Every year, the health of each of the thousands of trees in established research plots is checked, and if a tree has died, the cause of death is determined.
Nathan Stephenson
Dr. Nathan Stephenson is a Scientist Emeritus at the Western Ecological Research Center.
Earth’s vast forests provide human communities with irreplaceable goods and services such as carbon sequestration, hydrologic regulation, clean water, biodiversity, critical wildlife habitat, wood products, and recreational and spiritual opportunities. An overarching goal of Dr. Nathan Stephenson's research is to improve scientists' and land managers' ability to understand, forecast, and adapt to the effects of ongoing global changes – particularly changing climatic and disturbance regimes – on forests.
Accordingly, most of his research falls in three broad, complementary themes: (1) improving mechanistic understanding of forest and carbon dynamics, (2) detection, attribution, and interpretation of forest changes, and (3) adaptations to rapid global changes. The last theme extends well beyond forests, to natural areas in general.
RESEARCH INTERESTS
- Forest ecology
- Global change biology
- Climate change
- Fire ecology
- Natural areas management
- Adaptation
EDUCATION
- Ph.D., Ecology and Systematics, Cornell University, 1988
- B.S., Biological Sciences, University of California, Irvine, 1979
Science and Products
Cross-Park RAD Project (CPRP): A Case Study in Four National Parks Investigating How Institutional Context and Emotions Shape Manager Decisions to Resist, Accept, or Direct Change in Transforming Ecosystems
Natural & cultural resource managers are facing a slew of new challenges for managing public lands stemming from climate change and human-driven stressors like invasive species, fragmentation, and new resource uses. In some cases, the very landscapes and species they are managing are changing in significant ways, transforming from one set of conditions to another. As a result, previously...
Forest health and drought response
Forests provide society with economically important and often irreplaceable goods and services, such as wood products, carbon sequestration, clean water, biodiversity, and recreational opportunities. Yet hotter droughts (droughts in which unusually high temperatures exacerbate the effects of low precipitation) are projected to increase in frequency and intensity in coming decades, potentially...
Post-Fire Conifer Regeneration Under a Warming Climate: Will Severe Fire Be a Catalyst for Forest Loss?
The Southwest U.S. is experiencing hotter droughts, which are contributing to more frequent, severe wildfires. These droughts also stress vegetation, which can make it more difficult for forests to recover after fire. Forest regeneration in burned areas may be limited because seeds have to travel long distances to recolonize, and when they do arrive, conditions are often unfavorably hot...
Adaptations to Rapid Change
Management decisions are made at the intersection of facts and values, and WERC's role is to assist decision-makers by bringing the best available science to the table. Dr. Nathan Stephenson seeks to help managers and policy makers reassess their missions in light of rapid and unprecedented changes, develop broad concepts relevant to adapting to such changes, and provide hands-on assistance during...
Improving Understanding of Forest and Carbon Dynamics
The community's ability to understand and predict changes in forests and their feedbacks to the global carbon cycle increasingly relies on models spanning several scales of biological organization – from tree leaves to entire forested landscapes. Yet many model assumptions about key processes – such as tree growth and mortality – require long-term data that are sometimes difficult and time...
Detection, Attribution, and Interpretation of Forest Changes
Dr. Nathan Stephenson and colleagues seek to determine what changes are occurring in forests, why they are occurring, and what they mean. For example, they have documented a long-term, apparently climatically-induced increase of tree mortality rates in otherwise undisturbed old forests across the western U.S., implying that these forests could become net sources of atmospheric carbon dioxide.
Sequoia and Kings Canyon Field Station
The Sequoia and Kings Canyon Field Station is home to research programs that focus on wildfire patterns in Southern California, and the effects of drought on Sierra Nevada forests. Select the "Science" tab for a more comprehensive summary.
Leaf to Landscape: Understanding and Mapping the Vulnerability of Forests to Hotter Droughts
Forests across the southwestern U.S. are crucial components of recreation and play an important role in state and local economies. Healthy forests also provide needed habitat for many wildlife species and contribute many other important services to our planet. “Hotter droughts” (otherwise normal droughts whose effects on ecosystems are exacerbated by higher temperatures) are an emerging...
Fighting Drought with Fire: A Comparison of Burned and Unburned Forests in Drought-Impacted Areas of the Southwest
Drought is one of the biggest threats facing our forests today. In the western U.S., severe drought and rising temperatures have caused increased tree mortality and complete forest diebacks. Forests are changing rapidly, and while land managers are working to develop long-term climate change adaptation plans, they require tools that can enhance forest resistance to drought now. To...
Characterizing a link in the terrestrial carbon cycle: a global overview of individual tree mass growth
Forests sequester the majority of the terrestrial biosphere’s carbon and are key components of the global carbon cycle, potentially contributing substantial feedbacks to ongoing climatic changes. It is therefore remarkable that no consensus yet exists about the fundamental nature of tree mass growth (and thus carbon sequestration rate). Specifically, does tree mass growth rate increase...
Monitoring Trees
Every year, the health of each of the thousands of trees in established research plots is checked, and if a tree has died, the cause of death is determined.
Western White Pine
A western white pine (Pinus monticola) in Kings Canyon National Park, Calif., towers over USGS ecologist Nathan Stephenson.
A western white pine (Pinus monticola) in Kings Canyon National Park, Calif., towers over USGS ecologist Nathan Stephenson.
