When we build our cities with cement and asphalt, they trap heat. This trapped heat warms our cities, as much, in some cases, as global warming is expected to warm them by 2050. It makes them hot. It even changes the patterns of storms. More lightning. Less rain. The hotter, dryer conditions in turn affect animals and plants. Some pests do better. Those pests kill trees. Dead trees lead to more heat island effect. But it isn’t just trees. Even if you hate trees, you should still think about heat islands, because they also kill people. They smother them with warmth. They also smother them in pollution (which is worse when the trees die).

Here you can see a map of the urban heat island effect in my city, Raleigh. The map is derived from satellite imagery compiled by my friend Joe Sexton at the University of Maryland, and artfully presented by Lauren Nichols and Neil Mccoy. In the map, higher redder areas are hotter, hills of warmth. Lower, bluer areas are cooler. Much of the city is already hot even though we are the City of Oaks, even though we are (at least for now) among the greenest cities.


But this first map shows what is going on at a big scale. We can also zoom in. For example, this figure shows my walk to work.


It shows me leaving my house under the cool trees of Bedford Street. I then turn left onto Brooks Avenue where there are also quite a few trees. I walk past the trees at my friend Kevin’s house and then pass the trees at the house of my friends, Eleanor and Greg. But as I get closer to the university where I work, North Carolina State University, I encounter a larger road, a road with university buildings on one side and strip malls of various ilks on the other. I encounter a hot spot in the landscape, a spot hot enough, we know from data collected by Emily Meineke, to be much more unpleasant for humans but also for the remaining trees which are besot with heat-loving tree-sucking pests.

What are we to do? Of course the simplest answer is to stand paralyzed before our plight and bemoan the end of the world. This is a fine solution in as much as it is easy and, in requiring so little time (bemoaning is really very quick), allows more moments for pleasant relaxation (in some god forsaken hot patch of urbaness).

Then, there is the more challenging solution, the pinko, greeny, lefty, good-for-nothing, I-can’t-believe-this-guy-is-proposing-it answer. Plant trees. It is really that simple. Plant them along streets. Plant them instead of grassy lawns (which are nice as far as they go, but are really just ostentatious statements of wealth, the suburban equivalent of the peacock’s tail: “Look, I have enough left over money to pay for pesticides and herbicides to create a green space I hope no one steps on!”). Plant them on roofs. Plant them in right of ways. Plant back the forest into the hot cement, covered world and it will cool back down. And if some of the trees you plant, bear fruit, well, you can eat the fruit while sitting in the shade of your accomplishment, the cool, valley of shade, one of those goods, those public goods, those personal goods, that is simultaneously easy, rewarding, and, like a untended and ripe peach, delicious.

Funding and support to RR Dunn and SD Frank provided by the USGS Southeast Climate Science Center (Tree Eaters: Predicting the response of herbivores to the integrated effects of urban and global change) and the NC State University Department of Applied Ecology.