Agroforestry is an agricultural methodology that optimizes production by exploiting the benefits of interspecies interactions. By deliberately combining trees, shrubs, perennials, annuals, or livestock, a grower can enhance their farm economically, ecologically, and environmentally. In juxtaposition to popular monocultural farming practices, agroforestry reestablishes the complexity of time, place, and biodiversity that plants experience in the wild. From a sustainability perspective, it can serve as a bridge between natural resource management and agriculture, in a world that is in dire need of a better relationship between the two.
Agroforestry can be divided into several categories: Riparian Vegetative Buffer Strips, Intercropping, Sivopastoral, Windbreaks, and Forest Farming. Each represents a different circumstance in which agroforestry can provide benefit, ultimately with the same symbiosis methods at their core.
Riparian Vegetative Buffer Strip Systems are the establishment of agroforestry plantings along stream and riverbanks to protect aquatic habitats and reduce nonpoint source pollution in waterways.
Intercropping Systems are the planting of widely spaced trees with conventional crop rows in between allowing for diversified farm income, the abatement of soil erosion, mitigation of nutrient loading, and the protection of watersheds.
Silvopastoral Systems are the combination of trees and livestock as a means of maximizing the land for economic, wildlife habitat, fire protection, and forest management benefits.
Windbreak Systems are the simple and more commonly seen practices of today. Windbreaks are plantings around the perimeter of a field used to protect and enhance the production of crops and animals while creating environmentally more stable microclimates.
Forest Farming is the development of microenvironments resembling natural forest stands that look to mimic nature throughout a farm. Forest Farming develops suitable environments for growing specialty crops within its shaded settings.
Agroforestry offers a wide variety of both localized and macro benefits for the farm and the greater landscape. On a macro level, Agroforestry practices can increase productivity during successional changes, decrease weed competition, increase internal regulation, increase biological regulation of insect pest, increase solar radiation usage efficiency, increase soil organic matter, increase biodiversity, decrease agriculturally derived contaminants in riparian zones, decrease wind and water erosion, increase the uptake and fixation of carbon dioxide from the atmosphere, and increase the retention of nutrients in soils.
For the farmer, Agroforestry offers a variety of crop production benefits. Foremost are the benefits of wind damage protection. The creation of woody corridors traps windborne particles and slows windspeeds across sites. Small seeded, shallow sown, and newly emergent crops are particularly susceptible to wind and sandblast damage. Additionally, orchard fruit crops are often compromised from wind as well – which can cause the desiccation of petals and pollen loss as well as fruit drop, bruising, and scaring. Further, research indicates that livestock also benefit from the wind protection, with studies indicating that feed needs are decreased by up to 20% by offsetting the cold wind temperatures. Similar studies indicate benefits to livestock such as decreased newborn losses, increased cattle weight gain, and increased milk production as well.
Agroforestry offers erosion mitigation benefits as well in the form of wind and water erosion protection. It is estimated that conventional monocultural farming practices can result in the loss of five tons of soil per year per acre. A problem that agroforestry practices greatly eliminate. By retaining soil organic matter, farmers can greatly reduce or even eliminate their need for commercial fertilizer.
When using commercial fertilizers, Agroforestry practices can greatly resolve the problems of nutrient runoff. Riparian Vegetative Buffer Strips were found to greatly decrease negative externalities from farms, in particular. Forested Vegetative Buffer Strips 90 to 150 feet wide were found to reduce ground water nitrogen content by 68% to 100% and surface water runoff nitrogen by 78% to 98%. Further, Forested Vegetative Buffer Strips are able to reduce phosphorous concentrations in surface water by 50% to 85%. This runoff, when allowed to reach water bodies can have devastating ecological effects, causing life choking algae blooms in its extreme circumstances. Further, the preservation of soil health improves the quantity and quality of the soil microbiome. These resident bacterial and fungi are critical for making nutrients available to plants.
Agroforestry offers other water benefits as well. Locally, Agroforestry practices can increase soil porosity, reduce runoff loss, and increase soil coverage, which leads to higher water infiltration and retention in the soils. This is of particular benefit in drier climates and drought conditions for reducing soil moisture stress on crops. Further, through a process called hydraulic lift, trees with deep roots redistribute deep soil water supplies to higher strata, where other crop root zones can have access during drought.
Agroforestry practices reduce sedimentation in reservoirs as well. Conventional farming results in unnaturally high sedimentation. By mitigating this, reservoir life spans can be extended at a national savings of $200 million.
