Author: Idil Cazimoglu Edited by: Inês Barreiros
What was the last thing you ate?
An apple? Steak? Cake? Unless you have recently opted for an unconventional lifestyle, it’s most likely a product of modern agriculture.
Since the majority of us on Earth are no longer hunter-gatherers, humanity now relies on modern agriculture to be fed. Even though agriculture involves both the cultivation of plants and the rearing of animals, here we will focus on plants. All of our food, either directly or through animals, comes from plants most of which are grown by intensive agriculture. If agriculture isn’t done sustainably, our future doesn’t look bright. But why do we need to be sustainable? We have been cultivating plants for at least 23,000 years, and have been fine without putting much effort into sustainability. Why change things now?
There are a multitude of reasons why growing food sustainably is more important now than ever before. Our population is rising fast and is expected to reach 9.1 billion by 2050. To have enough food for everyone, we need to increase our overall food production by at least 70%. Expansion of agricultural lands to meet higher food demands would mean compromised biodiversity and ecosystem services. Our climate is changing, and extreme weather events such as storms, floods and droughts are becoming more severe and more frequent. We will lose some of our crop yields due to climate change, and in fact, are already losing a significant portion of our global yields for corn and wheat due to increased temperatures. Rising temperatures will also increase the prevalence of plant diseases by expanding the range and increase the activity of many pests. Due to a combination of surging energy demand for a growing population and shrinking fossil fuel supplies, energy prices are expected to increase. Agricultural methods, especially irrigation and fertiliser production, rely on energy. Extraction of nitrogen and mining of phosphorus, both main ingredients in fertilisers, are both energy-intensive processes. The Haber-Bosch process to generate nitrogen compounds for fertilisers consumes 2% of the world’s total annual energy production. Intensive agriculture is also taking its toll on soil quality and as a result, we are quickly depleting our most accessible phosphorus reserves, with about 80 years left before we have run out.
Even though there seems to be debate over how much phosphorus we have left and whether we should use mineral reserves or mineral resources for our estimates, diminishing reserves are not the only phosphorus problem. Leakages of phosphorus, the limiting nutrient in fresh water, cause disproportionate levels of eutrophication* resulting in the death of fish and other aquatic animals. This is the very opposite of sustainability.
Another chemical vital to life as we know it is water, and we are not doing too well on that front either. Almost a fifth of the current population lives in water-scarce areas, and an additional 500 million will soon find themselves in this situation. Agriculture draws 69% of global fresh water, and by 2050 this will increase by at least 19%, or more if we do not improve our crop yields and agricultural production efficiency.
As well as synthetic fertilisers, we currently rely on synthetic pesticides to keep our crop yields as high as possible. In pesticide synthesis, there are currently no alternative approaches to preparation from non-renewable petrochemicals. In addition, chemical pesticides often harm off-target plants and animals and can cause outbreaks of secondary pests, moving us further away from a sustainable system.
Have we done anything so far to make our agricultural practices more sustainable? Yes, several things. Many important crops have been genetically modified for improved drought resistance, pest resistance, herbicide tolerance, water and mineral absorption. New GM crops are subjected to field trials every year. According to a 2014 analysis, adoption of GM crops increased yields by 22% while decreasing chemical pesticide use by 37%. It must be noted that many are concerned about the economic implications of the way GM crops are currently produced and distributed, and these issues must be addressed if GM crops are here to stay.
Some other farming practices to enhance agricultural sustainability revolve around precision agriculture, the treatment of crops based on needs determined by site-specific measurements of soil conditions, nutrient levels and crop health. For example, imaging techniques can detect crop stress in a site-specific manner and at an early stage, decreasing crop losses as well as saving on the agricultural resources employed to prevent them. The most widely used imaging techniques in agriculture are thermography, fluorescence imaging and spectral imaging. Thermography monitors plant leaf temperatures, as a common symptom of plant stress is low rates of transpiration - the cooling mechanism of plants. Fluorescence imaging monitors the levels of certain pigments in the leaf, including chlorophyll. Spectral reflectance techniques monitor the electromagnetic radiation reflected from the leaf surfaces usually in the visible and near infrared ranges. Spectral images of large areas can be taken remotely from drones or satellites.
Various promising farming practices for sustainable agriculture exist. Integrated pest management, which combines multiple methods such as biological and mechanical controls, modification of agricultural practices, and conservative use of synthetic pesticides can reduce the amount of petrochemicals used for pesticide synthesis as well as the effect of pest control on non-target organisms. Crop rotation minimises the need for fertilisers by planting crops that either replenish the nutrients in the soil that were depleted in the preceding season or absorb different nutrients. Adoption of renewable energy sources such as wind turbines, hydro-electric turbines, solar panels, and biomass energy production can also improve agricultural sustainability, as these technologies reduce the dependence of agriculture on non-renewable fossil fuels. Capturing and recycling phosphorus from waste streams is a promising way to improve the sustainability of fertiliser use while preventing eutrophication. For example, only 37% of phosphorus recycled from human food waste, human excreta, and animal manure, has the potential to meet the annual phosphorus requirements of corn production in the United States.
If we are to survive beyond the next few decades, we have to do agriculture sustainably. We have started shifting towards more sustainable practices, but there is still a long way to go. Sustainable agriculture is a grand and complex challenge. In order to achieve it, we likely need to use all of the above possible solutions and more.