Agroforestry (also known as agro-sylviculture or forest farming) is a land use management system that integrates trees with crops or pasture. It combines agricultural and forestry technologies. As a polyculture system, an agroforestry system can produce timber and wood products, fruits, nuts, other edible plant products, edible mushrooms, medicinal plants, ornamental plants, animals and animal products, and other products from both domesticated and wild species.[1]
Agroforestry can be practiced for economic, environmental, and social benefits, and can be part of sustainable agriculture.[2] Apart from production, benefits from agroforestry include improved farm productivity,[3], healthier environments, reduction of risk for farmers,[4] beauty and aesthetics, increased farm profits, reduced soil erosion, creating wildlife habitat, less pollution, managing animal waste, increased biodiversity, improved soil structure, and carbon sequestration.
Agroforestry practices are especially prevalent in the tropics, especially in subsistence smallholdings areas, with particular importance in sub-Saharan Africa. Due to its multiple benefits, for instance in nutrient cycle benefits and potential for mitigating droughts, it has been adopted in the USA and Europe.
Contour planting integrated with animal grazing on Taylor's Run farm, Australia
Definition
At its most basic, agroforestry is any of various polyculture systems that intentionally integrate trees with crops or pasture on the same land.[5][2] An agroforestry system is intensively managed to optimize helpful interactions between the plants and animals included, and “uses the forest as a model for design."[6]
Agroforestry shares principles with polyculture practices such as
legumes to restore soil nitrogen fertility. The nitrogen-fixing plants can be planted either sequentially or simultaneously.[citation needed
]
History and scientific study
The term “agroforestry” was coined in 1973 by Canadian forester John Bene, but the concept includes agricultural practices that have existed for millennia.[7]
Scientific agroforestry began in the 20th century with ethnobotanical studies carried out by anthropologists. However, indigenous communities that have lived in close relationships with forest ecosystems have practiced agroforestry informally for centuries.[8] For example, Indigenous peoples of California periodically burned oak and other habitats to maintain a ‘pyrodiversity collecting model,’ which allowed for improved tree health and habitat conditions.[9] Likewise Native Americans in the eastern United States extensively altered their environment and managed land as a “mosaic” of woodland areas, orchards, and forest gardens.[10]
Agroforestry in the tropics is ancient and widespread throughout various tropical areas of the world, notably in the form of "tropical home gardens." Some “tropical home garden” plots have been continuously cultivated for centuries. A “home garden” in Central America could contain 25 different species of trees and food crops on just one-tenth of an acre.[11] "Tropical home gardens" are traditional systems developed over time by growers without formalized research or institutional support, and are characterized by a high complexity and diversity of useful plants, with a canopy of tree and palm species that produce food, fuel, and shade, a mid-story of shrubs for fruit or spices, and an understory of root vegetables, medicinal herbs, beans, ornamental plants, and other non-woody crops.[12] Relatively little formal study has been devoted to these systems, even though they are essential to the lives of many people in the tropics.
In 1929, J. Russel Smith published “Tree crops: A permanent agriculture," in which he argued that American agriculture should be changed two ways: by using non-arable land for tree agriculture, and by using tree-produced crops to replace the grain inputs in the diets of livestock. Smith wrote that the
honey locust tree, a legume that produced pods that could be used as nutritious livestock feed, had great potential as a crop. The book’s subtitle later led to the coining of the term “permaculture.”[13]
The most studied agroforestry practices involve a simple interaction between two components, such as simple configurations of hedges or trees integrated with a single crop.[14] There is significant variation in agroforestry systems and the benefits they have.[15] Agroforestry as understood by modern science is derived from traditional indigenous and local practices, developed by living in close association with ecosystems for many generations.[8]
Benefits
Benefits include increasing farm productivity and profitability, reduced soil erosion, creating wildlife habitat, managing animal waste,[16] increased biodiversity, improved soil structure, and carbon sequestration.[17]
Agroforestry systems can provide advantages over conventional agricultural and forest production methods. They can offer increased productivity; social, economic and environmental benefits, as well as greater diversity in the ecological goods and services provided.[18] It is essential to note that these benefits are conditional on good farm management. This includes choosing the right trees, as well as pruning them regularly etc. [19]
Biodiversity
Biodiversity in agroforestry systems is typically higher than in conventional agricultural systems. Two or more interacting plant species in a given area create a more complex habitat that can support a wider variety of fauna.
