genitalia were prepared if necessary. Determinations were
performed according to the ve volumes of Amiet (1996) and the three volumes of
Scheuchl and Schmid-Egger (1997) and the aid of the Stuttgart State Museum of Na-
tural History. e systematic classication follows Michener (2007). For species names
we followed Schwarz (1996), Gusenleitner and Schwarz (2002), Westrich et al. (2008,
2012), Westrich et al. (2000).
Statistical tests
To compare the two types of maintenance, we also used the Shannon Index and Even-
ness to evaluate the number of species and individuals (Mühlenberg 1993).
We performed Wilcoxon-tests to check the dierences between the intensely
mowed lawns and the areas with reduced maintenance. All statistical analyses were
performed with SPSS (SPSS 22, IBM).
Results
Species data
Over the entire sampling time, on the ve pairs of sampling sites, 177 wild bee indi-
viduals representing 43 species (Table 1) were found. e sampling sites (Fig. 1) were
equally distributed over the urban area of Tübingen. reatened or declining species
from both Germany (GER) and the state of Baden-Württemberg (BW) were only found
on areas with reduced maintenance. In Table 1, they are shown with the IUCN (Inter-
national Union for Conservation of Nature) and the BfN (German Federal Agency for
Nature Conservation) standards. e number of individuals per species on the study
sites varied from 1 to 21.
Plant data
e average number of dicotyledon species was to 13,6 species on the intensely mowed
plots and to 15,8 species on the extensively mowed sites.
Laura Wastian et al. / Journal of Hymenoptera Research 49: 51–63 (2016)
56
Table 1. List of bee species recorded from the ve pairs of study plots. e red list categories correspond to the classications of IUCN (3 = =vulnerable, V =near
threatened). e numbers of captured individuals is also given (A = intense mowing, B = reduced management). e months of capture are marked in Roman nu-
merals (I=January, II=February etc.). e dominance Di and the sampling sites are presented in the last two columns. e sampling sites are named as in Figure 1.
e mowing intensity is coded by numbers, i.e. 1 = intensely mowed lawn, 2 = reduced (twice a year) maintenance. Endangered species were only found on areas
with reduced maintenance. e total number of caught species per month was IV = 15, V = 28, VI = 15, VII = 13, VIII = 20, IX = 11. e structure of dominance
classies species from 10–31.9% as dominant, 3.2–9.9% as subdominant, 1.0–3.1% as recendent and 0.32–0.99% as subrecendent (Igić 1999; Mühlenberg 1993).
Scientic name Red List GER Red List BW No. of ind. A No. of ind. B month Di Sampling sites
Andrena cineraria (Linnaeus, 1758) 3 4 IV,V 3.95 B1,B2,D1,D2,E1
Andrena gravida (Imho, 1832) 5 1 IV,V 3.39 B1,E1,D1,D2
Andrena haemorrhoa (Fabricius, 1781) 0 1 IV,V 0.56 E2
Andrena labiata (Fabricius, 1781) 2 1 V 1.69 B1,C1,C2
Andrena minutula (Kirby, 1802) 0 1 V,VI 0.56 B2
