Integrating GIS into Food Access Analysis Daoqin Tong School of - - PowerPoint PPT Presentation

Integrating GIS into Food Access Analysis

Daoqin Tong School of Geography and Development GIS Day at Kansas University

Outline

Introduction Research questions Method Results Discussion

Introduction

Food insecurity issues

>14% U.S. households

SNAP

served 15% of the U.S. population from 2012-2014

Related health outcomes (Adams et al. 2003)

Higher incidence of obesity Diabetes High blood pressure

http://stateofobesity.org/food-insecurity/

“Food Desert”

UK Low Income Project Team

areas of relative exclusion where people experience physical and economic barriers to accessing healthy food

USDA

“urban neighborhoods and rural towns without ready access to fresh, healthy, and affordable food” Low access

Supermarket availability Urban areas: 1 mile; rural area: 10 miles

Low income/poverty

Food Desert in the U.S.

Low-income and low access

37.6 million live in food deserts

Data source http://www.ers.usda.gov/data-products/food- access-research-atlas/download-the-data.aspx

More about Food Desert Identification

Analysis Scale

Census tract Policy needs; consistent with multiple Federal agencies’ programs

Healthy, affordable food outlet

Follow the industry-standardized definition of a supermarket Focus on brand-name chain stores selling a full range of goods

Issues of Current Practices

Census tract might be too coarse

 Do not necessarily reflect the neighborhood divisions Fail to provide sufficient knowledge about the geographic variation among neighborhoods

How about other types of food retailers

smaller grocery shops may fill the gap (Apparicio et al. 2007; Joassart- Marcelli et al. 2014)

Research Questions

How does the scale definition affect the assessment

• f food deserts or food access in general?

Is there a difference? If yes, how the difference varies across different neighborhoods?

The role of independent stores

Whether these food outlets help reduce food deserts To what extent these food outlets change food access In what geographical and social locations such changes take place.

Relevant Work

Conflicting research findings about the relationships between food access and demographic and socioeconomic characteristics (Dutko et al. 2012) Regions of various sizes, cultural and historical background The two national level studies also gave contradicting results

Powell et al. (2006)-Zip code level USDA (2009) -1-square-kilometer grids

Alternative Food Stores

Independent stores (Apparicio et al. 2007; Joassart- Marcelli et al. 2014)

 Suggested the importance of small stores in filling the gap

Farmers’ markets and community gardens (Wang et al 2014)

 Help improve food access and relieve food desert issue to some extent

Study Area

Tucson, AZ

20.4% poverty rate 16% of the total population are found to be food insecure

Diverse demographic profile

Hispanic population Seasonal fluctuation of migrants College population

Data Collection

Chain stores

Official website and store locator 91 in total

Independent stores

ReferenceUSA, google search and groundtruthing 45 in total

Census demographic and socioeconomic information

Block group Census tract

Street network

Analysis Methods

Food Deserts Food access metrics (Apparicio et al. 2007; Larsen et al. 2008)

Proximity based measure

Travel distance to the closest food store

Variety based measure nearest

The number of food stores within a travel distance/time threshold

Diversity based measure

the average travel distance/time to a number of (k=3) different stores

Using the analysis scale of block group and tract With and without independent stores GIS, Network based distance

Measure I - Proximity

Distance to the nearest grocery store Immediate proximity Weighted aggregation based on blocks

𝐸𝑢

1 is the mean distance of census tract t from the nearest grocery store;

b is the index of blocks Mt is the set that contains all the blocks in tract t 𝑞𝑐 is the total population in block b 𝑒𝑐 is the distance from the centroid of block b to the nearest store.

 

 



Mt b b Mt b b b t

p d p D1

Measure II-Diversity

 

 



Mt b b Mt b b b t

p s p N

Nt is the mean number of grocery stores within a designated distance (i.e. 1 mile) of tract t; sb is the number of stores within a designated distance (i.e.1 mile) of block b

Measure III-Variety

  

  



Mt b b Mt b n j bj b t

p n d p D

,.., 1 2

𝐸𝑢

2 is the mean distance between census tract t and stores

under n different brands; is the distance between block b and the closest store of brand j; 𝑜 is the number of different brands (n=3 is used in this study)

bj

d

Food Deserts

 217 census tracts in total; 60 high poverty tracts

 Chain stores only: 31 census tracts (14.3%); 123,333 people (13.9%); 47% are Latino  All stores: 17 census tracts (7.8%); 76,373 people (8.6%); 57% are Latino

Food Access – Measure I

1.86 miles vs. 1.66 miles

Food Access – Measure II

Food Access – Measure III

2.4 miles vs. 1.9 miles

Food Deserts Identified at Different Scales

125,367 people (14.1%) are found to live in food desert at the block group level compared to 76,373 (8.6%) identified at the census tract level

Proximity based measure Variety based measure Diversity based measure

Discussion

Differences appear to exist in levels of food access

Assessment metrics Scales Coarser scale (tract) leads to underestimate of food deserts

Independent stores help improve food access

Diversity and Variety Proximity

Discussion (Cont’d)

Mode of transportation

Car

How about those who highly rely upon publication transportation

Transportation routes Schedule GTFS data ArcGIS provides the “Transit Analysis Tools”

Conclusion

GIS provides a critical role in food access and food desert assessment Caution should be given to the analysis scale used to perform food desert or food access assessment

Sensitivity analysis

A comprehensive assessment is needed for a policy intervention aimed at reducing food deserts