California’s Hotter Drought and Tree Death
California's hotter drought has already killed millions of trees, particularly in low-elevation forests.
California's hotter drought has already killed millions of trees, particularly in low-elevation forests.
Giant Sequoias and Hotter Droughts
Giant sequoias have fared better than other tree species in California's recent hotter drought, but many have shown unprecedented foliage dieback in response to the drought.
Giant sequoias have fared better than other tree species in California's recent hotter drought, but many have shown unprecedented foliage dieback in response to the drought.
Science and Products
Cross-Park RAD Project (CPRP): A Case Study in Four National Parks Investigating How Institutional Context and Emotions Shape Manager Decisions to Resist, Accept, or Direct Change in Transforming Ecosystems
Natural & cultural resource managers are facing a slew of new challenges for managing public lands stemming from climate change and human-driven stressors like invasive species, fragmentation, and new resource uses. In some cases, the very landscapes and species they are managing are changing in significant ways, transforming from one set of conditions to another. As a result, previously...
Forest health and drought response
Forests provide society with economically important and often irreplaceable goods and services, such as wood products, carbon sequestration, clean water, biodiversity, and recreational opportunities. Yet hotter droughts (droughts in which unusually high temperatures exacerbate the effects of low precipitation) are projected to increase in frequency and intensity in coming decades, potentially...
Post-Fire Conifer Regeneration Under a Warming Climate: Will Severe Fire Be a Catalyst for Forest Loss?
The Southwest U.S. is experiencing hotter droughts, which are contributing to more frequent, severe wildfires. These droughts also stress vegetation, which can make it more difficult for forests to recover after fire. Forest regeneration in burned areas may be limited because seeds have to travel long distances to recolonize, and when they do arrive, conditions are often unfavorably hot...
Adaptations to Rapid Change
Management decisions are made at the intersection of facts and values, and WERC's role is to assist decision-makers by bringing the best available science to the table. Dr. Nathan Stephenson seeks to help managers and policy makers reassess their missions in light of rapid and unprecedented changes, develop broad concepts relevant to adapting to such changes, and provide hands-on assistance during...
Improving Understanding of Forest and Carbon Dynamics
The community's ability to understand and predict changes in forests and their feedbacks to the global carbon cycle increasingly relies on models spanning several scales of biological organization – from tree leaves to entire forested landscapes. Yet many model assumptions about key processes – such as tree growth and mortality – require long-term data that are sometimes difficult and time...
Detection, Attribution, and Interpretation of Forest Changes
Dr. Nathan Stephenson and colleagues seek to determine what changes are occurring in forests, why they are occurring, and what they mean. For example, they have documented a long-term, apparently climatically-induced increase of tree mortality rates in otherwise undisturbed old forests across the western U.S., implying that these forests could become net sources of atmospheric carbon dioxide.
Sequoia and Kings Canyon Field Station
The Sequoia and Kings Canyon Field Station is home to research programs that focus on wildfire patterns in Southern California, and the effects of drought on Sierra Nevada forests. Select the "Science" tab for a more comprehensive summary.
Leaf to Landscape: Understanding and Mapping the Vulnerability of Forests to Hotter Droughts
Forests across the southwestern U.S. are crucial components of recreation and play an important role in state and local economies. Healthy forests also provide needed habitat for many wildlife species and contribute many other important services to our planet. “Hotter droughts” (otherwise normal droughts whose effects on ecosystems are exacerbated by higher temperatures) are an emerging...
Fighting Drought with Fire: A Comparison of Burned and Unburned Forests in Drought-Impacted Areas of the Southwest
Drought is one of the biggest threats facing our forests today. In the western U.S., severe drought and rising temperatures have caused increased tree mortality and complete forest diebacks. Forests are changing rapidly, and while land managers are working to develop long-term climate change adaptation plans, they require tools that can enhance forest resistance to drought now. To...
Characterizing a link in the terrestrial carbon cycle: a global overview of individual tree mass growth
Forests sequester the majority of the terrestrial biosphere’s carbon and are key components of the global carbon cycle, potentially contributing substantial feedbacks to ongoing climatic changes. It is therefore remarkable that no consensus yet exists about the fundamental nature of tree mass growth (and thus carbon sequestration rate). Specifically, does tree mass growth rate increase...
Monitoring Trees
Every year, the health of each of the thousands of trees in established research plots is checked, and if a tree has died, the cause of death is determined.
Every year, the health of each of the thousands of trees in established research plots is checked, and if a tree has died, the cause of death is determined.
Western White Pine
A western white pine (Pinus monticola) in Kings Canyon National Park, Calif., towers over USGS ecologist Nathan Stephenson.
A western white pine (Pinus monticola) in Kings Canyon National Park, Calif., towers over USGS ecologist Nathan Stephenson.
California’s Hotter Drought and Tree Death
California's hotter drought has already killed millions of trees, particularly in low-elevation forests.
California's hotter drought has already killed millions of trees, particularly in low-elevation forests.
Giant Sequoias and Hotter Droughts
Giant sequoias have fared better than other tree species in California's recent hotter drought, but many have shown unprecedented foliage dieback in response to the drought.
Giant sequoias have fared better than other tree species in California's recent hotter drought, but many have shown unprecedented foliage dieback in response to the drought.