POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
A large-scale study in ten European and two African
countries showed that organic farms have much smaller
effects on the diversity of habitats or species richness
at farm and regional scales than at the field scale. This
implies that to ensure positive benefits of biodiversity at
larger spatial scales, even organic farms have to support
biodiversity actively by maintaining and expanding habitats
and natural landscape features (Schneider et al., 2014).
In England, a study suggested that organic farming
should be mainly encouraged in mosaic (low productivity)
landscapes, where yield differences between organic
and conventional agriculture are lower. In less-productive
agricultural landscapes, biodiversity benefit can be gained
by concentrating organic farms into hotspots without a
commensurate reduction in yield (Gabriel et al., 2013).
This study also revealed a decrease in the abundance and
diversity of some pollinator groups with increasing yield in
both organic and non-organic (“conventional”) wheat farms.
The factors that co-vary with yield ultimately influence this
pattern, and could include management practices, and
management of habitats and/or cropping systems, in both
conventional and organic farms.
6.4.1.1.5 No-till farming
No-till farming is a practice for soil conservation that can
reverse long-term soil degradation due to organic matter
loss. No-till farming has increased in the Cerrado region of
Brazil from 180,000 hectares in 1992 to 6,000,000 hectares
in 2002. Producers have found that no-till techniques within
certain planting sequences each year, as well as longerterm
crop rotations, may increase production by 10%. The
estimated annual benefits of adopting no-till agriculture
techniques in Brazil amount to $1.4 billion on 35% and
$3.1billion on 80% of a total cultivated area of 15.4 million
hectares (Clay, 2004). In contrast a global meta-analysis
across 48 crops and 63 countries showed that overall notill
reduces yields, but this depends on the system. Yield
difference is minimised when no-till is combined with crop
residue retention and crop rotation, and no-till significantly
increases rainfed crop productivity in dry climates
(Pittelkow et al., 2015; see Chapter 2, section 2.2.2.1.3 for
more details).
No-till coupled with the use of cover crops might be
expected to enhance populations of ground-nesting bees,
as many species place their brood cells < 30 cm below the
surface (Roulston and Goodell, 2011; Williams et al., 2010),
but there is little evidence for this. One study found an
increase in squash bees Peponapis pruinosa, but not other
bee species, on no-till squash farms in the USA (Shuler et
al., 2005), while another study did not find this effect (Julier
and Roulston, 2009).
6.4.1.1.6 Change irrigation frequency or type
Although there is little evidence, similarly to no-till, changing
irrigation frequency or type can be a pollinator-supporting
practice. In arid irrigated systems, changing from flood
irrigation that may be detrimental for pollinators because
of nest flooding, to drip irrigation can reduce the impact
on pollinators, but in general irrigation can promote wild
insect abundance through higher productivity of flowering
plants or by making the soil easier to excavate (Julier and
Roulston, 2009).
6.4.1.1.7 Change management of productive
grasslands
Productive grasslands used for grazing or hay can be
managed to be more flower-rich by reducing fertilizer
inputs, or delaying mowing dates. In experimental studies in
Europe, these changes usually lead to increased numbers
of bees, hoverflies and/or butterflies (Humbert et al., 2012;
Dicks et al., 2014a). Adding legumes and other flowering
species to grassland seed mixtures is supported by some
agri-environment schemes in Europe (see section 6.4.1.3)
and probably benefits pollinators by supplying flowers in
grassland-dominated landscapes, but this has not been
clearly demonstrated (Dicks et al., 2010; Dicks et al., 2014).
Two European studies have shown that avoiding use of
rotary mowers and mechanical processors substantially
reduces mortality of bees or butterfly larvae when cutting
flowering meadows (Dicks et al., 2014b). However, studies
have not been designed to look for landscape-scale,
population-level effects of any of these management
changes on pollinators.
6.4.1.1.8 Diversify farming systems
Diversity is the foundation of any sustainable agriculture
system, and mixed crop types, crop-livestock mixtures,
intercropping and cover crops bring pollinator diversity to
the farm by providing floral resources and habitat for many
different species of pollinators, and promote wild pollinator
stability on farms (Kennedy et al., 2013). There is some
evidence in Western Europe and North America suggesting
that increased floral diversity achieved through diversified
farming can improve pollination (Batáry et al., 2009; Kremen
and Miles, 2012; Kennedy et al., 2013). Intercropping cacao
with banana or plantain is correlated with an increase in
the density of cacao-pollinating midges, as well as cacao
fruit set, in Ghana (Frimpong et al., 2011). A recent study
in Canada (Fahrig et al., 2015) suggested that reduced
field size may be a more important feature of diversified
farming systems than increased number of crop types,
if the aim is to increase or maintain farmland biodiversity
generally (including bees, hoverflies and butterflies). Recent
meta-analysis suggests that two management practices
that diversify crop fields – polyculture and crop rotations –
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6. RESPONSES TO RISKS AND OPPORTUNITIES ASSOCIATED
WITH POLLINATORS AND POLLINATION