Data Dive: Heatmap NYC and Environmental Justice
Data diving Conversations are ongoing with researchers at the Columbia Climate Institute to learn more about their work and explore hot topics through the lens of data science and visualization.
scientists
Yin Shu‘s research is at the intersection of climate change, social inequality and health, with a focus on community engagement work. As a social scientist and postdoctoral research scholar at the Columbia Climate Institute, she sees climate change as a sociopolitical crisis. Her research focuses on using climate change as an opportunity to challenge the status quo and promote structural change to alleviate the social inequalities that contribute to and exacerbate the climate crisis.
Joey Williams Directs the operation of the CAPA Heat Watch program, which provides high-resolution depictions of urban heat based on coordinated data collection activities. Combining his craft design skills as a former engineer with a passion for human and environmental health, he helps CAPA teams advance climate resilience work in cities across the United States and around the world. He holds a master’s degree in urban and regional planning from Portland State University and is a graduate research assistant in the Sustainable Urban Places Research Laboratory. In his free time, he enjoys backpacking, running, cooking new recipes and painting.
this project
The New York City Heatmap Project is national initiative. Williams’ team produced the heatmap data shown below using data collected by citizen scientists; Yoon is the Principal Investigator of the New York City Initiative. In the interview that follows, they discuss how the heatmap is made and what it can tell us about historical racism and inequality in society today.
data
Heatmap, North Manhattan and South Bronx, PM, July 24, 2021
July 24, 2021 afternoon. Blue is cooler than average and red is warmer.Hot Data: CAPA Policy [view data and final report]. Basemaps: Esri, HERE, Garmin, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), (c ) Community of OpenStreetMap contributors and GIS users
diving
How was the research project structured and what data were collected? How to prepare this raw data for further analysis?
Joey Williams: Community scientists collect readings of air temperature and relative humidity using Simple to use sensor [pdf] Quick connection to passenger cars and bicycles. Sensors automatically take measurements every second, and community members collect thousands of data points over an hour-long walk. The sensors also record latitude, longitude, time and speed, enabling CAPA’s data scientists to pinpoint the location of each measurement as well as important metadata that helps filter out outliers and other anomalies from the raw dataset. Field records collected by our community scientists help validate data and identify any disruptions to experiments, such as severe weather.
Afternoon heatmap measurements in the South Bronx. Shades of red indicate above-average temperatures.
How can you use high-resolution satellite imagery to describe the surrounding land use and land cover for each data point? How is this data used to inform the final heatmap?
Joey Williams: To model ambient heat across the study area, CAPA’s approach exploits the relationship between air temperature and the thermal properties of the urban environment. For example, materials such as asphalt and concrete tend to absorb and retain heat, while shaded areas reduce air temperature.Collected satellite imagery Sentinel-2 satellite constellation Helps to describe existing land and its material properties at multiple spectral wavelengths or bands in a 10 x 10 square meter unit. This set of land variables was then combined with thousands of environmental measurements collected by community scientists to inform a machine-learning model that could predict heat throughout the study area.
How does CAPA’s urban heatmap approach differ from other techniques?
Joey Williams: CAPA’s approach to urban heatmaps is unique in several ways. First, this method describes the heat we experience at human level, or about one to two meters above the ground. A more typical way to map urban heat is to use satellites to measure surface temperature directly, called land surface temperature or LST. Second, the high resolution of CAPA maps allows the use of finer-grained methods to understand the distribution of hot blocks to blocks, whereas typical LST methods provide coarser descriptions, such as at the neighborhood scale. Finally, CAPA’s heatmap program, hot watch, involving local community members and stakeholders in the co-creation process, adding a degree of “civic legitimacy” to the data and models. Through the process, community members are able to better understand the climate risks facing their region and what they can do about it.
As a social scientist, what do you think of when you see the final heatmap? What past or present stories does it tell?
Yin Shu: My first reaction when I saw the resulting graph was that I wasn’t surprised. The data corroborates previous research and satellite imagery showing that northern Manhattan and the South Bronx are hotter than other more affluent areas in the geographic area we studied. But I also see legacy issues in heat distribution and associated differences. For example, the image below shows a heat map overlaid on the historical map of the northern red line of Manhattan. The 1938 redline map is the Home Security Map from the Homeowners Loan Company, where areas deemed “high risk” are shown in red. These are basically black communities without mortgages and development funds. to this daythese previously redlined areas remain marginalized along racial and class lines, and Underserved resources including green space.
