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19th Annual Lake Tahoe Summit

The 19th Annual Lake Tahoe Summit was hosted by United States Senator Dean Heller, at the Round Hill Pines Beach Resort in South Lake Tahoe, Nevada on August 24, 2015.

Image right: In conjunction with the annual Tahoe Summit, the University of Nevada, Reno and the Desert Research Institute publishes a report highlighting their collective research and outreach efforts in the Tahoe Basin.

The 2015 Tahoe Summit Report

Download the 2015 Tahoe Summit Report [PDF]

Previous editions of the Tahoe Summit report are available for download from the Publications page.

Download the Preserving Tahoe poster

Preserving Tahoe, an illustrated map Preserving Tahoe: an illustrated map of university research at Lake Tahoe

Tahoe Science Consortium Update 2013

August 19, 2013

Dear Presidents Johnson and Wells,

On behalf of the Tahoe Science Consortium, I would like to recognize and thank researchers from the University of Nevada, Reno and DRI for their outstanding contributions to the Tahoe Science Program. Your scientists have worked on many projects over the last eight years to help provide a scientific basis to understand, protect and restore Lake Tahoe and its ecosystems. Scientists from the University and DRI worked in collaboration with researchers from the University of California, Davis, the U.S. Geological Survey, the U.S. Forest Service, Tahoe resource agencies and other organizations around the country to deliver data and expert advice to environmental policy makers, regulators and managers.

The Tahoe research community has advanced our knowledge of mountain aquatic ecosystems and provided the basis for science-based management of Lake Tahoe, a critical and unique national ecological treasure. They have pioneered work to understand nearshore ecology, reduce the impact of aquatic invasive species, model the production and transport of ozone and other pollutants in the Tahoe Basin, improve lake clarity, and restore stream environment zones. They worked diligently to protect special status species, reduce the risk of catastrophic wildfires, understand the impacts of climate change, quantify the impacts of the built environment on Tahoe’s ecosystems, determine the value of ecosystem services, and evaluate the risk of extreme events.

In addition to conducting scientific research, Tahoe scientists have served as subject matter expert advisors to federal and state management agencies and educated the next generation of environmental scientists, engineers, artists and policy makers about the importance of sustainable environmental stewardship. Your researchers have been integral to restoring and protecting Lake Tahoe and sharing this knowledge with similar communities around the world.

Thank you for these outstanding and continuing contributions.


Maureen McCarthy
Executive Director

Tahoe Research: Our common cause

Dear Friends,

Together, the Desert Research Institute and the University of Nevada, Reno have a proven record of collaboration at Lake Tahoe. We’ve helped provide this national treasure with needed science, program leadership and a plan for sustaining its health for the benefit of future generations.

It is interesting to note how far the Tahoe partnership between our two institutions has come since 1997, when President Bill Clinton and Vice President Al Gore, at the invitation of Nevada U.S. Sen. Harry Reid, convened the first Lake Tahoe Environmental Summit. The Lake Tahoe Presidential Summit held on July 26, 1997 (and preceded by several community events involving key cabinet members and what has been estimated at more than 1,000 cabinet and White House staff) brought about a resounding and exciting affirmation that teamwork, partnership and a common research vision would provide answers in saving Tahoe. Vice President Gore, hosting an event in a clearing of pine trees not far from Mount Tallac on Tahoe’s south shore the day before President Clinton’s arrival at Sand Harbor, spoke of a “consensus” of purpose that would include effort from all with a stake in Tahoe’s future.

Said Sen. Reid of the impact of the first Lake Tahoe Summit: “It led to our turning around the environmental degradation of that great lake.”

Since those heady days of 1997, our two institutions have joined forces with local, regional and national management agencies as well as other academic institutions, in an effort to strike that fine balance of consensus of purpose. Our institutions have helped lead the way in discoveries on nutrient loading, water quality and watershed ecology. Our scientists have helped develop innovative ways to monitor Tahoe’s precious ecology and in finding management strategies for the air, land and water of Tahoe that help, not hinder, the overall health of this unique natural resource. Our students and researchers have helped the public develop a more in-depth understanding of why Tahoe is important, and why it is of the utmost importance that the work of the past 16 years must continue at its quick and productive tempo. Our approach will continue to be interdisciplinary and inter-institutional. Our pledge to Lake Tahoe remains firm: our two institutions work in common cause, so that the lake’s heritage of beauty and clarity can be shared by our children’s grandchildren and beyond.


Marc Johnson
University of Nevada, Reno

Stephen Wells
Desert Research Institute

Air Quality in the Tahoe Basin

10 key questions and answers

Overall, the air in the Lake Tahoe Basin is still much clearer than major urban areas, according to Alan Gertler, vice president of research and chief science officer at the Desert Research Institute. However, because Tahoe is visited by millions of people each year and considered by many as one of the few remaining pristine environments in the West, Gertler knows how critical air quality and visual range are to the future of the basin.

With more than 35 years of air quality research experience at Tahoe and around the world, Gertler shared his expertise to help answer 10 of the most common questions about air quality.

  1. Why should we care about air quality in the Tahoe Basin?
    When we look around Tahoe, the air usually looks clean, but it is one of the few areas in the region where ozone is increasing. It is now at a point where it will likely violate ambient air quality standards. Research also shows that air is a significant source of pollutants that lead to declining water clarity. If we want to reverse this trend, we need to consider making some atmospheric changes.
  2. What air pollutants should we be concerned about?Both nitrogen and phosphorus lead to algae growth in the lake. We should also consider particulate matter because it, too, can deposit in the lake and reduce the clarity of the lake and its surrounding basin. A hazy day is caused by particulate matter. We’re also concerned about ozone because of the negative effects it has on human health and the ecosystem.
  3. What are the sources of the pollutants?Particulate matter comes from road dust or soil, wood burning and emissions from cars, trucks and boats. Nitrogen is also from cars, trucks and boats, while phosphorus is from the soil and wood burning. Ozone is completely formed by chemical reactions in the atmosphere. The sources that are precursors to ozone formation include the mobile sources and the natural emission of hydrocarbon from trees.
  4. air-qualityAre these air pollutants from inside or outside the basin?Studies have shown that a large majority of the pollutants come from sources inside the basin, as opposed to being transported from areas such as the Sacramento Valley or Bay Area. Since the wind tends to blow from west to east, the primary sources are also not from other locales in northern Nevada.
  5. Is wood burning a significant source of the pollutants?Clearly, it is. There are three major sources of wood burning: fireplaces, prescribed burns and wildfires. We’re not necessarily able to control wildfires, but we can control fireplaces and prescribed burns. In the future, we need to consider the weather conditions and air quality prior to scheduling prescribed burns. In winter, greater consideration should be given to controlling the use of fireplaces.
  6. How important is road dust as a pollutant?It’s surprisingly important in terms of contributing to the decline in water quality. Large particles kick up and get scattered in the lake, they reduce visibility, and they contain phosphorus from the soil that leads to the growth of algae in the lake.If we look at the two factors that lead to declining water quality, algae growth and sediment deposition, current estimates show that 55 percent of nitrogen and 15 percent of phosphorus that deposit into the lake come from atmospheric sources.
  7. What can we do to control road dust?Much of the dust comes from the sand and salt used on the roads during the winter snows. From a safety standpoint, we need to use it. However, what we could do instead is to increase the use of street sweepers and liquid de-icers, both of which would reduce soil on the road that can be re-suspended.
  8. What role does fire play in air quality?Fires are important from the standpoint of visibility in the basin. We want to be able to see across the lake, and fires greatly reduce the visual range. It’s important the air be as clear as possible for many reasons, including aesthetics, yet there are no federal standards regarding visibility. The Tahoe Regional Planning Agency, however, does have a visibility standard.
  9. What can we do to control sources of pollutants?The most important sources we have to control are boats and the mobile sources, cars and trucks. Those sources provide the precursors to forming ozone, and they are also a significant source of particulate pollution.
  10. How were the sources of the pollutants determined?Two types of studies were conducted to determine the most important sources of pollutants: a bottom-up approach and a top-down approach. The bottom-up approach involved developing an emissions inventory that counted all activity from traffic, burning and other sources. What we see is that the largest sources of nitrogen are cars, trucks and boats. We also found that major sources of hydrocarbons in the basin are from the mobile sources as well as natural sources such as trees.In the top-down approach, we conducted source-receptor modeling to establish where particulates were coming from. We wanted to determine the significance of road dust and emissions from wood burning and mobile sources.



The Role of Fire in the Tahoe Basin

10 key questions and answers

Lake-Tahoe-UNAE-0016Soil scientists Wally Miller and Dale Johnson, professors emeriti in the College of Agriculture, Biotechnology and Natural Resources at the University of Nevada, Reno, have studied the impact of wildfires in the Tahoe Basin for many years. Their study of the 2002 Gondola wildfire near the Nevada-California border at the south shore of Lake Tahoe has led to new soils management strategies in the basin.

