| Prairie's Past And Environment's Future
25, 2003 19:20 PDT
Those from the mid-west may be interested in the U of I at
Urbana-Champaign article below...
----- Original Message -----
From: Steve Wilent
To: SAF Member List ; Sparklist
Sent: Monday, August 25, 2003 10:54 AM
Subject: [saf-member] Prairie's Past And Environment's Future
Forestry Focus List Moderator
and SAF Member since 1982
Of Illinois At Urbana-Champaign
Weather Extremes Shed Light On Prairie's Past And Environment's
CHAMPAIGN, Ill. -- Highway travelers view much of the Midwest as
little more than barren flatlands. The formation of the region
and its rich soils, especially tall grass areas that seemingly
should support diverse forests, however, have long fascinated
scientists. Newly available, long-term climate data now say the
area is the product of weather extremes.
Compared with adjacent regions, the tall-grass area of the
plains endures more frequent periods of severe drought, more
lightning strikes and subsequent fires from frequent winter
thunderstorms, dryer cold weather and more rapid plant and soil
moisture evaporation, a team of researchers from the Illinois
State Water Survey and University of Illinois at
Urbana-Champaign says in the current issue of the journal
"Beyond the 100 years of scientific curiosity is that these
extremes of weather and their frequency or their non-frequency
that we have found to be critical factors for the plains are
actually very important issues as we face global climate
change," said Stanley A. Changnon, a water survey scientist
and professor of geography. "The long-term data we've
gathered and are analyzing can provide us with very useful
guidance as we talk about potential changes to our agricultural
systems and to the way we as people live in general."
Changnon and his State Water Survey colleagues have digitized
national climate data going back to 1890. Information from
before 1948, when the federal government began a formal
record-keeping procedure on computer punch cards, was taken from
records left by volunteer weather observers. Once they
interpreted and entered the information into digital records,
the researchers began analyzing individual weather factors and
The triangular-shaped tall grass area scrutinized in the study
stretches from Tulsa, Okla., to Fargo, N.D., to Indianapolis.
European explorers entering what they called "an inland
sea" found a humid area with grasses up to 6 feet tall.
Long before, the plains were bulldozed flat during four major
glacial advances and retreats that left behind sands,
nutrient-rich soils and rocks. Wide flat rivers drained the
melting ice finally about 11,500 years ago, at which time the
tall grasses arose. Shorter domesticated grasses and farmers'
fields of corn, wheat and soybeans have since replaced the tall
To the north and south of the tall-grass region, there emerged
extensive forests. A long-debated scientific question, the
researchers noted, is why the tall-grass prairie only supported
grass when the soil easily could have sprouted diverse forests.
Numerous ecological and climate-related theories have been
raised, disputed and discarded.
The newly acquired data -- housed at the Midwestern Regional
Climate Center at the State Water Survey -- are providing
scientifically strong details, Changnon said.
One of the factors that emerged in the study was not new. The
role of fire in sustaining the prairie and preventing the growth
of trees was first established in the early 1950s, based on
pioneer descriptions of deliberate actions taken by Indians in
pursuit of buffalo. The impact and frequency of fire, however,
are now strengthened by the new data on thunderstorms. The
plains average 60 to 80 storms and more than 10,000 minutes of
storm activity each year. Only Florida and the Gulf Coast
experience more. The tall grass region also faces a
three-to-five-times greater risk of fire from lightning.
In addition to the heat and searing of fires, severe droughts
struck the region in 15 percent of the almost 105 years covered
by the study; adjacent forested regions to the east and west had
droughts in less than 10 percent of the years, and areas to the
north and south were struck by drought even less frequently.
While rainfall was of similar frequency during summers,
cold-weather precipitation in the tall-grass plains has been
dramatically less. In 71 of the years covered, the tall-grass
prairie region received less than 15 inches of precipitation
during the winters; adjacent forested lands to the south had
only eight dry seasons.
The periods of dry winters also contributed to dry vegetation,
making the grasses more susceptible to fires set by Indians or
caused by lightning.
Another contributing factor to sustaining the grassland was the
frequency and amount of warm-season evapotranspiration -- a
process in which moisture evaporates from the soil and
transpires from plants.
Most of the tall-grass triangle had precipitation/evaporation
ratios of .75 or higher, a number that suggests unusually wet
warm-season conditions, in 70 percent of the years studied;
adjacent regions in the high plains had much lower ratios. The
researchers theorize that evapotranspiration rates played a
major role in the formation and maintenance of the western
boundary (Tulsa to Fargo) separating the short grasses of the
plains and the tall grass triangle. The tall grasses needed
enough warm-weather precipitation to produce the higher
evapotranspiration rate, the researchers found.
The experience of the Midwest's prairie is one of extremes,
including some of the very factors that could be more widespread
as a result of global warming, said Changnon, chief emeritus of
the State Water Survey.
"What this shows is that the whole environment of the
Midwest has been very sensitive to certain extreme weather
events," he said. "Having long-term data lets us talk
more intelligently about potential changes in global climate.
Most climate modeling generates average changes, not the
frequency of extreme events. Talk of the occurrence of a
100-year flood really hasn't been based on 100 years of data; it
may be extrapolated from just 40 years of records, so scientists
must say that a 100-year flood will happen at least once, not
necessarily only once, in 100 years."
Co-authors of the study, funded by the National Oceanic and
Atmospheric Administration, were Changnon, Kenneth E. Kunkel,
head of the atmospheric environment section of the State Water
Survey and professor of atmospheric sciences at Illinois, and
Derek Winstanley, chief of the State Water Survey and professor
of geography at Illinois.
This story has been adapted from a news release issued by
University Of Illinois At Urbana-Champaign.