Wish it is not in yellow can't read.
Thursday, June 11,
2009
Failing to see the forest for the
trees may be causing us to overlook the declining health of
Wisconsin's forest ecosystems.
Even areas with apparently robust trees and lush canopies are
threatened as forests are increasingly fragmented by roads and
development, becoming isolated green islands in a sea of
agricultural fields, housing tracts, and strip malls, say
University of Wisconsin-Madison researchers.
A new study is revealing that decades of fragmentation of
Wisconsin's forests have taken a largely unseen toll on the
sustainability of these natural ecosystems.
The long generation times of trees and other plants have masked
many of the ecological changes already under way in the patches of
forest that remain, says study co-author Don Waller, a professor in
the Department of Botany and Nelson Institute for Environmental
Studies at UW-Madison. "Things may look healthy, but over time we
see an erosion of biodiversity," he says.
To better catalog the changes at work, he and colleagues looked
beyond the trees to the forest understory — the shrubs, grasses and
herbs covering the forest floor — to witness how Wisconsin's
forests are really faring. Their results, published online June 8
and appearing in an upcoming issue of the journal Conservation
Biology, show that fragmentation is reducing the abundance and
diversity of native plants in southern Wisconsin forests.
The findings highlight the effects of increasing urban development
and road density, especially in the southeastern part of the state.
Land use changes have a pronounced impact on the islands of forest
that remain, even when these are protected as parks or natural
areas.
"These forest patches are not just losing species — their whole
biological nature is changing," says David Rogers, an assistant
professor of biological sciences at UW-Parkside who led the study
while a UW-Madison graduate student. "Surrounding landscape
factors, like urbanization and agricultural dominance, are now
determining which species can survive in these little
patches."
One unique quality of the current work is that it builds on a
detailed trove of historical data collected throughout the state in
the 1940s and 1950s by renowned UW-Madison ecologist John Curtis.
More than 50 years later, Rogers and others revisited many of
Curtis's sites in southern Wisconsin to see what changes time has
wrought.
Though negative effects of fragmentation on biodiversity have gone
largely unrecognized in the past, the impacts appear to be
intensifying over time, the researchers say. Nearby cities and
towns now strongly affect local woodlots, causing smaller plots in
particular to lose species.
"When we isolated these forest patches 50 or 100 years ago, we were
dooming species to extinction," says Waller. "It may not happen
right away — and in that sense it's an 'extinction debt' — but it
will accumulate over time."
They believe that isolation takes its biggest toll on forest plant
diversity by cutting off routes for native plants to re-colonize
areas where local populations may have disappeared. "Plant species
might go locally extinct for lots of different reasons," including
natural cycles of turnover, Waller says. "But typically the area
will be re-colonized very soon by nearby populations of the same
species. That's what does not happen once a habitat becomes
isolated or that patch becomes smaller."
The connections between local plant communities and more distant
landscapes have increased markedly. The bottom line is that humans
appear to be having larger cumulative impacts on Wisconsin's forest
communities than even ecologists previously appreciated.
This realization has important implications for how we should
manage southern Wisconsin's remaining forests, Rogers says. The
scientists are now working to identify the specific factors driving
the observed ecological changes.
"People are a really important part of the system," Rogers says.
"We are having a greater influence over our local ecology, whether
we want to or not. That puts the responsibility on people to take
care of it, protect it and maintain it."
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University of Wisconsin-Madison
Thanks to University of Wisconsin-Madison for
this article.
