US Government: USDA Zones Changing — Fears Admiting Climate Change to Blame

2012 USDA Hardiness Zone Map

The New Map

According to the Washington Post, the USDA is diminishing the climate change implications of the new Plant Hardiness Zone Map despite its obvious differences and their method changes designed to obscure the changes that have occurred in the last 22 years. The map was due to be released during the Bush years but inexplicably was not despite the data being ready. A host of excuses were given by the Bush administration but it was clearly just a smoke screen. Why obviously? Well, The Arbor Day Foundation — you know those folks who go around planting trees like modern-day Johnny Appleseeds — used the same data that the USDA had access to and made a new zone map without the USDA’s help [You can see it below].

So What’s the Trick?

One trick I learned while working in industrial research is that if a trend is accelerating and it’s bad news, you can dampen the visual and statistical effect by expanding the time frame of the data taken. Why is that? Because you’re not graphing the data over time, you’re averaging the data and by including earlier ‘friendlier’ data, you can minimize the actual state of current affairs. And that’s exactly what they did. The 1990 map used data from 1974 to 1986 — 12 years. The new map was not only delayed from 2005, it’s timeframe was extended from 12 years to 30 years! Talk about comparing apples and oranges! This methodology really damps down the effects of both extraordinary temperature swings and constant or accelerating changes in one direction. The first effect is desirable if you think the changes are due to one anomalous datapoint. The second is a form of skullduggery.

Let’s do an example. Let’s say you have the following dataset:

Average lowest temps 1975-1980 -5 C, 1980-1985 -4 C, 1985-1990 -3 C; 1990-1995 -2 C; 1995-2000 -1 C; 2000-2005 0 C; 2005-2010 1 C. If you average 1975-1900 you get – 3.0 C. If you average 1900-2010 you get -0.5 C.   It’s clear to anyone that the average temperature has changed 2.5 C. Now let’s spread the latest timeframe out averaging 1975 to 2010. Now you get 2.0 C average temperature change. Look! In one easy stroke they’ve reduced the amount of temperature change. Maybe if they average it in from the turn of the 19th century or the second century they can reverse global climate change entirely!

The Arbor Day Foundation 2006 Zone Map

Comparing 2012 to 2006

If you want to make your own comparisons, I’ve included the 1990 version of the USDA’s Hardiness Zone Map below. However, The Arbor Day Foundation has made it even easier to see the changes. On their site they have an interactive map where you can see where the zones were in 1990 and where they were in 2006. I hope they decide to add in the changes between 2006 and 2012. Even though the results have been damped down through the agencies sleight of hand, you can still see a big difference in the last six years. From 1990 whole states including Texas, Nebraska and Ohio have moved a zone warmer. If you look at Nashville, Tennessee, it’s moved a zone warmer as well. When I was a kid, we used to be in zone 5 here outside Detroit. For at least 10 years we’ve been zone 6A, now we’re zone 6B. If you go to the USDA website linked below you can see how much it changed in your zip code.

2010 USDA Hardiness Zone Map

So Why Release It at all?

Eventually someone more important than tree-hugging hippies (that’s me) would notice there wasn’t a current USDA chart. Not only that, but the chart wasn’t really developed so that Aunt Matilda would know when to put her petunias in. Those charts are vital for maximizing crop yield for farmers. The chart was getting so far outdated that it was not conducive to maximizing farming efficiency and income. Even more importantly, there are many fruits such as cherries and apples which depend on a minimum number of cold days in order to flower. If they don’t flower, they don’t have fruit. This year will sorely test some orchards and some have said that Maple Syrup will be a thing of the past soon. The new charts send warnings to orchard owners — plant trees that don’t require cold for fruit set if you’re in the path of a warmer zoneline heading your way.

But that’s just the tip of the iceberg. The problem is insects. Insects don’t care what fibs the USDA tells, they hatch when it’s warm enough. Most insecticides that kill/repel/deter insect pests are applied at specific times of the season and are designed to affect a specific stage that the insect is in at the time of application. If the USDA let the schedule vary too far from reality, insects would get a jump on farmers. Also, farmers need to be aware that insects and other pests are extending their growing season and have begun to get an extra breeding cycle in each year. This has had a profound effect in places like Yellowstone where bark beetle infestations are causing more destruction to trees because they get another life cycle in per year. Just ask the EPA.

How Will It Affect My Garden?

It’s a blessing and a curse. If you’ve always wanted to try those hardy rosemary’s but it was just too cold in your area, maybe now is a good time to try again. Yes, you may be able to plant earlier (1-2 weeks per half hardiness zone!) but those aphids are going to get a jump on you too. Not only will it extend your growing season by almost a month in some areas (1-2 weeks on either end of summer), but the change in growing season may require you to change your fertilization schedule and your watering habits as the temperature changes affect the rainfall. That’s another adjustments farmers will have to make as well. I highly recommend natural pest controls such as ladybugs and preying mantises. At least they will respond to the extended growing season the same as the insect pests do.

Seeds that need a cold period may not germinate unless you put them in the fridge. This will be bad for weed control. Most perennial flowers need a cold stratification period to germinate but most weed seeds are annuals. Since winter cold kills off many annual seeds, less winter means more stray annual weed seeds surviving. Overall, it’s probably better to start your seeds indoors where you can control the temperature now, but that won’t help with annual weeds. Plan on more time spent weeding or better weed control through mulch (or herbicides if you must).

Also, unless you live in the far north, you might want to not plant certain northern tree species. Look at where their natural zones were 50 years ago and see how close you are to those lines. While it may take a while for some established trees to suffer from climate warming, eventually it will have an effect.

On the bright side, those commercial plant growers for the home market may now have to admit that the times are a’changing and finally start selling flowers before Mother’s day. Here in Detroit, I’ve been planting half my crops around April fifteenth for twelve years now.  Only once has that led to early die off. But now, with the new zone map, maybe comercial merchants will start selling sooner than the end of May. I love seed starting but when you only want a few of something seed can be expensive and having to wait for the merchants to feel ‘safe’ selling you plants is tedious.

Source Credit: Washington Post, USDA, The Arbor Day Foundation, EPA