Andrena minutuloides (Perkins, 1914) 0 5 VI,VII,VIII 2.82 A2,B2
Andrena nitida (Müller, 1776) 2 0 IV,V 1.13 C1,D1
Andrena ovatula (Kirby, 1802) 1 0 V 0.56 E1
Andrena strohmella (Stoeckhert, 1928) 0 1 IV 0.56 D2
Andrena subopaca (Nylander, 1848) 2 0 IV,V,VI 1.13 A1,B1
Andrena ventralis (Imho, 1832) 2 0 IV 1.13 A1
Anthophora plumipes (Pallas, 1772) 1 2 IV,V 1.69 A1,C2,D2
Bombus hortorum (Linnaeus, 1761) 0 1 V-IX 0.56 D2
Bombus humilis (Illiger, 1806) vu, 3 vu, V 0 2 VI,VII,VIII 1.13 A2,B2
Bombus hypnorum (Linnaeus, 1758) 0 3 V,VIII 1.13 E2,D2
Bombus lapidarius (Linnaeus, 1758) 2 3 V-VIII 2.82 B2,C2,D1,D2
Bombus lucorum s.l. (Linnaeus 1761) 1 0 VIII 0.56 D1
Bombus pascuorum (Scopoli, 1763) 6 15 V-IX 11.86 B2,A1,A2,C2,D1,D2
Bombus pratorum (Linnaeus, 1761) 1 2 V 1.69 C1,C2,D2
Bombus sylvarum (Linnaeus, 1761) vu, V vu, V 0 2 VIII,IX 1.13 B2,A2
Bombus terrestris s.l. (Linnaeus, 1758) 0 5 V-VIII 2.82 B2,A2,C2
Chelostoma orisomne (Linnaeus, 1758) 6 8 V,VI 7.91 B1,B2,C1,C2,D2
Inuence of the reduction of urban lawn mowing on wild bee diversity... 57
Scientic name Red List GER Red List BW No. of ind. A No. of ind. B month Di Sampling sites
Colletes similis (Schenck, 1853) vu, V 0 1 V 0.56 B2
Eucera nigrescens (Pérez, 1879) 0 2 V 1.13 E1
Halictus simplex (Blüthgen, 1923) 0 2 V,VI,IX 1.13 B2,A2
Halictus tumulorum (Linnaeus, 1758) 9 6 V-IX 5.65 B1,B2,D1,D2,E1,E2
Halticus scabiosae (Rossi, 1790) vu, V 0 3 V 0.56 B2
Heriades truncorum (Linnaeus, 1758) 0 2 VI 1.13 D2
Hoplitis leucomelana (Kirby, 1802) 0 2 VI 1.13 D2
Hylaeus communis (Nylander, 1852) 0 3 VIII 1.69 B2,A2,D2
Hylaeus gredleri (Förster, 1871) 0 1 VII-IX 1.13 A2
Hylaeus punctatus (Brullé, 1832) 0 2 VIII 1.13 A2,B2
Lasioglossum calceatum (Scopoli, 1763) 1 1 V,VIII,IX 1.13 C1,D2
Lasioglossum glabriusculum (Morawitz, 1872) vu, V 0 2 IV, VII-IX 1.13 A2
Lasioglossum laticeps (Schenck, 1870) 2 3 IV,V,VII,VIII 2.82 B2,C1,C2
Lasioglossum leucozonium (Schrank, 1781) 2 2 V,VIII 2.26 C1,D1,D2
Lasioglossum morio (Fabricius, 1793) 4 5 IV,VII-IX 5.08 D1,D2
Lasioglossum pauxillum (Schenck, 1853) 9 14 V-IX 7.91 B2,A2,E1,C1,C2,D2,E2
Lasioglossum villosulum (Kirby, 1802) 1 0 VII-IX 1.69 B1,D1
Megachile circumcincta (Kirby, 1802) vu, V vu, V 0 1 V,VI 0.56 B2
Melecta albifrons (Forster, 1771) 1 1 IV,V 1.13 D1,D2
Osmia bicornis (Linnaeus, 1758) 6 8 IV,V 9.60 B1,B2,C1,C2,D1,D2
Osmia cornuta (Latreille, 1805) 0 1 IV 0.56 C2
Laura Wastian et al. / Journal of Hymenoptera Research 49: 51–63 (2016)
58
Comparisons between intensely and extensively mowed study plots
e comparison of intensely mowed lawns with areas with reduced maintenance show sig-
nicant dierences, both at the species and at the individual level. Figure 2 shows that the
number of species found on the intensely mowed lawns is signicantly lower compared
with the areas with reduced maintenance (RM) (paired t-test: p < 0.05, n = 5). e same
trend (paired t-test: p < 0.1, n = 5) is visible with respect to the number of individuals
(Fig. 3).
