[Pollinator] Global Changes and Earth Warming

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Global changes fool Mother Nature
 Arbor Day Foundation's new hardiness map reflects Earth's warming
 By Nancy Taylor Robson
 Special to The Sun
 Originally published April 22, 2007

 Does it seem as though your lilacs are opening earlier than they did in your 
childhood? Have you noticed the dogwood, wild columbine and Virginia 
bluebells blooming earlier?



It's not your imagination. Though there are certainly seasonal fluctuations 
from year to year, as the recent cool spell can attest, studies are showing 
global warming is having an effect on our gardens. "Many plants are blooming 
weeks earlier than they used to," says David Inouye, professor of biology at the 
University of Maryland, College Park.
 A 30-year Smithsonian Institution study of first-flowering dates from Jan. 1 
to June 1 in the Baltimore-Washington area shows distinct changes in bloom 
times. Scientists tracked 2,500 species, then selected 100 for which they had 
the most years of record.
 "Of 100 species, 89 were flowering earlier," says Stanwyn Shet- ler, 
emeritus curator of botany at Smithsonian Institution's National Museum of Natural 
History. "From a fraction of a day to up to 46 days earlier."
 The earlier warmth has prompted a recent revision in the hardiness map. 
Using the temperature data from the National Oceanic and Atmospheric 
Administration, the National Arbor Day Foundation revised the hardiness map to reflect the 
fact that the South is creeping north.
 The map has been adjusted twice before - once in 1965 to add data missing 
from the original, and then again in 1990 to incorporate changes in weather 
patterns.
 This time, the changes are striking. Chunks of many states have warmed one 
full hardiness zone. Some have even jumped two zones.
 While Baltimore has stayed the same, Western Maryland has shifted from Zone 
6 to Zone 7 and the Easton/Oxford/Cambridge area of the Eastern Shore has 
moved from Zone 7 to Zone 8.
 So what if spring comes earlier? Couldn't we just shift the cherry blossom 
festival? Plant more Southern cultivars? What's the big deal? For one thing: 
pollination. Just as with catching a plane, in the intricate dance of 
plant-and-pollinator: Timing is everything.
 "There is a rather tight schedule to meet, especially for forest-floor 
flowers," Shetler says. "They can't come out too early or there aren't pollinators 
there [to enable them to reproduce]. If they bloom too late, the canopy has 
closed over and they don't get enough sun to go through their full cycle."
 The pollinators have their own circadian clocks that determine emergence, 
feeding and reproduction times that are not purely reliant on warmth. If bloom 
time and pollen production don't coincide with pollinator emergence, insects 
(and insect-eating birds) starve. Without pollinators, plants don't produce seed 
or fruit.
 Despite this critical connection, most gardeners rarely give pollination a 
thought. "It's a service that's provided by ecosystems," Inouye says. "But 
there has been growing concern over the past few years about the status of 
pollinators in North America."
 While home gardeners may blithely assume pollination will just happen, 
commercial growers, keenly aware of their pollinator-dependence, often pay 
commercial beekeepers to transport bees into orchards and farms to pollinate their 
crops. But honeybees are suffering from colony collapse disorder, which kills off 
as much as 60 percent of a hive in a winter.
 Yet it isn't just a change in pollinators that will affect gardeners. Warmer 
temperatures also have paved the way for a new crop of invasives coming up 
from the south.
 "When you shift minimum winter temperatures up, that acts as less of a brake 
on where these invasives can grow," says Lewis Ziska, plant physiologist at 
the U.S. Department of Agriculture's Crop Systems and Global Change Laboratory 
in Beltsville.
 Another spur to invasive weed growth is increased carbon dioxide (CO2) 
levels, a key component of global warming. Since 1960, there has been a 20 percent 
increase in CO2 levels outside of urban areas and a 24 percent increase in 
Baltimore, Ziska says.
 While plants require CO2 in addition to light, nutrients and water, when one 
of the legs in that four-legged stool changes, it unbalances everything that 
rests on them. In this case, plants that do well with higher CO2 
concentrations multiply, while those that don't, die.
 "Unfortunately, what we've seen is selection for invasives - Tree of Heaven, 
Norway maple, [white] mulberry and invasive vines like [Japanese] 
honeysuckle, morning glory, English ivy and kudzu, which we didn't have here 20 years 
ago," Ziska says.
 In addition to pollinator decline and invasive onslaught, plant colonies are 
challenged by the weather extremes we're seeing now.
 "When we have rain now, we have a lot of it," says Paul Babikow, president 
of Babikow Greenhouses in Baltimore. "When we have drought, it lasts longer. 
When we have a cold spell, it's really, really cold and then two weeks later, it 
might be really, really warm. It's a lot more random than it used to be only 
20 years ago."



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