Shade can be recognized as a luxurious amenity that brings a touch of peace to this heat-laden forest of concrete and glass.
But with the growing heat island effect accompanied by the frequent 100-degree heat waves it brings, we need to consider shade as a useful public resource.
Remote sensing data processing with ArcGIS
Across U.S. cities, neighborhoods assigned lower grades by the federal government in the 1930s are hotter today
However, at least for now, this resource is not equitably distributed. In different cities across the United States, we can find evidence that the density of the tree canopy correlates with income or racial distribution, due to a complex set of historical factors.
The matter starts with the redlined，Beginning during the Great Depression and into the 1940s, the government-sponsored Home Owners Loan Corporation (HOLC), created a series of “security maps” in order to refinance mortgages in an effort to prevent widespread foreclosures.
These maps rated neighborhoods according to several different factors, including housing stock, sales and rental rates, physical attributes of the terrain. Thus, this policy forms the boundary in a physical sense.
Today, decades have passed since the disappearance of the redlining, but what is the situation in the United States today?
As the layers overlap, we can see that, with the exception of Midtown Manhattan, which is now inhabited by many white people, a large number of people of color still live within the red line area. And each race still maintains distinct boundaries. Although the physical boundaries have disappeared, there are still invisible boundaries in the city.
So it is up to us now to remedy these inequities as best we can.
New York has long been considered to be at the forefront of urban greening. New York's "Million Trees" project reveals the government's commitment to addressing environmental injustice.
In the government's presentation of the results, we can see that areas that were environmentally fragile have been well compensated with new trees. However, if we take a closer look at the actual condition of the trees, we can see that the situation is not as rosy as we thought.
With multispectral technology and Landsat8 satellite map resources, we can observe deeper information contained in the vegetation, such as health status.
Band 5-4-3: Color Infrared (vegetation)
Band 5-6-2: Healthy Vegetation
Band 7-5-4: Shortwave Infrared
For urban trees, Landsat8's resolution is still insufficient for effective analysis of the environment at the neighborhood scale. But we can also get the distribution of the tree canopy, that is, the shadows obtained at ground level.
If we using a change detection algorithm, we can calculate the canopy change. At this point, we can see that the tree canopy has suffered a significant reduction in areas that were originally environmentally vulnerable.
Subtraction of canopy from 2010-2017
In fact, it is estimated that today, seven years after the completion of the Million Tree Project, a quarter of the trees have died or are about to die. Perhaps by investing the money spent on these dead trees in tree maintenance, trees in the city could be given a more favorable environment.
Due to the complex and demanding environment, tree growth in the city requires care. The city does not provide enough maintenance and instead relies on an invisible labor force to make up the difference.
In the 2015 tree cences, trees in the Museum Street area registered the most stewards, and therefore the growth of trees in this area is ideal. But as is inevitable between data and reality, there are many well cared for trees that do not show registered stewards caring for them in the official record.
So if we want to think about how to protect and increase the urban canopy, we need to consider both environmental factors and invisible stewards.
By zooming in on the map to the Lower East area - an area that has shown anomalies in canopy decline - we can clearly see how the canopy is declining. I selected one of these sites for study and proposed a prototype neighborhood-scale tree protection system.
First, it needs to be clear that planting more trees in these low-income areas may not be a good solution. Even if the diversity of the environment is strong enough to withstand the effects of environmental negatives, this could be a wave of what David Gissen calls "environmental gentrification".
So I wanted a series of installations that would mimic the benefits of the tree canopy and provide protection for the existing canopy around it, rather than providing more tree canopy that may end up being a public liability, or a burden on the stewards demanding more free labor
The system has a variety of devices with different functions that detect and modify the micro-environment of the neighborhood to some extent. These devices are connected in series by circulation lines that fill the entire reduced canopy area, a way of projecting the equation between natural and artificial through substitution.
Thus, the project demonstrates a desire to truly promote environmental justice by focusing attention on people, allowing them to subjectively feel the condition of their environment and then go with the flow to make it better.
The project thus suggests a different set of priorities for the improvement of the urban environment - one that respects and engages both the communities, and communities of labor, so often burdened by an aestheticized, idealized, "healthy" environment, perhaps preventing another disaster for low-income areas.
