Urban ecosystems are expanding around the world as people migrate to cities and the human population continues to grow. What happens to other species as these urban ecosystems expand, and how species live and interact
Category Archives: urban planning
It’s Not Easy Being Green: Assessing the Challenges of Urban Community Gardening
From vertical gardens to succulent gardens to community veggie gardens like the San Francisco garden pictured above, city dwellers all around us have started embracing their (hopefully) green thumbs. For urbanites in particular, community gardening provides us with much needed “outside time” with likeminded individuals, with the added gift of hyper-local produce available throughout the growing season. These benefits have led to increases in residential and community garden participation in major cities across the US.
While many people are jumping on the garden-fresh bandwagon to reap the obvious, verdant benefits, it is important to consider the potential side effects that come alongside urban farming. Urban soil is not only closer to possible sources of pollution, like traffic and industrial areas, but could also contain residual chemicals from past land use. Residential land previously occupied by industrial buildings has been found to contain dangerous levels of toxins like lead, which can poison residents and contaminate food grown on-site. But it doesn’t take a former factory to contaminate your backyard. Soil can absorb and hold toxins left over from something as small as a previous homeowners dumping of cleaning water down the drain or off the back porch.
Researchers from Baltimore published an article in PLOS ONE earlier this month assessing Baltimore community gardeners’ knowledge of soil contamination risks and explored what steps can be taken to mitigate the dangers of urban pollution in urban gardens.
The authors, hailing from Johns Hopkins, University of Maryland, and the Community Greening Resource Network, conducted interviews with Baltimore’s community garden members, and found that unfortunately, the gardeners generally seem to have low levels of concern about potential contaminants in their soil. Those working in established community gardens were least concerned as they often assumed that any issues with soil contamination had been addressed in the early days of the garden’s use.
Participants listed lead as the most concerning pollutant—likely due to city interventions concerning lead poisoning—with 66% of surveyed gardeners mentioning it as something that would concern them if found in their soil. The study results also indicate that gardeners are more worried about the presence of pesticides and other added chemicals than most other residual chemicals in the soil. Soil quality and fertility even took greater precedence for some gardeners than the presence of contaminants.
By interviewing Baltimore officials knowledgeable about community gardening practices and soil contamination issues, the researchers determined key steps in assuring the safety of gardening sites. Above all, officials suggested the creation of a central source of information related to soil contamination concerns. Similar projects relating to regulation and urban agriculture are already underway in places like Los Angeles, though these resources aim to help residents navigate the maze of confusing legislation related to urban agriculture, and focus less on providing information on how to evaluate the safety of specific plots of land.
The authors suggest other important ways to determine the safety of a garden site, including learning about the site’s past uses and testing the soil for lingering chemicals, both of which might not seem necessary to those untrained in urban planning or chemical analysis. They also recommend that officials in urban areas provide services that will encourage use of these tools and help gardeners find and interpret the results of soil testing or historical research.
In the meantime, the authors suggest limiting exposure to potentially contaminated land. For instance, we should minimize contact with dirt from garden sites by washing our hands and taking off shoes before entering any indoor spaces. Many interviewed gardeners have tried to mitigate this problem by using raised beds, which they believe eliminates concern about contaminants in homegrown vegetables. However, researchers find this method ineffective, and it should not be seen as a fix-all. Raised beds do not prevent contamination from soil around the beds, which can still be ingested or tracked into the home, and surrounding pollutants have been known to blow into beds or seep into the soil from treated wood used to build the structures.
Urban community gardening is a trend that is here to stay, and we have it to thank for fresher local produce, greener surroundings, a greater sense of community, and for the physical, and sometimes therapeutic, activity it provides. The potential dangers associated with gardening in urban areas probably do not outweigh the benefits, as long as gardeners remain diligent and become better informed. Though their study focused on a limited group, this paper’s findings draw attention to the fact that they’re not. So, next time you’re digging into a grassy patch in your backyard with visions of veggies or working in your local community garden, take a minute to think about what you know about your area, discuss past developments with longtime residents, and above all, clean up afterward.
