Hedgerow and Grass Margin Stewardship Program

Hedgerows

Native trees and shrubs are planted on Delta farms through the Hedgerow Stewardship Program. These hedges provide year-round wildlife habitat along field edges. Over half of the bird species found on a typical piece of farmland can be attributed to hedgerows, even though the hedges may comprise only a small portion of the available habitat. Hedgerows provide a number of benefits, including:

  • Providing habitat for a diversity of songbird and raptor species
  • Acting as “insectories;” providing habitat for a host of beneficial insects, including pollinators like bumblebees and predators like lacewings
  • Creating microclimates conducive to improving field productivity; hedgerows act as wind barriers, preventing soil erosion
  • Creating shaded resting places for livestock
  • Providing nesting sites for Red-tailed Hawk and Bald Eagles in mature hedgerow trees like alder, cottonwood, and douglas fir.
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For more information on the Hedgerow Program, read our Hedgerow Fact Sheet.

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Grass Margins

The edges of farm fields can be planted with a mix of forage grasses through the Grass Margin Stewardship Program. These margins are beneficial to both wildlife and farming because they:

  • Provide habitat for small mammals, which are in turn preyed upon by raptors and wading birds
  • Provide nesting habitat for bumblebees
  • Provide refuges for beneficial insects, like predatory Carabidae beetles
  • Reduce the need for ditch cleaning by trapping sediment before it can run off of the field
  • Act as a buffer between organically-certified crop fields
Biodiversity

Over the past 25 years, Delta Farmland & Wildlife Trust has assisted in establishing 16 hedgerows throughout Delta totaling 6.7 km in length. Within an agricultural landscape, hedgerows provide year-round habitat for a suite of species, including birds and insects, and can have a major influence on biodiversity conservation.1 Preserving existing hedgerows and increasing the area of semi-natural habitat has been identified as one of the largest contributors to improving biodiversity on farmland.2 Biodiversity is the foundation of a healthy functioning ecosystem and is critical for the provision of ecological goods and services that are essential for human beings.3 Biodiversity contributes to things such as food security, human health, and clean air and water. Increasing biodiversity within agricultural landscapes can also improve crop yields and reduce pressures from crop pests.

Concerns

There are concerns when choosing to incorporate hedgerows on farmland, including: providing habitat for some crop pests; obstructing sunlight to sections of fields; reducing the area of land for agricultural production; and the costs associated with a new hedgerow planting that often surpass $10,000. However, between DF&WT’s Hedgerow Stewardship Program and recent research that found increases in crop yields from improved pollination due to the provision of semi-natural habitat, including hedgerows on farmland can benefit a farm operation’s bottom line.

Increased Crop Yields

Recent research out of Simon Fraser University shows that wild pollinators are needed to maximize yields in pollinator-dependent crops.4 Crops such as highbush blueberry in British Columbia could potentially increase by 30% if pollination was maximized. It was determined that producers have the potential to make an additional $7,800/ha for Duke and $18,400/ha for Bluecrop blueberries if pollination is maximized through wild pollinators. These findings are further supported by a study that assessed 41 different crop systems across the globe.5 The study found that “an increase in wild insect visitation enhanced fruit set by twice as much as an equivalent increase in honey bee visitation.” It went on to conclude that honey bees can only supplement, not substitute, for wild bee pollination. For cranberries and blueberries, another study conducted in the Fraser Valley found that bumble bee abundance has a greater influence on berry mass than honey bee abundance.6 This study’s results concluded that bumble bees are the most important pollinators for blueberries and cranberries. A study in Michigan showed that blueberry fields adjacent to wildflower plantings had a significantly higher percentage fruit set, berry weight, and mature seeds per berry resulting in higher yields.7 This increase in yields was sufficient to cover the cost of wildflower establishment and maintenance. For cranberries, bumblebees were found to collect pollen at a rate 1.4 times greater than honeybees.8 It was noted that “bumble bees are more likely to be more effective pollinators than honeybees.” In order to promote native pollinator populations, other studies found that “native bees respond positively to the abundance of wild flowering plants surrounding cranberry beds and highbush blueberry.”9

For field beans, self-pollination alone achieved 15% pod set compared to open pollination with wild pollinators which achieved 36% pod set.10 The result of open pollination with wild pollinators increased yields by 185%.