Diversity indices
e comparison of the Shannon Index revealed a signicant dierence between lawns
and areas with reduced maintenance (p < 0.05). On all sampling sites, Evenness was
between 0.81–0.95.
Discussion
Our results indicate that a reduction in mowing intensity has impacts on the wild bee
fauna at various levels. Figure 2 shows that the reduced mowing regime results in a sig-
nicant increase of wild bee species diversity. Buri et al. (2014), Goulson et al. (2008)
and others have found that the abundance and richness of wild bee species signicantly
Figure 2. Boxplots showing a comparison of the number of species from intensely mowed lawns with
that from areas of reduced maintenance . A Wilcoxon-test (N = 5) shows a signicant dierence between
the numbers of species (p = 0.042).
Inuence of the reduction of urban lawn mowing on wild bee diversity... 59
Figure 3. Boxplots showing a comparison of the number of individuals from intensely mowed lawns
with that from areas with reduced maintenance. A paired t-test (N=5) shows a distinct trend toward
signicance (p = 0.08).
Figure 4. Boxplots showing the comparison of the Shannon Index of lawns and areas with reduced
maintenance with paired t-tests shows a signicant dierence (p = 0.043). e Evenness values all lie
between 0.81–0.95.
Laura Wastian et al. / Journal of Hymenoptera Research 49: 51–63 (2016)
60
increases in meadows in which refuges were left uncut. e positive eects of undis-
turbed urban green spaces on wild bees has also been pointed out in Kutschbach-Brohl
et al. (2010). is has also been conrmed for other insect orders such as beetles (Ade et
al. 2012), grasshoppers (Hiller and Betz 2014), butteries (Kricke et al. 2014) and true-
bugs (Unterweger and Betz 2014). One reason for the observed dierences between the
intensely and extensively mowed sites can be seen in the direct eect that a single mow-
ing event can have by reducing the number of individuals of wild bees by up to 50%
(Hemmann et al. 1987, Oppermann and Claßen 1998).
Even the number of individuals of more common species can rapidly decline in
areas of high mowing intensity. As seen in Table 1, single captures of species (i.e. spe-
cies that could be detected only once during the investigation period) were made 12
times on areas with reduced maintenance and only four times on lawns over the whole
sampling time. Six endangered species were found on the research areas and exclusively
occurred on study plots with reduced maintenance. is shows the potential that a
reduction of mowing intensity in public green areas can have for the conservation and
maintenance of sub-populations of endangered wild bee species (Klaus 2013).
e number of sampled species had its maximum in May and August (IV = 15, V
= 28, VI = 15, VII = 13, VIII = 20, IX = 11), a nding that indicates that mowing be-
fore the end of May has the greatest eect on urban wild bee populations. e impor-
tance of unmown summer meadows follows from the second peak in species richness
in August. Wild bees often show a high preference for certain plant species and will
benet from the long-term reduction of maintenance (Weiner et al. 2011). It seems
that cutting once per year would support wild bees the most. Nevertheless two mow-
ing events per year has less impact than monthly mowing on the abundance and diver-
sity of entomophilous owering plants, which is important for nectar feeding insects.
Conclusion
Our results further support the conclusions drawn from studies of the initative “Bunte
Wiese Tübingen” on other insect orders such as Orthoptera, Hemiptera, Coleoptera
and Lepidoptera showing that a reduction of the maintenance of public urban green
spaces supports the diversity of insects. Such actions are relatively easy to achieve in
accord with local policy makers and form an eective way of meeting the demands of
the global aspiration to stop the loss of biodiversity. e reduction of maintenance and
the establishment of natural (infrequently, rather than intensely, mowed) green spaces
and waysides can have a signicant impact on mitigating the biodiversity crisis, even in
our highly populated and highly degraded areas (low abundance and diversity numbers
reported here indicate reduced mowing can lessen the impacts of urbanization but does
not cure them) and, at the same time, increase the awareness of ecological problems
occurring in urban human populations.
