just outside of the cvs that i could barely get myself to walk to, there was always a man sitting on the corner, covered in beads of sweat from the thick humidity and sun beating down on his bald head. earlier in the spring, when it wasn’t so hot, he asked for spare change. now, he asks if i can get him a bottle of water. 

heat already kills more americans than all other extreme weather events combined. by 2100, some projections show that deaths from heat may surpass the current rate of deaths from all infectious diseases combined.

and one of the greatest solutions to extreme heat is planting more trees. us cities are pouring millions into tree planting initiatives––washington, d.c., seattle and houston are already on track to meet million-tree planting goals by 2030. i dove into the heat issue last summer when i wrote a piece for the guardian about the shortfalls of these plans. i found that cities are really good at planting trees in high-income neighborhoods, and not so good at planting trees in low-income, majority minority neighborhoods, where it can be up to 15 f hotter.

the issue becomes even more complex when you factor in tree micro inequalities––yes, it’s actually a thing. boston seems to be doing pretty well in distributing tree canopy across all neighborhoods. but david meshoulam, president of boston tree nonprofit speak for the trees, described that low-income neighborhoods rank well in tree canopy because they have big parks nearby, which factor into the neighborhood total. boston is really struggling to plant street trees, which offer that shade on your walk to the grocery store, but you can’t see that in the data.

we really don’t know where to plant trees if we look at tree totals by neighborhood, like we have been. those totals will hide those micro inequalities that cities should be targeting. so, if houston has a goal to plant 1.6 million trees, where should they put them? 

that’s exactly what 100 community scientists in the city set out to answer.

on august 7, the nature conservancy and the city of houston had scientists with thermal sensors attached to their cars and bicycles to cover 300 square miles––the largest geographical mapping effort in u.s. history––in hopes to produce a detailed thermal map to inform their tree-planting decisions.

these 100 scientists, who i like to think were armed in their white lab coats, thick glasses and wirey hair––the archetype of a scientist––pedaling all over town with their heat-sensing devices, are sparking a trend across the country. the nature conservancy also has similar projects going on in phoenix, denver, los angeles and new york.

jaime gonzalez, tnc’s lead on the urban heat map community event, said strategic mapping like this will solve multiple problems at once. not only will it help with heat mitigation, but it will also fix inequities and help the city to laser-focus their mitigation efforts on areas that need it the most. 

many cities are starting to realize that many steps come before actually planting the trees. initiatives like finding where to put them are just as important as the planting itself––what’s another tree in an already tree-heavy area going to do? and it’s becoming more and more important as our summers continue to get hotter.

“this year there were 10 days that felt 105 f or greater in houston,” gonzalez said. “by 2065, if no actions are taken, that jumps to 74 f. that’s an entirely different city to live in, and we already see the inequity and we know that that’s going to get worse.”

as we see more lab coats hit the streets, hopefully we’ll also see city planners fill in those tree gaps. although we have a break from the heat for a little while, we can still prepare for what’s to come in just a few months.

this temperature difference can be very problematic when heat waves hit big cities for a number of reasons. for example, increased temperatures can increase energy consumption and increase the amount of air pollutants and greenhouse gases that are emitted. 

but these heat islands (uhis) also are problematic for individuals experiencing heat stress — which can cause heat injuries that sometimes lead to death — and can exacerbate global temperatures.

it’s a rising concern that’s being met with research on the subject — with the hope that the research can inform solutions and result in action. here are some solutions that can help reduce the impacts of the urban heat island effect.

increase the green 

shading

preserving and increasing the green space and canopy cover in urban areas can have a significant impact on how warm a city is. with increased canopy cover, the potential for more shade exists and consequently more cooling effects. most of the time this means planting more trees to increase tree canopy cover. but deciding where to plant trees in a city is crucial to the success of the trees and the cooling that they provide, as well as crucial to making sure that the urban canopy is distributed fairly.

aaron ramirez, an assistant professor at reed college, and hannah prather, a postdoc in ramirez’s lab, employ translational science when conducting their research, where they incorporate managers and other stakeholders into the process of research so that conversations can be started right away about how to act upon the research.

they are working with the city of portland to reduce the canopy disparities and make sure that less wealthy communities are not more adversely affected by the urban heat island effect. 

“our research interests in this area are focused on how uhis drive increased tree stress in urban forests,” ramirez said. “this is an important potential feedback loop whereby communities already underserved could experience higher rates of tree stress and mortality, which would strengthen the urban heat island effect.