With more than six decades of combined experience and extensive work in forestry, biogeochemical cycling and fire ecology, Miller and Johnson shared their expertise to help answer 10 of the most common questions about the role fire and forest management play in the runoff of nutrients into the upper watershed that feeds into Lake Tahoe, ultimately affecting water quality.

  1. How has the upper watershed been affected by historic fire management strategies?
    Prior to the 20th century, wildfire was a natural part of Sierran ecosystems. It created forests that were less dense, structurally more diverse, had larger trees with less ladder fuels, sparse undergrowth and greatly reduced dead and decaying downed timber. These conditions have been altered by fire suppression over the last 100 years.
  2. What has changed in today’s forest landscape in the upper watershed?
    The buildup of fuels from falling litter and plant life growing beneath the forest canopy has increased the potential for stand-replacing wildfires and resulted in the accumulation of much thicker, nutrient-rich organic residues that can release more available nutrients into runoff and percolating solutions that can reach Lake Tahoe.
  3. What are the potential effects of wildfire on nutrients in the forest floor?
    Wildfire was found to induce an immediate mobilization of inorganic nitrogen and phosphorus, both of which can affect water quality. Although this effect seems to diminish rapidly over time, a wildfire followed by a high water year within the first season after the fire would likely have a much greater impact on water quality than a wildfire followed by a low runoff water year.
  4. What other fire management strategies are available?The most commonly applied alternative to total fire suppression is fuel reduction by either mechanical thinning, prescribed burning or a combination of both.
  5. What are the long-term forest health consequences of controlling post-wildfire brush? Eliminating post-wildfire brush may preclude nitrogen fixation, the natural process by which nitrogen is converted to forms plants can use, and thus not allow replenishment of nitrogen lost during the wildfire. However, leaving brush may preclude the re-establishment of forest vegetation for many decades, creating quite a dilemma.
  6. What are the long-term water quality consequences of controlling post-wildfire brush?
    Thus far, we see no negative water quality effects of the most common nitrogen-fixing species, Ceanothus velutinus, a species of shrub with the common names of snowbrush, redroot and tobacco brush, native to western North America. Water quality effects should be minimal.
  7. What are the long-term forest health consequences of repeated prescribed burning as opposed to mechanical treatment?
    Repeated burning is likely to cause greater nitrogen removal than mechanical thinning, perhaps causing reductions in regenerative growth.
  8. What are the long-term water quality consequences of repeated prescribed burning as opposed to mechanical treatment?
    Repeated burning is likely to cause greater nitrogen removal than mechanical thinning, which may help improve water quality.
  9. What are the effects of combining mechanical thinning and prescribed burning on water quality?
    Prescribed burning in conjunction with mechanical harvest may potentially improve runoff water quality by reducing nitrogen and phosphorus litter mass pools and improving the overall health of forest ecosystems without the danger of a stand-replacing wildfire.
  10. Is climate change important?Absolutely.  The fate of these forest ecosystems in a changing climate will have a direct impact on forest health, fire hazard, biomass mitigation strategies and water quality.

Lake Tahoe to Pyramid Lake: Summer Research Experience in the Arid West

REUResearch combines creativity with a thorough understanding of a subject, as well as the quantitative, analytical and writing skills needed to effectively convey findings to your target audience. In order to build a future generation of talented researchers, it is crucial to give young students an opportunity to partake in the research process so that they may experience the challenges and rewards associated with research. During the past three summers (2010-2012), our National Science Foundation grant, “Lake Tahoe to Pyramid Lake: Summer Research Experience in the Arid West” has supported 27 nationally-recruited undergraduate students to conduct research during an intensive summer research experience for undergraduates or REU program. The overarching goal of our program was to explore the intersections between disciplines in the socioeconomic and natural sciences that inform adaptive watershed management. We also aimed to provide undergraduate students with a comprehensive research experience under the guidance of a faculty mentor in the student’s field of interest.

Over the course of a 10-week program each summer, undergraduate students worked closely with their University of Nevada, Reno, faculty mentor in the following disciplines: fine art, landscape, plant and wildlife ecology, business, hydrology, history, geography, tourism, conservation biology, resource economics, limnology and political science, to develop and implement an array of projects that addressed current issues regarding natural resource management within the watershed. Throughout the summer, students were exposed to local natural resource management issues through a series of lectures and discussions with local managers and scientists designed to highlight the complexity of balancing policy and science to make informed management decisions.

Our program expanded students’ knowledge of a specific topic related to natural resource management in the Lake Tahoe-Truckee River-Pyramid Lake watershed while allowing them to participate in all aspects of the research process.

Our research program culminated in an undergraduate research poster session where students presented the findings of their projects to their peers, faculty and the general public. All projects contributed to an increased scientific and/or socioeconomic understanding of regional conservation issues in an applied context.

Student feedback

Feedback from students was very positive. Of the 27 students that participated in our REU program during 2010-2012, 89 percent indicated this was their first undergraduate research experience. As a learning experience, 52 percent rated the REU program as “fantastic-this is a great way to learn”; the remaining 48 percent indicated they “learned a lot.” Students reported their overall experience with mentors was excellent or good (89 percent), with 88 percent indicating their overall research experience met or exceeded their expectations. When asked if their REU experience changed their perspective on continuing their education, 44 percent of the students indicated they already planned to go to graduate school and still did, while 52 percent reported that our REU program increased their interest in going to graduate school.

By Michael Collopy, 2013 Lake Tahoe Summit Report

Preserving Tahoe: illustrated map now available online

The illustrated map of Lake Tahoe is now available online in addition to the PDF download. The online version allows for online browsing and searching as well as links to related content on the site.

Tahoe Poster

Lake Tahoe to Pyramid Lake Research Experience

Summer research experience in the arid West

For the last three summers, students came from across the country to spend an intense 10 weeks immersed in a Research Experience for Undergraduates (REU) where they learned about the Tahoe-Truckee-Pyramid watershed while working on individual projects with faculty mentors.

Sponsored by the National Science Foundation, the program is organized by the University of Nevada, Reno’s Office of Undergraduate and Interdisciplinary Research and the Great Basin Institute.

The students took field trips to sites at  Tahoe, the Truckee River and Pyramid Lake, the three main bodies of water on which their projects were focused. This gave them a broad overview of the research, policy and management issues throughout the watershed.

They also attended weekly seminars presented by invited speakers and University faculty and staff. The opportunity to meet leaders from a variety of fields and learn about many different issues and viewpoints were key elements of this portion of the program.

Their faculty mentors helped the students develop research skills and complete research projects within their discipline of interest. In addition to the interaction with faculty, most students worked with the mentor’s research lab or group. They presented their own research findings at the University’s campus-wide Undergraduate Summer Research Poster Conference.

A highly successful program, the REU experience was wide-ranging and comprehensive, and it increased the interest in a number of students to attend graduate school.

2012 Tahoe Summit

Tahoe Summit Publication

Monday, August 13, 2012

In conjunction with the annual Tahoe Summit, the University of Nevada, Reno and DRI publishes a report highlighting their collective research and outreach efforts in the Tahoe Basin. This report, Tahoe: A Legacy of Research, Education & Outreach is available for download.

2012: Download the full report


Previous editions of the Tahoe Summit report are available for download from the Publications page.

Maureen McCarthy: Demonstrating a return on investment from Tahoe science

For Maureen McCarthy, her dream continues to make the wealth of information from 50 years of research in the Lake Tahoe Basin available to those facing the challenges of helping society and the environment coexist in sensitive mountain ecosystems throughout the country and the world. Her goal: create opportunities for the Tahoe Science Consortium (TSC) to make science a cornerstone of restoration and redevelopment in the Tahoe Basin and share this knowledge broadly so others can learn from what’s been accomplished there.

“We see the work at Tahoe in a broader perspective.” said McCarthy, TSC’s executive director. It’s bigger than just preserving the lake or understanding human development in a special environment. We can export our knowledge on changes we see in population, climate and economic realities. We can no longer base environmental protection on emotions. We have to present an economically-based argument as to why it’s the right thing to do for both government and private industry.”

Science-based decision-making is now becoming common practice in some agencies in the basin, according to McCarthy, but more work is needed to help organizations understand the linkages between the natural world and human society.

People from around the country attended the 2012 Tahoe Science Conference that included contributions from the social sciences and resource economics, as well as a public policy forum; all part of the TSC’s move to help science demonstrate a return on investment for protecting and restoring the environment.

Established in 2005, the TSC partners include the University of Nevada, Reno; the Desert Research Institute; the University of California, Davis; the U.S. Geological Survey; and the U.S. Forest Service, Pacific Southwest Research Station. The final round of Southern Nevada Public Lands Management Act (SNPLA) research grants were awarded this year. Work on these projects will continue through 2015.