The buzz around town

Sixty percent of the world’s population will be living in cities by 2030, according to the United Nations. That is a projected 5.2 billion people, equivalent to the total human family in 1989. In the United States, 559 points on the map will have between 1 million and 5 million residents.

Urban growth tends to be seen as bad news for the environment. It results in shrinking farms (60% of the world’s most productive cropland is on the outskirts of cities), lost habitat and biodiversity, and less capacity for absorbing carbon from the atmosphere.

Yet a study published this month by the Ecological Society of America offers a hopeful counterpoint. Based on work by scientists in the U.S., Australia, and Germany, it found that urban gardens are important diversity boosters for foundational ecosystem role-players like plants and insects. That shifts the view of humanity’s impact on nature. It shows that the qualities people express in their flower beds, like joy, beauty, and nurturing, can be vital factors of environmental health and its shared benefits.

The research suggests “a strong effect of human management on urban biodiversity and ecosystem function,” the paper concluded. “Careful design of urban gardens to include more rare plants may provide for increased rare bee species that in turn provide better pollination services across seasons and allow for longer crop production periods.”

The study is based on observations and species surveys in 18 urban community gardens in three counties in California. It found an important difference between natural ecosystems and those shaped by people. In the former, rare species tend to be highly susceptible to climate change and other habitat disturbance. But urban gardens have higher rates of well-tended rare (or infrequently found) species, reflecting the conscious decisions of gardeners. And rarity, the study found, begets rarity. More individuality from one urban garden to the next means more diversity of bees and birds.

The social impact of urban gardens may be just as important. The study found that urban gardens promote a sense of shared purpose within communities, and that rarity within those gardens more often reflects the environmental and social concerns of women.

One who might agree is Holly Caggiano, a postdoctoral fellow at Princeton University’s Andlinger Center for Energy and the Environment. As a climate scientist, she wrote in an essay in Grist last month, she battles feelings of hopelessness, anger, and betrayal. But through “generosity and connection,” she noted, “people who steward their local neighborhoods witness environmental transformation firsthand, and it makes them happier.”

As cities continue to grow, the buzz in their green spaces offers evidence of humanity’s capacity for enhancement.