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Environmental impact of agriculture put into perspective – finding where improvement is needed

DOI: 10.5281/zenodo.1171028

Environmental impact of agriculture put into perspective – finding where improvement is needed

a perspective of the article 2017 Environ. Res. Lett. 12 064016

Clark and Tilman (2017) show the relative potential of a couple of strategies impacting the environmental footprint of agriculture and its upstream activities, using currently available life cycle assessments. Analyzing several environmental impacts, they compare the influence of different food types, methods of food production, and levels of agricultural input-use efficiency. It is particularly important to study an extensive dataset to assess the real impact of practices on the environment, beyond trends and politics, in order to make fact-based decisions about the future of agriculture and food. Especially a life-cycle assessment (LCA) of the environmental footprint can give real in-depth information. Additionally, the database generated and shared can be used to inform further analyses and expanded as new research becomes available. This is particularly necessary in order to avoid misinterpreting of the results, with data so far suggesting sticking to conventional, intensive agriculture in order to achieve sustainability.

The study shows clearly that the diet type (meat-rich rather or plant-based) is having a far larger impact than the production type (organic vs conventional), which is an important aspect to point at while considering sustainability of food production. Thus, regardless of the way of conducting agriculture, a new look on diet habits will have a major impact, especially in industrialized countries with massive animal protein consumption. Interestingly, the very aspect of sustainability might give the lead for this shift. An article by Muller et al (DOI: 10.1038/s41467-017-01410-w) shows that suppressing the food/feed competition and thus limiting meat production to non-arable land will reduce overall meat production with positive consequences on environmental factors. In parallel, an increase of legumes in the diet will compensate for the reduction of protein intake and at the same time increase the fertilization through nitrogen fixation, a necessary part of organic agriculture. It is worth to note that legumes or pulses have the lowest environmental impact among all food categories.

The article explains that indeed it is the lack of sufficient and reliable data that motivated the choice for the geographical zone (high-income, industrialized countries) as well as the environmental factors considered, namely GHG emission, Land use, Eutrophication potential, Acidification potential and energy use. It is also to note that the analysis is lacking data on vegetable and fruit growth; the data provided in the article is mainly on dairy, meat and other animal produce.

 

Choice of environmental factors

If this study is used to make a choice between conventional agriculture and organic, there are some points that are essential to consider before jumping to the conclusion suggested by the title. To answer in a more realistic way the choice of the agricultural type that corresponds to a sustainable and environmental friendly way there are data that need to be found or created, to fill the knowledge gap that forced the choice for the environmental criteria analyzed in this study.

Indeed, it is important to determine which are the environmental factors that matter. Maier (2017) proposes to count 10 planet boundaries, that we need to respect to ensure a sustainable use of our resources and a viable future. Among the categories that are considered crossed or close to critical values, we count nitrogen and phosphorus cycles, that can be summed up as eutrophication potential; land system change (or native forest loss), considered as land surface use, and climate change, which corresponds to GHG emissions (see table 1). However, biodiversity loss is crossed by far and not included in the present study. This is an important factor to consider when choosing the type of agriculture. Other boundaries like freshwater usage and release of unknown substances (not yet quantified) are additional criteria not taken into consideration.

Table 1: Comparison of considered environmental factors and planet boundaries

Environmental factors analyzed Impact ratio organic:conventional Planet boundaries crossed Agricultural part (Maier, 2017) Positive effects of organic agriculture (FAO)
Biodiversity loss >300% About a third biodiversity
GHG emissions About the same (except meat <1 and vegetables mitigated) Climate change >100% About a third
Energy use Mostly <1 Energy efficiency
Stratospheric ozone depletion <100% Not significant
Atmospheric aerosol loading >300% Less than a quarter Air quality
Acidification potential Mostly >1 Ocean acidification <100% About a quarter
Eutrophication potential Mostly >1 Nitrogen cycle >200% Mostly due to agriculture
Phosphorus cycle 200% About 2/3
  Freshwater use <100% More than half
Land use >1 Land-system change >100% Mostly due to agriculture Landscape function and aesthetics
  Novel entities release ? ? Water quality
  Soil fertility
  Soil stability
  Other ecological services

 

This table shows that among the boundaries where agriculture is an important contributor, nitrogen and phosphorus cycles are the factors with the highest impact, followed by biodiversity and land use together with climate change. Additionally, it is to note that the boundary of novel substances release, or chemical pollution is not quantified; this can be an important point considering the large use of pesticides in agriculture. In particular, the FAO (http://www.fao.org/docrep/005/y4137e/y4137e02b.htm) reports organic agriculture having several benefic effects on the environment (soil fertility increase, bioactivity, water and air quality, energy efficiency, biodiversity, ecological services, landscape function and aesthetics).