“in our work, we are developing new methods for measuring tree stress in the urban landscape and working with managers to explore ways to prevent these dangerous feedbacks between increased tree mortality risk and human health risks.”

management decisions, informed by their research, could be anything from updating approved planting lists to including more drought-tolerant trees to changing how the city manages irrigation of city parks. this is especially important for portland and other cities that have some of the highest urban heat island effects around the country. portland, ranked no. 4 in the difference between rural and urban temperatures, is up to 19 degrees hotter in urban areas, while no. 1-ranked las vegas has a difference of up to 24 degrees. 

green roofs 

increasing the amount of green spaces in cities can happen in seemingly unlikely places. green roofs have the ability to help combat the urban heat island effect by providing shade, reducing rooftop temperatures, and increasing insulation in buildings, which reduces energy consumption. green roofs can even remove greenhouse gas emissions and other pollutants from the air via sequestration and storage. 

solar 

the use of solar energy can have many of the same effects as increasing green spaces in cities in addition to acting as a mitigator of climate change and the heat island effect. in using solar panels, the need for non-renewable energy is reduced and fewer amounts of detrimental emissions are put into the atmosphere in the first place, which can help reduce temperatures by not contributing to the greenhouse effect.

depending on the type of solar array installed, it can provide shading and cooling similar to that of vegetation.

additionally, when installed on rooftops, solar panels are able to insulate buildings. in the summer months this can create a cooling effect during the day, while in the winter months it can help prevent heat loss at night. this means less cooling energy and costs in the summer and less heating energy and costs in the winter.

city management

vegetation is a great way to adapt to urban heat islands, but how we manage man-made materials is also very important in how we react to rising temperatures. 

cooling materials

the materials that buildings, cars, pavements and other surfaces are made of and what color they are affect how much heat is retained in those objects and how much heat stays in urban spaces.

lighter colors have high albedo — a measure of how much light that hits a surface is reflected without being absorbed — and trap less heat than darker colors. cool roofs and cool pavement can help lower temperatures, but there are more areas that can also be evaluated.

the heat island group at berkeley labs is looking at cars, pavements, roofs, and walls to evaluate what materials and colors can help create cooler cities. often this means lighter colors and more reflective materials will provide the most benefits.  

city planning 

the urban heat island effect is a complex network of many factors, such as those discussed above. researchers like vivek shandas at portland state university point out that there are other factors to consider as well in addition to the ones already discussed. designing our cities so that there are varied building heights, varied canopy cover, and varied street widths can immensely help reduce the heat island effect by increasing air flow that can then cool down the city environment. the hope is that research like shandas’ can help inform city planners and managers so they can adapt to the detrimental urban heat island effect. 

so: what do we do?

whether mitigating it in the first place or adapting to the urban heat island effect, there are many ways in which researchers have the potential to work with bureaucracy to bring about much needed change. this can be accomplished by increasing urban green spaces and cover, choosing better materials to build with, planning cities in better ways by being informed by research, and reducing our reliance on energy from fossil fuels.

these ideas — along with reducing our footprints in other ways including eating more plant-based foods, reducing fuel consumption for travel, using less single-use packaging, and interacting with our legislators to let them know how we feel about a changing climate — have the potential to reduce the urban heat island phenomena and make cities safer for residents in the years to come. the research has and will continue to guide us to solutions. now is the time to act upon it.

in 2009, i set out to change that by launching white caps, green collars llc, a company devoted to coating flat roofs white in st. louis–a city with hot, humid summers and hundreds of thousands of flat roofs. white coatings reflect 85 to 90 percent of sunlight. that blocks heat absorption to keep homes, schools and businesses comfortably cool, dramatically reducing air conditioning usage with savings of 20 to 40 percent in hot weather months.

but the benefits for our cities and planet may be even more far-reaching. reducing electricity consumption lowers air and greenhouse gas pollution from coal-burning power plants, and u.s. energy secretary steven chu points out that because white surfaces reflect the sun’s rays back into space rather than heating our atmosphere, they offset greenhouse gas emissions through the albedo effect, too. studies have shown that cool white roofs can help reduce the urban heat island effect.

in addition to providing white roof-painting services, i’ve been a staunch advocate for their benefits and for stronger energy efficiency policies, and was named a “clean air success story” in 2010 by the st. louis regional clean air council. we donate empty, 5-gallon pails to habitat for humanity’s restore, and provide new job opportunities for graduates of st. patrick center’s “go green!” training program. white caps, green collars and several of our customers have been featured in a front-page article in the st. louis post-dispatch, on kmov-tv, in numerous articles and even a high school textbook about entrepreneurship. “green”, for me, is a roadmap for success.

see white caps, green collars on the local news:
http://www.kmov.com/video/featured-videos/go-green-white-roofs-save-money-91963704.html

watch u.s. energy secretary steven chu explain the benefits: