Monday, April 09, 2007

It's a wild, wild state of warming

From the Detroit Free Press:

Phil Myers still remembers the night in 1985 when he saw a possum crossing the path of his headlights near the tip of Michigan's Lower Peninsula.

"I was absolutely thrilled," said Myers, who saw the animal while driving in Wilderness State Park.

Not many people get so excited about a lowly possum.

But Myers is a biologist who studies the critters and had never seen one that far north. Scientific collections dating to 1857 showed that possums were rare in northern Michigan. The creatures, common in the southeastern United States, evolved in the tropics and don't do well in brutal winters.

Those that survive lose the tips of their ears and tails to frostbite. But research shows that starting around 1980 -- as winters got warmer -- possums began a steady trek north.

The possum is among many Michigan species, from flying squirrels to ticks to birds, that have changed their behavior in response to warmer temperatures, especially on winter and spring nights, over the past 25 years.

Forget predictions about melting polar caps and rising sea levels, say Michigan and Great Lakes region scientists: If you want evidence of global warming, it's right here, right now.

In some cases, new species are moving into Michigan, bringing diseases with them. In others, the shift is altering the ecosystem's delicate balance. In some areas, creatures have disappeared.

Usually cautious scientists are using words like "dramatic" and "startling" to describe the changes...

"Hundreds of species have already changed their ranges and ecosystems have been disrupted," said Rosina Bierbaum, dean of U-M's School of Natural Resources and Environment and former head of the U.S. delegation of the global Intergovernmental Panel on Climate Change.

On Friday, the IPCC released a report on warming-linked change in species around the globe. For example:

• In Vermont, sap from sugar maple trees is rising as much as a month earlier than it did 40 years ago, apparently triggered by warmer winters. The season for collecting sap is shorter, causing losses for the state's maple sugar and syrup industry. In Michigan, some maple syrup farmers report similar complaints, although no systematic studies of the subject have been done in the state.

• Some species of Central American frogs have disappeared because warmer nighttime temperatures pushed them to higher, cooler places, where they encountered a killer fungus.

• Disease-carrying ticks have moved into once-chilly Sweden, pestering humans and animals.

• Some bird species are migrating earlier and moving farther north. Because of warming, scientists theorize that in the next century, the Baltimore oriole may end up well north of Maryland, where it is the state bird.

The ranges of some Michigan trees, frogs, birds, insects and mammals are expected to change, too. Some already have...

It's not the ravages of memory that make people 40 and older think winters were harsher when they were kids. They were harsher then.

Today, Michigan has shorter, milder winters than it used to, said Jeff Andresen, the state climatologist and a professor at Michigan State University. Since 1980, average statewide temperatures have increased 2 degrees.

Most of the change is in winter and spring night temperatures, which have risen 3 to 5 degrees. Although the numbers are still within the range of natural variation, what has happened in Michigan matches changes globally. Researchers say they believe carbon dioxide and other greenhouse gases in the atmosphere have led to the temperature change.

Andresen has other startling facts. From the 1850s to the 1970s, Grand Traverse Bay's surface froze an average of eight years each decade. Since the 1970s, the number has dropped sharply to three times per decade. Satellites show ice cover on the Great Lakes also dropped precipitously from 1973 to 2003, Andresen said.

Plant, animal and winged species sensitive to temperature have reacted. The life cycle of the tart cherry, one of Michigan's most popular products, follows temperatures. In Berrien County, cherries began ripening as many as 10 days earlier starting around 1980, Andresen said.

Among some creatures, startling changes have occurred in the past decade. The Lone Star tick, a southern pest that can carry the bacterial disease tularemia, used to be found in Tennessee, Texas and Florida. But now the ticks have established themselves along Lake Michigan.

"This has happened in the past 10 years or so," said Ned Walker, a professor of entomology at MSU. In the same time frame, a type of mosquito common in the southeastern United States, the psorophora ferox, has arrived in Michigan, Walker said.
The aggressive mosquito can carry the West Nile virus.

"Now, it has really quite dramatically shown up all over lower Michigan, as far north as Grand Rapids and east to Saginaw Bay," Walker said of the mosquito. He said he believes milder weather has allowed it to survive winters.

"It heralds the possibility of invasive species occurring in areas where winters are usually too harsh," he said.

Another tick, Ixodes dentatus, which is thought to carry the bacteria that cause Lyme disease, has arrived.

"We first found it in Kalamazoo, way out of its range," Walker said. "Now it's spread all over. It's very common on birds and rabbits."

Scientific literature from just a decade ago said the tick lived in Georgia, South Carolina and Alabama. "I speculate it is because of milder weather allowing it to overwinter," Walker said...

Biologist Myers has watched big changes among the small mammals -- mice, chipmunks and flying squirrels -- that he studies at U-M's biological station on Douglas Lake, near Pellston. Warming temperatures have allowed the southern, cold-sensitive version of each species to push north, displacing their cold-adapted cousins. The cold weather species' numbers have dropped sharply and in some places, they have become extinct, Myers found.

"The very fabric of the small mammal community has changed," he said.

In the Upper Peninsula, tiny woodland deer mice used to prevail over their warmer-weather relations, white-footed mice. In the 1930s, the white-footed mouse was found only in Menominee County, near Wisconsin. Since about 1980, white-footed mice have hotfooted it all across the UP, and the number of woodland mice has shrunk.

Myers has looked at many causes, including their habitat and food, and said he believes warmer temperatures are the cause...

Root is a lead author of the report that was issued Friday. She said bird-watchers have kept good records in Michigan. In Germfask in the east-central UP, records show that in 1970, the sandhill crane first arrived April 29. By 1995, it was a month earlier. Mourning doves arrived there on May 30 in 1965 and on March 1 by 1995.

An analysis of more than 100 studies on different species shows widespread changes across the globe already...

Root's analysis shows that above the 45th parallel, a line that crosses Michigan from Suttons Bay in the west to Alpena in the east, spring events like blooming and migration are coming two weeks earlier than they had. Below that line, the change is a week earlier.

Not all species react to temperature. Some mate or bloom based on the length of the day, which hasn't changed. That means two species that depend on each other -- like predators and their prey or flowers and their pollinators -- could fall out of sync. In the Midwest, many bird species will disappear this century. Expect fewer warblers and more outbreaks of forest pests they eat, such as spruce budworms...

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