Towards the development of a GIS method for identifying food deserts: Geographic access in Vermont, USA
Jesse McEntee and Julian Agyeman
Food deserts
have become an increasing concern among many different groups of researchers. A
food desert is often defined as an area of relative exclusion where people
experience physical and economic barriers to accessing healthy foods. Much of
the current research and studies done on food deserts have been carried out in
the United Kingdom and/or urban areas. McEntee and Agyeman attempted to fill in
the gap in the literature by completing a study based on rural food deserts.
GIS has
increasingly become a tool in helping to bridge public health research with
neighborhood level information across multiple disciplines. In this particular
study, they utilized GIS to analyze the location of supermarkets and
residential units to identify census tracts that were considered food deserts.
Food
security is defined as all people at all times having access to enough food for
an active and healthy life. Geographic, economic, and informational barriers
are the main concerns when analyzing food security. McEntee and Agyeman focused
on the geographic barriers for their research.
Research was
carrier out in the state of Vermont because it is a primarily rural state.
There are a total of 608,826 people living in the state and 21% of the state’s
land is dedicated to farms.
Information
about food retailers was gathered from the North American Industry
Classification System, using the indicator ‘Supermarket and Other Grocery
Stores larger than 2500 square feet.’ Food retailers larger than 2500 square
feet was used to filter out smaller convenience stores and gas stations that
typically sell low nutritional value food items at high prices. Information for
residential units was obtained from the Vermont Center for Geographic
Information. Information for roads was obtained using ArcGIS software. The
network analyst extension closest facility feature of Arcmap was used to
calculate distances.
The mean
distance to food retailers within census tract was calculated by dividing the
sum of distances between residential units and retailers by the total number of
residential units in the census tract. The mean distance values are illustrated
in the map below.
According to
the national transportation survey (MSU 2003), the average US
resident travels approximately 8 miles to obtain groceries. For the purpose of
this study, census tracts that had greater than a 10 mile mean distance value
between food retailers and residential units was considered a food desert.
Twelve
census tracts were considered food deserts, equal to 4.5% of the state’s
population. The mean distance traveled in the food desert tracts was 13.15
miles, significantly greater than the statewide mean of 4.14 miles. The map
below shows the location of census tracts considered food deserts.
McEntee and
Agyeman’s use of GIS in the study of rural food deserts provides information
about food deserts on the rural level, which as been relatively absent in
previous research. Because their research did no require extensive time or
resources, this study could be easily replicated in other locations and
contribute to food desert identification strategies.
Though there
are some set-backs to their research, this study provides a great base for
future research. Better defining and including what qualifies as a food
retailer may improve future studies. Including retailers such as community
gardens and community-supported agriculture could provide a more detailed and
accurate study. Also, allowing the study to cross state lines would provide for
a more realistic and accurate portrayal of food access and security.
- Lisa Morse
Source: McEntee, J., Agyeman, J. Towards the development of a GIS method for identifying rural food deserts: Geographic access in Vermont, USA, Applied Geography (2009), doi:10.1016/j.apgeog.2009.05.004
Great point about the state lines, the 'Food Deserts' seem close to state borders and they should have included the neighboring tracts.
ReplyDeleteAlso on another note, Food Deserts seem to be more of a problem for people who do not own a car. Relying on public transport for groceries is often a driving force for people being in food deserts. An interesting study would be comparing the travel time, as opposed to the travel distance. Distance is felt differently based on the speed that you go. Finding a survey on how long someone will travel to a grocery and then compare that to travel times through various modes of transportation can show that 'food deserts' are more shaped by transportation systems. Since car ownership is usually correlated to income, lower income people may experience food deserts in places that someone with an higher income would consider great access.
I agree with the study's limitations of what consitutes access. For example, 10 miles is a somewhat arbitrary numbers particularly when the average is 8 miles. This arbitrary measurement doesn't take into account that someone who may live in a food dessert may have the economic means to drive 10 miles and therefore may not be affected by the distance to the grocery store.
DeleteFurther, I wish the study would have linked very high agricultural areas and food deserts rather than compare against "rural" and "urban" which seem like ambiguous categories.
Great job!
This is definitely a different subject, and location definitely plays a big part in food availability. The way that cities are set up, beyond just rural and urban, are important. A state like Texas doesn't compare to where I live in the Bay Area, where our local grocery store is a five-minute walk away. At the same time, we're also very heavily agricultural, and it would be interesting to look at whether highly agricultural parts of the country tend to sell their food locally or ship it elsewhere.
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