The above statistics are primarily derived from overwintering records supplied by
beekeepers via survey. However, recent trends indicate that honey bees face significant stressors throughout the year and not just winter, at least in the United States.
For the 2014–2015 season beginning and ending in April, the United States
Department of Agriculture reported a 42.1% loss of managed honey bee colonies.
Winter colony loss records, considered from October 2014 through April 2015,
posted a small improvement over previous years, but 2014 summer losses exceeded
winter for the first time at 27.4%. The 2014–2015 US losses exceeded the previous
period’s 34.2%.
Noncommercial beekeepers were more prone to mite infestations due to less
aggressive mite control methods than commercial beekeepers, but commercial
beekeepers saw more losses during the summer, indicating other factors were and
are still at play [47].
4.2 Causes
The notable decrease in honey bee colonies and probable wild bee populations is
believed to be caused by numerous factors acting in conjunction: climate change,
exposure to certain pesticides or herbicides, loss of natural foraging sources leading
to inadequate diets, parasitic mite infestations and ensuing diseases, among other
things [24, 37].
The interactions among variables correlating with pollinator decline can be
complex, with some of the posited variables themselves under contention. Some
pesticides affect pollinators synergistically instead of additively. Many elements
from chemical exposure to difficult weather and poor food sources can suppress
immune response, which in turn promotes parasites and disease. Regional differences can also alter each variable’s effect or produce a unique combination of
stressors specific to a geographical area [48].
Seasonal mortality plays a significant role in overall honey bee population health,
particularly in northern climates across North America and Europe, where cold
winters and lack of flowering plants make foraging impossible. This is called the
overwintering period. By late summer or early autumn, honey bees will have
accumulated significant honey and pollen stores in their hives that serve as their
only food source over winter. Overwintering is thus the period of winter survival and
a key setting in which the many variables interact to increase stress and mortality rate
on bees [49].
However, given the latest data (2014–2015) on summer colony losses in the
United States, overwintering is only one period of expected bee stress [47]. The fact
that data for annual including summer losses were only added recently in the major
US Department of Agriculture honey bee reports means there is still much to learn
about how bee stressors interact to produce mortality across the seasons.
18
C. Li
beekeepers via survey. However, recent trends indicate that honey bees face significant stressors throughout the year and not just winter, at least in the United States.
For the 2014–2015 season beginning and ending in April, the United States
Department of Agriculture reported a 42.1% loss of managed honey bee colonies.
Winter colony loss records, considered from October 2014 through April 2015,
posted a small improvement over previous years, but 2014 summer losses exceeded
winter for the first time at 27.4%. The 2014–2015 US losses exceeded the previous
period’s 34.2%.
Noncommercial beekeepers were more prone to mite infestations due to less
aggressive mite control methods than commercial beekeepers, but commercial
beekeepers saw more losses during the summer, indicating other factors were and
are still at play [47].
4.2 Causes
The notable decrease in honey bee colonies and probable wild bee populations is
believed to be caused by numerous factors acting in conjunction: climate change,
exposure to certain pesticides or herbicides, loss of natural foraging sources leading
to inadequate diets, parasitic mite infestations and ensuing diseases, among other
things [24, 37].
The interactions among variables correlating with pollinator decline can be
complex, with some of the posited variables themselves under contention. Some
pesticides affect pollinators synergistically instead of additively. Many elements
from chemical exposure to difficult weather and poor food sources can suppress
immune response, which in turn promotes parasites and disease. Regional differences can also alter each variable’s effect or produce a unique combination of
stressors specific to a geographical area [48].
Seasonal mortality plays a significant role in overall honey bee population health,
particularly in northern climates across North America and Europe, where cold
winters and lack of flowering plants make foraging impossible. This is called the
overwintering period. By late summer or early autumn, honey bees will have
accumulated significant honey and pollen stores in their hives that serve as their
only food source over winter. Overwintering is thus the period of winter survival and
a key setting in which the many variables interact to increase stress and mortality rate
on bees [49].
However, given the latest data (2014–2015) on summer colony losses in the
United States, overwintering is only one period of expected bee stress [47]. The fact
that data for annual including summer losses were only added recently in the major
US Department of Agriculture honey bee reports means there is still much to learn
about how bee stressors interact to produce mortality across the seasons.
18
C. Li