John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.
Planting zones (and pests and invasive species) are ever-more marching northward.
There's ample evidence climate change is messing with the world's phenology, aka the timing of natural life cycles. Warmer temperatures are hastening the emergence of butterflies and driving short-range migratory birds north weeks earlier. They're melting Arctic ice and blocking polar bears from their main prey, seals, creating shrunken bears more than 140 pounds lighter than those of the '80s.
And in the United States, the effects of the great heat-up have become pronounced in our gardens, where warm weather-loving plants now thrive in once-cool environments.
The mutation of the nation's growing seasons is clear in this map comparison NOAA made for the American Public Garden Association. It shows how average overnight minimum temperatures have changed between the former U.S. Climate Normals (tracked between 1971 and 2000) and the current normals (1981 to 2010). Watch how planting zones lurch northward with time:
Here's another view of the expanded planting territory:
With that rate of change, California's poppies could soon become a common sight in Seattle. Seriously: Scientists expect a vast northward shift in planting zones over the coming three decades, as depicted in this NOAA/Garden Association graphic:
So what's the upshot? For those who obstinately focus on the positive—"vegetation will likely grow faster with higher yields than ever before in places where such growth was once impossible," say these Fox News opinion-havers—it won't all be sunshine and daisies.
Balmy weather will speed the march of invasive plants like Kudzu and noxious blady grass. It'll give a boost to crop-decimating pests, which are already venturing about two miles farther north and south each year. And given that ragweed-pollen season is weeks longer now, allergy sufferers might look forward to months of huffing and weeping like they're attending the world's most-painful wedding.