Disadvantages of Agroforestry: Complexity
by George Powell
In my first post in this series on the disadvantages of agroforestry, I discussed how time can work against you. In this second post in the series I cover the complexities of complexity.
I’m attracted to complexity. My interests in agroforestry and range management began as undergraduate pursuing my interests in applied ecology and integrated production systems for both agriculture and forestry.
But one’s academic interests should not be the driving force behind business decisions.
Agroforestry offers many potential production, economic and social advantages for agriculture and forestry producers. But only when these systems are designed and implemented with care. Because of the potential for complex interactions and unpredicted consequences, even basic shifts in management, such as tree spacing or spatial orientation of trees and shrubs, can alter a whole host of other factors. These include: microclimate in the understory, crop maturation dates, pest populations, livestock behaviour, and crop plant form altering the economic yield, to name a few.
With agroforestry, there is a much higher level of initial planning, and ongoing monitoring necessary to be successful. In contrast, simple production systems may only have one or two dynamic elements that need to be factored in at any given time. And these relationships are generally much better documented for conventional agriculture and forestry. Moreover, there is a greater risk of setting up for failure. Especially for first-time producers that lack operational experience in dealing with multi-dimensional production.
A few examples hopefully to help make this point clearer.
Complexity in the Root Zone
In alley cropping, as with most agroforestry applications, as the tree and shrub rows mature, they become the dominant structural elements in the production landscape. Both above and below ground. Some producers will carefully consider tree heights and row orientation to manage the light levels reaching the row crops. However, fewer will fully consider the below-ground dynamics.
Tree and shrub roots serve many functions: they exploit the soil for water and nutrients. They provide stability and structural properties holding the large mass of above-ground material in place and firm against wind throw. And root architecture is complex and not fully understood in relation to alley cropping. For example, lateral roots can be sheared by soil cultivation in the alleys, diminishing tree/shrub production. Or, irrigation and fertilizer applied to the row crops may draw roots closer to the surface than normal. This can make trees less wind-firm because it now lacks all the necessary deeply-rooted anchors in the ground.
Mature trees and shrubs slow air flows across the landscape. This increases humidity in the understory and decreases evaporation. This can work to your advantage when you are producing in arid environments through more effective capture and use of soil moisture. But in cooler, more humid climates it can impede crop drying. Forages or grains produced in the understory or alleys now need additional drying days. Or supplemental forced drying may be needed after crops are removed from field. This drives up costs or leaves the crop susceptible to fungal infections or other diseases that thrive in humid, moisture-laden conditions.
Complex Animal Behaviour
Tree orientation or individual tree shape can either block or enhance sight lines for livestock (and their predators) in silvopastures. Basic, evolutionary behaviour will always predominate in livestock herds. Therefore, how a site is layed out can stimulate a flight or fight response.
Sheep are notoriously skiddish and may prefer tree and shrub spatial patterns that give them hiding cover. With choice, they opt for cover over long, straight rows and sight lines that may trigger a sense of vulnerability. Putting animals in stressful environments for prolonged periods will have negative consequences for their production.
Added Complexity Equals Added Planning
As these examples show, the greatest advantage and challenge for agroforestry is in the diversity and complexity of these integrated systems. A potential disadvantage for anyone considering agroforestry production options lies in the added planning and operational monitoring needed to make these systems successful.
In my next post, I discuss a final disadvantage of agroforestry: support.
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