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Posted: Sep/03/2007 8:47 PM PST
The bottom two maps are the 1990 climate zones, on the left, and the updated one to the right. Above them is a metamap showing which parts of the country had their zones changed, by how much, and in which direction. It is tempting to read both more and less into the maps than one should. Those tan stripes across the country in the top map likely had as much change in climate as the red or blue ones, but defining zones in multiples of ten degrees means a place that went from 21 degrees average winter low to 29 degrees will stay in the same zone and thus be colored tan, while a neighboring, warmer area with a smaller change - say from 28 to 31 degrees - will shift zones. It's startling to look at the difference in the maps between the Adirondacks, or Shenandoah National Park and see whole islands of color wink out between 1990 and 2004, and those may well be devastating changes - or they may be artifacts of the gradient itself. But a surprising number of places have warmed by more than ten degrees, enough to bump them up two whole zones. Included are a couple stretches near North Cascades National Park, a huge swath of the Salmon River headwaters, Kalispell, the Wasatch Plateau and Glen Canyon and Los Alamos, a patch near the Straits of Mackinac, some of northeast Missouri, a spot along the Platte near Grand Island, and almost all of Cape Cod. Superficially counterintuitively, some of the country seems to have gained colder winters as a result of global warming. Most of that land is in the arid southwest, where winters are warmed by sunny weather. Boil more winter storms up out of the Pacific to blanket the desert in overcast and the temperature will drop. Winters near the west end of Grand Canyon National Park have cooled by more than ten degrees, dropping that land from Zone Eight (20° minimum) to Zone Six (0° minimum.) All of this in 14 years. While warmer winters in and of themselves might seem benign, many plants rely on cold winters for survival or reproductive success. For instance, balmy winters in Upstate New York may mean economic ruin for orchardists, whose apples need a certain number of chilling hours per winter to set fruit. And it takes more than average winter lows to gauge what will grow in your garden, and climate changes broad enough to so radically shift isotherms will likely have other effects as well. Warmer winters may mean either drier winters, or warmer summers, or both. Thus a shift in average winter low from 10 to 20 may correlate to drought deaths of forests, as trees struggle to thrive in warmer summers with less water. Frosts help control insect and pathogen populations, and reducing their frequency and severity may well cause irruptions of pest organisms such as bark beetles. Unfortunately, drawing ecological conclusions from a gardener's map of average temperatures carries a special risk all its own. Averages are useful to gardeners, because gardeners can play the odds. If I plant tomatoes on April 15, and two times out of ten a killing frost hits on May 1, I can remain perfectly happy and fulfilled, accepting a one in five risk that I'll have to run to the nursery for more plants in mid-May. But the Grand Canyon was not carved by average rainfalls. It was carved by 100-year flash floods. The northern limit of a wild tree's range is circumscribed not by average winter lows, but by the low temperatures hit in especially cold years. 99 years in 100, the winters a hundred miles north might be just warm enough for the tree to thrive, but so what? That hundredth year will wipe them all out. The same goes for floods, summer highs, droughts. Averages are close to meaningless in the ecological realm. What shapes the wild environment around us is the extremes. The Earth's climate is a complex, dynamic system. It cycles and fluctuates in proportion to the amount of energy put into the system. The more energy is kept in the system, the wider one can expect its fluctuations to be. Current climate change, caused by increasing the amount of CO2 and other greenhouse gases, is a result of those gases' prevention of excess solar energy from radiating out into space. That energy has to go somewhere. Storms will get larger, fronts stronger, the differences between average and extreme seasons greater. These maps are frightening enough as it is. They are more so for the information they do not include. Attachments:  |
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Posted: Sep/05/2007 10:22 AM PST
Thanks for the info. It is a bit scary. There is also the plant heat zone map. Go to www.ahs.org I noticed it on the tags on my transplants this year. Now you can have info about which plants can tolerate the heat of the summer in your zone. |
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Posted: Sep/06/2007 6:26 AM PST
Amazing post. Thanks! Where do those maps come from. Are they online? |
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Posted: Sep/06/2007 6:07 PM PST
wow according to that map I am in Zone 8 instead of 7 like I thought..hmmmmmm wonder how much difference there is.. |
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Posted: Sep/07/2007 11:38 AM PST
Quote: Originally posted by EvonneStoryteller Amazing post. Thanks!Where do those maps come from. Are they online? Yes you can find zone maps online. Most of the online gardening catalogs have it in their garden help section. They usually have the zip-code search on it. Just type in your zip-code and click. It will tell you what hardiness zone you are in. I always thought I was in zone 6, but now it is 6b. I believe someone posted one in the zones forum as well. Tam |
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Posted: Sep/07/2007 12:40 PM PST
I should have been more specific. I can find the current zone map. I am wondering how to get the yearly comparison map and the breakout map shown? In any case, things seem warmer and milder where I live. However, I find I lost lots of plants even though we had such a mild winter. This is the first year the smaller clumping Dianthus did not come back! THEY ALWAYS COME BACK! Someone suspects that the snow we got used to protect these plants. Now we get a lot of ice due to freezing rain so late in the winter, it was almost spring. The winter before this everyone lost lots of plants all blamed on the severe ice storm we received. I am not finding that I can plant up to the stated zone number. I have to plan for at least a half notch below it! |
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Posted: Sep/07/2007 1:46 PM PST
Maybe Maggie will come back by and give you the info on the maps she found. You could do a google search or go to ask.com to do research. It seems to me, that every map I see is just a little bit different. Some can be down right confusing. I understand your frustration. Our winters run the gambet here in KY. We tell our visitors to bring short sleeve and long sleeve shirts with them when they visit spring, fall and winter. It can be 68 degrees for three or four days in a row and drop off below freezing and stay there for weeks at a time. I have read that snow, in the colder climates does help to insultate the plants. Also, the ice freezing and thawing over and over again can heave a plant up from the soil and kill it. I have had that happen before. This year I am going to make sure I mulch everything really well. We haven't been getting the snow like we use to, but boy we sure do get those nasty ice storms. |
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Posted: Sep/07/2007 8:24 PM PST
Here is the link to maps I found on the web. http://arborday.org/media/map_change.cfm |
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