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Science Alert: Experts Respond

Wild pollinators crucial – experts respond

Posted in Science Alert: Experts Respond on March 1st, 2013.

A massive international study of 600 field trials from around the globe (including New Zealand) highlights the importance of wild insects in spreading pollen for agricultural crops, and warns of excessive reliance on honeybees.

One of the dominant pollinators in red clover (Trifolium pratense) is the buff-tailed bumble bee (Bombus terrestris). [Photo by Maj Rundlöf]The study, published in Science, found that wild insects pollinate crops more effectively than managed honeybees, leading to twice as much fruit set (flowers that develop into mature fruits or seeds).

Honeybees only add to the pollinating power of wild insects, and can’t replace their pollination services, the researchers also discovered.

Wild pollinators, including bees, flies, butterflies and beetles, usually live in natural or semi-natural habitats, such as the edges of forests, hedgerows or grasslands. As these habitats are lost, primarily owing to conversion to agriculture, the abundance and diversity of pollinators decline and crops receive fewer visits from wild insects.

Without steps to conserve wild species and protect their habitats, “the ongoing loss of wild insects is destined to compromise agricultural yields worldwide,” the authors conclude.

In a commentary article to be published alongside the research in Science, Prof Jason Tylianakis from the University of Canterbury writes that the study “challenges the validity of land-sparing conservation approaches, which advocate the protection of biodiversity only outside farmed areas, and the further intensification of agricultural land use.”

The SMC has rounded up the following expert commentary. Feel free to use these quotes directly in your reporting, or, if you would like contact details for further follow up, reach us on 04 499 5476 or smc@sciencemediacentre.co.nz

Dr Brad Howlett, Research Scientist, Plant & Food Research, was a co-author on the study. He comments:

“I contributed data on onion pollination in New Zealand. This shows that a wide variety of fly and bee species contribute to the pollination of this crop. In New Zealand, the flowers of many crops (eg Brassica, carrot, radish, kiwifruit) attract a wide range of insects other than honey bees. These can make a big contribution to their pollination (measured to be about 50% in Brassica rapa crops).

“There are currently no management procedures aimed at better utilising these insects. Therefore, there is a great opportunity to develop strategies to build and stabilise their populations. Increasing pollinator diversity within crops can lead to better yields because it increases the abundance of efficient pollinators that can be active under weather conditions that are less suitable to honeybees.” 

Prof Jason Tylianakis, School of Biological Sciences, University of Canterbury, comments:

“New Zealand’s economy is highly dependent on insect-pollinated crops such as kiwifruit, canola, apples, and clover, such that bees are estimated to be worth over $5 billion to the NZ economy each year. Currently this sector is highly dependent on managed honeybees, which clearly serve a purpose, but our reliance on that one species carries risks if they should fail due to threats like colony collapse disorder or the Varroa mite. In addition to providing risk management against the threat of such failures, wild bees can also contribute positively to the productivity of crops.

“This study by Garibaldi and colleagues, along with similar studies on single crops from different regions, suggests that diverse wild pollinators may enhance successful pollination (and crop yields) over and above the contribution of any single species such as the honey bee. This presents us with the opportunity to improve the yields of these important crops by managing our wild pollinators. Yet, there is a lack of research in New Zealand about how this can best be achieved. We need research to underpin policies that protect wild pollinators in the agricultural landscapes where they are most needed. As well as being a source of pride and enjoyment, New Zealand’s biodiversity is the very foundation of our economy.”

Dr David Pattemore, Research Scientist, Plant & Food Research, comments:

“Honeybees are relied on as the cornerstone of crop pollination in New Zealand, because hives can be easily managed and monitored. But that doesn’t necessarily mean that they are the most effective pollinator or that they are sufficient on their own

“Alternative pollinators can make significant contributions by promoting cross fertilisation and by supplementing the base pollination service contributed by honeybees.

“We believe the continued reliance on a single managed pollinator is not in the best interests of New Zealand Inc. We’re preparing a major proposal to develop methods to manage free-living bumblebee populations in orchard environments, enhance native pollinator populations, and manipulate pollinators to increase their effectiveness. The evidence from papers such as this one demonstrates that a more diversified approach to pollination will increase yields of higher quality fruit and seeds, thus leading to an economic gain for growers and New Zealand.”

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