Constructed Climates

People subject urban nature to the concept of “value,” a concept completely irrelevant to the ecological and evolutionary context of natural ecosystems. In this chapter I first explore what it means to value something, then examine how people value vegetation, and finally investigate whether people gain social and psychological benefits from vegetation.

Certainly, the development of an agrarian lifestyle subjected various plants and animals to artificial selection through their value as food and resources. A recent effort finds environmentalists pushing the idea of valuing nature for the economic benefits it provides humans through “ecosystem services.” Pursuit of itemizing ecosystem services primarily involves the economics and values of marketable goods that can be bought and sold. This market valuation gained recent favor as a response to lawsuits involving environmental damage, but also as a result of several presidential “directives” that required the analysis of costs and benefits when instituting new environmental regulations.

Urban nature also gets shaped by values of another sort, so-called nonmarket goods, things that can’t be easily packaged and sold, such as the enjoyment of a walk through the woods. These nonmarket influences go back in time more than 800 years, when England’s King Edward I wrote laws commanding roadside vegetation be pruned to remove any hiding places for robbers. These attitudes associating vegetation and crime persist institutionally and in people’s minds.

I show that, indeed, people enjoy various aspects of nature and make clear their views that life without vegetation means a lower quality of life. However, people’s preferences tend toward the neat and tidy parklike setting reminiscent of new suburban lawns rather than the messy, chaotic natural forests preferred by naturalists and found perfectly acceptable by natural selection. Yet, even these stated appreciations of nature seem shallow when people flock toward unnatural, human-made environments like shopping malls.

Having views of and access to nature bring clear benefits. Public housing apartment buildings in Chicago, Illinois—housing complexes with high concentrations of economically disadvantaged people — served as the site of several studies linking crime and emotional development with vegetation. In contrast to preexisting historical attitudes, these studies indicate that places with more vegetation reduce crime, in part, by serving as social gathering points that enhance vigilance by watchful citizens. Studies of children also show that girls earn better scores on several developmental measures when they have better views of nature from their apartments. Nature also provides calming influences and helps fight childhood obesity beyond public housing situations, even extending to greater benefits with increased species richness.

Adding more urban trees provides additional “nature” beyond just a greater abundance of vegetation, including a more diverse collection of bird and plant species. Despite difficulties in measuring the value of physical and emotional health, it seems safe to conclude that urban nature makes people healthier.