Warning: Agricultural Chemicals!

In order to grow our food faster, cheaper and bigger, modern agriculture has opted to a wide variety of chemical pesticides and inorganic fertilisers. Fertilisers in the form of manure and compost have been used for centuries but the use of chemical fertilisers only relates to the industrial Green Revolution in the 20th century. Fertilisers, especially nitrogen based, have seen a dramatic tenfold increase since 1950s (Robertson and Vitousek, 2009). But due to the fact that we are unable to keep nitrogen from leaving cropped ecosystems though various pathways (mainly waterways and atmosphere), fertiliser use brings well-documented and significant environmental impacts. Nitrogen is a central element in living systems but overuse and mismanagement have severe consequences (Robertson and Vitousek, 2009).

One of the first synthetic pesticides, dichlorodiphenyltrichloroethane (DDT), was widely used during World War II to kill malaria-bearing mosquitos and typhus-carrying lice. After the war, it became a popular pesticide to kill off unwanted pests on farms. In 1972, DDT was banned in the United States as the Environmental Protection Agency (EPA) noticed an adverse affect on wildlife as well as humans. Today, due to its persistence in the environment, DDT is considered as a human carcinogen and is still in use in some parts of the world. This proves how little we know about the effects of chemical fertilisers on humans but also the environment.

Modern agricultural industry takes advantage of many synthetic fertilisers pushing up yields and helping to feed the planet's growing population. But at what price? The use of synthetic fertilisers causes a systematic change in the way we think about soil and organic matter. Before chemical fertilisers, healthy soil was packed with microorganisms, retaining nutrients and moisture to grow plants. In addition, topsoil organic matter sucked up atmospheric nitrogen, converting it to ammonia and nitrates that was consumed by the plants. This biological cycle breaks down as soon as soil is treated with synthetic fertilisers, leading to topsoil loss and the release of carbon dioxide, a major greenhouse gas causing global climate change.

Nitrogen is used in nearly all synthetic fertilisers as it acts as an important nutrient for plants. When nitrogen fertilisers are used on soils, the chemical processes following cause the fertiliser to break down and the releasing of nitrous oxide. In fact, synthetic fertilisers are to blame for more than 75% of all agricultural nitrous oxide emissions (EPA, 2012). But what is so special about nitrous oxide?

Global Greenhouse Gas Emissions by Gas

Source: IPCC, 2007

To answer that, we need to look more specifically how effective nitrous oxide is in trapping heat. If we compare carbon dioxide to nitrous oxide, the latter is 296 times more powerful in trapping heat, leaving us more than worried. While carbon dioxide takes the biggest piece of the pie for greenhouse gas emissions (IPCC, 2007), it may not be the most dangerous one in terms of climate change potential.

But what about the production of fertilisers? It turns out, the modern agriculture industry has transformed soil fertility into a fossil fuel intensive 'business'. Consider this: in order to produce a ton of fertiliser, more than 930 litres of natural gas. Furthermore, raw materials for the fertilisers often have to be mined or manufactured away from production sites, adding the transportation cost in terms of emissions. Not to mention how half of the nitrogen fertiliser applied on crops in the United States is leaching through to the soil and the waterways. This makes fertiliser use wasteful, harmful for the environment and dangerous for humans.

Promotion of fertilisers in 1942 by the Tennessee Valley Authority- right-hand side field was treated with phosphate and lime, the left-hand side was not treated.

It is important to realise another dramatic consequence of excessive nitrogen release into the environment: hypoxia. This phenomenon occurs when nitrogen gets released into waterways and 'high nutrient levels stimulate algal growth, and when algae sink into deeper water and die, their sub- sequent decomposition by bacteria consumes dissolved oxygen deep in the water column faster than it can be replenished from the sur- face, leading to the development of hypoxia and the reduction or elimination of deeper-water organisms that require oxygen' Robertson and Vitousek, 2009:103). This process dramatically disturbes the natural habitat of biodiversity and leads to the unbalancing of natural nitrogen cycles. 

 

Looking through the evidence that I have gathered here, it is clear that both humans and the environment have taken a hit due to the introduction of the synthetic fertilisers and chemical pesticides. In order to reduce the human health hazards, reduce the impacts on climate change and to make way for more sustainable farming, the focus should lie on organic fertilisers, which preserve the soil's organic matter. With modern technology advancements and our knowledge of past mistakes, there is hope that such fertilisers will come to dominate the future food production.



Till next time,
Laura