Additionally, woody corridors have the added benefit, in winter, of increasing water availability through snow capture. This snow capture is also important as insulation preventing winter kill of more sensitive perennial crops.
Agroforestry practices overall act as valuable climate modulators. These forested settings better moderate against extreme temperature fluctuations that can be very destructive to crops. Agroforestry farms have higher humidity, soil moisture, nighttime CO2 levels, and lower nighttime air temperatures compared to their conventional monoculture counterparts. These regulatory effects were found to increase crop productivity 10% to 25% in dry climates.
It is estimated that 18% of all crop loss is the world is due to insect pests. As global warming progresses, this problem is likely only to get worse. Agroforestry practices can impact the pest mitigation aspects of farming in a variety of ways. Through the creation of woody habitat for birds and bats, these spaces can increase the presence of the predators that prey on insect pest in the fields. Though this won’t eliminate pests in their entirety, it helps to keep populations under control.
Additionally, these wooded spaces provide the habitat needed for beneficial insects as well such as arthropod predators and parasitoids who further suppress pest insect populations. These spaces offer stable habitats for reproduction, overwintering, and refuge free from the from perturbations of conventional farming practices. Additionally, reducing wind through farms can also significantly help beneficial insects find and consuming pests. It is estimated that the wind barriers that agroforestry practices provide can improve crop pest reduction by beneficial insects up to 40%. Lastly, Agroforestry practices reduce visibility for pests, decreasing the chances of epidemic by making pests that target a single species less prolific. Overall, these predatory species serve a critical ecological role in the farm. It is estimated that these insects provide ecosystem services worth $4.5 billion per year.
Agroforestry practices can play a critical role in the protection and creation of critically endangered habitats for both aquatic and terrestrial species. In sensitive aquatic areas, the forested zones shade and stabilize stream banks. This reduces erosion while improving aquatic insect habitat, raising dissolved oxygen levels, reducing denitrification, reducing evaporation, and ultimately raising fish population levels. Further, these buffers play an important role in bioremediation, breaking down and capturing chemicals that drift from the farmland, decreasing their ecological destruction effects.
Over 30% of the crops we cultivate for food rely on insect pollinators. These pollinators largely come as wild native bees and European honeybees. Over the last century, due largely to the chemical and habitat destruction practices of industrial farming, populations of these bees have been significantly reduced. The practices involved in conventional monocultural farms are largely incompatible with the needs of many of the 4000 species of North American bees.
Approximately 30% of our native bees are wood nesters that require trees and shrubs for nesting. About 70% create nests underground requiring undisturbed soil away from the tilling of conventional farm practices. Agroforestry is a poignant way to address the habitat needs of both species. Bumble bees for instance, were found to be twice the density in wooded habitats as compared to grassland habitats. By bringing the habitats of these species closer to the crops by better interspersing woodland, fields can experience greater pollination levels and ultimately better crop production.
The many pest reduction benefits of Agroforestry decrease the need for chemical pesticides, commonly used in conventional farming. These chemicals wreak havoc on bees through direct contact and inadvertent spray drift. With the ecological service value of these bees over $3 billion, farming faces a critical need for solutions like agroforestry that can help bring the bee species back from the brink.
Agroforestry offers significant values in regard to air quality improvement as well. In addition to reducing chemical spray drifts up to 90% through woody buffers, Agroforestry farms serve a valuable role as greenhouse gas reducers, smog reducers, particulate catchers, and odor reducers in livestock areas where this can be a major concern.
Beyond the role that Agroforestry plays productively, it also can play a valuable role for the farmer themselves and the local community. First, from a biophilia perspective, agroforestry natural mimicry creates aesthetically pleasing spaces that are psychologically inviting for people. From a real estate perspective, greenspaces are among the top 5 things people seek when choosing a place to live. Greenspaces are proven to raise property values up to 32%. This land value is not shared by spaces juxtaposed to monoculture farms. These agroforestry spaces can play a valuable social role as leisure spaces for walkers, joggers, birdwatchers, and wildlife spectators – improving the quality of life. They also can serve as grounds for hunters as a secondary value.
From a practical perspective, agroforestry systems reduce the need for building snow fences, saving the farmer capital costs. Additionally, the microclimate affects reduce utility costs for dwelling units on site. Lastly, by better holding water on site, overall usage can be decreased. These effects cumulatively, ultimately, lower overall farm expenses.
