As the consumer population of the world increases, natural forests are cleared out to make land for agricultural use. An innovative way of preserving these forests and ensuring food security is establishing a balance between the two through a practice called tropical agroforestry.
Agroforestry is a land-use system which involves the interaction between woody perennials and agricultural crops or animals in the form of practices like contour farming, intercropping, established shelterbelts, riparian zones/buffer strips, etc. Specifically, agroforestry uses trees in agriculture and also includes activities like farming in and around forests or tree-crop production involving crops like coffee, cocoa, rubber, etc. This method increases social, economic and environmental benefits by increasing land production.
Tropical agroforestry can prove to be very productive if implemented properly. For example, trees required to produce timber and other commercial purposes can be grown alongside commercial or agricultural crops. Meanwhile, agroforestry also increases the yield of crops to meet the increasing demand for adequate and nutritious food. Additionally, trees also help protect the crops and animal from winds and increases soil fertility. Unsurprisingly, tropical agroforestry also helps in the conservation of natural forests.
Additionally, these systems provide ecosystem services like protecting natural resources by mitigating pollution, controlling soil erosion, creating wildlife habitat. Tree roots reach deep into the soils and release carbon, enriching the soil and binding it together to prevent erosion due to rain or wind.
Moreover, the total output of growing both trees and crops per unit is higher than growing each individually as it makes best use of the land area available. Lastly, agroforestry also increases the farmer’s flexibility and enhances income.
Tropical Agroforestry in the Western Ghats
Commercial agriculture in the Western Ghats has existed for centuries. Today, agroforestry systems involving crops like coffee, tea, rubber, pepper, etc are prevalent in these landscapes. For instance, the Kodagu district in the Western ghats houses many agroforestry areas and contributes to one-third of India’s coffee production. Specifically, many coffee estate plantations can be found in this region with trees like silk oak or silver oak (a species that had been introduced in Asia and Africa decades ago) forming the canopies of these agroforestry systems.
Introduced tree species are easier to harvest as they are not restricted by government rules and control over native trees (native trees would require permits to harvest). Over the years, plantation farmers have also converted Arabica coffee (Coffea arabica) plantations into more resistant Robusta coffee (Coffea canephora) plantations as result of pest attacks. Moreover, other forms of agroforestry seen in this region involve spices, tea or coffee plantations in association with different tree species, rice-based cropping systems, coconut based cropping systems, etc.
The Ecological Impacts of Tropical Agroforestry
The agroforestry system was designed and introduced to maximise productivity and improve ecological health. Trees provide a range of benefits to the soil, other plant species and overall biodiversity in an agricultural set up. Consequently, agroforestry systems provide stability and better adaptability in the face of climate change as they have the potential to reduce overall volume of greenhouse gases in the atmosphere.
Agroforestry has multiple positive and negative social, economic and ecological impacts:
Biodiversity
Agroforestry provides habitats for wildlife and creates corridors between habitats. Moreover, this practice can help combat species loss outside conservation areas. Depending on the structure of the agroforestry system, they can provide ecosystem services similar to forests. Due to increased diversity in the agricultural land as a result of introduction of trees, bird richness has been reported to have increased in coffee plantations. Characteristics like canopy cover, canopy height, canopy depth, etc. form a habitat for birds to thrive in.
With increase in tree species richness and agroforestry systems resembling forest habitats, small mammals have increased in number and species richness. Meanwhile, tropical agroforestry has been observed to be beneficial for pollinators and insects that feed on pests, reducing the use of pesticides and increasing crop yield in such ecosystems.
Moreover, canopy characteristics, abundant food resources, closeness to forests, etc. have all contributed to increase in insect diversity. Lastly, tropical agroforestry systems act as corridors that allow easy movement of animals and connect fragmented forest lands.
Soil fertility
Agroforestry helps conserve water, enhances soil quality and prevents soil erosion that occurs due to wind and water. The tree shade reduces evapotranspiration from the crops and other plants below the trees, increasing the soil water content. Many trees and crops that are planted in agroforestry systems release Nitrogen, thereby enhancing soil nutrients.
