glyphosate concentrations. Furthermore, after a second release at a release site, the
proportion of direct homeward flights performed increased in control bees but not in
treated bees, where one would expect the bees to remember the local topography due
to experience. This result suggested that exposure to glyphosate doses commonly
found in agricultural settings impairs the cognitive capacities needed to successfully
return to the hive, such as navigation and memory. Long-term negative effects on
pollinator colony health are likely as forager bees are lost and house bees are forced
to begin foraging while still young, creating a social structure imbalance [64].
4.2.5 Habitat Loss
Habitat loss, which is the reduction of natural and seminatural home environment, is
believed to negatively affect pollinators by loss of diverse floral resources from their
diet. This is likely more of an issue for wild bees, which are major yet largely
invisible participants in crop pollination, than for managed honey bees. Managed
beehives are rented out to farmers and thus can be physically moved between floral
sources, but wild bees do not have such a luxury.
For honey bees, deficiencies in quantity and quality of pollen and nectar lead to
decreased colony population. A pollen deficiency causes low colony populations and
further reduces the number of foraging bees responsible for food gathering.
Modern industrial agriculture systems that use an annual cropping schedule and
simple rotations across large swaths of land have resulted in monocultures, particularly wind- or self-pollinated crops, with greatly reduced plant diversity. Monocultures of bee-pollinated crops may not only have a short duration of massive
flower blooming but also insufficient nectar and pollen variety for honey bee needs.
Then, once the mass bloom is over, there is little else for bees to forage upon across
the large monocropped landscape, which can prove challenging to their
overwintering preparation.
Besides nectar as a basic food source, pollen quality and diversity have been
shown to improve bee immune system health. Both are so important in the bee diet
that beekeepers must often provide supplements to prevent nutritional deficiency and
potential colony failure. However, pollen supplements and sugar syrup do not
provide the same nutritional quality as natural pollen and nectar [65].
In comparing the seasonal contribution of rapeseed and sunflower mass-flowering
crops versus other floral resources in the bee diet, scientists found that bees collected
nectar mainly from the crops, but pollen came from a diverse range of plant species
in nearby seminatural habitats or from weed plants among crops. Weed species
actually constituted the bulk of the honey bee diet between the mass flowering crop
periods [66].
One of the first studies to specifically address wild bee participation helped
illustrate the importance of diverse habitat alongside crop lands. A study set in
France investigated effects of forest edges upon pollinator activity in rapeseed fields.
Scientists caught bees within the crop fields at measured distances from forest edges
and found that, out of several thousand identified bees representing multiple taxa,
24
C. Li
proportion of direct homeward flights performed increased in control bees but not in
treated bees, where one would expect the bees to remember the local topography due
to experience. This result suggested that exposure to glyphosate doses commonly
found in agricultural settings impairs the cognitive capacities needed to successfully
return to the hive, such as navigation and memory. Long-term negative effects on
pollinator colony health are likely as forager bees are lost and house bees are forced
to begin foraging while still young, creating a social structure imbalance [64].
4.2.5 Habitat Loss
Habitat loss, which is the reduction of natural and seminatural home environment, is
believed to negatively affect pollinators by loss of diverse floral resources from their
diet. This is likely more of an issue for wild bees, which are major yet largely
invisible participants in crop pollination, than for managed honey bees. Managed
beehives are rented out to farmers and thus can be physically moved between floral
sources, but wild bees do not have such a luxury.
For honey bees, deficiencies in quantity and quality of pollen and nectar lead to
decreased colony population. A pollen deficiency causes low colony populations and
further reduces the number of foraging bees responsible for food gathering.
Modern industrial agriculture systems that use an annual cropping schedule and
simple rotations across large swaths of land have resulted in monocultures, particularly wind- or self-pollinated crops, with greatly reduced plant diversity. Monocultures of bee-pollinated crops may not only have a short duration of massive
flower blooming but also insufficient nectar and pollen variety for honey bee needs.
Then, once the mass bloom is over, there is little else for bees to forage upon across
the large monocropped landscape, which can prove challenging to their
overwintering preparation.
Besides nectar as a basic food source, pollen quality and diversity have been
shown to improve bee immune system health. Both are so important in the bee diet
that beekeepers must often provide supplements to prevent nutritional deficiency and
potential colony failure. However, pollen supplements and sugar syrup do not
provide the same nutritional quality as natural pollen and nectar [65].
In comparing the seasonal contribution of rapeseed and sunflower mass-flowering
crops versus other floral resources in the bee diet, scientists found that bees collected
nectar mainly from the crops, but pollen came from a diverse range of plant species
in nearby seminatural habitats or from weed plants among crops. Weed species
actually constituted the bulk of the honey bee diet between the mass flowering crop
periods [66].
One of the first studies to specifically address wild bee participation helped
illustrate the importance of diverse habitat alongside crop lands. A study set in
France investigated effects of forest edges upon pollinator activity in rapeseed fields.
Scientists caught bees within the crop fields at measured distances from forest edges
and found that, out of several thousand identified bees representing multiple taxa,
24
C. Li