Human actions threaten the world's pollinating insects
22 April 2013, by Tamera Jones
A combination of multiple, mostly man-made pressures are largely responsible for the continued global decline in honeybees, bumblebees, and other insect pollinators, say scientists.
The oil-collecting bee Rediviva longimanus delves deep into the orchid Pterygodium schelpei to extract oil with absorbent hairs on its elongated front feet.
It seems individual stresses like intensive farming, climate change, the spread of alien species and diseases are almost entirely to blame for pollinator losses.
But the researchers say complex interactions between these separate issues may be making matters worse.
The situation is so grave that our ability to supply adequate nutrients and dietary diversity to the world's growing population is seriously threatened.
This is because honeybees, bumblebees and other pollinating insects are vital for many fruit, vegetable, seed, nut, and oil crops around the world. Since 1961, the number of these crops grown worldwide has grown so much that demand for pollination has increased threefold. One estimate suggests the annual worth of pollination to the global economy is about $215 billion.
Not just that, but globally, pollinating insects improve the yields of around three-quarters of crops, while up to 94 per cent of wild flowering plants depend on pollinators for reproduction.
'There is no single smoking gun behind pollinator declines. Pollinators face many threats and it's likely that these combine to exacerbate the negative impacts of each.'
Dr Adam Vanbergen, NERC's Centre for Ecology & Hydrology
And it's not only honeybees and bumblebees that matter. Around the world, wasps, flies, beetles, butterflies and moths also contribute to pollination.
'There is no single smoking gun behind pollinator declines. Pollinators face many threats and it's likely that these combine to exacerbate the negative impacts of each,' says Dr Adam Vanbergen from NERC's Centre for Ecology & Hydrology, lead author of the report.
'Intensive farming reduces the availability of nectar and pollen foods for these insects and such malnourished pollinators will be more susceptible to pathogens and pesticide impacts, for example,' he adds.
So he and 39 scientists from 27 institutions in six countries pulled together multiple studies in a new review providing the first detailed fusion of the evidence that the causes of pollinator losses are multifactorial in nature.
All of the researchers involved received funding from the Insect Pollinators Initiative (IPI), which aims to understand the causes and consequences of insect pollinator declines and inform appropriate mitigation strategies. The IPI brings together academics from a range of disciplines to try to achieve this.
Vanbergen and his co-authors argue that the best way to get to the bottom of pollinator losses is for researchers from different disciplines to together examine how multiple interacting pressures affect pollinators from the level of individual genes to communities of species.
'This interdisciplinary approach is happening within the IPI. It's one of its strengths and was in fact a key objective,' says Vanbergen.
'We need a holistic approach to landscape management to restore and link-up habitats to provide havens for these vital insects. Broadening pesticide risk assessments by assessing subtle sub-lethal effects and including more pollinator species will also help. In future we must develop innovative pest management approaches to secure food supplies but minimise impacts on pollinators,' says Vanbergen.
'If demand for insect-pollinated crops continues to rise while pollinator number persistently fall, then crop shortages will likely follow,' say the authors in the report.
The report is published in Frontiers in Ecology and the Environment.
The IPI is a joint initiative between the Wellcome Trust, BBSRC, Defra, NERC and the Scottish Government, and is funded under the auspices of Living With Environmental Change.
Adam J Vanbergen and the Insect Pollinators Initiative, Threats to an ecosystem service: pressures on pollinators, Frontiers in Ecology and the Environment, published 22 April 2013
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