Trees also release organic matter, recycle nutrients and enhance soil properties to a great extent (especially with regard to soil properties which influence water holding capacity, moisture, etc.). Agroforestry has also shown to be able to reclaim degraded land (i.e., helpful in eco-restoration), conserve soil moisture and control soil salinization and acidification. Through litterfall and decomposition of organic matter, these systems have the potential to increase soil organic carbon.
Air quality
Windbreaks and shelterbelts are features in which trees are planted such that the crops are less affected by high wind speeds. These are prevalent tree planting patterns observed in agroforestry which benefit air quality, reduce soil erosion by wind, provide habitats for wildlife, reduce noise pollution and livestock odour, and aid in reducing pollution in multiple ways. These mechanisms also help to remove atmospheric carbon dioxide and improve oxygen circulation.
Climate change
Trees have the ability to sequester large amounts of carbon compared to other vegetation like crops. Trees also help in increase soil carbon content, contributing to enhanced carbon sequestration. Trees also provide fuelwood and durable wood which can be used in place of energy intensive materials. Since trees are conserved in agroforestry, it reduces anthropogenic pressures on natural forests (although it must be a priority to protect and conserve natural forests). Agroforestry systems reduce the reliance on fossil fuels and forest firewood. Internal nutrient cycling and enhanced pest and disease control in agroforestry fields reduces the need for oil-based chemicals.
Economic advantages
Agroforestry provides income based on crops and wood and has the potential to provide multiple harvests a year. This ensures stable income and labour throughout the year. The farmer, as a result, is less vulnerable to crop failure and has increased financial stability. As agroforestry practices increase soil fertility, the productivity and yield of the land increases as well. Trees and forest products provide diverse options for income as they can be used as raw materials in multiple scenarios. Farmers are thus less vulnerable to climate and market shocks.
Cultural significance
Traditional agroforestry landscapes like orchards and wood pastures are valued as visual attractions. Local cultures shape these landscapes and help conserve traditional knowledge and traditions that have lasted for centuries.
What about the negative impacts of tropical agroforestry?
Agroforestry has proved to be very beneficial over the years and can be a viable practice to combat climate change and conserve natural forests. However, there are a few negatives to this as well.
If the upper storey trees in an agroforestry system contribute to increased shade, the yield of the crops below decreases as the amount of sunlight they receive is reduced. The northern temperate regions face this problem as sunlight is a limiting resource in these regions. The competition for water between the trees and crops is likely to limit productivity in regions that are governed by semi-arid conditions.
Sometimes, the weed -like nature of trees in an agroforestry set up may make cultivation more labour intensive. The close proximity to natural forest fragments may attract elephants and other wildlife that destroy plantation crops. Since the trees in agroforestry systems are introduced species, they may threaten native biodiversity by turning invasive. The colonisation of invasive alien tree species can out-compete indigenous species which are comparatively less aggressive.
Written by: Rishabh Sr
References
- https://www.fao.org/forestry/agroforestry/80338/en/
- https://www.worldagroforestry.org/about/agroforestry
- https://www.soilassociation.org/causes-campaigns/agroforestry/what-is-agroforestry/
- https://www.aftaweb.org/about/what-is-agroforestry.html
- Joannès Guillemot, Guerric le Maire, Manjunatha Munishamappa, Fabien Charbonnier, Philippe Vaast, Native coffee agroforestry in the Western Ghats of India maintains higher carbon storage and tree diversity compared to exotic agroforestry, Agriculture, Ecosystems & Environment, Volume 265, 2018, Pages 461-469, ISSN 0167-8809, https://doi.org/10.1016/j.agee.2018.06.002
- Kumar, B.M., Takeuchi, K. Agroforestry in the Western Ghats of peninsular India and the satoyama landscapes of Japan: a comparison of two sustainable land use systems. Sustain Sci 4, 215–232 (2009). https://doi.org/10.1007/s11625-009-0086-0
- http://www1.cifor.org/sentinel-landscapes/sentinel-landscapes-sites/regional-sentinel-landscapes/western-ghats-india.html
- K Murthy, Indu & Dutta, Subhajit & Varghese, Vinisha & Joshi, Priya & Kumar, Poornima. (2017). Impact of Agroforestry Systems on Ecological and Socio-Economic Systems: A Review Impact of Agroforestry Systems on Ecological and Socio-Economic Systems: A Review. Global Journal of Science Frontier Research: H Environment and Earth Science. 16. 15 – 27.