Washington Post [no paywall]: “When a large share of a city’s canopy is made up of just a few types of trees, the ecological benefits that trees offer are at greater risk of being lost. It is analogous to putting all your eggs in one basket, explained ecologist Emma Hudgins. “Places that have more [tree] diversity actually have more different pests, but they don’t have super impactful ones,” Hudgins said. The Washington Post sourced tree inventory data from 35 cities to see what tree types make up our urban canopies… The trees that end up in our cities are determined in part by what is available in the market, which typically tends toward species that have historically sold well. And commercial developers, who are most likely to buy large volumes of trees, tend to prefer species that offer a lot of bang for the buck and have a track record of thriving in that area. That cycle means that trees that are already dominant in urban landscapes are the ones that nurseries tend to grow and developers tend to buy. “If you have a big part of the market driven by a client who really doesn’t care what’s out there, it pushes the market toward the weediest, fastest-growing trees,” said Andrew Koeser, a professor of landscape management and environmental horticulture at the University of Florida. There’s also the fact that trees have their own timeline. While municipal budget cycles are annual, trees take the better part of a decade to grow to a salable size. With the uncertainty of whether cities will be able to purchase down the line, nurseries shoulder significant risk when choosing to cultivate less popular varieties…”