In the Fight for Food Security, Sustainable Land Management Plays a ‘Growing’ Role

As an environmental concern, food security is no longer something that only ‘foodies’ or farmers care about. Increasingly, the links between climate change and the fragility of food systems are becoming clearer, making innovative solutions in agriculture highly necessary. The production sector seems to be a natural hotbed for research, as conventional agriculture (large-scale, row-crop farming that requires tillage and high fertilizer inputs) is known to be a significant source of carbon emissions into the atmosphere. However, comprehensive reviews of the effects of sustainable agriculture practices on production yields have been scant.

In a literature review published in Agronomy for Sustainable Development, the authors conducted a comprehensive summary of the latest such research, with special attention paid to the practices of organic fertilization, water harvesting, agroforestry, and minimum soil disturbance. Their findings suggest much promise for a future with uncompromised crop yields and minimized carbon emissions—a “have your cake and eat it too” type of situation.

Through a database review of 160 studies displaying original field data, Branca et al. gathered 217 separate crop yield measurements (tons/hectare), with variable scopes, some short and others long-term (over and under five years, respectively). By only including studies that used a control group—farm fields that used conventional agriculture practices—the authors were able to measure the percent change in average crop yields when using conventional and sustainable techniques. Practices of interest included: cover cropping, or the planting of crops in a field post-harvest, which allows for reduced soil erosion; planting of nitrogen-fixing crops that reduce the amount of carbon escape in harvesting; field fallowing, where fields post-harvest are left to idle and build up soil moisture; organic fertilization that avoids introducing erosion-prone nitrates and phosphates into the soil; minimum soil disturbance, which avoids tillage and instead uses mulching to preserve soil cover; construction of ‘water terraces’ that minimize irrigation flooding; and agroforestry, which includes the use of riparian zones or buffer strips to enhance soil fertility.

Though the authors found consistently positive (i.e. increased) yields for cover cropping, organic fertilization, mulching, and water harvesting, even more compelling is the meta-analysis examining the potential for climate change mitigation. Here, ‘mitigation’ is taken to mean the stabilization of organic carbon density in the soil, or any land practice that increases natural carbon or nitrous oxide stocks in the soil. Alternatively, this could also include practices that reduce nutrient loss, such as no-till agriculture. Tillage is a plowing method that conventional farmers use to attack weeds, but it often leads to high soil erosion. In heavy rain events, pesticides and fertilizers have a greater chance of running off into water bodies and polluting them.

To conduct this meta-analysis, the authors looked at cereal crop yield impacts, where all aforementioned practices were shown to increase yields. According to the authors, studies generally found that adopting sustainable land management practices lead to an increase in the amount of carbon sequestered in the soil. Interestingly, amount of rainfall was a key influence. With the exception of water management practices (use of terraces, micro catchment using buffer strips), mitigation effects were higher in areas of more annual rainfall. The latter observation is particularly interesting, as climate change is thought to lead to an exacerbation of heavy rain events in habitats where heavy rain is the norm. This finding, therefore, could merit a look into negative feedback systems combating climate change.

Dry climates, in contrast, produced higher yield effects than mitigation effects, while humid areas displayed more balanced results. Based off of the tons of emissions reductions per hectare observed, the authors concluded that [these measurements] “provide an economic basis for supporting higher transaction costs in mitigation crediting programs.” Though not explicitly stated, such a statement seems to be one of the few recent endorsements for cap-and-trade systems in a pro-sustainability context.

Other scholars and researchers seem to avoid the politically charged topic of cap-and-trade emissions systems. This may be because the robustness of research results differs across various technologies. A simplistic explanation for this is that many studies typically involve a ‘package’ of practices, such as reducing soil disturbance and water harvesting simultaneously. In these cases, it can be challenging to isolate the impact of any one strategy. Other caveats to the general finding include the wide geographic spread of the studies gathered, the limited data sources (excluding research plots), and the variable timing of yield effects. In many of the studies considered, increased yield effects were only observed over the long run, but these same measurements displayed an increase in average yields, as well as consistency of yields from year to year.

This remarkable consistency may diminish the validity of short-term findings—findings that also display increased production. Interestingly, differing farm sizes for the studies collected were not found to be a factor determining impact on yields. In making the leap to discussing cost-benefit analysis, such an assertion is promising for those skeptics believing that sustainable agriculture can only be profitable for medium and large-sized farming enterprises.

In crafting appropriate public policies—those, for example, that provide technical assistance to farmers wishing to convert from conventional to sustainable agriculture practices—it is necessary to be mindful of these caveats, but to not dismiss the ‘big picture’ findings. After all, the authors were not conducting statistical analyses on crop yields but were trying to summarize large trends in the literature. Policymakers can funnel their energies into creating a robust funding platform for research. This platform should prize investigations that report results for single practices (not ‘packages’), consider a larger data pool, and, most obviously, explore the financial feasibility of implementing these practices on a large scale. Without this practical lens, the idea of sustainable land management remains confined to the research lab.

Article Source: Food security, climate change, and sustainable land management. A review, Branca et al., Agronomy for Sustainable Development, 2013

Featured Photo: cc/(tim caynes)