Inuence of the reduction of urban lawn mowing on wild bee diversity... 61
Acknowledgements
e English of this manuscript was corrected by Dr. eresa Jones. Hans Schwen-
ninger (Stuttgart) veried the species identications. We thank the editor and our
anonymous reviewers for their helpful comments.
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... Die häufig im Jahr gemähten Rasenflächen bieten am wenigsten Lebensraum für Pflanzen und Tiere. Hier konnten von uns sowohl weniger Pflanzen-als auch Insektenarten nachgewiesen werden als auf Wiesen (Ade et al. 2012, Hiller & Betz 2014, Kricke et al. 2014, Wastian et al. 2016, Unterweger et al. 2017, Sehrt 2017 ...
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Introduction of the initiative "Colourful meadow - How to create species-rich habitats in urban space". In 2010, both students and employees of the University of Tübingen (Baden-Württemberg, Southwest Germany) founded a pressure group to support national and international aims to protect biodiversity. This group chose the name “Initiative Bunte Wiese – Für mehr Artenvielfalt auf öffentlichem Grün” (“The Colourful Meadow Initiative – Species Diversity in Public Greenspaces”) and aimed at persuading decision makers to improve inner urban green areas with respect to greenspaces (with model areas in and around Tübingen city). The goal was to optimize the management of the grassland areas to improve their quality with respect to conservational and ecological issues. The effects of such a management reduction were evaluated in several research projects on plants, grasshoppers, true bugs, wild bees, beetles and butterflies. All of these investigations have revealed a statistically significant positive impact of reduced grassland maintenance towards species diversity as well as the occurrence of rare or endangered species. This shows that simple measures such as the reduction of grassed area maintenance can make an important contribution to international efforts to reduce the loss of biodiversity.
... The decline in pollinator abundance has been attributed, in part, to reduced pollen and nectar resource (Powney et al., 2019). No-mow has been proven to very effectively increase early season floral abundance and richness in domestic lawns, which in turn support a greater abundance and/or richness of bees (Del Toro & Ribbons, 2020;Lerman et al., 2018;Wastian et al., 2016). Floral abundance has been used as a proxy measure for pollinator resource, but the availability of U.K. wildflower nectar values has since enabled more precise quantification (e.g. ...
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Popular campaigns such as No Mow May seek to encourage early‐season forage resource for pollinators in urban green spaces. Land managers need to balance ecological benefits with extent of accessible amenity grassland. To pilot the identification of a ‘tipping point’ when the nectar resource of unmown grassland exceeds that mown, we surveyed floral abundance in 30 plots on an amenity grassland site at 11 time points between late April and July. Each species’ floral abundance per 1 m2 was multiplied by published nectar sugar values to obtain an overall nectar sugar value per plot. The nectar sugar value of no‐mow plots was overall significantly higher than for mown plots. However, week‐by‐week analysis revealed that the first significant difference did not occur until mid‐late May when no‐mow plots yielded three times the nectar sugar value of the mown plots. In early‐mid June, there was a significant eightfold divergence followed by a late June to early July decline. Common Ragwort (Senecio jacobaea) provided the greatest nectar sugar value, driving significant differences again in mid‐July. No‐mow plots contained twice as many (22 vs. 11) open flower broadleaf species compared to the mown plots. Land managers could consider extending No Mow May management into June and beyond to maximize nectar sugar resource for pollinators. To comply with S. jacobaea legislation, a management plan and financial resource should be allocated to no‐mow projects. No Mow May aims to provide early season forage resource for pollinators. To identify any phenological ‘tipping point’ when the nectar sugar value of no‐mow exceeded that of mown amenity grassland, a case study site was surveyed at weekly intervals between late April and mid‐July. Abundance of open flowers in the no‐mow and mown plots was multiplied by published nectar values, revealing that there was no significant difference until mid‐late May: the study suggests that no‐mow could continue into at least June to be of real benefit.
