Benefits of Agroforestry

Story at a glance:

• Agroforestry is a land-use method that combines forestry practices and the cultivation of crops and/or livestock animals under the same management system.
• There are five types of agroforestry systems commonly practiced in the United States: windbreaks, alley-cropping, riparian forest buffers, forest farming, and silvopasture.
• The benefits of agroforestry include improved soil health, increased productivity and profitability, carbon sequestration, increased biodiversity, and more.

For hundreds of years the dominant agricultural model has been at odds with forestry, often necessitating widespread clearcutting for the expansion of farmland. It’s estimated that roughly 80% of global deforestation is a direct result of agricultural production, with the clearing of forests for pastures and fields the leading cause of habitat destruction.

As Earth’s population continues to grow, it’s imperative that we find better, more sustainable ways to feed that population—and agroforestry is often regarded as one of the most promising solutions.

In this article we’ll provide an in-depth look at the basics of agroforestry, explore a few of the most common agroforestry systems, and take a look at the benefits agroforestry has to offer.

What is Agroforestry?

Also known as agro-sylviculture, agroforestry is best understood as a land-use management system that cultivates trees and shrubs in close proximity to crops and/or livestock. Agroforestry practices manage all of these elements as a single integrated unit rather than as separate systems, creating symbiotic relationships that strengthen and reinforce the inherent biological connections between all living things.

This approach to land management ultimately creates and maintains ecosystems that more closely resemble the complex, interconnected habitats found in nature—and as such, agroforestry operations are much more ecologically diverse than conventional farms.

The term ”agroforestry” was coined in the 1970s, but the practice of cultivating trees, agricultural crops, and/or livestock in conjunction with one another is not a new concept. Archaeological evidence suggests humans have been intentionally growing woody perennials alongside crops since at least early Roman times. Many Indigenous peoples continue to practice agroforestry to this day, and agroforestry systems are extremely prevalent in South America, Central America, and certain parts of Africa.

Types of Agroforestry Systems

There are a variety of ways agroforestry principles may manifest or be applied, with different systems tailored to suit local conditions. The USDA identifies five distinct agroforestry applications or systems as the best suited to the temperate climates of North America: windbreaks, alley-cropping, riparian forest buffers, forest farming, and silvopasture.

Windbreaks

As the name suggests, windbreak agroforestry systems are primarily intended to provide soil, crops, livestock, and even buildings with protection from the wind. Windbreaks reduce wind speeds up to 30 times their height downwind and consist of at least one row of trees and/or woody shrubs planted around the perimeters of fields, typically either in an arc or L-shape to effectively shield multiple directions from troublesome winds. As a general rule the height of a windbreak must be taller than what is being protected in order to be effective against strong winds.

Properly designed and managed windbreaks, however, can provide a range of additional benefits, including the production of marketable produce, improvement of crop and livestock health and productivity, reduced energy costs, snow management, and more.

Alley-Cropping

Another common agroforestry practice is alley-cropping—also known as inter-cropping—or the planting of various agricultural or horticultural crops in the wide alleyways between closely-spaced rows of maturing trees. The combinations of tree species and crops in alley-cropping systems are virtually limitless, though it is important for landowners to plan accordingly and ensure that the trees and crops selected are compatible with one another to avoid competition for resources.

In most alley-cropping systems both crops and trees are intended to serve as some form of income generation, allowing farmers to diversify their income by providing both annual and long-term sources of revenue.

Riparian Forest Buffers

As perhaps the least-intensive form of agroforestry, riparian forest buffers are strips or patches of trees, shrubs, and grasses cultivated along rivers and other water bodies. The primary function of riparian forest buffers is to prevent agricultural runoff—which typically contains pesticides, excess macronutrients, and sediment—from entering and polluting local waterways, but they also help stabilize stream banks, provide shade and shelter for aquatic organisms, act as wildlife corridors, and provide additional opportunities for income from timber and specialty forest crops.

Most riparian forest buffers consist of three distinct zones: an unmanaged woody zone nearest to the water body followed by a woody zone that may be managed for additional income and which is bordered by a zone of grasses, sedges, and herbaceous non-woody vascular plants (e.g. wildflowers).

Forest Farming

Forest farming is an agroforestry practice in which farmers cultivate high-value non-timber forest products (NTFPs) under the protection of specially modified forest canopies designed to provide optimal shade for the production of said NFTPs. Forest farming is achieved through the careful and conscientious thinning of existing forests, in which only the best canopy trees are left to ensure continued timber production while still supplying understory crops with the proper growth conditions.

