In New York you can’t see the forests for the buildings, but the forests are there.
The expansive yet overlooked “forested natural areas” contain more than five million trees, and 82% of them are native species, according to a comprehensive inventory by scientists from Yale University and the Natural Areas Conservancy, US.
That means natives significantly outnumber the 666,000 street trees planted in an attempt to expand the city’s tree canopy.
The researchers say their findings, published in the journal Ecological Applications, confirm that healthy and productive native forests still exist in New York and highlight the importance of having conservation policies and management strategies that reflect this.
“You can create and design spaces that increase biodiversity or tree canopy by planting a lot of different trees, but it’s not the same as having these natural spaces,” says Clara Pregitzer from Yale’s School of Forestry and Environmental Studies.
New York has been managing these forests for more than 35 years, she adds, without fully quantifying the structure and proportion of native species.
“Until you do that you can be distracted by counter-narratives or conceptions that urban forests are degraded or designed,” she explains.
“What we’ve found is that there is a huge opportunity for conservation in urban forests. And now that we know what we have we can begin to manage them with a new perspective.”
While 40% of New York is considered “green space”, much of that includes parks, cemeteries and backyards. Only about an eighth is forested natural areas, though this still represents a not inconsequential 4000-plus hectares amid the skyscrapers and 8.6 million people.
For their study, the researchers spent two years collecting data in 53 designated forested natural areas, measuring the structure and composition in more than 1200 plots and measuring more than 40,000 individual trees.
Although they found that 82% of the average forest stand in natural areas contained native species, that fell to 75% and 53% respectively in the mid-storey and understorey, suggesting the dominance of native species could decline in coming decades unless there is investment in a more in an active forest-management program.