Does this mean that conventional agriculture is still performing better from the environmental point of view than organic agriculture, and therefore should be chosen as the way to provide food and other goods for a sustainable future?

This seems, regarding the available data about the environmental factors chosen, a legitimate conclusion. Indeed, four out of five show a better outcome for conventional agriculture. However, it is also necessary to have a closer look at each of these categories to make a sustainable choice for the future.

Land use: About surface dedicated to agriculture and farming including animal breeding, deforestation and erosion

The article states clearly that the data are mostly from countries in highly industrialized regions. This means that is analyses regions from Europe and Northern America, which count for only 16% of the world produces. Additionally, they represent mostly temperate regions. Tropical and arid climates, which are more vulnerable to soil depletion, erosion or drought, are not considered in this analysis. This is to keep in mind if conclusions are drawn about feeding the world, knowing that the majority of the population precisely lives in developing countries.

Some arguments suggest that a more intensive agriculture locally, even one that destroys biodiversity would liberate the space needed for biodiversity conservation. While this could be regarded as a solution at first sight, there is no guarantee that it would be done this way, as other authors suggest using the space freed by a more intense agriculture for the growth of energy crops (Bos, 2009). Furthermore, a recent report by the UN Convention to combat desertification (UNCCD) (Global Land Outlook, Chapter 4: Convergence of Evidence, sept 2017) clearly shows all the implications of agriculture and land use in many different fields of human activity and environmental effects. A non-neglectable part of the world’s agricultural land is already degraded by this activity. It is therefore more than suitable to consider the soil-degradation or soil-conservation potential of a land-use type even before considering the size of the surface used for it. In other words, it is prudent to consider on the mid- and long term the total surface used, also including the land that has been degraded and cannot sustain agriculture anymore, thus forcing to extend into more natural land. This is especially true in arid zones, facing desertification after damageable land management. A recent study analyzed this apparent functioning of soils before the collapse, calling them ecological ghosts (Vidiella 2017).

 

Agriculture is, with urbanization, one of the main drivers for deforestation, and therefore an important threat to biodiversity in tropical or other native forests. However, looking more closely to the statistics, it appears that subsistence farming has a very low impact on forest clearing compare to large, industrial farming and pasture. “Rural population growth is not associated with forest loss, indicating the importance of urban-based and international demands for agricultural products as drivers of deforestation” (DeFries, Nature Geoscience 3, 178–181 (2010) doi:10.1038/ngeo756). Even more, forests as such constitute an important source of revenue for local small subsistence farmers (UNCCD, Global Land Outlook, Chap 4: Convergence of Evidence, sept 2017) (animal feed, medicine, honey, mushrooms, etc.) therefore the pressure to eliminate the forest is much lower.

Thus, the main and most significant pressures on land resources used for food production include (UNCCD, 2017, Global Land Outlook, Chap 7 – Food Security and Agriculture):

Most significant pressures on land resources according to UNCCD Factors addressed in the present study   Towards a solution
Poor management practices resulting in suboptimal yields, due mainly to resource use inefficiencies associated with irrigation, fertilizers, livestock, crop selection, etc. Choice organic agriculture vs conventional –

organic agriculture uses more land for the same production

More integrative methods and informed land management
Food demand and waste increasing rapidly with population growth, increased incomes, and globalization. This is the factor that raises all the concern about land use: feeding present growing and future population

A concern also together with carbon footprint of poverty eradication (Hubacek , 2017 DOI: 10.1038/s41467-017-00919-4)

Reducing food waste

Food demand is a more complex question (population and life-style)

