Plenary session
Aquatic Science in the 21st Century: The Human Imprint on Freshwaters
Sandra Postel, Director Global Water Policy Institute, Amherst MA (spostel@mtholyoke.edu)
Human Impacts on the Earth's Fresh Water: Trends, Consequences, and Proposed Actions
Ellen Wohl, Department of Earth Resources, Colorado State University (ellenw@cnr.colostate.edu)
Virtual Rivers: Historical Legacies of Land Use in the Colorado Front Range
Cathy Tate, U.S. Geological Survey, Denver CO (cmtate@usgs.gov)
Assessment of Water Quality in the South Platte River Basin: Challenges of Documenting
Human Effects on a River System.
Brian Richter, Director Freshwater Initiative, The Nature Conservancy, Hereford AZ (brichter@theriver.com)
Rivers of Hope: Emerging Opportunities for Restoration
The "theme" of this plenary is meant to convey the increasing recognition
among aquatic scientists that Homo sapiens has become a dominant component in the
ecological functioning of freshwater ecosystems. Aquatic science in the 21st Century must
take this into account. By contrast, the 20th century could be characterized as one of
discovery of basic principles, where "natural" processes could be isolated and
understood by conducting research in relatively "pristine" environments. It is
now apparent that such pristine ecosystems are not only diminishing, but they may
themselves carry the imprint or legacy of historical human alteration.
Recently, rapid human growth and associated pressure on water resources has resulted in
conspicuous landscape alteration that increasingly threatens the integrity and
sustainability of freshwater systems. This requires us to better understand how human
activity at multiple spatial and temporal scales influences ecological processes in
aquatic ecosystems. The need for this scientific understanding will only grow in the
future. Further, as water resources become more limiting, we can expect the social context
of aquatic science to become increasingly relevant. The issues are likely to be couched in
terms of how to maintain, restore, and manage critical system properties that provide
human-valued services, such as sustainability, biodiversity, and water quality.
The ascension of areas such as urban ecology, restoration biology, ecosystem valuation,
and conservation planning are emblematic of the large-scale transition of aquatic science
to a more "applied" and socially relevant context. Freshwater aquatic scientists
are now being, and will continue to be, challenged to make this transition, in the process
overcoming the philosophical, scientific, and institutional inertia of our own academic
and cultural legacies.
In the Plenary Session of NABS 2000, four distinguished speakers will address some of
the issues confronting aquatic scientists as we enter a new century of challenges.
Thematically, the Plenary is organized around four general issues:
- What is the scope of the problem? What is the magnitude of the current
human imprint on freshwaters and how is it likely to change over the coming decades? How
does the future demand on freshwaters by a burgeoning population affect water availability
for freshwater ecosystems? What can (or should) we do?
Sandra Postel directs the Global Water Policy Project in Amherst,
Massachusetts, where her research focuses on international water issues and strategies.
She is author of Last Oasis, which now appears in eight languages and was the basis for a
1997 public television documentary. Her most recent book, Pillar of Sand, examines the
history and sustainability of irrigated agriculture. In 1995, Sandra became a Pew Fellow
in Conservation and the Environment. She currently serves as senior advisor to the World
Commission on Water for the 21st Century. Sandra will provide a global perspective on the
human imprint on freshwaters by sketching out major global water trends, the principal
drivers of those trends, and the signs and consequences of unsustainable water use in the
world today. She will make the case for doubling water productivity-getting twice as much
service or benefit from each unit of water extracted from natural systems-and discuss the
critical role of aquatic scientists in helping meet this challenge. Finally, she will
discuss water policy reforms that can promote the protection and restoration of the
freshwater environment, including examples from Australia, South Africa, and the United
States.
- Where have we been? In many ways our science of the 20th Century was
"delusional" because our systems were really not as "pristine" as we
imagined. Was our understanding not already conditioned by a sizeable (if unrecognized)
human imprint? What historical legacies have we inherited and how do we account for these
in understanding how freshwater systems "work" today?
Ellen Wohl is a fluvial geomorphologist at Colorado State University.
She has broad research experience in streams and rivers around the world. Her presentation
will provide a historical view of the types and magnitudes of human disturbance on streams
and rivers along the Front Range of Colorado over the past 150 years. Ellen has a book in
press (Virtual Rivers) that documents the historical land uses and inferred physical and
biological changes in Front Range rivers. The extent of these changes suggests that
apparently pristine mountain rivers may no longer be fully functioning river ecosystems.
She will discuss how recognizing the potential discrepancies between river form (its
appearance) and river function (its integrity) is a key component of understanding the
human imprint on freshwaters.
- Where are we now? In many places, human activities have obviously and
significantly altered freshwater ecosystems. Much of our science is already focused on
understanding how freshwater ecosystem structure and function has responded to the impact
of humans. Gaining this knowledge is critical to projecting into the future where the
pressures on freshwater systems are likely to be much greater. How is this knowledge
gained in human-dominated river basins?
Cathy Tate, a biologist with the U.S. Geological Survey in Denver, has
studied the structure and function of many types of stream ecosystems across the
continental US and Antarctica. For the past nine years she has been involved in an
ecological assessment of water quality in the South Platte River Basin as a part of the
USGS National Water-Quality Assessment Program or NAWQA program. Recently, she produced
the public-outreach video "South Platte River--Lifeline of a Region" to
demonstrate the many ways natural and human factors affect the river system. Cathy will
describe for us some of the very extensive ecological biomonitoring work that has been
conducted by NAWQA along the South Platte River from its headwaters out onto the Great
Plains. This "case study" will provide concrete examples of how freshwater
ecosystems respond to growing human populations in a semi-arid region with limited
freshwater, and the challenges in documenting these responses in a large and complex river
basin.
- Where might we go? What can aquatic scientists "do" to help
safeguard the integrity of freshwater ecosystems? What aspects of ecosystem structure and
function are most at risk in the future? One such critical issue is biodiversity
conservation. As human activities increasingly pervade the "natural world,"
pressure will build to preserve species and ecosystems that have special social or
scientific value. What actions can aquatic scientists engage in now to minimize future
problems, and how can water management activities become ecologically sustainable in the
future?
Brian Richter directs The Nature Conservancy's new Freshwater
Initiative. He works with scientists, conservation project teams, and water managers
across the U.S. and internationally to identify strategies for meeting human needs for
water while protecting river flows necessary to sustain native species and river
ecosystems. He has published numerous scientific papers on the importance of restoring
natural flow regimes, in journals such as Conservation Biology and BioScience. Brian will
address some of the challenges of freshwater biodiversity conservation in a future of
increasing human pressure on available water supplies. He will highlight some promising
ways that water managers can meet human needs while maintaining the river flows necessary
to sustain a river ecosystem's ecological integrity. His talk will draw from case studies
across the U.S. Brian will also speak to the role of scientists in being
"advocates" for freshwater systems, in the context that "mainline"
(traditional) academic training has downplayed the notion of advocacy and pro-active
research.
