POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
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2. DRIVERS OF CHANGE OF POLLINATORS,
POLLINATION NETWORKS AND POLLINATION
and Stout, 2014). In contrast, plants in the adjacent areas
that flower two to three weeks after blooming of canola,
may benefit from enhanced local bee abundances (Kovács-
Hostyánszki et al., 2011; see also spill-over in section 2.2.1).
Pollinators often have to move back to the wild flower land
cover elements at the end of crop flowering, becausethese
elements provide the only – and in general more permanent
– foraging resources (Kovács-Hostyánszki et al., 2013). At
this time pollination of native plant species in the nearby wild
flower patches can also profit from the spill-over of diverse
and abundant pollinator communities, supplemented with
efficient pollen and nectar gain in the adjacent crop fields
(Kovács-Hostyánszki et al., 2013; see also section 2.2.1)
(Figure 2.2.3). Thus, spatial and temporal changes in
landscape composition can cause transient concentration
or dilution of pollinator populations with functional
consequences (Tscharntke et. al., 2012).
2.2.2.1.9 Orchards
Some of the economically most important fruit trees such
as apples, almond, cherries (cross pollination essential) and
pears (partly or entirely self-sterile) require insect pollination
(Abrol, 2012), which affects both the quantity and quality of
production, influencing size, shape, taste and seed number
(Garratt et al., 2014). Pollination in orchards is usually
supported by honey bees, while wild pollinators play also
important role in fruit tree pollination (Brittain et al., 2013;
Javorek et al., 2002; Vicens and Bosch, 2000). Pollinating
efficiency of wild bees is often higher compared to honey
bees (e.g. Osmia spp. in apple orchards, Vicens and
Bosch, 2000). Unfortunately, there are already examples
of the drastic consequences of decreased numbers of
pollinators in orchard pollination. In Maoxian County of
south-western China farmers apply hand-pollination by
‘‘human pollinators’’ to pollinate apple and other fruit crops
to secure yields due to the loss of both wild pollinators and
honey bees because of intensive management practices,
e.g., intensive pesticide use (Partap and Ya, 2012). After
pollinating 100% of apple in the County in 2001, recently,
farmers tried to replace apples with plums, walnuts,
loquats, and vegetables that do not require pollination by
humans. However, hand pollination by human pollinators is
still practiced with apples to a lesser degree. The number
of bee colonies leased to pollinate the crops is still low,
because the communication campaigns about the benefits
of bee pollination for higher yield and better quality of
Chinese crops are still yet to be done with a focus on major
provinces, to improve awareness.
The within-orchard management has strong impact on
the pollinator assemblages through both chemical and
mechanical practices. The control of vegetation in the
undergrowth by herbicides and/or mechanical means
eliminated native flowers. However, undergrowth flowers
are highly beneficial for insect pollinators through diversity
of food resources that is important for flower visitor health
(Alaux et al., 2010a), stability of pollinator assemblages
(Ebeling et al., 2008), and they can even mitigate negative
effects of land management and/or isolation from natural
land cover types (Carvalheiro et al., 2011, 2012). Formerly
it was recommended to remove the ground vegetation to
avoid potential competition with fruit trees for pollinators
(Somerville, 1999), however other studies emphasised the
strong positive effects of additional flower resources on
bee abundances, for example within cherry and almond
orchards (Holzschuh et al., 2012; Saunders et al., 2013).
The heterogeneity of surrounding landscape around the
orchards has great influence on pollinator assemblages
and pollination efficiency of fruit trees within the orchards
(Schüepp et al., 2014). The distance at which beneficial
foraging and nesting resources out of the orchards may
have a positive effect on the within-orchard assemblages
depends on the flight and foraging distances of the
pollinators. In the case of solitary bees maximum foraging
range is between 150 and 600 m (Gathmann and
Tscharntke, 2002), while Holzschuh et al. (2012) found
increased wild bee visitation of cherry with the proportion of
high-diversity bee habitats in the surrounding landscape in
1 km radius. Fruit set of almond was higher with increasing
percentage of natural land cover types surrounding the
orchards (Klein et al., 2012). In intensive orchard regions,
however, orchard-dominated landscapes can drastically
reduce wild bee species richness and abundance in the
orchard compared to landscapes dominated by either
grassland or forest (Marini et al., 2012).
2.2.2.1.10 Greenhouses
Greenhouse production increased worldwide over the
past three decades (Pardossi et al., 2004). In China alone
there are 2.7 million ha, in South Korea 57 thousand ha
of greenhouses (University of Arizona Board of Regents
2012), and there are large areas of greenhouses also in the
Mediterranean region, such as Spain, Turkey, Italy, Southern
France, Israel and Greece (Jouet, 2001). Production of some
greenhouse crops (e.g. tomatoes, melons, strawberries and
beans) depends on insect pollination. Greenhouses can be
closed systems with only introduced managed pollinators,
or semi-open, which allows wild pollinators and managed
pollinators from outside to enter. Bees and flies are among
the most important pollinators, and honey bees and bumble
bees are also commercially used for greenhouse pollination
(James and Pitts-Singer, 2008). In the tropics stingless bees
are used effectively for greenhouse crop pollination (see
details in section 2.4.2.3). Moving of pollinator species and
introduction for example of non-native bumble bee species
into other continents for greenhouse crop pollination,
however, caused severe problems, e.g. pathogen transfer
between managed and wild bees (see section 2.4). More
details on the importance of bumble bees in greenhouse