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.
- Forest ecology
- Global change biology
- Climate change
- Fire ecology
- Natural areas management
- Ph.D., Ecology and Systematics, Cornell University, 1988
- B.S., Biological Sciences, University of California, Irvine, 1979
Science and Products
Causes and implications of the correlation between forest productivity and tree mortality rates
At global and regional scales, tree mortality rates are positively correlated with forest net primary productivity (NPP). Yet causes of the correlation are unknown, in spite of potentially profound implications for our understanding of environmental controls of forest structure and dynamics and, more generally, our understanding of broad-scale...Stephenson, Nathan L.; van Mantgem, Philip J.; Bunn, Andrew G.; Bruner, Howard; Harmon, Mark E.; O'Connell, Kari B.; Urban, Dean L.; Franklin, Jerry F.
Comment on "Changes in climatic water balance drive downhill shifts in plant species' optimum elevations"
Crimmins et al. (Reports, 21 January 2011, p. 324) attributed an apparent downward elevational shift of California plant species to a precipitation-induced decline in climatic water deficit. We show that the authors miscalculated deficit, that the apparent decline in species' elevations is likely a consequence of geographic biases, and that unlike...Stephenson, Nathan L.; Das, Adrian J.
Long-term effects of prescribed fire on mixed conifer forest structure in the Sierra Nevada, California
The capacity of prescribed fire to restore forest conditions is often judged by changes in forest structure within a few years following burning. However, prescribed fire might have longer-term effects on forest structure, potentially changing treatment assessments. We examined annual changes in forest structure in five 1 ha old-growth plots...van Mantgem, Phillip J.; Stephenson, Nathan L.; Knapp, Eric; Keeley, Jon E.
The contribution of competition to tree mortality in old-growth coniferous forests
Competition is a well-documented contributor to tree mortality in temperate forests, with numerous studies documenting a relationship between tree death and the competitive environment. Models frequently rely on competition as the only non-random mechanism affecting tree mortality. However, for mature forests, competition may cease to be the...Das, A.; Battles, J.; Stephenson, N.L.; van Mantgem, P.J.
Guiding concepts for park and wilderness stewardship in an era of global environmental change
The major challenge to stewardship of protected areas is to decide where, when, and how to intervene in physical and biological processes, to conserve what we value in these places. To make such decisions, planners and managers must articulate more clearly the purposes of parks, what is valued, and what needs to be sustained. A key aim for...Hobbs, Richard J.; Cole, David N.; Yung, Laurie; Zavaleta, Erika S.; Aplet, Gregory H.; Chapin, F. Stuart; Landres, Peter B.; Parsons, David J.; Stephenson, Nathan L.; White, Peter S.; Graber, David M.; Higgs, Eric S.; Millar, Constance I.; Randall, John M.; Tonnessen, Kathy A.; Woodley, Stephen
Responding to climate change: A toolbox of management strategies: Chapter 11
Climate change and its effects are writ large across the landscape and in the natural and cultural heritage of parks and wilderness. They always have been and always will be. The sculpted walls of Yosemite National Park and the jagged scenery of the Sierra Nevada wilderness would not be as spectacular if periods of glaciation had not been followed...Cole, David; Stephenson, Nathan L.; Millar, Constance I.
Shifting environmental foundations: The unprecedented and unpredictable future: Chapter 4
As described in Chapter 2, protected area managers have been directed, through statutes and agency policy, to preserve natural conditions in parks and wilderness. Although preserving naturalness has always been a challenge for managers, there has never been much question about whether this is the right thing to do. But given what is known now...Stephenson, Nathan L.; Millar, Constance I.; Cole, David
Climate-induced tree mortality: Earth system consequences
One of the greatest uncertainties in global environmental change is predicting changes in feedbacks between the biosphere and the Earth system. Terrestrial ecosystems and, in particular, forests exert strong controls on the global carbon cycle and influence regional hydrology and climatology directly through water and surface energy budgets [Bonan...Adams, Henry D.; Macalady, Alison K.; Breshears, David D.; Allen, Craig D.; Stephenson, Nathan L.; Saleska, Scott; Huxman, Travis E.; McDowell, Nathan G.
Proceedings of the Second All-USGS Modeling Conference, February 11-14, 2008: Painting the Big Picture
The Second USGS Modeling Conference was held February 11-14, 2008, in Orange Beach, Ala. Participants at the conference came from all U.S. Geological Survey (USGS) regions and represented all four science discipline - Biology, Geography, Geology, and Water. Representatives from other Department of the Interior (DOI) agencies and partners from the...Brady, Shailaja R.
Options for national parks and reserves for adapting to climate change
Past and present climate has shaped the valued ecosystems currently protected in parks and reserves, but future climate change will redefine these conditions. Continued conservation as climate changes will require thinking differently about resource management than we have in the past; we present some logical steps and tools for doing so. Three...Baron, Jill S.; Gunderson, Lance; Allen, Craig D.; Fleishman, Erica; McKenzie, Donald; Meyerson, Laura A.; Oropeza, Jill; Stephenson, Nathan L.
Widespread increase of tree mortality rates in the Western United States
Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from unmanaged old forests in the western United States showed that background (noncatastrophic) mortality rates have increased rapidly in recent decades, with doubling periods...van Mantgem, P.J.; Stephenson, N.L.; Byrne, J.C.; Daniels, L.D.; Franklin, J.F.; Fule, P.Z.; Harmon, M.E.; Larson, A.J.; Smith, Joseph M.; Taylor, A.H.; Veblen, T.T.
Spatial elements of mortality risk in old-growth forests
For many species of long-lived organisms, such as trees, survival appears to be the most critical vital rate affecting population persistence. However, methods commonly used to quantify tree death, such as relating tree mortality risk solely to diameter growth, almost certainly do not account for important spatial processes. Our goal in this study...Das, Adrian; Battles, John; van Mantgem, Phillip J.; Stephenson, Nathan L.