... Reduced mowing regimes have a positive effect on insect abundance and diversity (Wastian et al., 2016) and indeed on the abundance of parasitic wasps in vineyards (Zanettin et al., 2021). Due to high levels of disturbance, the abundance of natural enemies can be low in agroecosystems (Landis et al., 2000), and perennial grasses may provide refuge for natural enemies during such disturbances . ...
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Traditional vineyards are generally intensive monocultures with high pesticide usage. Viticulture is one of the fastest‐growing sectors of English agriculture, although there is currently limited research on habitat management practices. In a vineyard in East Sussex, England, we tested five inter‐row ground cover treatments on their potential in supporting beneficial insects: two commercially available seed mixes (meadow mix and pollen and nectar mix), a wild bee seed mix (formulated based on pollinator foraging preferences), natural regeneration, and regularly mowed grass. Over two years, from May to August, we conducted monthly floral surveys and insect surveys using transect walks and pan traps. The abundance and richness of flowers in the natural regeneration treatment were twice that of the regularly mown inter‐row treatment. By year 2, the abundance of “total insects” sampled was significantly higher in the wild bee mix compared to mown. Likewise, there was a significant effect of treatment type on pollinator richness, with a higher mean richness found in wild bee mix. Solitary wasp family richness was highest in the natural regeneration treatment and lowest in the mown treatment. Given the rapid growth and lack of specific environmental recommendations for British viticulture, we demonstrate a simple and effective approach for supporting beneficial insects and ecosystem services. Promotion of perennial wildflowers through sowing or allowing natural regeneration in inter‐row ground cover in vineyards has the potential to boost biodiversity in vineyards on a large scale if widely adopted.
... Mowing frequency can modify the taxonomic composition of the road verges communities(Auestad et al. 2011;Persson 1995) but there is no consensus on the ideal frequency of mowing(Chaudron et al. 2016). In particular, reduced frequency helps to promote pollinators such as wild bees(Wastian et al. 2016). In addition, a reduced mowing width, limited to the areas closest to the road, can ensure visibility for motorists and prevent collision with wildlife(Milton et al. 2015) while allowing plant and animal biodiversity to thrive(Valtonen, Saarinen and Jantunen 2006). ...
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A road verge, also known as a roadside, is a strip of grass or vegetation, sometimes shrubs and trees, that forms a space on the public property located along a road or highway. They require regular maintenance, one of the most relevant reasons being the safety of road users, which implies for territory planners making decisions about the period of maintenance, frequency, the mowing height, or whether or not remove cut biomass from the roadside among others. As highlighted in previous studies, the maintenance strategy decided on has a range of positive and negative impacts on the ecosystem services provided by road verges. Today, however, there is a lack of a formal and holistic view of how these maintenance practices affect the ecosystem services (ES) provided by the roadside. In order to improve the sustainability management of these areas, this paper proposes to use the concept of causal diagrams from the systems theory and literature analysis. This concept helps to structure and represent the impact of road verge maintenance decisions on ES and their interrelationships through causal networks. Nine interrelated causal diagrams were then developed. These diagrams are the first attempt at a qualitative assessment of the impact of roadside management on ES. This work is the first step towards a formal holistic model to assess the sustainability impacts of road verges and the development of decision-making tools.
... Low-intensity meadows with less frequent mowing have a higher diversity of plants, bees and butterflies (Weiner et al 2011). Reducing mowing frequency enhances insect diversity (Del Toro and Ribbons 2020;Wastian et al 2016) and in a vineyard setting has been found to benefit parasitic wasps (Zanettin et al 2021). ...
