Scientists urge transition to pollinator-friendly agriculture
Present scale of use of neonicotinoid pesticides put pollinator services at risk
Honeybee disorders and high colony losses have become global phenomena. An international team of scientist led by Utrecht University synthesized recent findings on the effects of neonicotinoid pesticides on bees. Scientists conclude in the scientific journal Current Opinion in Environmental Sustainability that owing to their large scale prophylaxic use in agriculture, their high persistence in soil and water, and their uptake by plants and translocation to flowers, neonicotinoids put pollinator services at risk.
Rapidly emerging scientific insights
One third of the world food production and 87,5% of all flowering plants on earth critically depend on pollinators. To protect honeybees, the European Commission decided on 24 May 2013 to ban the use of the three most toxic neonicotinoids in crops attractive to bees.
Over the past two years more than 150 new scientific studies on the effects of neonicotinoids on bees have been published. An international team of six European scientists led by dr. Jeroen van der Sluijs from Utrecht University’s Copernicus Institute of Sustainable Development, for the first time made a comprehensive synthesis of these new insights. The study appeared today in the leading journal Current Opinion in Environmental Sustainability. Last month, the same group discovered that the large scale pollution of surface waters in Europe with imidacloprid has led to a dramatic decline (on average a loss of 70%) in insect richness in and around the polluted surface waters and wetlands.
Nowadays most flowering crops and an unknown proportion of wild flowers have neonicotinoid residues in their pollen and nectar.
Large scale prophylaxic use transformed the agrochemical landscape
Massive reliance on neonicotinoids as prophylaxis has led to an unprecedented scale of use. In just twenty years neonicotinoids boomed and became the most widely used insecticides with a world market share of 26%, used in more than 120 countries on hundreds of crops and ornamentals. Neonicotinoids easily leach into the environment. Their high persistence in soil and water lead to high levels of pollution. Neonicotinoids are taken up by plants making the whole plant toxic to insects from the inside, including its flowers.
For pollinators such as honeybees and bumblebees the agrochemical landscape has changed dramatically. As Van der Sluijs explains: “Nowadays most flowering crops and an unknown proportion of wild flowers have neonicotinoid residues in their pollen and nectar. A large fraction of the water that bees need for drinking and for cooling the hive also contain neonicotinoid residues.” Recent findings show that even very low residue levels in pollen, nectar and water can be lethal to bees when exposure is sustained over a longer period.
Low concentrations weaken colonies
At concentrations now widely found in agricultural landscapes, neonicotinoids cause a wide range of adverse behavioral and development (“sublethal”) effects in bees. Effects confirmed in recent scientific studies include: impairment of foraging success, impairment of brood and larval development, impairment of memory and learning, impairment of the waggle dance, damage to the central nervous system, increased susceptibility to diseases and decreased hive hygiene. All these effects weaken the colonies. Even very low doses of neonicotinoids make honeybee colonies prone to infectious agents such as Nosema ceranae which together can produce colony collapse.
Authorization based on flawed field tests
The guidelines for field tests used for marketing authorization of neonicotinoids were not developed to detect behavioral nor long-term effects on the colony level. Major weaknesses of existing field studies are the small size of the colonies, the frequent presence of neonicotinoids in the untreated control hives, the very small distance between the hives and the treated field, the short observation times, and the very low surface of the test field. Consequently, the real exposures of the honeybees during these field tests is highly uncertain. It can be much smaller than what bees encounter in agricultural areas with multiple crops treated at different times in the year with different neonicotinoids.
Given all the major limitations to the reliability of these field studies, the scientists recommend to give more weight in the risk assessment to reproducible results from controlled lab and semi-field studies. “The ratio between the environmental concentration and the no-effect concentration should be used as the key risk indicator” according to Van der Sluijs.
Pollinator friendly alternatives urgently needed
Given its broad spectrum (non-selective) toxicity, at its present large scale of use neonicotinoids put pollinator services at risk. The scientists conclude that a worldwide transition to pollinator-friendly alternatives to neonicotinoids is urgently needed and welcome the recent European ban as a first step in that direction.
Should Japan be the next to restrict the use of neonicotinoids?
Dr Van der Sluijs and colleagues present their new findings in Tokyo this week at an international IUCN symposium. In Asia, neonicotinoids are sprayed as prophylaxis in rice paddies and massively pollute wetlands. European and Asian scientists will discuss the implications of new scientific evidence on neonicotinoids for the protection of pollinators and vulnerable wetland ecosystems in Japan and Asia. Should Japan follow Europe in restricting neonicotinoids and pave the way for the rest of Asia?
The paper written by Jeroen van der Sluijs, Noa Simon-Delso, Dave Goulson, Laura Maxim, Jean-Marc Bonmatin and Luc Belzunces has been published in Current Opinion in Environmental Sustainability. Part of the research Part of the research was financed by a grant from the Triodos Foundation, which has set up a special fund for independent research on this controversial group of insecticides.