POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
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1. BACKGROUND TO POLLINATORS,
POLLINATION AND FOOD PRODUCTION
et al., 2009; Potts et al., 2010; Burkle and Alarcón, 2011;
Kennedy et al., 2013). Although these individual drivers have
received some attention in relation to pollinators, studies
addressing multiple drivers are few (Tylianakis et al., 2008;
see Chapter 2.7; Schweiger et al., 2010; González-Varo et
al., 2013; Vanbergen and The Insect Pollinators Initiative,
2013; Goulson et al., 2015). Pollinator populations are
highly variable in time and space, therefore, it can be difficult
to discern clearly trends in abundance as opposed to
richness estimated from distribution records (Herrera, 1990;
Petanidou et al., 2008; Rader et al., 2013a).
High pollinator diversity increases the chances that
an effective pollinator is present and actively providing
pollination at any given time and location. A diverse array of
pollinators is therefore likely to buffer pollination against the
effects of perturbations, such as land-use (Ricketts, 2004;
Garibaldi et al., 2011b; Cariveau et al., 2013; Garibaldi et al.,
2014) and climate change (Bartomeus et al., 2013; Rader
et al., 2013b). This is because different pollinator species
respond differently to changing conditions, due to their
physiological, behavioral or other mechanisms (Petanidou
et al., 2008; Winfree and Kremen, 2009). A long-term
study of bees in the northeastern United States found that
complementarity amongst bee species’ periods of activity
enabled synchrony between bee activity and peak apple
flowering. This permitted a stable trend in pollination over
time because various bee species displayed differential
responses to climate change (Bartomeus et al., 2013). The
effects of climate change on plant-pollinator interactions
are still mostly unknown and the indirect effects upon
interacting species and networks of species are poorly
represented in the literature. However, one of the three
key recommendations of the IPCC report for agriculture,
in terms of adaptation measures to climate change, is the
maintenance of biodiversity (IPCC, 2014).
Climate change is anticipated to bring about changes in
rainfall distribution, wind patterns, temperature, air pollution
and occurrence of extreme weather events, among other
environmental changes (IPCC, 2014; Yuan et al., 2014).
These changes may affect crop pollinators via changes
in their spatial distribution, physiology and/or seasonal
phenology through spatial and temporal mismatches
between plants and their pollinators (Schweiger et al., 2008;
Hegland et al., 2009; and see Chapter 2). Land use change,
including intensification and extensification, is sometimes
associated with local or regional declines in pollinator
diversity, abundance and altered foraging behaviour
(Westphal et al., 2003; Westphal et al., 2006; Kremen
et al., 2007; Williams et al., 2012; Gonzalez-Varo et al.,
2013; Kennedy et al., 2013; Woodcock et al., 2013; Rader
et al., 2014). The landscape context can mediate these
responses whereby local management factors may become
important only in particular landscape contexts (Kleijn and
van Langevelde, 2006; Rundlöf and Smith, 2006; Rundlöf et
al., 2008). For example, pollinator richness and abundance
can be high on organic farms in homogeneous landscapes,
but not on organic farms in heterogeneous landscapes
(Rundlöf and Smith, 2006). Landscape heterogeneity and
less-intensive farm management methods are thus thought
to mitigate pressures upon pollinators in some ecosystems
(Kennedy et al., 2013). A strong relationship between bee
diversity and heterogeneity of the urban landscape has also
been found (Sattler et al., 2010).
As a consequence of global change (e.g. climate, land-use
intensification and farming systems), pollinator communities
may be changed in a non-random way, resulting in losses of
particular functional guilds or species (Larsen et al., 2005;
Flynn et al., 2009; Winfree et al., 2009; Williams et al., 2010;
Rader et al., 2014). Individual taxa respond to land use
change in different ways due to the varied morphological
and behavioural characteristics within pollinator communities
(Steffan-Dewenter, 2002; Tylianakis et al., 2005; Winfree
et al., 2009; Shackelford et al., 2013). For example, social
and solitary bees species may each respond differently to
pesticide use (Williams et al., 2010) and dietary specialists
and large-bodied taxa tend to be more strongly affected by
habitat loss than less specialized and smaller-bodied taxa
(Winfree et al., 2011a; Rader et al., 2014).
Different life history traits are associated with the quality
and quantity of the pollination delivered. For example, body
size measures correlate with pollination efficiency (Larsen
et al., 2005; Vivarelli et al., 2011), foraging duration (Stone
and Willmer, 1989; Stone, 1994) and foraging distance
in some bees (Greenleaf et al., 2007). Frequent visitation
may however also entail a cost (e.g., loss of pollen) to
plants when pollinators are over abundant (Aizen et al.,
2014). Within a given pollinator community, the variation in
functional traits between species (i.e., functional diversity)
itself improves the quality of pollination and reduces the
variation in crop pollination and yield (Hoehn et al., 2008;
Winfree and Kremen, 2009; Bluthgen and Klein, 2011).
1.9 THE ECONOMICS OF
POLLINATION, RISKS AND
UNCERTAINTY
(dealt with in more detail in Chapter 4)
The link between pollination and human quality of life is
measured through the benefit that humans gain from this
service. Due to the complexity of what a good quality life
entails (Díaz et al., 2015), the benefit can have multiple
dimensions depending on the type of contribution from
pollination, such as the availability of basic foods or quality
of food. This multidimensional benefit is called the value of
pollination. However, values express a belief about a desired