Common NTFPs cultivated and collected in forest farming systems include mushrooms, medicinal plants, nuts, berries, seeds, plant oils, and tree sap.

Silvopasture

Finally, silvopasture agroforestry systems combine livestock operations with forestry by managing livestock animals, foraging, grazing, and trees all on the same acreage. Silvopasture systems typically consist of sparsely-forested areas in which cattle and other livestock animals may graze on native grasses, wild greens, and other vegetation that populates the forest floor.

Silvopasture systems provide livestock with shade and protection from the elements, reducing heat and cold stress, while also allowing farmers to diversify their income by way of foraged forest crops (e.g. certain mushrooms), timber, or a combination of the two.

Benefits of Agroforestry

A variety of environmental and economic advantages are associated with the adoption and implementation of agroforestry concepts, many of which actively build off of and reinforce one another. Here are a few of the most significant benefits offered by agroforestry:

Improved Soil Health

One of the most significant benefits of agroforestry is the positive impact it has on soil health and fertility. The soil in forested areas, for example, has a naturally high organic matter content on account of forest detritus, or the leaves, branches, seeds, and other organic debris that fall from trees and other plants as they grow. When these organic materials begin to break down, they release key nutrients—like nitrogen—back into the soil that are then mineralized by fungi, bacteria, and other microbiota into forms more available to plants.

Trees and other woody plants that send out long roots also help cycle nutrients up from deeper soil layers, reducing the risk of topsoil layers becoming depleted or devoid of nutrients. This, in conjunction with the regular introduction and breakdown of organic matter, effectively creates a self-regulating soil profile and greatly reduces the need for supplementary fertilizers.

Reduced Soil Erosion

Erosion and the loss of arable soil is a major threat to food production around the world—and while it is technically a natural process, erosion is heavily influenced by human activities. Indeed, much of the agricultural erosion that happens is the result of unsustainable farming practices like plowing fields and leaving soil exposed to the elements for long periods of time, allowing livestock to overgraze on ground-cover crops that hold soil in place, and nutrient depletion caused by monocropping.

Erosion becomes a serious problem when wind and rain start to carry off healthy, fertile soil faster than it can be regenerated, causing the land to become less productive or making it entirely unsuitable for crop production.

Agroforestry systems help reduce soil erosion caused by wind and rain in two key ways. Firstly, leafy forest canopies shield fields from high-speed winds and reduce both the amount and velocity of precipitation that reaches the ground, resulting in less soil disturbance and minimizing loss of soil carried away by runoff. Second, trees and woody shrubs possess long, complex root networks that help physically bind and hold soil in place, preventing it from being washed or blown away by heavy rains and strong winds.

Alley-cropping systems are amongst the most effective agroforestry methods when it comes to reducing erosion, as the dense rows of trees drastically reduce wind speed and protect the crops planted in-between them. Riparian forest buffers are also ideal for stabilizing the sides of rivers, streams, and other waterways, greatly reducing bank erosion.

Improved Water Quality

Agroforestry practices also help to improve water quality by drastically reducing the amount of sediment and sediment-bound contaminants—such as chemical pesticides and fertilizers—entering local watersheds as a result of agricultural runoff. Tree roots, low-lying shrubs, native grasses, and forest-floor detritus all help to trap and filter out unwanted pollutants before they reach nearby waterways.

Preventing nutrient-rich fertilizer from entering rivers, lakes, and streams is especially important in that high concentrations of phosphates, nitrates, and other macronutrients can lead to eutrophication, or the rapid growth of algae and other plant life. This explosive proliferation of plant matter causes the water’s oxygen level to drop, resulting in the mass death of fish and other aquatic organisms.

Agroforestry systems like riparian forest buffers are incredibly well-suited to capturing runoff and preventing eutrophication.

Increased Biodiversity

Another benefit of agroforestry is that it helps reintroduce and encourage the growth of biodiverse ecosystems—something that most modern agricultural models actively discourage through the replacement of natural habitats with genetically-uniform monocultures.

Trees and other flowering plants provide both food and shelter for birds, bees, butterflies, and other crucial pollinators, helping to facilitate cross-pollination between wild plants and crops. Cross-pollination is key to the creation of healthy ecosystems as it bolsters reproductive success and encourages genetic variation, which in turn improves crops’ resistance to disease, pests, and other environmental stressors.

