The Role of Agroforestry Systems in Increasing Water Availability
Agroforestry in the Mediterranean: Enhancing Water Availability in Agriculture
(Cover photo by Seppe Deckx from the Agroforestry plot at La Junquera Regenerative Farm)
The agroforestry system is an agricultural land-use system distinguished from intentionally cultivating trees, crops, and/or livestock. The system has received considerable attention as an alternative approach to farming and food production due to the environmental and climate-change mitigating benefits that the intentional cultivation of trees along with crops and/or livestock may provide.
One predominant hypothesis is that “agroforestry systems increase water availability of land-use systems.” As an intern at the Regenerative Academy at La Junquera, I have had the chance to visit and participate in the organization’s Agroforestry plot and see the challenges and effects of such a system in one of the dryest regions of Spain, Murcia. With that in mind, this article will focus on the Mediterranean region since the effects of climate change are much more significant in this region, which is experiencing an increasing severity of droughts. Examples from other areas of the world will also be included to understand these systems’ capabilities better. This article aims to inform you about this hypothesis by presenting and explaining academically supported arguments for and against it.
Arguments supporting that agroforestry helps in improved water availability.
- Trees have deeper roots that allow access to water at deeper soil levels.
One of the most important benefits of trees in a farming system is their ability to reach deeper soil layers and increase water inputs due to their deeper root structures, as seen in a study in China (Wu et al., 2022). Additionally, trees can redistribute water from higher soil layers, thanks to a phenomenon known as Hydraulic Lift (Alagele et al., 2021), making it available for crops.
Figure 1: Hydraulic lift water flows during dry and wet season (Amenu & Kumar, 2008)
- High water uptake of trees may increase competition for water resources.
On the other hand, trees are known to have a higher rate of transpiration, which may lead to higher competition for water with the intercropping plant species, while soil moisture has been found to decrease near tree rows in Alley Cropping systems (Jacobs et al., 2022). The figure below illustrates the various interactions between trees and crops.
Figure 2: Effects of alley cropping on flows of the water balance (Jacobs et al., 2022).
- Trees can reduce evapotranspiration by environment manipulation (microclimate).
Trees have more to offer than just deep rooting. A Mediterranean alley-cropping study found a buffering effect on wind speed and air temperature (Inurreta-Aguirre et al., 2022), creating what is commonly referred to as a Microclimate. These conditions are found to protect crops from heatwaves and drought while also maintaining higher levels of soil moisture, thus increasing the water availability for crops, as seen in a different study in the south Mediterranean (Temani et al., 2021).
Figure 3: Windbreaking functions of trees (Windbreaks & Hedgerows, 2023)
- Rainfall interception by tree canopy.
A double-edged argument is that the tree canopy intercepts the rainfall. The tree canopy not only increases light-interception competition but also competition for rainwater. This can lead to significant rainwater losses for crops growing beneath trees, as seen in a cocoa agroforestry study in Bolivia (Niether, 2018). On the other hand, this effect can also protect crops during rainy seasons by intercepting high-velocity water droplets before they can damage the crops under the canopy (Gaitán et al., 2016).
- Trees can improve soil properties.
The sheltering effect of trees does not stop at the crop level but also benefits the soil ecosystem. Tree litter can significantly reduce soil erosion by intercepting raindrops and increasing water infiltration and holding capacity thanks to trees’ extensive and deep rooting structures (Pavlidis & Tsihrintzis, 2018). Furthermore, tree rows can intercept and slow down runoff water, reducing soil erosion and increasing infiltration (Jacobs et al., 2022).
- Higher Knowledge demand.
One of the biggest obstacles to adopting agroforestry systems is the higher knowledge needed due to their inherently higher complexity than conventional agricultural systems. Limited access to information on how to establish an Agroforestry system that provides the benefits it promises can become a determining factor of its success.
Conclusion
Agroforestry promises to improve water availability, while competition between trees and crops remains one of the biggest concerns.
