Canola growers like what happens when they enlist hives of honeybees to help tend their crops.
According to figures presented to the Manitoba Agronomist Conference earlier this winter by Melanie Dubois of Agriculture and Agri-Food Canada, pollination increases production by as much as 46 per cent. And the quality of the seed set is significantly improved.
Many of the plants we depend on need pollinators to be productive, but which crops require which pollinators can vary a lot.
“Different crops have different dependencies on insect pollination,” Dubois says. “Often we bring in managed bees. Honeybees and leaf cutter bees are familiar to most producers.”
Here’s where we’re benefiting from an ancient bargain struck between bees and flowering plants when they first appeared almost 100 million years ago. We think bees descended from predatory wasps that developed a vegetarian taste for pollen. Flowering plants found, for a small loss of pollen, they could get the bees to take it from flower to flower, ensuring properly fertilized and genetically diverse seeds.
In exchange, the bees could make a good living collecting protein-rich pollen to eat and to feed their young. Some plants even sweetened the pot by giving the bee a shot of sugary nectar as a reward for service and to encourage them to visit other flowers of its kind. It’s a very reliable and much more precise delivery system than the random gusts of wind that carry pollen for the grass species.
Consequently, the world now sports a dazzling array of flowering broadleaf plants, with around 20,000 different bee species to service them. Over the last few millennia we’ve chosen 124 of these plants as our most important food crops and a full 70 per cent of them still require bees to pollinate them or they won’t produce. While the European honeybee provides a huge industry with canola pollination and honey production, there are a lot of wild bees working away out there and now we’re finding out just how important they are.
“Honeybees actually aren’t that great at pollinating certain crops,” Dubois says. “When you’re looking at wild bees you’re looking at a better pollinator by a factor of about 1.4 to 3.2 and that becomes important when your margins are getting thinner and thinner.”
Manitoba farmers know they have a lot of unsung helpers out working their fields but they may not know the scope of it. Manitoba has about 350 different species of wild bees ranging in size from the tiny sweat bees, about as big as a wheat kernel, to the large and familiar bumblebees we see visiting the blossoms from April to September every year.
Since there are so many different types of plants and such a variety of flowers, wild bees are vital to plant health and crop profitability. The honeybee certainly has its place but it can’t do everything. With the variety of flowering plants we grow we can’t cast the honeybee as a “one-size-fits-all” pollinator.
“Which makes sense,” Dubois says. “A honeybee is one species of bee. How can you possibly replace the efficiency of an entire suite of 350 different types of bee? They perform differently at different times of the year throughout the blooming time when you need them for different types of crops.”
Bumblebees have an odd talent that makes them ecologically indispensable. They buzz pollinate. If you’ve ever watched a bumblebee at work you can hear it making a strange, high-pitched whine as it collects the pollen and it does this by disengaging the wings from the flight muscle. Once the drive train is in neutral it revs the engine and uses the vibrations to shake the pollen out of the anther.
Some flowers produce their pollen in a long, thin, tubular anther and sonication, as it’s sometimes called, is the only way to get it out. It’s like slapping that old glass ketchup bottle. This is vital if you’re growing blueberries or cranberries or if you’re growing greenhouse tomatoes. All of them require buzz pollination.
Blueberry farmers find that once the bumblebees have gone to work, other bees can pick up surplus pollen and move it around but the bumblebees are the front line. Honeybees may be ideal for canola and leaf cutters work for alfalfa but this shows how agriculture depends on other pollinators and why we should be protecting them.
“There have been studies looking at the different systems of agriculture and how vulnerable they are to the loss of pollinators,” Dubois said. “Canada and the U.S. were lumped together and tied for about fourth out of 16 of the systems they looked at. That illustrates just how vulnerable we could be.”
