Hommels

De Europese Unie is op 1 december 2013 moedig begonnen met een verbod van twee jaar op bepaalde toepassingen van drie neonicotinoide pesticiden die schadelijk voor honingbijen en andere bestuivers zijn. Het Europese verbod gaat over neuroactieve insecticiden die in hun werking vergelijkbaar zijn met nicotine. De bekende gevolgen voor bijen variëren van negatieve beinvloeding van foerageergedrag en navigatie (die hun vermogen om gewassen te bestuiven vermindert) tot de dood. Bestuivers zijn essentieel voor onze voedselvoorziening en landbouweconomie. Ze zorgen voor meer dan een derde van het voedsel dat we eten, verbeteren de productie van 75 procent van alle soorten gewassen, en zijn essentieel voor talrijke gewassen, zoals amandelen, avocado's, appels en kersen. Maar we moeten veel meer doen, en uitgroeien tot een wereldleider in duurzame alternatieven voor schadelijke pesticiden.

In less than 20 years, neonicotinoids have become the most widely used class of insecticides with a global market share of more than 25%. For pollinators, this has transformed the agrochemical landscape. These chemicals mimic the acetylcholine neurotransmitter and are highly neurotoxic to insects. Their systemic mode of action inside plants means phloemic and xylemic transport that results in translocation to pollen and nectar. Their wide application, persistence in soil and water and potential for uptake by succeeding crops and wild plants make neonicotinoids bioavailable to pollinators at sublethal concentrations for most of the year. This results in the frequent presence of neonicotinoids in honeybee hives. At field realistic doses, neonicotinoids cause a wide range of adverse sublethal effects in honeybee and bumblebee colonies, affecting colony performance through impairment of foraging success, brood and larval development, memory and learning, damage to the central nervous system, susceptibility to diseases, hive hygiene etc. Neonicotinoids exhibit a toxicity that can be amplified by various other agrochemicals and they synergistically reinforce infectious agents such as Nosema ceranae which together can produce colony collapse. The limited available data suggest that they are likely to exhibit similar toxicity to virtually all other wild insect pollinators. The worldwide production of neonicotinoids is still increasing. Therefore a transition to pollinator-friendly alternatives to neonicotinoids is urgently needed for the sake of the sustainability of pollinator ecosystem services.

An increasing body of scientific evidence indicates that many chemicals have biological effects at doses previously considered negligible. It is increasingly evident that more subtle deleterious effects can occur due to longer-term exposure to relatively low doses of chemicals, individually or in mixtures. New concerns have recently been raised about the impact of pesticides on non-target organisms including insects, especially bees, and amphibians. Studies suggest that low doses of neonicotinoids, a group of neurotoxic chemicals widely used in many countries as insecticides, could have sublethal effects on honey bees and bumble bees with serious consequences for wild populations of these crucially important pollinators and therefore for agriculture and the environment. It has also been suggested that detailed investigation of the effect of neonicotinoids on mammalian brain function, especially brain development, is needed to protect human health, especially that of children.

Researchers with Friends of the Earth US and the Pesticide Research Institute say that more than half of the nursery plants studied contained residues of “neonicotinoid” pesticides, a substance increasingly thought to be contributing to mass die-offs of global honey-bee populations. “At the levels observed in our report, the high percentage of contaminated plants and concentrations suggest this problem is widespread,” Lisa Archer, a co-author of the new report and director of Friends of the Earth US’s food and technology program, told Inter Press Service (IPS). “Unfortunately, too many home gardeners have likely become a source of exposure to pesticides that have been shown to harm, weaken and kill bees. It’s pretty shocking that consumers who may be purchasing these plants specifically to help bees could, in fact, be poisoning them.”

Although bee advocates have focused on farmers and their use of insecticides, homeowner use of chemicals also can affect bee populations. Many homeowners apply neonicotinoids, a widely used class of insecticides, when lawn weeds, such as dandelions and white clovers, are blooming; This practice can have a negative effect on native pollinator populations. Jonathan Larson, a University of Kentucky doctoral student, recently published the results of his homeowner research in the journal PLOS ONE. Declines in honeybee populations have captured media headlines. But other pollinators, such as bumblebees, also are on the decline due to diseases, pesticides and habitat loss. “With honeybee populations struggling, we need to rely on native bees, such as bumblebees, to pick up the slack on plant pollination,” Dan Potter, UK entomologist and Larson’s adviser, said in the release. “Many native bees are much more efficient at pollinating certain types of crops, like tomatoes, urban flowering plants and vegetables grown in home gardens.”

Rachel Carson described her fears about the use of systemic insecticides like neonicotinoids 50 years ago when she wrote Silent Spring. Now, we are witnessing first-hand as her predictions become a reality: “The world of systemic insecticides is a weird world, surpassing the imaginings of the brothers Grimm… It is a world where the enchanted forest of the fairy tales has become the poisonous forest in which an insect that chews a leaf or sucks the sap of a plant is doomed. It is a world where a flea bites a dog, and dies because the dog’s blood has been made poisonous, where an insect may die from vapors emanating from a plant it has never touched, where a bee may carry poisonous nectar back to its hive and presently produce poisonous honey.” Compounding the problem is a shift away from integrated pest management (IPM) and agroecological practices, systems that, to varying degrees, mitigate the indiscriminate use of toxic chemicals. Industrial agriculture practices rely on pesticides whether they are needed or not, thus putting an unsustainable load of chemicals into the environment and adding weight to Carson’s frightening predictions. As one report notes, “Over the last 20 years or so, the shift in pest management has moved away from reactive to prophylactic. Now many fungicides, pesticides and herbicides are applied to the seeds before sowing. Application of the chemical before pest damage has occurred often involves routine spraying and pre-emptive treatments.”