Agroforestry is important for biodiversity for different reasons. It provides a more diverse habitat than a conventional agricultural system in which the tree component creates ecological niches for a wide range of organisms both above and below ground. The life cycles and food chains associated with this diversification initiates an agroecological succession that creates functional agroecosystems that confer sustainability. Tropical bat and bird diversity for instance can be comparable to the diversity in natural forests.[20] Although agroforestry systems do not provide as many floristic species as forests and do not show the same canopy height, they do provide food and nesting possibilities. A further contribution to biodiversity is that the germplasm of sensitive species can be preserved.[21] As agroforests have no natural clear areas, habitats are more uniform. Furthermore, agroforests can serve as corridors between habitats. Agroforestry can help to conserve biodiversity having a positive influence on other ecosystem services.[21]
Soil and plant growth
Depleted soil can be protected from soil erosion by groundcover plants such as naturally growing grasses in agroforestry systems. These help to stabilise the soil as they increase cover compared to short-cycle cropping systems.[22][23] Soil cover is a crucial factor in preventing erosion.[24][25] Cleaner water through reduced nutrient and soilsurface runoff can be a further advantage of agroforestry. Trees can help reduce water runoff by decreasing water flow and evaporation and thereby allowing for increased soil infiltration.[26] Compared to row-cropped fields nutrient uptake can be higher and reduce nutrient loss into streams.[27][28]
Land restoration through reducing soil erosion and regulating water availability [26]
Multifunctional site use, e.g., crop production and animal grazing
Reduced
fuelwood
Possibility of reduced chemicals inputs, e.g. due to improved use of fertilizer, increased resilience against pests,[19] and increased ground cover which reduces weeds [30]
Growing space for
medicinal plants
e.g., in situations where people have limited access to mainstream medicines
According to FAO's The State of the World’s Forests 2020, adopting agroforestry and sustainable production practices, restoring the productivity of degraded agricultural lands, embracing healthier diets and reducing food loss and waste are all actions that urgently need to be scaled up. Agribusinesses must meet their commitments to deforestation-free commodity chains and companies that have not made zero-deforestation commitments should do so.[31]
Other environmental goals
Carbon sequestration is an important ecosystem service.[32][21][33] Agroforestry practices can increase carbon stocks in soil and woody biomass.[34] Trees in agroforestry systems, like in new forests, can recapture some of the carbon that was lost by cutting existing forests. They also provide additional food and products. The rotation age and the use of the resulting products are important factors controlling the amount of carbon sequestered. Agroforests can reduce pressure on primary forests by providing forest products.[35]
Adaptation to climate change
Agroforestry can significantly contribute to climate change mitigation along with adaptation benefits.[36] A case study in Kenya found that the adoption of agroforestry drove carbon storage and increased livelihoods simultaneously among small-scale farmers. In this case, maintaining the diversity of tree species, especially land use and farm size are important factors.[37]
Poor smallholder farmers have turned to agroforestry as a means to adapt to climate change. A study from the CGIAR research program on Climate Change, Agriculture and Food Security (CCAFS) found from a survey of over 700 households in East Africa that at least 50% of those households had begun planting trees in a change from earlier practices. The trees were planted with fruit, tea, coffee, oil, fodder and medicinal products in addition to their usual harvest. Agroforestry was one of the most widespread adaptation strategies, along with the use of improved crop varieties and intercropping.[38]
Tropical
Trees in agroforestry systems can produce wood, fruits, nuts, and other useful products. Agroforestry practices are most prevalent in the tropics,[39][40] especially in subsistence smallholdings areas[41] such as sub-Saharan Africa.[19]
Research with the leguminous tree
Faidherbia albida in Zambia showed maximum maize yields of 4.0 tonnes per hectare using fertilizer and inter-cropped with the trees at densities of 25 to 100 trees per hectare,[42] compared to average maize yields in Zimbabwe of 1.1 tonnes per hectare.[43]
Hillside systems
A well-studied example of an agroforestry hillside system is the Quesungual Slash and Mulch Agroforestry System (QSMAS) in Lempira Department, Honduras. This region was historically used for slash-and-burnsubsistence agriculture. Due to heavy seasonal floods, the exposed soil was washed away, leaving infertile barren soil exposed to the dry season.[44] Farmed hillside sites had to be abandoned after a few years and new forest was burned. The Food and Agriculture Organization of the United Nations (FAO) helped introduce a system incorporating local knowledge consisting of the following steps:[45][46]
Plant maize in rows. This is a traditional local crop.