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Traditional vineyard landscapes are generally intensively managed with heavy reliance on synthetic pesticides. Viticulture is one of the fastest-growing sectors of English agriculture and information on land management is essential to secure a sustainable future. We surveyed viticulturists to ascertain vineyard pest presence, pest control, inter-row ground cover and wildflower use. The majority of viticulturists reported the presence of vineyard pests and relied heavily on pesticides, with 74% using synthetic pest control, 40% using herbicides, 40% using fungicides. Inter-row, 66% of vineyards have grass-only cover and frequent summer mowing, with only 6% sowing wildflowers. However, 60% use natural pest control, 80% reported existence of wildflowers in headlands, and 29% mentioned reduced mowing. We discuss spontaneous and sown wildflowers and benefits for biodiversity, integrated pest management and the commonly perceived barriers to adaptation. We conclude there is huge variation in management styles and more evidence-based environmental advice for viticulturists is needed.
... Each country has different native species of flowers that attract bees, and their cultivation in gardens and parks should be promoted for bee conservation. In this context, programs that increase the bee-friendly residential gardens are important, as well as the reduction of lawn mowing (Wastian et al. 2016;Baldock et al. 2019). Taken together, these actions help prevent local and regional extinctions. ...
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Context Urbanization is one of the largest causes of habitat loss and fragmentation, factors that modify community structure and can lead to species extinction. Since bees are the main pollinating agents in most ecosystems, losses of bee diversity can have negative consequences on plant diversity and associated services. Objectives This study aims to understand how bees and their functional traits, such as social behavior, nesting sites, trophic specialization and kleptoparasitism, are affected by an urban landscape. Methods Ten sites were selected with different levels of urbanization. Bees were sampled with entomological net for 6 h, one day per month, for 10 months. The response variables evaluated were species diversity, number of bees, and the richness of bee functional traits. Nine landscape metrics were used as predictors, including the proportion of vegetation cover and landscape diversity. Results Urbanization predictors negatively influenced bee richness but not diversity. Specialist bees were the most susceptible to urbanization, followed by ground nesters and solitary bees. Kleptoparasites also responded negatively to different urbanization metrics. Above-ground nesters and eusocial bees were more resilient to the urban environment and were not affected by urbanization. The proportion of vegetation cover and landscape diversity were the most important predictors for the preservation of bee diversity, followed by the proximity of fragments and the proportion of grasslands. Conclusions The most responsive and vulnerable functional groups—particularly specialists—should have conservation priority in cities. Analyses of richness and species diversity should not be decoupled from functional traits since doing so may overlook bees’ complex response to urbanization.
... All these circumstances made Belgrade almost the perfect environment for the establishment and persistence of a large free-living honey bee population. There are also less specific favourable aspects, common to many large urban areas [91], but they certainly contributed to the overall good conditions for wild bees: variable and long-lasting floral resources, and decreased exposure to pesticides (relative to dominating agricultural systems, etc.). ...
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It is assumed that wild honey bees have become largely extinct across Europe since the 1980s, following the introduction of exotic ectoparasitic mite (Varroa) and the associated spillover of various pathogens. However, several recent studies reported on unmanaged colonies that survived the Varroa mite infestation. Herewith, we present another case of unmanaged, free-living population of honey bees in SE Europe, a rare case of feral bees inhabiting a large and highly populated urban area: Belgrade, the capital of Serbia. We compiled a massive data-set derived from opportunistic citizen science (>1300 records) during the 2011–2017 period and investigated whether these honey bee colonies and the high incidence of swarms could be a result of a stable, self-sustaining feral population (i.e., not of regular inflow of swarms escaping from local managed apiaries), and discussed various explanations for its existence. We also present the possibilities and challenges associated with the detection and effective monitoring of feral/wild honey bees in urban settings, and the role of citizen science in such endeavors. Our results will underpin ongoing initiatives to better understand and support naturally selected resistance mechanisms against the Varroa mite, which should contribute to alleviating current threats and risks to global apiculture and food production security.
