Intensive farming hurts native bees, study says

Native bees struggle in areas of intensive farming practices.
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Native bees struggle in areas of intensive farming practices.

Intensive farming is bad news for native bees, a first-of-its-kind Kiwi study has found.

Native bee populations declined by 90 per cent, and some species disappeared completely, in areas of intensive farming.

Exotic pollinator species, however, flourished in intensive farming areas – with populations increasing by 150 per cent.

The experiment included planting plots of flowers in farm land.
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The experiment included planting plots of flowers in farm land.

And although the study's lead author, University of Auckland's Jamie Stavert, said intensive agriculture was unlikely to cause any native bee extinctions any time soon, it could cause "large declines in the abundance of the species".

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The university research team conducted the study by planting fields of flowering plants in areas with intensive and non-intensive agriculture in the surrounding landscape. 

New Zealand bees, such as the one featured here, are highly specialised at pollinating native plants.
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New Zealand bees, such as the one featured here, are highly specialised at pollinating native plants.

They then collected and identified insects visiting the flowers at each site to measure the abundance of different pollinator species.

​Exotic pollinators such as honeybees, hoverflies and blowflies thrived in the farming intensive sites, whereas native bee populations dived and were sometimes not found at all. 

By contrast, native bees were very common at low-intensity sites.

Native bee numbers were counted and compared to exotic pollinator species.
BRIAN CUTTING

Native bee numbers were counted and compared to exotic pollinator species.

"This has important implications because native bees play a vital role as pollinators of many native plant species and crops in New Zealand," Stavert said.

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"They are super important pollinators in native ecosystems, and also in agricultural and horticultural systems. They are super effective, they deposit lots of pollen."

He said this was because the native bees and plants evolved or "grew up" together. 

"They have this specialised relationship with our native plants, if we lose these native bees we can't replace that."

As to why they struggled in areas of intensive farming, Stavert suggest it was because native bees nest underground in natural, unmodified soil and only forage for food within a short distance from the nest: "so they are vulnerable to intensive farming".

Exotic pollinators, however, have no central nest site and can readily use resources like cow manure in intensive agricultural areas.

"The exotic honeybee is an important crop pollinator and no-one disputes that," Stavert said.

"But they are also vulnerable to disease and we cannot become too reliant on one species for pollination. We need a wide range of pollinators to do the job."

- The study was published in Proceedings of the Royal Society B: Biological Sciences on Wednesday.

 - Stuff

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