Harvest from the dried plant and plant beans. The maize stalks provide an ideal structure for the climbing bean plants. Bean is a nitrogen-fixing plant and therefore helps introduce more nitrogen.
Pumpkins can be planted during this time. The plant's large leaves and horizontal growth provide additional shade and moisture retention. It does not compete with the beans for sunlight since the latter grow vertically on the stalks.
Every few seasons, rotate the crop by grazing cattle, allowing grass to grow and adding soil organic matter and nutrients (manure). The cattle prevent total reforestation by grazing around the trees.
With shade applications, crops are purposely raised under tree canopies within the shady environment. The understory crops are shade tolerant or the overstory trees have fairly open canopies. A conspicuous example is shade-grown coffee. This practice reduces weeding costs and improves coffee quality and taste.[48][49]
Crop-over-tree systems
Crop-over-tree systems employ woody perennials in the role of a cover crop. For this, small shrubs or trees pruned to near ground level are utilized. The purpose is to increase in-soil nutrients and/or to reduce soil erosion.
With alley cropping, crop strips alternate with rows of closely spaced tree or hedge species. Normally, the trees are pruned before planting the crop. The cut leafy material - for example, from Alchornea cordifolia and Acioa barteri - is spread over the crop area to provide nutrients. In addition to nutrients, the hedges serve as windbreaks and reduce erosion.[50]
In tropical areas of North and South America, various species of Inga such as I. edulis and I. oerstediana have been used for alley cropping.[51]
Faidherbia albida. In one example, a ten-year experiment in Malawi showed that, by using the fertilizer treeGliricidia (G. sepium) on land on which no mineral fertilizer was applied, maize/corn yields averaged 3.3 metric tons per hectare (1.5 short ton/acre) as compared to 1 metric ton per hectare (0.45 short ton/acre) in plots without fertilizer trees or mineral fertilizers.[52]
Weed control is inherent to alley cropping, by providing mulch and shade.[50]
Syntropic farming, syntropic agriculture or syntropic agroforestry is an organic, permaculture agroforestry system developed by Ernst Götsch in Brazil.[53][54] Sometimes this system is referred to as a successional agroforestry systems or SAFS, which sometimes refer to a broader concept originating in Latin America.[55] The system focuses on replicating natural systems of accumulation of nutrients in ecosystems, replicating secondary succession, in order to create productive forest ecosystems that produce food, ecosystem services and other forest products.[56]
The system relies heavily on several processes:
Dense planting mixing perrinneal and annual crops
Rapid cutting and composting of fast growing pioneer species, to accumulate nutrients and biomass[57]
A temperate Syntropic system in Dordogne France, including heavily mulched Sunflower plants.Creating greater water retention on the land through improving penetration of water into soil and plant water cycling
The systems were first developed in tropical Brazil, but many similar systems have been tested in temperate environments as soil and ecosystem restoration tactics.[58]
The framework for the syntropic agroforestry is advocated for by Agenda Gotsch an organization built to promote the systems.[59]
In Burma
Taungya is a system from
Burma. In the initial stages of an orchard or tree plantation, trees are small and widely spaced. The free space between the newly planted trees accommodates a seasonal crop.[60]
Instead of costly weeding, the underutilized area provides an additional output and income. More complex taungyas use between-tree space for multiple crops. The crops become more shade tolerant as the tree canopies grow and the amount of sunlight reaching the ground declines. Thinning can maintain sunlight levels.
