Study shows the amount of city greenspace has a bigger influence on number of species than connectedness and other factors.
Hawks in Senate Park, Washington, D.C.
Image Credit: U.S. Capital via Wikicommons
A recent study at the University of Maryland showed that the total area of greenspace was often the most important factor influencing the number of bird species in cities by a wide margin. The impact of greenspace area--parks, cemeteries and golf courses--exceeded the impacts of factors that are typically considered important to urban biodiversity, like whether the greenspace was broken up or fragmented, or the flexibility of species’ diets.
In addition, the data showed that as the amount of greenspace in a city increased over time, so did the number of birds with a wider range of characteristics that are traditionally considered ill-adapted to city living, like a limited diet or range.
The study appears in the September, 2024, issue of Landscape and Urban Planning.
“When we talk about what makes an urban species, we focus on what traits help them do well in cities,” said Daniel Herrera, a PhD candidate in UMD’s Department of Environmental Science and Technology, and the study’s lead author. “This analysis kind of flipped that script and found it’s not the traits that make an urban bird, it’s the city that allows a bird to live there. The amount of habitat is actually more important.”
Herrera and his colleagues analyzed historical city maps and data from an annual census of birds called the Christmas bird count for Washington, D.C., Pittsburgh, PA, and Minneapolis, MN, between 1900 and 2020 to reveal how greenspace and bird populations changed over time. In each city bird diversity increased as the total area of greenspace grew.