Composite: Red Line and Heatmap, North Manhattan
Use the slider to adjust the heatmap opacity. The heatmap has been changed to overlap the historical redline graph – areas are approximate. Red Line Map: mapping inequalities
what used to be Surprisingly, parts of the Upper East Side are as hot as the less affluent parts of northern Manhattan. But it’s important to remember that populations in high-income areas are more likely to have better buffers against extreme heat, such as air conditioning, working indoors in climate-controlled offices, and access to consistent and high-quality healthcare.
How can heatmap data be expanded or combined with other information to generate new insights? What other questions need to be asked?
Yin Shu: The goal of our project is not simply to show which parts of the city are hotter, but by presenting thermal data alongside other maps depicting social inequality. We want to connect the dots between extreme heat, social inequality and health – all within the broader context of climate change as a threat multiplier. For example, consider the overlap with the map below showing median household income across the city.
Map: Median Household Income, 2017. source: social explorer
It’s no coincidence that hotter parts of the city also happen to have lower incomes. This again suggests that residents of these areas are less likely to have buffers against extreme heat and associated health risks, such as adequate air conditioning and quality healthcare.
These regions also show higher rates of chronic diseases, such as high blood pressure and diabetes, This increases a person’s chances of developing heat-related illnesses.
Map: 5-Year Average Heat Stress Hospitalization Rates, Age-Adjusted Rates
data: NYC Environmental and Health Data Portal
It is important to remember that residents of these areas are not “inherently more susceptible to these diseases”. Instead, as with many health conditions, there are social and environmental determinants.For example, lower quality food and healthcare, and weathering effect (The idea that stress manifests itself physiologically, and that the effects are felt more strongly by disadvantaged groups) are some of the social determinants that may contribute to this apparent overlap.
Poor air quality also exacerbates the effects of extreme heat—another environmental problem common in low-income communities. Poor air quality is a chronic problem in the South Bronx, especially in the Mott Haven-Port Morris area, known as the “asthma alley‘ because it has one of the highest rates of childhood asthma in the country.
Map: Asthma Emergency Department Visits, Children Ages 5-17
Estimated annual rate (per 10,000 inhabitants), 2018. source: NYC Environmental and Health Data Portal
Polluting industries, heavy traffic and lack of green space all contribute to poor air quality in this field. Heat, smog, and poor air quality all increase the risk of asthma attacks.
We can also see that these hotter low-income areas also have less green space.
Map: Canopy Coverage
data: NYC Environmental and Health Data Portal
The COVID-19 pandemic has revealed compounding and cascading problems associated with a lack of green space. In the early days of the pandemic, the public was advised to seek shelter from the virus outside and maintain good physical and mental health.but Many in the Mott Haven-Port Morris area have no option for healthy green spaces, the outdoors are just industry, waste transfer facilities and highways. Such advice is even less helpful when the effects of extreme heat are added to the list.
One remaining problem is the extreme nature indoor hot. For example, residents of these areas told us that their homes retain heat from the start of the day, so they don’t get relief even at night when the outside air cools. This can lead to poor sleep and fatigue, which can affect a person’s overall health and well-being.While indoor heat is beyond the scope of our project, organizations like WEACT has been working with community members on this issue.
How can this data be used to make meaningful change in the community? What are the next steps?
Yin Shu: Here are some of the project initiatives that came out in consultation with South Bronx Unite:
- We’re producing an online story map that connects the dots between extreme heat, social inequality and health – all against a backdrop of rising urban populations and climate change as a threat multiplier. We also plan to include maps of various social indices, such as population data, health disparity data, and other relevant socio-environmental determinants, to explore overlaps and connections. Our goal is to get this done before this summer’s heatwave hits.
- Christian Braneon, co-researcher on this project, I am both New York City Panel on Climate Change (Christian is the co-chair.) The group is conducting its fourth assessment, so these most recent details will be configured into the report.
- By partnering with the New York City Department of Health and Mental Health, we hope our data will help strengthen the city’s efforts to eliminate heat-related disparities. For example, our street-by-street granularity data can help cities find additional cooling centers or green spaces in the hardest-hit areas, as well as programs such as allocating free air conditioning to hard-hit neighborhoods.
- South Bronx Unite has been advocating for more green and blue spaces in their communities.They plan to use this recent data to help drive their efforts.
More about the project: Study maps urban heat islands with environmental justice focus
More information on the CAPA heatmap method: Integrating satellite and ground measurements to predict locations of extreme urban heat
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