| Is
the earth getting hotter? Are the severe storms being experienced
worldwide due to global warming? Such topics have scientists and
politicians debating man’s impact on the environment.
Feng Sheng Hu, assistant professor of Plant
Biology, is also very interested in the effects of global climate change
on ecosystems and biogeochemical processes—but over a geological time
scale. "There is no doubt that the
climate has changed. But to understand the effect of those changes, I
study the ‘natural experiments’ of the past that are archived in
geological deposits, such as lake sediments," says Hu.
The wide variety of proxy environmental
records in these deposits have major advantages over other eco-logical
data. "These records provide a long holistic perspective into
ecosystem states and biogeochemical processes that do not exist today, but
may be analogs of what may happen in the future."
Hu’s laboratory uses such proxy
indicators as pollen, stable isotopes, and elemental chemical composition
of sediments to address questions of biotic response to climate change at
various spatial and temporal scales.
They are also developing a new area of
study, molecular paleoecology. They are using molecular genetics
techniques to help identify species represented by the pollen grains found
in sediments. "The pollen grains of various spruce species, for
example, visually look the same. Using genetic markers will allow us to
more accurately determine species and ecosystem composition."
Hu and other scientists have found that
climate can shift abruptly. "About 11,000 years ago, there was a
major warming event of about 8 degrees Celcius in a several decade time
frame. This event is well documented in the north Atlantic, and was
probably driven by changes in ocean circulation patterns. I am
investigating the effects of this abrupt change in the North Pacific
region."
They have also recently reported in a Nature
article that there were sudden cooling events within the last 10,000
years. Hu and colleagues from the University of Minnesota studied
sediments from Deep Lake in northern Minnesota and previously published
data on ice cores from near the summit of the Greenland ice sheet. They
looked at the thickness of sediment layers in the lake bottom, which
accumulate seasonally and reflect the amount of dust, organic material,
and other debris settling in the lake over time.
They found that the northern Great Plains
experienced a prolonged cooling between 8,900 and 8,300 years ago,
apparently caused by the collapse of a huge ice dome, a remnant of the
last ice age, in what is now Hudson Bay. With this mile-high dome of ice
no longer blocking the way, polar air flowed into the northern plains.
Warmer air masses from the Caribbean and the Gulf of Mexico no longer
dominated the weather patterns, and snow accounted for a greater
proportion of the total precipitation.
Even without man’s influence, climate can
shift abruptly, over a period of only about 50 years, resulting in
long-term environmental effects. "Understanding the naturally
occurring climate variations of the past will help give us a framework
against which human effects can be assessed."
For some Americans, the
"dust-bowl" days of the 1930s are very bad memories of drought,
crop failure, and hardship. But was this an unusual event, or was it just
part of the natural climate cycle? If it is part of the natural cycle,
what events signal the approach of the next drought, and can those signals
be overridden by other factors, such as human-induced climatic warming? Hu’s
laboratory is conducting climate cycle studies to address such questions.
To begin to understand whether the 20th
century has been a particularly warm one, Hu is conducting experiments in
Alaska. Such high-altitude regions are projected to be highly susceptible
to global warming, and there is evidence for warming in the last several
decades in Alaska. "My data show that there has been a warming trend
during the last 150 years, but that increase may be within the range of
natural variation in the past 2,000 years."
Answering questions of global climate
change within ecological contexts is not an easy process. "The earth
is a complex system affected by numerous factors. You really need to have
an understanding of all of those factors to be able to predict future
change."
To help understand mechanisms of ecosystem
response, Hu is studying one of the National Science Foundation’s
Long-Term Ecological Research sites in northern Alaska. This site is
particularly intriguing. There is one landscape study area approximately
500,000 years old, which was not glaciated during the late Quaternary,
immediately adjacent to a landscape area that was exposed by the retreat
of the last glacier and is only about 15,000 years old.
The "old" landscape has been
subject to extensive weathering, so there is a finer substrate texture,
lower nutrient availability, and more extensive cover of tussock plant
communities. Soils rich in organic carbon are confined almost entirely to
the "old" landscape.
"We know these two areas have been
subject to the same climatic events. By studying them, we can begin to
understand the interactions between climate and landscape factors in
determining carbon cycling and ecosystem states." The assessment of
these complex interactions among climatic change, landscape factors, and
carbon cycling is funded by the National Science Foundation.
"Although I started out as a botanist,
I have always been very interested in the interfaces between different
disciplines—atmospheric sciences, chemistry, geology, and biology."
Hu’s unique blend of disciplines and
insight has recently been recognized by The David and Lucile Packard
Foundation. They have awarded him one of 24 Fellowships for Science and
Engineering in 2000. These 5-year fellowships, providing $125,000 each
year, are designed to allow the nation’s most promising young professors
to pursue their innovative research programs with few funding restrictions
and limited paperwork requirements. Only 50 universities in the US are
asked by the Packard Foundation to submit nominations.
Hu earned his BS in biology from Xiamen
University in 1983, his MS in botany from the University of Maine in 1990,
and in 1994 his PhD in ecosystem science and conservation from the
University of Washington. Hu was a postdoctoral fellow at the University
of Minnesota in the NSF Research Training Group on Paleorecords of Global
Change. He came to the University of Illinois in 1998.
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