To increase crop pollination, year-round habitat is required to support abundant and diverse populations of wild pollinators.11 Planting biologically diverse native-plant hedgerows along farm field borders has been identified as an important component for increasing a suite of agriculturally important insect species.

Another common concern with hedgerows is that they have the potential to lure managed honey bees away from pollinating cash crops. As some research has shown greater abundance of managed honey bees in hedgerows than in unmanaged weedy field edges this concern is valid.12 The same study however, concluded that hedgerows act as net exporters of native bees into adjacent fields. As a growing body of research supports the importance of wild pollinators for reducing pollination deficits,4 the increased rate of crop pollination due to a higher abundance and diversity of wild pollinators as a result of the provision of hedgerow habitat may offset the increased concentration of managed honey bees in hedgerows.

Biological Pest Management

In addition to increased yields, hedgerow habitat on farmland has been shown to support biological pest management by acting as reservoirs for natural enemies of pests.13,14 A review of 24 different studies concluded that agricultural landscapes with increased complexity, i.e. hedgerows, grassy margins, etc. support higher populations of predatory insects.15 Other studies show that hedgerow habitat supports higher ratios of beneficial insects to pests than in weedy field edges.16-19 In another study assessing insects in tomato fields, “predatory lady beetles were more abundant and aphids were lower in fields with hedgerows, up to 200 m into fields[.]”19 The same study found that fields with hedgerows were less likely to reach threshold pest levels requiring insecticide application. In another review of 72 independent case studies, it was concluded that “landscapes with higher proportions of semi-natural areas exhibited lower pest abundance or higher pest control in fields.”20 Although hedgerows may provide habitat for pest populations, current research shows that these populations are often mitigated through concurrent increases in predatory and parasitoid populations.

Increased Profitability

Between increased pollination services and biological pest control, incorporating hedgerows into a farm operation can result in increased revenue due to higher yields for pollinator-dependent crops and decreased costs associated with reductions in required pesticide applications. For a 16-hectare canola field with hedgerows, greater pollination from wild pollinators resulted in a 21% increase in yields equating to a US$151/ha increase in profit.21 As well as a reduction in the average cost for aphid control from roughly US$25/ha for fields with no hedgerows to US$5/ha for fields with hedgerows.

Conclusion

As the costs to farm in a heavily urbanized region are exorbitantly high and the availability of land for production is at a premium, hedgerows for some operations may not be economically viable without some form of additional cost-share for the provision of ecological goods and services. However, for farms growing pollinator-dependent crops, perhaps the potential increase in yields and reduction in required insecticide applications may support the preservation of existing hedgerows or the establishment of new hedgerows. Although research evaluating the impacts of wild pollinators and beneficial insects on a farm operation’s profitability is still in its infancy, many studies completed to date support the notion that hedgerows are an investment that will pay-off over time. Preserving existing farmland hedgerows and/or establishing new biologically diverse hedgerows will not only significantly contribute to the conservation of biodiversity, but may also be an opportunity for improving a farm operation’s profits. If you’re interested in learning more or planting a hedgerow on your property, please contact DF&WT.

References

1 – Kremen, C., & M’Gonigle, L.K. (2015). Small-scale restoration in intensive agricultural landscapes supports more specialized and less mobile pollinator species. Journal of Applied Ecology 52: 602-610.

2 – Billeter, R., et al. (2008). Indicators for biodiversity in agricultural landscapes: a pan-European study. Journal of Applied Ecology 45: 141-150.