In India
Itteri agroforestry systems have been used in Tamil Nadu since time immemorial. They involve the deliberate management of multipurpose trees and shrubs grown in intimate association with herbaceous species. They are often found along village and farm roads, small gullies, and field boundaries.[61]
Bamboo-based agroforestry systems (Dendrocalamus strictus + sesame–chickpea) have been studied for enhancing productivity in semi-arid tropics of central India.[62]
In Africa
A project to mitigate climate change with agriculture was launched in 2019 by the "Global EverGreening Alliance". The target is to sequester carbon from the atmosphere. By 2050 the restored land should sequestrate 20 billion tons of carbon annually[63]
In Hawai'i
Native Hawaiians formerly practiced agroforestry adapted to the islands' tropical landscape. Their ability to do this influenced the region's carrying capacity, social conflict, cooperation, and political complexity.[64] More recently, after scientific study of lo’I systems, attempts have been made to reintroduce dryland agroforestry in Hawai’i Island and Maui, fostering interdisciplinary collaboration between political leaders, landowners, and scientists.[65]
Temperate
Alley cropping corn fields between rows of walnut trees
Although originally a concept in tropical agronomy,[17] agroforestry's multiple benefits, for instance in nutrient cycles and potential for mitigating droughts, have led to its adoption in the USA and Europe.[66][67][68]
Alley cropping can also be used in temperate climates. Strip cropping is similar to alley cropping in that trees alternate with crops. The difference is that, with alley cropping, the trees are in single rows. With strip cropping, the trees or shrubs are planted in wide strips. The purpose can be, as with alley cropping, to provide nutrients, in leaf form, to the crop. With strip cropping, the trees can have a purely productive role, providing fruits, nuts, etc. while, at the same time, protecting nearby crops from soil erosion and harmful winds.
Forest farming
In forest farming, high-value crops are grown under a suitably-managed tree canopy. This is sometimes called multi-story cropping, or in tropical villages as home gardening. It can be practised at varying levels of intensity but always involves some degree of management; this distinguishes it from simple harvesting of wild plants from the forest.[17]
Riparian buffers are strips of permanent vegetation located along or near active watercourses or in ditches where water runoff concentrates. The purpose is to keep nutrients and soil from contaminating the water.[17]
Silvopasture
Silvopasture over the years (Australia)
Trees can benefit fauna in a silvopasture system, where cattle, goats, or sheep browse on grasses grown under trees.[17][69]
In hot climates, the animals are less stressed and put on weight faster when grazing in a cooler, shaded environment. The leaves of trees or shrubs can also serve as fodder. Similar systems support other fauna. Deer and pigs gain when living and feeding in a forest ecosystem, especially when the tree forage nourishes them. In aquaforestry, trees shade fish ponds. In many cases, the fish eat the leaves or fruit from the trees.
Windbreaks reduce wind velocity over and around crops. This increases yields through reduced drying of the crop and/or by preventing the crop from toppling in strong wind gusts.[17]
In Switzerland
Since the 1950s, four-fifths of Swiss Hochstammobstgärten (traditional orchards with tall trees) have disappeared. An agroforestry scheme was tested here with hochstamm trees together with annual crops. Trees tested were walnut (Juglans regia) and cherry (Prunus avium). Forty to seventy trees per hectare were recommended, yields were somewhat decreasing with increasing tree height and foliage.[71] However, the total yield per area is shown to be up to 30 percent higher than for monocultural systems.[72]
^ abVira, Bhasakar; Wildburger, Christoph; Mansourian, Stephanie (2015). Forests and Food: Addressing Hunger and Nutrition Across Sustainable Landscapes. Open Book Publishers. pp. 73–136.
^"Silvopasture". Agroforestry Research Trust [in England]. Archived from the original on 20 April 2015. Retrieved 19 August 2015.
^Fra. Paleo, Urbano. (2010). "The dehesa/montado landscape". pp. 149–151 in Sustainable Use of Biological Diversity in Socio-ecological Production Landscapes, eds. Bélair, C., Ichikawa, K., Wong, B.Y.L. and Mulongoy, K.J. Montreal: Secretariat of the Convention on Biological Diversity. Technical Series no. 52.
This article incorporates text from a free content work. Licensed under CC BY-SA 3.0 IGO (license statement/permission). Text taken from The State of the World’s Forests 2020. Forests, biodiversity and people – In brief, FAO & UNEP, FAO & UNEP.
