New approach to plant growing zones shows effect of climate change

Will there be orange trees in Prospect Park someday? A new map produced by a professor at City College, Nir Krakauer, gives a more accurate picture of changing growing zones in the US, showing which trees and perennials can thrive at various latitudes. As the climate warms, tropical plants like fig trees can already brave the New York winter.

Dr. Krakauer observed that the current USDA planting zone map, updated just earlier this year, is already obsolete because it doesn’t take into account the fact that the seasons are warming at different rates, with the biggest changes in the coldest months. Plant hardiness is related to the lowest temperatures, which are rising faster than high temperatures, and Dr. Krakauer has developed a method to compensate for this shift in future zone maps. He found that the lowest yearly temperatures warmed roughly two and a half times faster than average temperatures. “The winter is warming faster than the summer…hardiness temperatures are based on minimum temperatures each year, they are changing faster than the average temperatures,” Dr. Krakauer said.

His analysis also showed that the country is changing unevenly; more warming is occurring over the eastern interior and less in the Southwest.

Professor Krakauer’s technique will allow gardeners and farmers to reassess more frequently what will survive the next year’s winter. “The idea is that you could use this method to keep updating the zone map year by year instead of waiting for the official map – just keep adding new data and recalculate.”

Image: Nir Krakauer