On a broader scale, agroforestry serves as a means of increasing domestic food security – enabling the production of diverse products locally. Further, research suggests that, if utilized at scale, agroforestry systems could help mitigate climate change through significant carbon sequestration. And lastly, increased forest covering in watersheds can reduce the total amount of runoff from storms and mitigate flooding risks during peak stormflows. In these many ways, agroforestry offers environmental services values that are difficult to quantify.
Though many of the different agroforestry benefits are externalities outside the direct capture of the farmer, many are still measurable as the relate to the economics of the farm. From the broad perspective the values vary greatly as the mixture and effectiveness of agroforestry can vary greatly between different crops’ symbiosis and settings. However, as a mean, agroforestry has been proven to increase overall yields on the average between 6% and 56% – overall, increasing IRR to the farmer 4% to 11%.
However, the landscape of farming is changing. Agroforestry offers several other valuable properties as well. In an increasing labor challenged industry, agroforestry offers flexibility to the farmer that monocropping does not, as all crops do not need harvesting in mass at one time. Further, Agroforestry reduces risk by offering multiple harvest timings and products for sale rather than risking a year on a single yield. This also allows many fixed costs to be spread across a variety of products rather than laying idle for long periods of time.
From a startup perspective, Agroforestry offers a means of creating revenue sooner, rather than waiting years for the first crop as is seen in a conventional orchard. Additionally, it allows for the phasing out of equipment as it depreciates and succession to other crops becomes necessary.
Lastly, from a land scarcity perspective, agroforestry offers better overall utilization of land. This is particularly valuable for islands, for example, that are running up against a delicate balance of natural resource conservation and food security.
Agroforestry faces a number of unique challenges to wide adoption still today. Although there is becoming an ever-vaster databank of resource for learning best practices for agroforestry, there still limited research conducted in the field. Overall, there is little graduate study emphasizing agroforestry. This stems from overall limited employment opportunities in the field and as such limited funding. Given the breadth of the field and its variability across locales, there is a need for more localized testing of the practices.
Public perception holds agroforestry back from wide adoption as well. Generally, people believe that high establishment costs and high management expertise is needed. Many seem to believe that the economic gain would be lower than traditional farming. Others are disinterested in adopting systems whose rotational length may exceed the landowner’s life expectancy. Much of this is misconception only exacerbated by the public sectors disinvolvement, assuming that landowners would be unwilling to follow the land management prescriptions necessary for developing and maintaining agroforestry systems properly.
Public policy overall has a way to go in catching up with the needs of agroforestry becoming the norm. Currently some states offer extensions to the conservation reserve program to compensate farmers for the differences in payments they would have received from non-agroforestry practices. This is neither across the board nor a full compensation for the externalities that agroforestry provides. Currently, agroforesters are excluded from certain programs that are based on tree planting density. Considerations are being made through regarding valuing agroforestry for its carbon sequestration value. The challenge has largely been from organized commodity groups who feel that subsidizing producers entering the market through federally funded programs would give them and “unfair advantage”.
Lastly, agroforestry faces physical challenges as well. Overall, scale and time are necessary for realizing many of the benefits of agroforestry. Additionally, there can be added expenses to undergoing the practice. Sivopastoral systems, for instance, add additional costs for fencing and risk of tree damage from the livestock. Further, in some circumstances, agroforestry practices have been found to exacerbate pest problems by protecting insect pests with alternative hosts, allowing them to rebuild populations and reinvade crop areas the next season.
In 1935, the Dustbowl showed us the consequences of not having any agroforestry practices across the Midwest. In its wake, the Prairie States Forestry Program planted more than 200 million trees as shelterbelts, to reclaim the land ravaged by the Dust Bowl. To a great extent, agroforestry is a return to the old way of farming of ancient times – but this time with more information.
Agroforestry offers a solution to many of traditional farming’s biggest issues today. It can address the climate crisis, the biodiversity crisis, soil depletion, air and water quality, and the struggles of smaller scale farms trying to stay in business. The evidence posits that agroforestry can sustainably increase production per unit of land area while enhancing economic, social, and environmental services. While demand for local and organic specialty crops continues to grow exponentially to support the market, the time for shift has never been better or more necessary. What we need now is a policy environment that recognizes the valuable macro externalities of agroforestry better and compensates farmers for the transition in a manner more appropriate to its true value.
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Tannenbaum Design Group | Landscape Architecture and Outdoor Design | Agroforestry