The lack of homogeneity and high complexity of these farming systems make it harder to draw concrete conclusions on the overall effect of trees in agricultural systems. Research-based on uniform agroforestry designs across different regions could provide the insight needed to deepen our understanding of trees’ role in agriculture and potentially their necessity in the ever-more challenging conditions due to climate change.
Thanks to the efforts of farms like La Junquera to establish and maintain an Agroforestry System, more data regarding its benefits and challenges in water-limited areas can be gathered, as can knowledge on how to manage these systems in this context.
References
Alagele, S. M., Jose, S., Anderson, S. H., & Udawatta, R. P. (2021). Hydraulic lift: processes, methods, and practical implications for society. Agroforestry Systems, 95(4), 641-657. doi:10.1007/s10457-021-00614-w
Amenu, G. G., & Kumar, P. (2008). A model for hydraulic redistribution incorporating coupled soil-root moisture transport. Hydrology and Earth System Sciences, 12(1), 55-74.
Gaitán, L., Armbrecht, I., & Graefe, S. (2016). Throughfall and soil properties in shaded and unshaded coffee plantations and a secondary forest: a case study from Southern Colombia. Journal of Agriculture and Rural Development in the Tropics and Subtropics (JARTS), 117(2), 309-321.
Inurreta-Aguirre, H. D., Lauri, P.-É., Dupraz, C., & Gosme, M. (2022). Impact of shade and tree root pruning on soil water content and crop yield of winter cereals in a Mediterranean alley cropping system. Agroforestry Systems, 96(4), 747-757. doi:10.1007/s10457-022-00736-9
Jacobs, S. R., Webber, H., Niether, W., Grahmann, K., Lüttschwager, D., Schwartz, C., . . . Bellingrath-Kimura, S. D. (2022). Modification of the microclimate and water balance through the integration of trees into temperate cropping systems. Agricultural and Forest Meteorology, 323, 109065.
Niether, W., Armengot, L., Andres, C., Schneider, M., & Gerold, G. (2018). Shade trees and tree pruning alter throughfall and microclimate in cocoa (Theobroma cacao L.) production systems. Annals of Forest Science, 75(2). doi:10.1007/s13595-018-0723-9
Pavlidis, G., & Tsihrintzis, V. A. (2018). Environmental benefits and control of pollution to surface water and groundwater by agroforestry systems: a review. Water Resources Management, 32, 1-29.
Temani, F., Bouaziz, A., Daoui, K., Wery, J., & Barkaoui, K. (2021). Olive agroforestry can improve land productivity even under low water availability in the South Mediterranean. Agriculture, Ecosystems & Environment, 307, 107234
Windbreaks & Hedgerows – Flathead Conservation District. (n.d.). https://flatheadcd.org/windbreaks-hedgerows/
Tramblay, Y., Koutroulis, A., Samaniego, L., Vicente-Serrano, S. M., Volaire, F., Boone, A., . . .Burak, S. (2020). Challenges for drought assessment in the Mediterranean region under future climate scenarios. Earth-Science Reviews, 210, 103348.
Wu, J., Zeng, H., Zhao, F., Chen, C., Singh, A. K., Jiang, X., . . . Liu, W. (2022). Plant hydrological niches become narrow but stable as the complexity of interspecific competition increases. Agricultural and Forest Meteorology, 320, 108953.
Further reading
https://wikifarmer.com/category/sustainability/agroforestry/
Climate-Smart Forestry: Strategies, Benefits and Challenges
Syntropic Agroforestry Orchard with Red Fruit as a Cash Crop in the Mediterranean
Water Conservation Measures: The Role of Mombasa Grass in a Syntropic System
The Impact of Syntropic Agroforestry on Water Usage and Farm Resilience
What is Silvopasture and how can farmers apply and benefit from it
Agroforestry: Intercropping with trees on farms and pastures – with a focus on the subhumid tropics
