Hedgerow and Grass Margin Stewardship Program
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.
For more information on the Hedgerow Program, read our Hedgerow Fact Sheet.
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
Importance of Hedgerows and Grass Margins
Biodiversity and agriculture are inextricably linked. Biodiversity is the basis of agriculture. Agriculture can also contribute to the conservation and sustainable use of biodiversity. Some specific examples of how biodiversity supports agriculture include crop pollination, pest control, disease regulation, soil fertility, nutrient cycling, and mitigation of soil erosion. Biodiversity can be seen as an insurance policy against abrupt changes and alterations to an agricultural system. The greater the biological diversity the more resilient the system.
Habitat loss is the greatest driver of biodiversity loss. One approach to mitigate this continued decrease in biodiversity is to enhance farmland with natural habitat (including hedgerows and grass/wildflower strips), which in addition to preserving biodiversity can also potentially improve a farm operation’s profitability.
Natural Habitat Increases Beneficial Insects
Increases in natural habitats leads to increases in abundance and diversity of beneficial insects.1-3 Beneficial insects include ladybugs, ground beetles, parasitoid wasps, syrphid flies and native bees. Beneficial insects support improved crop pollination and can reduce crop damage from pests, which can result in an increase in yields and profitability.4 One study out of central England found that converting 3-8% of farmland primarily along field edges to wildlife-friendly habitat resulted in no impact on overall yield and even increased some crop yields.5
Improved Crop Pollination
Wild pollinators are more effective at pollinating crops than managed honey bees on a bee per bee basis. For example, only 250 mason bees are needed to pollinate an acre of apples as opposed to 10-20,000 honey bees (1.5 to 2 hives).7 Native bees will forage in poorer conditions (i.e. wetter and cooler weather) over longer periods of the day. Bumble and other native bees perform buzz pollination, which is where the bee vibrates its flight muscles while on the flower resulting in a greater release of pollen. As a result, pollination by native bees can lead to better quality crops (larger and more abundant).
Research recently completed has found that wild pollinators are needed to reduce pollination deficits.8 A pollination deficit is the loss of potential crop yield as a result of suboptimal pollination. Yields for two common varieties of highbush blueberry in the Lower Mainland could potentially increase by 30% if this pollination deficit was eliminated. The study along with others went on to conclude that honey bees can’t replace wild bees but in fact the two complement each other when it comes to optimal crop pollination.6 In order to maximize yields for pollinator-dependent crops one would have to manage their farm for both wild and honey bees.
Biological Pest Control
In addition to supporting crop pollination, beneficial insects also support biological pest control.9,10 A review of 72 independent case studies found that “landscapes with higher proportions of semi-natural areas exhibited lower pest abundance and higher pest control in fields.”11 Multiple other studies have found that non-crop (natural) habitat support higher ratios of beneficials to pests compared to weedy field edges.12-15 Increases in beneficial insect populations have been found to spill over into adjacent farm fields and assist with reducing pest populations. For some of these studies, the impact of predatory insects on pest populations was significant enough to reduce the amount of insecticide applications required.16,17 That is that these predatory populations were able to reduce pests below the threshold where insecticide applications are typically required. Other studies have found that the more biologically diverse the agricultural landscape, in terms of field hedges and the larger landscape context, the more biological pest control one can expect to see.1,2
Increased Yields and Profitability
Hedgerows, grass margins and wildflower strips have been shown to increase farm profitability through improved crop pollination and reductions in needed insecticide applications. One study found that the costs of establishing a hedgerow can be recuperated within seven years and that every subsequent year resulted in increased profits.16 Another study examining perennial wildflower plantings adjacent to highbush blueberry fields found higher yields and associated revenue compared to control fields with no wildflower plantings.18 Costs of establishment and maintenance of these wildflower plantings were recuperated within four years.
Important Factors to Consider when Enhancing Field Margins
When planting hedgerows, grass and wildflower margins important things to consider include:19,20
• Perennial Flowering Species: Maximizing perennial flowering species is “often the single most important strategy to increasing abundance and diversity of beneficial insects.”19 Perennial species as opposed to annual/biennials once established persist and re-seed themselves for years.
• Season-long Bloom: Ensure that species selected for a hedgerow, margin, etc. provide a continual supply of flowers in order to provide a stable food source over the growing season.
• Native Plants: Species that are native to the environment are adapted to the local climate and often have lower water, nutrient and pest-control needs than non-native species. Native species have also been found to support higher numbers of beneficial insects compared to non-native species.
• Variety: Select at least 10 species of plants with varying flower sizes, shapes, and colors, as well as varying plant heights and growth habits.
• Avoid Nuisance Plants: Avoid species that are susceptible to disease, weeds and harboring pests. Selecting native plants, in most cases, alleviates this concern as pests often tend to prefer crops as opposed to native wild plant species.