More information on soil testing and good gardening practices can be found on this site from the EPA.
Citation: Kim BF, Poulsen MN, Margulies JD, Dix KL, Palmer AM, et al. (2014) Urban Community Gardeners’ Knowledge and Perceptions of Soil Contaminant Risks. PLoS ONE 9(2): e87913. doi:10.1371/journal.pone.0087913
Image: Tenderloin People’s Garden by SPUR
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Biking the Distance… In 30 Minutes or Less: The Impact of Cost and Location on Urban Bike Share Systems
Those of us who commute to the PLOS San Francisco office have noticed the emergence of bike share stations cropping up along the San Francisco Bay and on the city’s main drag. And we’re not alone here in San Francisco: the picture above is from the New York City Department of Transportation’s bike share. Around the world, bike share systems, which aim to make bicycles available on a short-term basis to anyone, have experienced massive growth as cities work to decrease gas emissions and encourage people to stay active. However, not everyone is ready to forgo the convenience of four wheels for two just yet. To understand why more people haven’t made the switch from cars to bike share systems, the author of a recently published PLOS ONE paper delved into possible factors affecting our willingness to don a helmet and cycle the distance.
Using publically available data from Washington DC and Boston, Dr. Jurdak, an Australian researcher, conducted a series of statistical analyses designed to examine the impact of bike share system pricing and neighborhood layout on potential bikers. It turns out cost is a major factor for commuters and tourists alike, but distance is not. Although analyses showed a bias towards shorter trips with a tendency towards a peak of 6 minutes—averaging 13 minutes per trip—a sharp drop off occurred in the likelihood of trips right around 30 minutes.
Why the decline at around 30 minutes? In both Boston and Washington DC, trips under 30 minutes incurred no additional cost in the bike share pricing system. Registered users of the bike share, typically commuters, must pay an initial registration fee but have a grace period for all trips completed in less than 30 minutes. Trips extending beyond 30 minutes, however, incur additional fees. In other words, public bicyclers are looking to maximize the distance biked and time spent without incurring any additional cost. Researchers have labeled this as ‘cost sensitivity.’
Statistical analyses also demonstrated the same cost sensitivity in casual users, or those who do not have a monthly or annual membership, and who likely use the bike share system for tourism. However, instead of noting a decline in the likelihood of trips around 30 minutes, Dr. Jurdak found a decline for casual users at around 60 minutes (another price point).
On the other hand, despite sensitivity to cost, bikers appeared less dissuaded from bike trips based on neighborhood layout. Although stations in Boston were on average much closer to other nearby stations than in Washington DC, in general, the trip distribution for both cities was remarkably similar. Perhaps not surprisingly, the most popular routes taken in both Boston and Washington DC were relatively flat.
To encourage more people to cut the car usage and grab a rental bike, Dr. Jurdak recommends that cities consider incentivizing their constituents with what they care about: cost. Modified prices for bike rental during peak hours may decrease car traffic on congested roads; an extension of grace periods for biking difficult topology, like up a steep San Francisco hill, might encourage us to bike even though the clock is ticking to 30 minutes and an incurred rise in price. As cities look to evolve public transportation systems and increase responsible urban mobility, and as city dwellers look for cost-effective ways to get around, bike share programs continue to offer healthy solutions for all, even at 30 minutes or less.
For more on the effects bike share systems are having around the world, check out another recent PLOS ONE paper and the researchers’ blog post on bike webs, visualizations of bike share schemes.
Jurdak R (2013) The Impact of Cost and Network Topology on Urban Mobility: A Study of Public Bicycle Usage in 2 U.S. Cities. PLoS ONE 8(11): e79396. doi:10.1371/journal.pone.0079396
Image 1: Citi Bike Launch by New York City Department of Transportation