Changes in diet further drives agricultural expansion as consumers increasingly demand food that is land-intensive, particularly processed foods and meat. As analyzed in the article of Clark and Tilman (2017), meat and animal products have a great negative impact on environment Change in diet: reduction of animal product consumption, especially meat – stay under the food/feed competition limit
Competing land uses reduce the area available for food production, including for biodiversity and ecosystem services, urbanization, infrastructure, tourism, and energy as well as biofuels and other non-food crops. Not only against natural forests, but also other land uses constitute a pressure on the natural environment Have overlapping land uses (tourism/agriculture, biodiversity/agriculture, urban agriculture, ..)
Land grabbing and virtual natural resource trading undermine food and nutritional security as well as smallholder tenure and resource rights in poor and vulnerable communities Economical and political factors that go beyond the kind of agricultural practice chosen Include social aspects internationally
Climate change expected to reduce crop yields in many countries resulting in greater food insecurity Not only a consequence but also a cause for agriculture practice changes Climate mitigation is a must to integrate into agriculture conception to ensure food security

 

 

It is true that one of the main issues of organic farming is its lower yield per surface unit (or larger area for the same production). Organic farming resembles in this case a conventional agriculture with no synthetic pesticides. There is a lot more to change in order to make a sustainable, productive agriculture.

This means that it is essential, when planning a more sustainable and organic agriculture, to reduce the area used for production (including the energy, water and raw material). Some trends suggest indoor, vertical farming as the way to go, sustaining that a carefully monitored growth optimizes inputs to a minimum, and the exclusion of outer influences makes the use of pesticides needless.

The ways out of the dilemma are a shift towards conservation farming as agroforestry and a shift towards cultivation of degraded land. This would allow both to save space and start regenerating land instead of degrading ecosystems.

GHG Emissions, Carbon cycling and climate change

Energy use is sometimes included in the GHG emissions because of its impact on climate change. Thus, an agriculture using less energy would be an advantage. It is interesting to note that while GHG emission are higher for organic farming, it is not true for fruit production. Fruit are mostly perennial plants…

Nitrogen and phosphorus cycles – Eutrophication

The data do not all agree on this. Organic agriculture is sometime shown to cause increased N-release, or sometimes reduced.

The main source of eutrophication caused by organic farming is given by the manure application. Again, a better management of fertilization through a better planning of crops and partners could reduce the need of manure application and a year-round soil usage diminish this impact. Data on the eutrophication potential of fruit trees would be appreciable in this context.

 

Water and water cycling – desertification

Agriculture counts for 20% of the drought events, 70% of the water withdrawal is done by agriculture alone. This is a remarkable impact that is not reflected by this study. It would be interesting to measure the impact of different types of agriculture on water cycling, to evaluate a sustainable management of fresh water. Especially when shifting studies to climates that cause a higher turnover ie faster degradation of organic substances through a high microbial activity as it is the case in tropical regions.

A recent study analyzed the apparent functioning of soils before the collapse, naming them ecological ghosts (Vidiella 2017). In this aspect, an analysis over time of the impact of certain types of agriculture is essential. This is mostly of concern in regions of the world (arid and semi-arid) that have not sufficient data to be included in the analysis.

Not-quantified factors

Furthermore, the impact of chemical pollution on water quality has to be taken in consideration for the evaluation of the environmental impact of agriculture. Not only does agriculture release nitrogen and phosphorus, main drivers for eutrophication, but also a range of other chemical substances used as pesticides, herbicides etc. These are found not only in the produce harvested, but also in surface water and ground water. This is especially important, from the human perspective, in particular for fishing activity and water consumption.

 

The collection of data about environmental impacts is essential for the future of policies regarding our way to plan agriculture and food consumption. The study presented gives important insights over the importance of animal produce on the environment and therefore the impact of the food choices of the industrialized countries. Even if a first glance at the results suggests a better ecological outcome for conventional agriculture, a deeper look at the data does not permit to draw such conclusions on a global scale, given the lack of data included. I rather suggest considering it as a motivation for an extension of the dataset to other countries and more vegetable and fruit produce and a wake-up call to draw the attention on the weak parts of organic agriculture as it is practiced in industrialized countries and a well-founded argument to improve organic agriculture where it needs to, namely a more efficient use of fertilizers and land.