Urban agriculture is generally painted with one of two brushes. It is either the most amazing thing that will save the world or it is a health risk that is detrimental to our urban areas and needs policy enacted to keep it out of our cities. I think both sides are a bit extreme. I am a strong supporter of urban agriculture because it has so many social and ecological benefits and provides interesting design challenges by taking so many forms. I do, however, think that large scale agricultural systems need to be more critically examined before determining if urban ag can in fact save the world. I also think that a few of the concerns from the other side might have a bit of merit and warrant some thought.
Most risks from engaging in urban agriculture are related to health and environmental factors. They most often arise from a lack of knowledge or planning that results it being done in the wrong places or in the wrong way. To avoid this, research what you’re doing and be aware that your actions will ripple out and affect other natural and urban systems.
The first group of health risks are not very common in the United States, but can be more of a problem in developing countries. There is a risk of contamination of crops with pathogenic organisms (bacteria) if the crops are being irrigated with insufficiently treated wastewater. There can also be a potential risk of diseases if there was an infestation, such as rats. There is a small risk of some livestock passing diseases to humans, but not from the types of livestock that would be kept in North America, such as chickens.
The second group of potential health risks does require more attention in the United States. This health risk is associated with the possibility that it might be taking place on contaminated land. Due to the fact that urban agriculture often occupies vacant or derelict land that is undesirable to other development, there is a very real possibility that it could be taking place on a brownfield site. Heavy metals such as lead, cadmium, chromium, zinc, copper, nickel, mercury, manganese, selenium, mercury or arsenic could contaminate crops. Many plants can absorb these metals into their roots and bioaccumulate in the plant, leaving them to ingested after they are harvested. Air pollution from nearby highways or roads is another concern. One needs to also keep in mind that these risks can also affect large scale traditional agriculture.
However, these concerns don’t mean that urban agriculture is too risky. Knowing the possible risks allows practitioners to take steps to create a safe and healthy environment. Simple steps such as avoiding areas of known contamination, growing crops in raised beds, importing topsoil, or using soil amendments to immobilize heavy those heavy metals will alleviate the risks. A phytoremediation strategy (the use of plants to decontaminate soil and/or water) could also be put in place to prep the site and mitigate the risks.
Risks to the Environment
Urban agriculture is generally really positive for the urban ecosystem. It is good to have any vegetation, but especially something as productive as food, growing where there was previously nothing or just lawn. There is also increased biodiversity, increased evapotranspiration for cooling urban heat island and increased stormwater management. The only potential risks to the environment would be that pesticides and fertilizers could get into and contaminate the water system. However, most urban agriculturalists prefer not to use them or use them sparingly. Traditional agriculture is a much greater offender when it comes to fertilizers and pesticides.
In my first post on urban ag, I listed its benefits and the drawbacks of traditional farming. There is plenty of anecdotal evidence for the benefits of urban agriculture over traditional industrial farming but why is there is a lack of statistical evidence to back up these claims? This is most likely because urban agriculture is too varied and decentralized to be able to accurately measure the inputs of resources, energy and costs.
In my third post I discussed different categories of urban agriculture (vertical vs. horizontal and both large and small scales of both). Small scale implementation is much more common and yields great results. However, large scale implementation is where problems begin to arise. The increase in scale seems to exponentially increase the required inputs of resources, energy and cost. For example, someone growing their own produce in a small plot in a park or on a wall requires low input of initial resources or cost. This is far more efficient than growing that same produce with large machines hundreds of miles away and shipping it to the store. On the other end of the spectrum, a skyscraper full of agriculture would be cool, but the initial costs to build it, plus the high amounts of energy and water it would require to maintain the hydroponic systems would most likely have a resulting higher carbon footprint than traditional agriculture.
Although there are some risks to health and environment when engaging in urban ag, they can be easily mitigated with effective planning, management and training. Even though today’s larger scale urban agriculture might have high resource and energy inputs, that isn’t to say that urban agriculture can’t still save our environment and food supply.
The next step is crucial to understanding if it is possible to amplify the benefits that urban agriculture currently provides to a small population to a larger constituency. Despite some difficulties and risks involved in urban agriculture, there is definitely a place for it in our cities.
I really believe urban agriculture is an area in which landscape architects can play a strong role by cultivating innovative practices and expanding its presence in our cities. The book Carrot City: Creating Places for Urban Agriculture has some examples of how designers have interfaced with this movement in powerful ways.
Looking back at the competition I entered with Fadi Masoud, Karen May, Denise Pinto, and Drew Adams, we had a larger objective to propose a reframing of the aesthetics and productivity of ‘the landscape’ and our relationship to it. We created a series of new organizations and piggybacked existing infrastructure to create a new form of urban agriculture that could have large-scale fiscal, ecological and social benefits. Suggesting these types of innovative, big-impact yet ecologically-grounded proposals are where our profession can take a leading role in in furthering the discussion.