POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
2.4.2.4 Solitary bee management
2.4.3 Conclusions
Solitary bees have been used for agricultural crop pollination
for almost a century. The longest-managed and described
species are undoubtedly the alfalfa leafcutter bee (Megachile
rotundata) (Pitts-Singer and Cane, 2011; Ruz, 2002),
introduced to North and South America and Australia, the
alkali bee (Nomia melanderi) (Cane, 2008), the blue orchard
bee (Osmia lignaria) (Bosch and Kemp 2001), both used
in North America, the hornfaced bee (O. cornifrons) in
Japan (Maeta, 1990), the horned bee (Osmia cornuta) and
the red mason bee (Osmia bicornis) in Europe. All these
species require relatively simple handling including the use of
standardized nesting boxes for their nesting aggregates and
simple cocoon collection and cleaning procedures for further
breeding (Bosch and Kemp 2002; Sedivy and Dorn, 2013).
In return, they significantly increase crop yield and often
provide better crop quality compared to crops pollinated
mostly by honey bees (for details see Table 2.4.2.). Due
to their effectiveness as crop pollinators and their simple
handling, solitary bees are often introduced to new locations
as managed pollinators. They are mostly used in open field
pollination, but they also do well in greenhouse conditions
(Bosch and Kemp, 2000; Wilkaniec and Radajewska,
1997). Recently, solitary bees have also been supported
by introducing of artificial nesting sites, so-called “bee
hotels”, to promote not only wild bee conservation but
also pollination of both crops and wild plants on a small
scale (Gaston et al., 2005). However, the effectiveness of
these artificial nesting sites was questioned by MacIvor and
Packer (2015), who showed that bee hotels might promote
introduced species more than native ones, and also may act
as population sinks for bees through facilitating the increase
of parasites and predators.
Managed solitary bees, in contrast to honey bees and
bumble bees, are less studied concerning the risk they
pose to their environment (for details see Table 2.4.2).
Managed solitary bees, which are transported or just simply
introduced into new localities (Bartomeus et al., 2013),
can impact native pollinator species and the pollination
they provide. However, the only well-documented case of
invasiveness of an introduced pollinator is the giant resin
bee (M. sculpturalis), a legume pollinator from Central Asia.
Giant resin bees were accidentally introduced to the USA,
where they started to outcompete the native carpenter
bee (Xylocopa virginica) at its nesting sites (Laport and
Minckley, 2012). Disease spread by managed solitary bees
requires further studies, especially studies on procedures
for controlling pathogens and internal parasites, and the
impact of management on native bees. Lack of appropriate
disease control, together with large aggregation sizes,
may facilitate disease spread and therefore impact native
pollinators and their pollination. (For further details see
section 2.4.1.4).
Bee management is a global and complex driver of pollinator
loss. Spreading of diseases by managed honey bees and
bumble bees into wild bee species has been shown to
present a threat to some wild species and populations.
Preservation of some of the economically important (for their
pollination in crop production) bee species that otherwise
could decline is also important from a conservation point
of view. In some cases, like honey bees or bumble bees,
both pros and cons of their large-scale management for
pollination are well known. These managed bees provide
convenient pollination, because they can be moved in large
numbers to large-scale pollinator-dependent monoculture
plantings that have high pollination requirements at specific
time points. However, these managed bees can also
transmit diseases to local populations of wild pollinators,
further diminishing naturally-occurring pollination, which
already tend to be low in large, monoculture croplands
that supply few natural nesting habitats or floral resources
across time for wild bees (see section 2.2.2). The logical
conclusion is to create pollinator-friendly habitats to promote
pollinator abundance and diversity instead of migratory bee
management, when possible. However, if pollinator-friendly
habitats cannot be created, it is advisable to manage
native or in some cases naturalized populations rather
than non-native bee species, because the greatest risk
by bee management occurs when species are moved out
of their native range. In case of solitary and stingless bee
management the picture is less clear because empirical
studies on the impact they have on their environment are
still scarce. Yet, to foresee and avoid possible pitfalls of
managing solitary and stingless bees it is important to keep
in mind the negative impacts observed from honey and
bumble bee management thus far.
2.5 INVASIVE ALIEN
SPECIES
2.5.1 Introduction
Especially since the 1950s, the growth in global economic
wealth, trade and commerce and transport efficiency
has facilitated the ongoing worldwide human-mediated
dispersal of organisms into novel environments (Hulme,
2009; Mack et al., 2000). This represents a key component
of global environmental change as once introduced
beyond their natural range, and given evolutionary and
ecological constraints or opportunities, these alien plant
and animal species can become invasive, altering the
biological and physical nature and processes of the recipient
ecosystem (Jones and Gomulkiewicz, 2012; Mack et
al., 2000). ‘Alien species’ are defined as a (non-native,
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2. DRIVERS OF CHANGE OF POLLINATORS,
POLLINATION NETWORKS AND POLLINATION