Agroforestry is an intensive land management system that integrates the benefits from biological interactions created when trees or shrubs are intentionally grown with crops or livestock. Agroforestry differs from traditional forestry and agriculture by its focus on the interactions among components rather than the components alone.
In Canada, agroforestry systems are classified according to descriptions adopted by the Association for Temperate Agroforestry: integrated riparian systems, intercropping, windbreaks (shelterbelts), forest farming, and silvopastoral systems. In addition, bioenergy systems - the production of heat or electricity from woody biomass - are currently being explored for their compatibility with mainstream agroforestry practices.
Widespread agricultural settlement on the Prairies accompanied the expansion of the railroads west in the early 1880s. Many settlers of the treeless plains strongly felt the need for shelter and tree planting began in the 1890s for farmyard protection. Settlers who arrived from the Ukraine and the steppes of Russia brought with them a thorough understanding of the need for trees to protect crops and soils. Shelterbelt networks on the Prairies date back to their initiatives in the early 1900s.
In 1903, the Government of Canada created a Dominion Forest Nursery Station at Indian Head, Saskatchewan (then the North West Territories) to supply tree seedlings to meet the needs of the new farmers. In the 1930s, the combination of drought, Economic Depression, and soil erosion led the Government to pass the Prairie Farm Rehabilitation Act of 1935. Field shelterbelt planting efforts were greatly increased as a result, including extensive networks near Lyleton, Manitoba, Conquest, Sask, and Aneroid, Sask.
Since that time, municipal, provincial, watershed, and environmental organizations have supported programs of tree planting and care. Agriculture and Agri-Food Canada continues to conduct agroforestry research and programming on the prairies. Its Agri-Environment Services Branch promotes appropriate agroforestry measures throughout Canada.
Currently windbreaks represent the most accepted and widespread agroforestry system in Québec. Windbreaks can be designed to protect farmyards from drifting snow, to retain an even snowpack in fields to protect the soil, or to reduce wind erosion when fields are bare in spring and fall. Windbreaks also buffer daily temperature extremes and reduce evapotranspiration rates. With approximately 4000 hog farms in Québec producing 7 million hogs each year, shelterbelts have a useful role in reducing odours as well as reducing the heating costs of livestock buildings. Riparian tree planting to help stabilize banks and to intercept agricultural nutrients from entering waterways is currently underway in several regions of Ontario and Québec.
While all types of agroforestry systems have been extensively researched in southern Ontario, there has been an emphasis on tree-based intercropping (TBI) systems. Since 2004, federal and provincial funding agencies have supported such research in Québec. TBI systems, which consist of widely spaced tree rows with annual alley crops, are multifunctional and provide landowners with a large range of economic and environmental benefits.
When successfully applied, TBI system components maximize resource utilization while maintaining complementary interactions, such as nutrient cycling, enhanced soil C sequestration, moisture retention, increased micro and macro faunal diversity, biodiversity and lower soil temperature. When these occur, productivity per unit of land area is enhanced, resulting in higher economic returns. Research in Québec demonstrated that monocultures of each component would require between 1.5 to 2.3 times more land to obtain equivalent yields of a TBI system. Research indicates that TBI has potential to address important environmental problems (eg, groundwater pollution, degradation of soil quality, loss of biodiversity) while producing high-quality timber products, to supply Québec's furniture and wood cabinet industry, for example. If applied on a large scale, TBI would contribute to climate change mitigation through carbon sequestration and greenhouse gas emission reductions. The tangible benefits from eco-biological processes, along with combined yields of the trees and crops, place this land use practice above conventional agriculture in terms of long-term overall productivity.
The Atlantic Region
Windbreaks occur throughout the agricultural areas of the Atlantic region as either natural or planted hedgerows. Given the strong seasonal winds, coupled with soils that are naturally low in organic matter, and with low residues left by Potatoes or other crops, hedgerows have been valuable for wind erosion protection. Whereas past agricultural development programs supported the removal of trees to encourage modernization and mechanization of large-scale crop production, programs of today encourage planting and hedgerow maintenance in recognition of their value on the landscape.
Hedgerows have special value in blueberry production systems, where forests are cleared to allow the blueberries to flourish on the acidic soils of the forest understory. When blueberry fields are made too large, production declines because of insufficient habitat for native Bees and other pollinators. Incorporating narrow forested strips of mixed species provides food, habitat and shelter for native pollinators and, at the same time, provides a microclimate within which they can do their work efficiently.
Awareness of risks from agricultural runoff on water quality and public safety has led to an emphasis on careful riparian management in the Atlantic region. Water erosion is also costly to producers in terms of lost soil and crop inputs. Fish, shellfish and other valuable marine life may be affected, impacting the region's commercial and sport fisheries. In New Brunswick and Prince Edward Island, where intensive potato production has contaminated watercourses by sediments, nutrients, and pesticides, especially on sloping fields, riparian buffers are encouraged through education, programs, and legislation. Establishment and maintenance of riparian buffers is a focal area of agroforestry in the Atlantic region, including fostering the natural regeneration of native trees and shrubs.
There is a growing interest in generating renewable energy (see Biomass Energy) on the farm, as the price of fossil fuels continues to increase or fluctuate. Woody biomass may represent a farm energy alternative and an income generator. As practised in northern Europe, biomass can be produced as a field crop from fast-growing species, such as willows. Or, trees and shrubs used in riparian buffers can be harvested to yield biomass in addition to the environmental benefits of anchoring the soil with a permanent cover.
Several non-timber forest products generate significant income in the Atlantic region. Maple Syrup production, mostly in New Brunswick, is foremost among these, but other products contributing to forest farming incomes include: wild Fiddleheads (young fern shoots as a green vegetable); Canada Yew (Taxus canadensis); wild mushrooms; and conifer boughs for Christmas wreaths.
Several factors have converged to increase interest in agroforestry in British Columbia in recent years: the introduction of grazing as a silvicultural management tool; the economic diversification opportunities from managed woodlots; and the landscapes altered by the mountain pine beetle (Dendroctonus ponderosae) epidemic that affected 17.5 million hectares of mature lodgepole pine (Pinus contorta) interior forest. Producers, resource managers, and researchers are actively seeking alternatives that will complement and supplement conventional production systems as well as diversify local economies. The interest in agroforestry systems is based on conservation and environmental concerns and agroforestry's potential for a "triple-bottom-line" of economic, environmental, and social dividends.
Agroforestry and Sustainability
With increasing demand for sustainable agricultural practices and the need for a local, viable agriculture industry, interest in agroforestry approaches is growing. Integrated Resource Management demonstration projects are being undertaken to attempt a balance of environmental and socio-economic outcomes on agricultural lands. Projects encompass the harvest of: high-value hardwoods within riparian buffers; hawthorn from riparian areas for natural health products; and native shrubs for floral markets while restoring watercourse habitats. Similar field production models are being tested using alley cropping (TBI) systems to yield multiple, sustainable, high-value niche market commodities.