It's getting hot in here

How about an avocado tree for Christmas?

Your gardening loved ones are in luck this holiday season. New data from the National Climactic Data Center indicates that hardiness zones – climate regions determined by lowest annual temperature – have shifted significantly in all fifty states since 1990.

While the USDA has yet to comment on the new data or offer updated zone maps, just this week the National Arbor Foundation has released maps delineating the redefined hardiness zones. The Foundation’s news release affirms that the new data “is consistent with the consensus of climate scientists that global warming is underway.”

The new data reflect the lowest annual temperatures as recorded at 5000 research stations for the past fifteen years. Nationwide, the changes are dramatic. Entire states have changed zones since 1990. Iowa, for instance, was once more than half Zone 4, with an average annual low of -30 to -20 degrees. Now, the entire state is reclassified Zone 5, with a low of just -10 to -20. Much of the Northeast is now Zone 6 (-10 to 0 degrees), while Zone 7 spreads across the South.

Agricultural extension agents affirm that adventurous gardeners now stand a chance at growing palms and other tropical plants. Warm-weather plants previously restricted to the South, such as the lovely winter-blooming camellia, are now creeping across the Mason-Dixon line.

Meanwhile, however, cold-weather plants are struggling to keep their cool. North Carolina cooperative extension agent Karen Neill notes that white pines in her area have struggled recent years; not surprising when the ten hottest days on record have all occurred since 1990, as Arbor Day spokesman Woody Nelson notes.

Changes in plant distribution may have serious affects across the food chain. As plant species change in abundance, the animals that depend on them for food and shelter will also be forced to adapt. Humans, too, may feel unexpected impacts. Scientists expect that continued climate change may seriously impact farming and crop distribution.

To see the maps for yourself, check out the Arbor Day Foundation’s website. The Foundation recommends planting trees as a means of combating this change. Trees remove carbon dioxide, a greenhouse gas that contributes to global warming, from the atmosphere, and provide shade that keeps the ground cool and reduces energy use.

By Sara Kate Kneidel
Greener Magazine

Keywords: hardiness zones, climate change, global warming