• Nesting Resources: Approximately 70% of native bees are ground nesters and need access to bare soil surfaces as a result. The remaining 30% nest in old beetle tunnels of dead or dying trees. It is important to preserve dead plant material as opposed to removing it in order to provide ample habitat for certain species of native bees. Bumble bees nest in colonies in abandoned mouse holes and in bunches of grass, which is why it’s important to also consider including some species of grass.
Increasing biodiversity on farmland often results in many benefits including improved crop pollination and pest control among a long list of others. More and more research is showing that enhancing farmland with natural habitat doesn’t have to come at the expense of profitability.5,16,18 Increasing biodiversity on farmland when done right is a long-term investment in overall profitability and can act as an insurance policy against ever-increasing changing environmental conditions. Enhancing field margins with hedgerows and grass/wildflower strips is one approach to increasing biodiversity on farmland.
1 – Gardiner, M. M., D. A. Landis, C. Gratton, C. D. DiFonzo, M. O’Neal, J. M. Chacon, M. T. Wayo, N. P. Schmidt, E. E. Mueller, and G. E. Heimpel. 2009. Landscape diversity enhances biological control of an introduced crop pest in the north-central USA. Ecological Applications 19(1): 143-154.
2- Woltz, J. M., R. Isaacs, D. A. Landis. 2012. Landscape structure and habitat management differentially influence insect natural enemies in an agricultural landscape. Agriculture, Ecosystems, and Environment 152: 40-49.
3 – Walton, N. J. & R. Isaacs. 2011. Influence of native flowering plants on natural enemies and herbivores in adjacent blueberry fields. Environ. Entomo. 40(3): 697 – 705.
4 – Isaacs, R., J. Tuell, A. Fiedler, M. Gardiner, & D. Landis. 2009. Maximizing arthropod-mediated ecosystem services in agricultural landscapes- the role of native plants. Frontiers in Ecology and the Environment 7(4): 196-203.
5 – Pywell, R. F., M. S Heard, B. A. Woodcock, S. Hinsley, L. Ridding, M. Nowakowski, & J. M. Bullock. 2015. Wildlife-friendly farming increases crop yield: evidence for ecological intensification. Proc. R. Soc. B. 282: 20151840.
6 – Garibali et al. 2013. Wild Pollinators Enhance Fruit Set of Crops Regardless of Honey Bee Abundance. Science 339(6127): 1608-1611.
7 – Vaughan, M., J. Hopwood, E. Lee-Mader, M. Shepherd, C. Kremen, A. Stine, & S. H. Black. 2015. Farming for Bees – Guidelines for Providing Native Bee Habitat on Farms. Xerces Society for Invertebrate Conservation. Retrieved from https://www.xerces.org/wp-content/uploads/2008/11/farming_for_bees_guidelines_xerces_society.pdf
8 – 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.
9 – Altieri, M.A. (1999). The ecological role of biodiversity in agroecosystems. Agriculture, Ecosystems & Environment 74:19-31.
10 – Garratt, M.P.D., Senapathi, D., Coston, D.J., Mortimer, S.R., & Potts, S.G. (2017). The benefits of hedgerows for pollinators and natural enemies depends on hedge quality and landscape context. Agriculture, Ecosystems and Environment 247: 363-370.
11 – 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.
12 – Cibulova, J. & Henderson, D. (1998). Weed and Insect Surveys of Hedgerows, Setasides, Grass and Crop margins 1997. E.S. Cropconsult Ltd.
13 – 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
14 – 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
15 – 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.
16 – 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.
17 – Hopwood, J., E. Lee-Mader, L. Morandin, M. Vaughan, C. Kremen, J. K. Cruz, J. Eckberg, S. F. Jordan, K. Gill, T. Heidel-Baker, & S. Morris. 2016. Habitat Planning for Beneficial Insects – Guidelines for Conservation Biological Control. Xerces Society for Invertebrate Conservation. Retrieved from http://xerces.org/habitat-planning-for-beneficial-insects/
18 – 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.
19 – Hopwood, J., E. Lee-Mader, L. Morandin, M. Vaughan, C. Kremen, J. K. Cruz, J. Eckberg, S. F. Jordan, K. Gill, T. Heidel-Baker, & S. Morris. 2016. Habitat Planning for Beneficial Insects – Guidelines for Conservation Biological Control. Retrieved from: https://xerces.org/habitat-planning-for-beneficial-insects/
20 – Isaacs, R., J. Tuell, A. Fiedler, M. Gardiner, & D. Landis. 2009. Maximizing arthropod-mediated ecosystem services in agricultural landscapes- the role of native plants. Frontiers in Ecology and the Environment 7(4): 196-203.