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Are Urban Farms Actually Bad for the Environment?

Raz Godelnik
| Friday July 8th, 2011 | 10 Comments

Edward Glaeser doesn’t see the point in urban farms. Well, it’s not completely true – the Harvard Professor does see educational value in them for school kids, but that’s it. Last month Glaeser wrote an interesting piece on the Boston Globe about urban farms (“The locavore’s dilemma“), where he made a very persuasive argument that urban farms actually represent an inferior alternative from an environmental point of view. His main point was that devoting scarce urban land to farms and not to people will reduce cities’ density level, which will then cause the rise of carbon emissions.

When you read the piece it makes sense, especially when it comes from a bright well-known economist such as Glaeser, who knows a thing or two about the urban sphere. So do we have here the urban version of the food vs. fuel debate? Well, not so fast.

Glaeser’s argument is very simple: When you look at the environmental costs and benefits of urban farms, the costs outweigh the benefits, mainly because “farm land within a metropolitan area decreases density levels and pushes us apart, and carbon emissions rise dramatically as density falls.” Why? Because “lower density levels mean more driving.”

Glaeser provides many figures to back up his argument but forgets two important details: First, there are options like rooftop farms or vertical farming that don’t reduce cities’ density levels at all. Second, many old industrial cities have large number of vacant lots where no one wants to live and it might take decades until these lots will be populated again. In these cities, urban farms can be an excellent interim use for these lots, contributing to their revival and  helping to fill them again with residents.

Let’s look first above the ground, or more specifically to the rooftops of buildings. You’ll find there plenty of room for urban farming – according to Laurie Schoeman, director of New York Sun Works, a nonprofit group that promotes the use of rooftop greenhouses, just in New York there are 14,000 acres of unused rooftop space. Schoeman estimates that this area filled with greenhouses can feed as many as 20 million people in the New York metropolitan area.

And it’s not just New York. According to phigblog, GIS data from PASDA reveals that there are 162,000 buildings in Philadelphia with a total rooftop area of over 16,000 acres. Now I’m not sure how many acres of rooftop space are available nearby to Glaeser in Boston, but I’m sure there’s plenty of space there to grow food. One example can be found at Boston University, which has a rooftop greenhouse since the 1930s. Even at Harvard University they’re experimenting nowadays with a green roof as part of the university’s efforts to reduce its carbon emissions.

Now, this is by no means a theoretical argument. Although rooftop greenhouses are just making their first steps in the urban sphere, you can already see some successful sprouts. Only last month I wrote here about BrightFarms, a NYC-based company, which has developed a win-win model of  building and leasing hydroponic farms on supermarket rooftops. As I mentioned there, the company has already signed up eight supermarket chains around the country, including three of the largest 30 national chains and four of the farms are under construction.

The second element Glaeser is ignoring is the fact that cities have vacant lots, which no one is interested in. Detroit is a well-known example (just take a look at this graph), but you can find a large number of vacant lots in many other cities, especially old industrial ones that experience processes of deindustrialization and decline of population. For example, in Philadelphia according to one estimate there are about 40,000 vacant lots.

As the authors of the book, Urban Agriculture: Food Jobs and Sustainable Cities (Smit, Nasr and Ratta) point out many of these vacant lots will not come back to life in the near future and urban agriculture can be an interim use for them. The authors mention the slogan ‘Plant First, Build Later’, which was popular in Germany after World War II when the Germans reconstructed bombed out cities. This slogan can definitely be a good fit 65 years later for Detroit and other cities that don’t have any other solution for the vacant lots.

The point is that in a perfect world, vacant lots are just undeveloped properties waiting for the right developer to build on them, but in the real world it is much more complicated. In the real world, you have cities that people don’t want to live in and the value of the property is going down. You can wait couple of decades and hope that the invisible hand will bring back these cities to life, but you can also take an active approach and use these lots for urban agriculture, creating jobs and opportunities that will encourage people to come back and helping the density level to rise again. It might be only interim solution but it’s still better than the alternative in the real world which is more years of decay.

After all, it looks like Glaeser’s dilemma is not a dilemma at all. There is a way of making sure the environmental benefits of urban farms outweigh their costs – it’s just a matter of taking all the elements into consideration and realistically looking at all the options, both on and above the ground.

