The term pollinator decline refers to the reduction in abundance of insect and other animal pollinators in many ecosystems worldwide during the end of the twentieth century.
Pollinators participate in sexual reproduction of many plants, by ensuring cross-pollination, essential for some species, or a major factor in ensuring genetic diversity for others. Since plants are the primary food source for animals, the reduction of one of the primary pollination agents, or even their possible disappearance, has raised concern, and the conservation of pollinators has become part of biodiversity conservation efforts.
Consequences
The value of bee pollination in human nutrition and food for wildlife is immense and difficult to quantify.60 to 80% of the world’s flowering plant species are animal pollinated, and 35% of crop production and 60% of crop plant species depend on animal pollinators. It is commonly said that about one third of human nutrition is due to bee pollination. This includes the majority of fruits, many vegetables (or their seed crop) and secondary effects from legumes such as alfalfa and clover fed to livestock.
In 2000, Drs. Roger Morse and Nicholas Calderone of Cornell University, attempted to quantify the effects of just one pollinator, the Western honey bee, on only US food crops. Their calculations came up with a figure of US $14.6 billion in food crop value. In 2009, another study calculated the worldwide value of pollination to agriculture. They calculated the costs using the proportion of each of 100 crops that need pollinators that would not be produced in case insect pollinators disappeared completely. The economic value of insect pollination was then of €153 billion.
There has not been sufficient study to quantify the effects of pollinator decline on wild plants and wild life that depend on them for feed. Some plants on the endangered species list are endangered because they have lost their normal, native pollinators. Honey bees are not native to the Western Hemisphere. The role of honey bees in the Western Hemisphere is almost exclusively agricultural.
Increasing public awareness
The steady increase in beekeeper migration (for pollination service on agricultural crops) has masked the issue of pollinator decline from much public awareness, however sudden blocks to such migration could have catastrophic results on the global food supply.There are international initiatives (e.g. the International Pollinator Initiative (IPI)) that highlight the need for public participation and awareness of pollinator, such as bees, conservation
Possible explanations
Pesticide misuse
Studies have linked neonicotinoid pesticide exposure to bee health decline. These studies add to a growing body of scientific literature and strengthen the case for removing pesticides toxic to bees from the market. Pesticides interfere with honey bee brains, affecting their ability to navigate. Pesticides prevent bumble bees from collecting enough food to produce new queens.Neonicitinoids are highly toxic to a range of insects, including honey bees and other pollinators. They are taken up by a plant’s vascular system and expressed through pollen, nectar and guttation droplets from which bees forage and drink. They are particularly dangerous because, in addition to being acutely toxic in high doses, they also result in serious sub-lethal effects when insects are exposed to chronic low doses, as they are through pollen and water droplets laced with the chemical as well as dust that is released into the air when coated seeds are planted. These effects cause significant problems for the health of individual honey bees as well as the overall health of honey bee colonies and they include disruptions in mobility, navigation, feeding behavior, foraging activity, memory and learning, and overall hive activity.
A study that focused on the neonicotinoid pesticide thiamethoxam, which is metabolized by bees into clothianidin, a pesticide cited in legal action, tested the hypothesis that a sub-lethal exposure to a neonicotinoid indirectly increases hive death rate through homing failure in foraging honey bees. When exposed to sub-lethal doses of thiamethoxam, at levels present in the environment, honey bees were less likely to return to the hive after foraging than control bees that were tracked with RFID, but not intentionally dosed with pesticides. Higher risks are observed when the homing task is more challenging. The survival rate is even lower when exposed bees are placed in foraging areas with which they are less familiar.
Another study examined the impacts of the pesticide imidacloprid on bumble bee colony health. Researchers exposed colonies of the bumble bees to levels of imidacloprid that are realistic in the natural environment, then allowed them to develop naturally under field conditions. Treated colonies had a significantly reduced growth rate and suffered an 85% reduction in production of new queens compared to unexposed control colonies. The study is particularly noteworthy because it shows that bumble bees, which are wild pollinators, are suffering similar impacts of pesticide exposure to “managed” honey bees. Wild pollinators provide essential services both in agriculture and to a wide range of wild plants that could not survive without insect pollination.
On March 21, 2012, commercial beekeepers and environmental organizations filed an emergency legal petition with the U.S. Environmental Protection Agency (EPA) to suspend use of clothianidin, urging the agency to adopt safeguards. The legal petition is supported by over one million citizen petition signatures, targets the pesticide for its harmful impacts on honey bees. The legal petition points to the fact that the EPA failed to follow its own regulations. EPA granted a conditional, or temporary, registration to clothianidin in 2003 without a required field study establishing that the pesticide would have no “unreasonable adverse effects” on pollinators. Granting conditional registration was contingent upon the subsequent submission of an acceptable field study, but this requirement has not been met. EPA continues to allow the use of clothianidin nine years after acknowledging that it had an insufficient legal basis for initially allowing its use. Additionally, the product labels on pesticides containing clothianidin are inadequate to prevent excessive damage to non-target organisms, which is a second violation of the requirements for using a pesticide and further warrants removing all such mislabeled pesticides from use.
It is a label violation to apply most insecticides on crops during bloom, or to allow the pesticide to drift to blooming weeds that bees are visiting. Yet such applications are frequently done, with little enforcement of the bee protection directions. Pesticide misuse has driven beekeepers out of business, but can affect native wild bees even more, because they have no human to move or protect them.
Bumblebee populations are in jeopardy in cotton-growing areas, since they are dosed repeatedly when pesticide applicators apply insecticides on blooming cotton fields while the bees are foraging.
Widespread aerial applications for mosquitoes, med-flies, grasshoppers, gypsy moths and other insects leave no islands of safety where wild insect pollinators can reproduce and repopulate. One such program can reduce or endanger pollinator populations for several years.
Many homeowners feel that dandelions and clover are weeds, that lawns should only be grass, and that they should be highly treated with pesticides. This makes a hostile environment for bees, butterflies and other pollinators.
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