3 – UNEP (United Nations Environment Programme). (n.d.). Strategic Plan for Biodiversity 2011-2020 and the Aichi Targets. Retrieved from https://www.cbd.int/doc/strategic-plan/2011-2020/Aichi-Targets-EN.pdf

4 – Button, L. & Elle, E. (2014). Wild bumble bees reduce pollination deficits in a crop mostly visited by managed honey bees. Agric Ecosyst Environ 197:255–63

5 – Garibali et al. (2013). Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance. Science 339(6127): 1608-1611

6 – Ratti, C.M., Higo, H.A., Griswold, T.L., & Winston, M.L. (2008). Bumble bees influence berry size in commercial Vaccinium spp. Cultivation in British Columbia. Can. Entomol. 140: 348-363.

7 – Blaauw, B.R. & Isaacs, R. (2014). Flower plantings increase wild bee abundance and the pollination services provided to a pollination-dependent crop. J Appl Ecol 51: 890-98.

8 – Broussard, M., Rao, S., Stephen, W.P., & White, L. (2011). Native Bees, Honeybees, and Pollination in Oregon Cranberries. HortScience 46(6): 885-888.

9 – Loose, J.L., Drummond, F.A., Stubbs, C., & Woods, S. (2005). Conservation and Management of Native Bees in Cranberry. Maine Agricultural and Forest Experiment Station Technical Bulletin 191.

10 – Nayak, G.K., Roberts, S.P.M., Garratt, M., Breeze, T.D., Tscheulin, T., Harrison-Cripps, J., Vogiatzakis, I.N., Stirpe, M.T., & Potts, S.G. (2015). Interactive effect of floral abundance and semi-natural habitats on pollinators in field beans (Vicia faba). Agriculture, Ecosytems & Environment 199: 58-66.

11 – M’Gonigle, L.K., Ponisio, L.C., Cutler, K., & Kremen, C. (2015). Habitat restoration promotes pollinator persistence and colonization in intensely managed agriculture. Ecological Applications 25(6): 1557-1565.

12 – Morandin, L.A., & Kremen, C. (2013). Hedgerow restoration promotes pollinator populations and exports native bees to adjacent fields. Ecological Applications 23(4): 829-839

13 – Altieri, M.A. (1999). The ecological role of biodiversity in agroecosystems. Agriculture, Ecosystems & Environment 74:19-31.

14 – Garratt, M.P.D., Senapathi, D., Coston, D.J., Mortimer, S.R., & Potts, S.G. (2017). Agriculture, Ecosystems and Environment 247: 363-370.

15 – Bianchi, F.J.J.A., Booij, C.J.H., & Tscharntke, T. (2006). Sustainable pest regulation in agricultural landscapes: a review on landscape composition, biodiversity and natural pest control. Proc Biol Sci 273(1595): 1715-1727.

16 – Cibulova, J. & Henderson, D. (1998). Weed and Insect Surveys of Hedgerows, Setasides, Grass and Crop margins 1997. E.S. Cropconsult Ltd.

17 – Gareau, T.L.P, Letourneau, D.K., Shennan, C. (2013). Relative densities of natural enemy and pest insects within California hedgerows. Environmental Entomology 42(4): 688-702

18 – Morandin, L., Long, R.F, Pease, C., & Kremen, C. (2011). Hedgerows enhance beneficial insects on farms in California’s Central Valley. California Agriculture 65(4): 197-201

19 – Morandin, L.A., Long, R.F., & Kremen, C. (2014). Hedgerows enhance beneficial insects on adjacent tomato fields in an intensive agricultural landscape. Agriculture, Ecosystems & Environment 189: 164-170.

20 – Veres, A., Petit, S., Conord, C., & Lavigne, C. (2011). Does landscape composition affect pest abundance and their control by natural enemies? A review. Agriculture, Ecosystems and Environment 166: 110-117.

21 – Morandin, L.A., Long, R.F., & Kremen, C. (2016). Pest control and pollination cost-benefit analysis of hedgerow restoration in a simplified agricultural landscape. Journal of Economic Entomology 109(3): 1020-1027.