Image credit: everywhereATonce, Flickr Creative Commons

Raz Godelnik is the co-founder of Eco-Libris, a green company working to green up the book industry in the digital age. He is also an adjunct professor in the University of Delaware’s Alfred Lerner College of Business and Economics.


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  • http://twitter.com/JamesMastaler James Mastaler

    I appreciate your emphasis on the practical nature of urban agriculture, noting the difference between the theoretical (and perhaps ideal) use of open urban space for housing and business and the actual existence of vacant urban land that won’t realistically be built upon for a long time.

    The importance role population density plays in urban economics, efficiency, culture, etc. is well noted and so Glaeser makes a good point. However, you make an excellent counter argument and observation that just because a plot of urban land should contain a vibrant business and residential community, doesn’t mean it necessarily will…urban ag plots can go a long way in improving the quality of urban life, especially when business and residential developments aren’t likely to fill those blighted areas and vacant lots that urban ag plots usually end up filling.

    Thanks for the back-and-forth on such an important topic.

  • http://www.chris-hamby.com Chris

    Glaeser seems to have a very different idea of what urban agriculture looks like. Density and local production of food can complement each other.

  • Nick Aster

    Great article Raz. It’s ridiculous to argue that urban ag reduces density without looking at exactly the two things you bring up. THe only reason urban ag even exists is because of vacant lots that people wanted to put to productive use.

    If I wanted to play devils advocate, the only REAL argument against urban ag that I can think of us one of economies of scale – it is (probably) cheaper and more efficient to grow food in vast, flat fields and to mechanize it as much as possible. Granted, there may be negative aspects to that too, depending on how industrialized it gets. But the argument would be that feeding the world is more efficiently done on a large scale.

  • http://www.facebook.com/people/Rob-Bryan/1119106971 Rob Bryan

    We probably should remember that economists believe in perpetual growth. There are limits to growth and those apply to population density as well. I also don’t see where the food that’s NOT shipped into the city, with its large carbon footprint, is credited.

  • http://www.klynnbusinessconsulting.com Kurt D. Lynn

    Glaeser’s perspective is surprisingly narrow. In general, he seems to suggest that green things are a threat to the urban environment is the same way that logging is a threat to the Brazil rain forests. Specious. As you point out he also fails to deal with rooftop farms which can co-exist, but as much to the point he fails to identify the food distribution chain as the principal catalyst for declining food quality. The issue certainly isn’t “food miles” — it’s food AGE and the types of decisions that are catalyzed by having large distribution chains (like choice of cultivar’s, use of chemicals, etc.)
    Lufa Farms in Montreal has make it clear that farms can reclaim lost arable land from the city in a way that does not negatively impact the city and at the same time produce a higher quality, and fresher result. Lastly, his argument further misses out on cause-effect by ignoring that cities consume arable land and creating more arable land consumes forests. In failing to distinguish between Food Inc. farming and responsible farming, Glaeser can add his name to the list of people that catalyze lasting problems by not understanding the true interdependencies intrinsic in the problem. Next he’ll be trying to convince us that food picked early, passing 1-2 weeks in shipment from Food Inc farm in Ecuador is somehow better quality than the tomato picked off the vine this morning. Hah!

  • http://www.facebook.com/people/John-Danforth/100002650230483 John Danforth

    Interesting

  • http://terracycle.net Jason Kane

    Most important, this article points out the pros of urban farming, stressing the benefits local farming specifically. Building in a city should reflect sustainable growth, which ideally requires local farming and thereby urban farming, especially since cities are where most people live in the USA.

  • Christophe L Lachambre

    I am definitely a fan of these urban vertical farming projects. I got a great enthusisatic support from my academic fellows when I have proposed this topic as a thesis subject of my executive MBA. it will be about value creation through different proposals (community, supermarkets, food business etc.). Thanks for the contribution of this good article to my researches.

  • Alexsambrown

    I feel like the main point is being missed here. It’s fine to use vacant lots for agriculture, I don’t think that anyone, including glaeser, is saying otherwise. However, that is only a short term solution. Density is why cities work. If everyone in the city had enough space to grow their own food, it would pretty much look like the suburbs. Yay for urban farms, but they should be cleared the minute that someone wants to build on that land, well, maybe after the harvest.

  • Alexsambrown

    Also, I think we can all agree that this Christophe guy above me is a pretentious douche. Sorry man….