Pollinator decline
Pollinator decline is the reduction in abundance of insect and other animal pollinators in many ecosystems worldwide that began being recorded at the end of the 20th century. Multiple lines of evidence exist for the reduction of wild pollinator populations at the regional level, especially within Europe and North America.[1][2][3][4] Similar findings from studies in South America, China and Japan make it reasonable to suggest that declines are occurring around the globe.[5][6][7][8] The majority of studies focus on bees, particularly honeybee and bumblebee species, with a smaller number involving hoverflies and lepidopterans.[9][1][10][11][12]
The picture for domesticated pollinator species is less clear. Although the number of managed honey bee colonies in Europe and North America declined by 25% and 59% between 1985-2005 and 1947-2005 respectively, overall global stocks increased due to major hive number increases in countries such as China and Argentina.[13][14][15] Nevertheless, in the time managed honeybee hives increased by 45% demand for animal pollinated crops tripled, highlighting the danger of relying on domesticated populations for pollination services.[15]
Pollinators participate in the sexual reproduction of many plants by ensuring cross-pollination, essential for some species and a major factor in ensuring genetic diversity for others. Since plants are the primary food source for animals, the possible reduction or disappearance of pollinators has been referred to as an "armageddon" by some journalists.
Possible explanations[edit]
Although the existence of pollinator decline can be difficult to determine, a number of possible reasons for the theoretical concept have been proposed, such as exposure to pathogens, parasites, and pesticides; habitat destruction; climate change; market forces; intra- and interspecific competition with native and invasive species; and genetic alterations.[26][27]
Honey bees are an invasive species throughout most of the world where they have been introduced, and the constant growth in the amount of these pollinators may possibly cause a decrease in native species.[21] Light pollution has been suggested a number of times as a possible reason for the possible decline in flying insects.[28][29][30][31] One study found that air pollution, such as from cars, has been inhibiting the ability of pollinators such as bees and butterflies to find the fragrances of flowers. Pollutants such as ozone, hydroxyl, and nitrate radicals bond quickly with volatile scent molecules of flowers, which consequently travel shorter distances intact. Pollinators must thus travel longer distances to find flowers.[32]
Pollinators may also face an increased risk of extinction because of global warming due to alterations in the seasonal behaviour of species. Climate change can cause bees to emerge at times in the year when flowering plants were not available.[33]
Solutions[edit]
Several scholars have called for application of the precautionary principle.[27][49]
Efforts are being made to sustain pollinator diversity in agricultural and natural ecosystems by some environmental groups.[50] In 2014 the Obama administration published "the Economic Challenge Posed by Declining Pollinator Populations" fact sheet, which stated that the 2015 budget proposal recommended congress appropriate approximately $50 million for pollinator habitat maintenance and to double the area in the Conservation Reserve Program dedicated to pollinator health, as well as recommending to "increase funding for surveys to determine the impacts on pollinator losses".[51]
Some international initiatives highlight the need for public participation and awareness of pollinator conservation.[52] Pollinators and their health have become growing concerns for the public. Around 18 states within America have responded to these concerns by creating legislation to address the issue. According to the National Conference of State Legislatures, the enacted legislation in those states addresses five specific areas relating to pollinator decline: awareness, research, pesticides, habitat protection and beekeeping.[53]
A 2021 global assessment of the drivers of pollinator decline found that "global policy responses should focus on reducing pressure from changes in land cover and configuration, land management and pesticides, as these were considered very important drivers in most regions".[54]