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1. This study highlights the potential of urban dry grasslands for diverse pollinator communities of wild bees and hoverflies, including rare and endangered species. 2. By using pan trap sampling on 49 study sites distributed across the urban environment , responses of wild bee and hoverfly communities to urban features at two spatial scales (urban matrix and local habitat) were examined. 3. A total of 1246 hoverfly individuals (Syrphidae) from 31 species and 1463 bee individuals (Apoidea) from 107 species were collected. Our analysis showed that hover-flies are impacted by urban matrix features and local floral resources, whereas wild bees only respond to patch size at the local habitat scale and endangered wild bee species additionally to non-native pollinator-friendly plants. 4. Given the different responses of wild bees and hoverflies to the urban environment, we recommend multi-taxon approaches for urban conservation practice. Urban dry grasslands and the diversity of pollinator-friendly plants, including non-native species , should be conserved and promoted to support urban pollinator diversity.
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Loss of natural habitat through land‐use change threatens bees. Urbanisation is a major, increasing form, of habitat loss, and a novel, pervasive form of disturbance known to impact bee diversity and abundance in a variety of often inconsistent ways. We conducted a comprehensive, semi‐quantitative review, involving 215 studies, on responses of bees to urban landscapes, and local and landscape variables proposed to influence bee abundance and diversity. Urban areas tend to be favourable habitat for bees compared with agricultural ones, but compared with natural areas, urban areas often host more abundant populations yet fewer species. Factors associated with urban landscapes, including changes in foraging resources and nesting substrate types and availability, contribute to changes in abundance, species richness, and composition of native bee assemblages. However, the conclusions of studies vary greatly because of the difference in the ecological traits of bees, habitats surveyed, and geographic region, as well as noise in the data resulting from inconsistencies in sampling methodology, and definitions of ‘urban’ and ‘natural’. Identifying what biotic and abiotic features of cityscapes promote or threaten the persistence of urban bee diversity is critical. We provide a comprehensive evaluation of how bees (both in aggregate and according to their ecological guild) have responded to the urban environment, identify gaps in knowledge in urban bee ecology, and make recommendations to advance our understanding of bees in urban environments to promote conservation of diverse bee communities. Reviewing 215 studies, factors associated with urban landscapes, including changes in foraging and nesting resources, contribute to changes in abundance, species richness, and composition of native bee assemblages. Urban areas tend to be favourable habitat for bees compared with agricultural ones, but compared with natural areas, urban areas often host more abundant populations yet fewer species. Seven key knowledge gaps are identified, and recommendations on how to advance urban bee conservation.
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Native bees are declining in many regions, often associated with loss of natural habitat. Urbanisation replaces natural vegetation with a highly-modified landscape, where residential gardens are a major component of urban greenspace. While many cities retain native vegetation remnants within the urban matrix, these are often small, isolated and degraded. However, there is little empirical evidence on the capacity of residential gardens to provide equivalent or beneficial habitat for native bees, and which local and landscape factors influence bee assemblages. We surveyed bee assemblages in the southwest Australian biodiversity hotspot at seven residential gardens and seven bushland remnants over two years. We recorded 153 species/morphospecies of native bees. Native bees were more abundant in bushland remnants than residential gardens. Abundance of the introduced honeybee Apis mellifera was generally high, and did not differ between habitats. Bushland remnants hosted more species, and rare and unique species, than did residential gardens. Native bee body-size and nesting guilds varied in their response to habitat type. Native bee abundance and richness increased with abundance of native plant species, but decreased with total flower species richness. Native bee species richness was negatively impacted by urbanisation (built space and isolation from bushland reserves). There were no significant relationships between honeybee abundance and local and landscape factors. Our study demonstrates that while residential gardens can host native bees, urban bushland remnants harbour a more comprehensive suite of species and are key for the conservation of native bee populations.
