Last spring, I spent quite a bit of time wading my way through chest high canola, sampling insects in the quest of determining if on farm biodiversity pays off.
Most people know that pollinators are important in food production. The bee pollinates a flower and the flower forms into a fruit, encapsulating seed. The humble bee, an expert pollinator, delivers an ecosystem service that is estimated to be worth US$577 billion* globally. What is less understood is how farm design can encourage or inhibit pollinators like bees from delivering their services. This spring I took to the paddock to determine if any correlation exists between pollinators, on-farm biodiversity and the bottom line.
If you think about it, if you see more bees, you would expect more pollination and could therefore expect more production. In 2005, two researchers undertook a study in the Western Australian wheatbelt to determine if yield productivity in canola was enhanced through insect pollination. Their findings backup up previous research conducted in Canada which determined a strong correlation between canola crop seed set, yield and the abundance of bumble bees (European bees). However, the Aussie researchers put a figure on it. Their figures determined a yield increase over 20% with pollinators present. They also found that as distance from the bee hives increased the pollinator activity decreased, therefore yield declined with distance from the bee’s home.
Both these studies focused on the European bee, which is the most identifiable and abundant insect that we think of when it comes to pollination. However, a further study in southern NSW in 2012 specifically considered the correlation between some of the 3000-estimated species of Australian native bees and distance from remnant vegetation. Again, researchers found a relationship between insect abundance and distance to areas of native vegetation.
So, what does it matter? In modern agriculture, our highly modified landscapes and broadacre monoculture cropping may reduce the occurrence and useful proximity of refuge areas for pollinators. The further away from fallen logs, tree hollows, flowers and grasses, the less pollinating mini beasts we are likely to find.
In the mid north of South Australia, broadacre cropping systems are mainly monocultures, relying on external inputs to improve fertility and control pests and diseases. Typical crop rotations in this
region incorporate canola, pulses and lucerne which can benefit from insect pollination. Also, cropping in the area, exists in a modified landscape where the remaining native vegetation is fragmented and mainly confined to isolated pockets, linear roadsides and riverine buffer strips.
Pollinators need habitat, food sources and shelter. Areas of native vegetation, flowering plants, non-tilled soil, fallen timber, tree hollows make good habitat for native and European bees.
While transacting canola crops with a sweep net for 6-weeks, I concluded a positive relationship between proximity to native vegetation buffers and number of insects found, most common of which was the European bee. Also, interestingly, the closer to areas of natural habitat, the more diversity in the insect species i.e. more species, flies, spiders, dragonflies, native bees etc.
Although there are questions still to answer, including homing range of beneficial insects, seed size and impacts of pesticide use, we do know that proximity to habitat refuge increases pollination and therefore yield potential of flowering crops like canola. By establishing native vegetation buffer strips among crops, paddock trees and increasing the diversity of plants in these areas, we can assist in providing a year-round food source for insects, encouraging pollinators to persist there and increasing potential for pollination and yield increases.
To further add to the argument, here in Australia with our sea borders and well-resourced biosecurity systems we have so far remained free of the parasitic varroa mite which has devastated European bee populations worldwide. It is not a matter of if the varroa mite will reach Australia, but when. With a potential pollination disaster looming, it might be time to look at those isolated paddock trees, fallen logs and scrubby roadsides with renewed respect.
*IPBES – Intergovernmental Science-Policy Platforms – Biodiversity and Ecosystem Services (2016)