Silvopasture and forest farm systems also incorporate a diverse range of vegetation—trees, shrubs, grasses, wildflowers, et cetera—that creates habitats for terrestrial as well as aerial organisms. These habitats act as travel corridors for wildlife and provide helpful predator species with spaces to hunt pests that would otherwise eat or destroy crops, reducing the need for chemical pesticides and inhumane pest control methods.

Agroforestry systems like riparian forest buffers can even help increase aquatic biodiversity in addition to terrestrial biodiversity, as trees growing along the banks of rivers and other waterways provide shade, shelter, and food for a variety of aquatic species.

Carbon Sequestration

All plants absorb and sequester carbon through photosynthesis as they grow, but the sheer size and longevity of trees makes them incredibly effective at removing carbon from the atmosphere and storing it for long periods of time. According to the Arbor Day Foundation, a mature live tree is capable of absorbing over 48 pounds of carbon dioxide each year, storing that carbon in its leaves, branches, trunks, and roots until it is cut down, burns, or dies.

Some agroforestry practices even qualify for carbon credits and offset programs, allowing farmers to generate additional income by selling their credits to businesses and other entities.

Improved Air Quality

In addition to enhancing both soil health and water quality, agroforestry also helps reduce air pollution and improve outdoor air quality. As we’ve already discussed, trees and other plants remove carbon dioxide emissions from the atmosphere during photosynthesis—but carbon isn’t the only gaseous pollutant that they absorb.

Forests also help remove sulfur dioxide, nitrogen dioxide, and ozone from the air by absorbing them through their stomata, or the tiny openings in their leaves. Once absorbed, these pollutants are translocated to other parts of the tree where they then begin to break down or become diluted to a safe level. Larger pollutants like airborne particulate matter are not absorbed in the same manner as gaseous pollutants, but they do collect on plant surfaces and are thus still removed from the atmosphere.

By improving outdoor air quality agroforestry systems reduce the risk of developing asthma and other respiratory conditions. Aside from absorbing GHG emissions, agroforestry operations also improve air quality by blocking livestock odors.

Protection From Inclement Weather

In addition to shielding soil from wind and rain, agroforestry practices serve to protect farm operations in general from harsh or inclement weather. Windbreaks and alley-cropping systems, for example, protect crops from high-speed winds that might damage or destroy them, while silvopasture methods safeguard livestock from environmental stressors—like wind, rain, and sun—that might otherwise negatively impact their productivity.

Depending on their height and location, windbreaks can also protect sheds, barns, and other agricultural buildings from inclement weather, reducing the potential for costly damage and repairs.

Riparian forest buffers, on the other hand, are designed to offer protection against flooding during periods of high rainfall by slowing runoff and absorbing or storing excess water. Riparian buffers are particularly useful in lessening the severity of downstream flooding, reducing the impact of floodwaters on nearby farming operations.

Increased Crop & Livestock Productivity

By enhancing soil health, improving water quality, increasing biodiversity, and protecting crops and livestock from environmental stressors, agroforestry systems ultimately help to increase the overall productivity of farming operations, minimizing the need to expand and convert existing forests to new farmland. Different agroforestry systems impact productivity at different rates, but all can help to increase crop yield.

Well-maintained windbreaks, for example, can increase crop yields by as much as 56% simply by improving per-land-unit productivity, according to a 2018 report issued by the US Forest Service entitled Agroforestry: Enhancing Resiliency in US Agricultural Landscapes Under Changing Conditions.

Diversified Income

One of the main economic benefits of agroforestry systems is that they allow landowners to expand and diversify their income while at the same time reducing market risk and vulnerability throughout the year. Trees, for example, have the potential to provide a range of products—nuts, fruit, seeds, and eventually, timber—over the course of their lifetime, of which can all provide supplementary or alternative streams of income should the main crop fail.

Some agroforestry systems, like forest farms, are specifically designed to provide an extremely diverse array of income opportunities by carefully managing forests and woodlands to capitalize on a wide variety of specialty NFTPs. Other practices, such as alley-cropping, can provide farmers with both annual (e.g. vegetables, fruit, grain crops) and long-term (e.g. timber) streams of revenue.

By providing farmers with diversified income agroforestry systems can help farms operate year-round without experiencing significant seasonal peaks or lows, making for greater stability and security.