Increasing habitat for Pollinators
Native Pollinators and Agriculture in Canada , published by Agriculture and Agri-Food Canada (AAFC) in 2014, is the first general guide to wild pollinators in Canada, their importance to agriculture and what we can do to keep them.
Mark Wonneck, an ecologist with AAFC and lead author in the booklet says, “Producers were asking for information. There was interest from producers who would directly benefit from the pollination service wild bees provide, but also from producers just interested in the environment they are living in. Extension people were getting questions from their clients. At the time there was not much information specific to Canadian agriculture so I began to cobble together a starter kit.”
Wonneck’s initial interest in pollinators was spurred by research done in canola in northern Alberta by Dr. Lora Morandin. For her PhD she modelled improved yield in canola with increased native bee populations, which she then correlated with increased native habitat.
Wonneck says his research found as you went further into the canola fields there was a drop off in bee numbers. This makes sense when you think about the fact that bees centre their activities around where they have established their nests. Some are solitary. Some make hives like honey bees but much smaller. The majority nest in the soil.
“Crop fields are not conducive to nesting, so bees tend to nest in field margins or other uncropped areas, and rangelands. Bigger bees (like bumble bees) forage farther, maybe a kilometer or so from their nests. Smaller bees don’t go that far, ranging from 50 m to 400 m, depending on their size. So because of its distance from nesting habitat, there are fewer bees in the centre of the field,” says Wonneck.
“Canola is largely self-pollinating,” says Wonneck, “but bees enhance pollination to a degree, depending on environmental conditions. Canola pollen is quite heavy, so if it’s windy there will be good self-pollination. But if it’s calm and hot the flowers dry up more quickly and the chance for self-pollination is lower. In those conditions the bees are more valuable to canola seed set. They also contribute to uniform and early pod setting.” Native bees provide important pollination services to other field crops, like sunflower, and in forage seed production.
Wonneck points out the nature of the pollinator benefit in grassland is more indirect, having more to do with the health of the ecosystem rather than the production of a particular grass species. “In any system there are lots and lots of critters that support lots of ecosystem services,” says Wonneck.
The rangeland system is subtle; it’s a complex web of interacting parts. These parts depend on each other. Wonneck points out good range managers intuitively understand that and focus on the whole system and keeping the grassland healthy.
“In general, you can increase grassland resilience by increasing biological diversity (for example, having more different kinds of species present) and the redundancy of the functions they provide (having many species providing similar functions, such as pollination or pest suppression). If one part gets damaged there are alternatives. So a robust pollinator community supports the overall resilience of the grassland. You are going to be much better off not to rely on just one egg in the basket,” says Wonneck.
The secret lives of pollinators is well described in the Native Pollinators and Agriculture in Canada booklet http://publications.gc.ca/site/eng/461538/publication.html . There are three broad areas to consider in protecting pollinators and enhancing their habitat. 1. Save what you’ve got. 2. Create new habitat. 3. Manage to benefit pollinators.
If you have native range or naturalized areas those are the areas you want to protect from cultivation, disturbance or toxic substances. Bees and other pollinators need to have access to flowers and nesting sites. Most are ground nesters so need access to undisturbed soil. They will dig nests in soil, nest in cavities under rocks and grass tussocks, and in old rodent burrows. About 70 per cent of native bees are soil nesters and 90 per cent are solitary.
If you are considering creating habitat for pollinators, the booklet goes into detail for the three main considerations: site(s) selection, habitat design and planting and establishment. The maximum distance the bees would have to travel to reach the most distant crop flowers should be no more than about 150 m. So you should try to keep field sizes where you grow pollinator-dependent crops no more than 300 m wide and make sure the field margins provide pollinator habitat.
Increasing habitat could mean deliberately planting up to 25 different annual grazing species as does Gabe Brown, a producer from Bismark, North Dakota. He says healthy soil needs a diverse plant mix and so do the pollinators. He deliberately chooses to add flowering species the cattle might not graze because he wanted the pollinators and the predator insects like lady beetles.
AAFC scientists Dr. Alan Iwaasa and Dr. Mike Schellenberg, at the Swift Current Research and Development Centre, are researching how to manage your grazing in native grass pastures as well as a means to encourage native legumes such as purple or white prairie clover usage which increase grazing productivity, biodiversity and are pollinator magnets.
“Protecting bees and their habitat from products like pesticides designed to kill invertebrates is important. Bees get up later in the morning; they are usually not active until temperatures of at least 8-10C, and when temps cool off later in the day they tend to go back to their nest,” says Wonneck. Most producers like to spray very early in the morning when it is calm and that’s when it’s also cool so that will decrease the opportunity for bee-pesticide interaction. Producers also watch to make sure there is minimal drift.
There is increasing interest in pollinators and more and research is being conducted. Megan Evans worked for Wonneck looking at pollinators, native grassland, and canola yield before she started a Masters’ program at the University of Calgary. Her study was looking at the smaller scale effects of grazing and larger effects of landscape composition on pollinators in rough fescue along the foothills from Cochrane to the Oldman River.
“First we did range health assessments on all sites to compare more heavily grazed to more lightly grazed areas. We netted bees, counted flowers and set out pan traps which are filled with soapy water and collected all kinds of flying bugs,” says Evans.
“Identifying bees is tough,” says Evans. “Bumble bees are difficult but the solitary bees are really hard. There are about 300 species in Alberta. We have about 30 species of bumble bees here. Honey bees are non-native and just one species. They are generally smaller, narrower and less hairy than a bumble bee. Bumble bees look big and kind of fuzzy. It’s only just two years ago that Bumble Bees of North America was published with a key to identifying bumble bees in western Canada.“
Evans was trying to determine what effect grazing had on native bee populations in an ideal habitat of native prairie and naturalized areas. While she didn’t find that grazing pressure directly affected bee abundance or diversity, she did find that specialist species were more greatly affected by grazing than generalist species, suggesting that grazing impacts on native pollinator communities are complex.
“We know bees are important. We know they are important in rangelands as part of our natural ecosystems. But overall we don’t really know that much about our native bees or how well their populations are doing,” says Evans.
by Peg Strankman