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The relationship between resource availability and biodiversity of consumers has gained particular attention with the increasing loss of species in recent decades. In this study we evaluate resource availability of extensively (low/unfertilised, mown once per year) and intensively used meadows (higher fertilisation, mown 2-4 times) before and after the first mowing in relation to network specialisation, species richness and composition of flower visitors. In 2007, we studied 40 meadows, simultaneously sampling one extensively and one intensively used meadow. All actually flowering plant species and all flower-visitors were recorded on an area of 1000 m² per plot. Species composition with regard to plants as well as to flower visitors differed between the two land use types. Extensively used meadows are significantly richer in bee, butterfly and plant species before the first mowing. They also showed higher numbers of plant-flower visitor interactions and flowering areas. In addition, higher Simpson’s Diversity of plants and butterflies was recorded as well as higher individual numbers of butterflies. Interestingly, after the first mowing all these differences except the higher species richness of flowers on extensively used meadows disappeared. We conclude that the management regime may strongly affect plant-flower visitor interactions. Differences in plant species composition may play an important role to diversity and species composition of some flower visitor groups, probably as more specialized flower visitors depend on certain plant species for survival and reproduction.
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Influence of Urban Mowing Concepts on the Diversity of Butterflies – Investigations on public green space in the city of Tübingen The University initiative ”colourful meadows – improving species diversity on public green areas“ campaigns for the enhancement of species diversity on public green space in the city of Tübingen in Baden-Württemberg. One of its major aims is the reduction of the mowing frequency. In order to investigate the effects of an adjustment of the mowing regime on species diversity the study compared the number of diurnal butterfly species on intensely managed areas in the city of Tübingen to extensively managed sites, mapping the fauna of diurnal butterflies on 10 study sites. All sites were divided into two subareas with different mowing regimes. One half of each site was mown every three weeks whilst the other half was only mown once during the duration of the study. In total, 31 species belonging to six different families were observed. The results showed an increased diversity of butterfly species on the extensively managed sites. Furthermore, a correlation was found between the number of dicotyledonous plant species and the number of diurnal butterfly species observed. These results support the initiative’s assumption that the change to an extensive mowing programme for the city’s green areas would enhance species diversity.
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Effects of Different Mowing Concepts on Locust Populations in Urban Greenspaces – Investigations in greenspace in the town of Tübingen The study investigated the effects of lawn mowing frequency on the locust population of public greenspaces in a medium- sized town. In the town of Tübingen (Baden-Württemberg) it compared the amount of species and individuals living on rarely cut grasslands against intensively mowed lawns, sampling eleven sites between May and October 2012. A total of 15 species out of four families were recorded. On the less intensively managed areas both species diversity and number of individuals were significantly higher, whereas on the short cropped grass areas only a few individuals could be found. In addition, a correlation between the biodiversity of blooming grasses and herbs and the number of locust species could be confirmed. The results recommend to extend of the practice of less intense mowing to further urban meadows in Tübingen. This research supports the initiative “Colourful Meadow – Species Diversity in Public Greenspaces” of the University Tübingen which is campaigning for the enhancement of species diversity in public greenspace in Tübingen by reorganizing the intensive mowing into a “twice a year”-programme.
Article
Selected species of Coleoptera were collected in public green spaces of Tübingen (Southwest Germany) by sweep netting and direct hand collecting. The natural communities of green spaces that were mown twice per year were compared with those of green spaces that were mown several times per year. On six sampling sites a total of 50 species of Coleoptera was recorded. The species richness of Coleoptera in public green spaces that were mown several times per year was lower than in those that were mown twice per year. The higher number of species of Coleoptera found in green spaces that were mown twice per year confirms the hypothesis that this biotope offers more developing and feeding habitats as well as hiding places than green spaces that are mown several times per year. This is also indicated by statistical comparisons of similarities which show that there is hardly any overlap of species between the two different habitats. For some species of Coleoptera there is a direct correlation between their occurrence and the frequency of mowing. Based on these results it is suggested to abstain from mowing public green spaces several times per year and to adopt a maintenance concept that will lead to a higher beetle species diversity.