(This post was written by Maggie Schmaltz, a rising sophomore Biology of Global Health major at the University of St. Thomas. Maggie spent June 2019 in Cape Town, South Africa on a course entitled “Urban Agriculture and Social Innovation”)
The scientific community is bad at getting its point across.
Exhibit A: It is common knowledge that ice caps and glaciers are melting as a result of global warming, leading to rising sea levels. But, how bad is that? Well, 11 percent of the world’s population (about 800 million people) live within 33 feet of sea level. Rising oceans may displace many of these coastal residents in the coming century, undermining economies, infrastructure, and ecosystems around the world.
Exhibit B: Most people know that soil erosion is “bad”- but do people know how bad? Desertification across the globe is leading to less arable farmland available to feed an ever-growing population, and the situation is rapidly getting worse. For example, in South Korea, dust storm season is now 118 days per year, up from 39 days per year in the 1980s (Brown LR (2012) Full planet, Empty Plates, pg 50-).
Maggie (the author) planting at an Abalimi farm
An inability to effectively communicate the likely impact of climate change and global resource management is a significant failure of the scientific community. It is hard for people to take difficult steps to address a problem if they don’t understand the impact a lack of such action will have.
I can illustrate this communication gap by using my own experience as an example. Our class this June worked with an urban farming organization (Abalimi Bezekhaya) in Khayelitsha, a township outside of Cape Town. Throughout our work, a common topic was the critical need for composts and manure fertilizers for the urban farmers. These resources are necessary to enrich Khayelitsha’s sandy, nutrient-poor soil, which cannot otherwise support the growth of most vegetables and herbs. The Abalimi farmers were very knowledgeable about the nutrients within the soil, which they reverently referred to as “living soil,” and often described the process of nutrient recycling (the cyclic flow of element nutrients between the living and non-living components of a soil environment). Nutrient cycling is an essential process in an ecosystem; carbon, oxygen, hydrogen, phosphorus and nitrogen must be recycled for life to exist. Plants take up nutrients from the soil to grow (in varying amounts, as different plants can be referred to as heavy feeders, medium feeders, light feeders, etc.), and some of those nutrients are lost when crops are harvested. If these nutrients that were “taken” from the soil by the plants are not replenished, then the nutrient content of the soil will be depleted, with negative consequences for future crop yield and quality. Nutrients like nitrogen can either be replaced via legumes (like peas and beans) that can take nitrogen from the air and convert it into a usable source for plants or via application of composted organic material (food wastes, leftover plant material, etc.). Nutrients like phosphorus can be replaced via manure or, often in commercial agriculture, chemical fertilizers.
One of the Abalimi farms in Khayelitsha
Upon working in the urban farms, I realized I had hardly any prior knowledge about the importance of composting and, more generally, nutrient cycling. From what I had learned previously, I thought composting was just an efficient way to get rid of food waste. However, observing the lack of fertile soil in areas like the Cape Flats, the desertification happening elsewhere, and the decreasing availability of essential elements like phosphorus around the world helped me understand that efficient nutrient recycling is essential in a world that must prepare to feed a growing population.
Compost bins at an Abalimi farm in Khayelitsha
Today, it is really easy to name environmental hazards with potentially global implications: climate change, finite fossil-fuels, and the risk of water scarcity (as we viewed in Cape Town, which experienced a severe water crisis in 2017 and 2018) quickly come to mind. But, many scientists want concern for nutrient cycles added to that list.
The story of phosphorus underscores the importance of nutrient cycling in a growing world (Cordell et al. 2009). Phosphorus is essential for all living things. It is a component of DNA and bone, among other things. People acquire the phosphorus they need from food; agriculture uses about 90% of mined phosphorus. For much of history, farmers replenished phosphorus in soil by spreading animal waste, human waste and plant remains as fertilizer. Those processes fed a cycle of use and replenishment of the rare element. But these days, phosphorus is more likely to come out of a sack as a key ingredient in processed fertilizers. This phosphorus fertilizer is a finite resource that is mined from rock in only a few countries that have significant reserves; according to the US Geological Survey in 2015, Morocco, China, Algeria, Syria and South Africa together control 88% of the world’s phosphate rock. This means the rest of the world is potentially subject to supply and price fluctuations. The US used to be the world’s largest producer, consumer, importer and exporter of phosphorus, yet now has only about 20 years of reserves remaining. Meanwhile, China recently imposed a 135% export tariff to secure domestic fertilizer supply, which has halted most exports. Experts point to an approaching “peak phosphorus” (much like peak oil)- a time when humanity will reach the maximum global production rate of phosphorus as an industrial and commercial raw material. According to some researchers, Earth’s commercial and affordable phosphorus reserves are expected to be depleted in 50-100 years and peak phosphorus to be reached in approximately 2030 if we maintain our current trajectory.
While oil and other non-renewable resources can often be substituted with other sources when they peak (like wind or solar energy), phosphorus has no substitute in food production. This makes phosphorus cycling relevant because climate change and resource management impacts on food and water systems are catalysts for social breakdown and conflicts. A prime example is how food issues, namely food price inflation due to a spike in grain prices, catalyzed the Arab Spring. In a world with over 80 million more people each year, dependable agriculture is necessary but could be undone by interrupted nutrient cycles.
Human actions often disrupt nutrient cycles, but we can also help to restore them. Nitrogen levels are diminished as harvesting crops strips soils, but composted food wastes can be added to restore nitrogen levels while also decreasing the contribution of households to global waste. Phosphorus is mismanaged in the food system, with four-fifths of phosphorus meant for food production being lost or wasted during mining and processing and fertilizer application where it can run into water and cause toxic algal blooms. But, much of these phosphorus and nitrogen losses can be avoided through improved practices, while the remaining waste (banana peels to manure) could be captured for reuse as fertilizer.
Nutrient cycling is one of the least talked about and most poorly understood environmental issues today despite having a huge effect on food systems and by extension, civilization as we know it. In Cape Town, we witnessed just how important nutrient cycling is and how feasible composting can be at the Khayelitsha farms and at the Oranjezicht city farm (another farm we visited), where even local restaurants bring their food waste for composting. The waste produced by urban areas is more than enough to enrich the soil within them and beyond, and communicating the relevance of composting to households and businesses can encourage the practice and bridge gaps in the nutrient cycle.
Biophilia 
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