The bad news is that wild bee populations are dropping due to several factors including pesticides and climate change. One of the bigger ones is habitat loss. We often think of bees as social insects because we know honeybees but most bees live very different lives. Over 80 per cent of our native bees are solitary ground nesters. They find a suitable place to build a small nest and raise their broods there. One of the requirements is undisturbed soil.
“Tillage has an extreme impact on our ground-nesting bees,” Dubois says. “About 20 per cent of our bees are wood nesting so they go on stems or on punky wood. Bumblebees account for about 24 species and they live in abandoned mouse holes, tussocky grass and things like that.”
Bees with broods are nest-centric. They go foraging for pollen and nectar but they must return to the nest where their brood lives. Consequently they need lots of food nearby. For instance, to feed one larva from hatching to maturity a leaf cutter bee takes about 1,000 trips. If she’s in a canola or alfalfa field then there are a few weeks of plenty but once the blossoms fall they need to find something else. In a native meadow there’s always something blooming so there’s always something to collect and eat.
Additionally, they may not be able to fly too far because range is dependent on their size. Some of the larger bees will travel up to 1,000 metres. The smaller ones may only go as far as 50 and each journey has its risks. There are predators out there or they may get caught in wind gusts.
“So that’s when natural areas become really important,” Dubois says. “If you have an insect-dependent crop, you’re going to want those bees to survive through your rotations. You need the bees to be there when you plant it.”
A lot of farms have a trailer in the yard or an older house for hired labour. Some of the bigger vegetable operations may even have a bunkhouse.
It’s cost effective to gather your seasonal workers close to the operation so they’re on the site when you need them. The same is true for pollinators. Setting them up with proper habitat is good business.
“What they’re finding is that it’s cheaper to increase your native areas to support your wild bees than to import honeybees simply because of the pollination efficiency,” Dubois said. “The amount of suitable habitat is the main driver of pollination potential in these agro-ecosystems so without the habitat you’re not going to have bees. That’s really the simplest way I can put it.”
The big question is, how much land should be devoted to habitat? Studies show that for every one per cent of crop area converted to habitat, there is a 1.1 per cent increase in yield over the remaining land. A five-year study out of the University of Calgary looked at 240,000 sq. kms of land and found there is a small increase in production when farms are associated with complex landscapes, things like shrub lands and potholes. They wanted to see if a variance in yield could be explained by the landscape and by the pollinators. They found there was a positive influence.
“It was small, you’re looking at three to four per cent, but what was also important is that they didn’t see negative association to crop yield with these more natural areas,” Dubois said. “And when we’re trying to promote retention of semi-natural vegetation for carbon sequestration, biodiversity refugia or erosion control we really want to make sure these areas aren’t having any negative impact disproportionate to their size on the landscape.”
No one is suggesting that farmers take any of their prime land out of production. Instead they could look at marginal land close by, such as shelterbelts, ditches or any kind of scrub land, meadow or pasture.
Dubois says Environment Canada is developing a pollinator potential index, an inventory for better overall land use, to go with farmland. It looks at pesticide use, tillage and other farming practices that may affect the local pollinators. Then it produces a map that outlines how best to use the land to satisfy both requirements.
“We can use these habitat maps to guide us, to tell us we have crops that need pollinators but the potential is low,” she said. “We’ll look at landscape-scale vegetation and then we’ll look at the natural areas, what type of forage is available, what nesting habitat is available and look at management practices. We can target that area for habitat installation and management so that we can actually grow the crops we need.”
It’s a way to have the best of both worlds. Farms need to be productive and they need bees. Bees, on the other hand need stable, healthy habitat that they can’t find in a farm field. Having both these things can keep land profitable while maintaining certain wild characteristics for the sake of ecological stability. It can be a fine balance but an important one. Losing our pollinators could have dire consequences.
“We have seen this happen, though, around the globe,” Dubois said. “There are some provinces in China where they’ve lost all their pollinators so they hand pollinate their fruit crops. If we were in a state where we had to hand pollinate our crops, it wouldn’t really work out well for the crops we’re dependent upon.”