Publications by authors named "John T Abatzoglou"

25 Publications

  • Page 1 of 1

Anthropogenic climate change is worsening North American pollen seasons.

Proc Natl Acad Sci U S A 2021 Feb;118(7)

Mailman School of Public Health, Columbia University, New York, NY 10032.

Airborne pollen has major respiratory health impacts and anthropogenic climate change may increase pollen concentrations and extend pollen seasons. While greenhouse and field studies indicate that pollen concentrations are correlated with temperature, a formal detection and attribution of the role of anthropogenic climate change in continental pollen seasons is urgently needed. Here, we use long-term pollen data from 60 North American stations from 1990 to 2018, spanning 821 site-years of data, and Earth system model simulations to quantify the role of human-caused climate change in continental patterns in pollen concentrations. We find widespread advances and lengthening of pollen seasons (+20 d) and increases in pollen concentrations (+21%) across North America, which are strongly coupled to observed warming. Human forcing of the climate system contributed ∼50% (interquartile range: 19-84%) of the trend in pollen seasons and ∼8% (4-14%) of the trend in pollen concentrations. Our results reveal that anthropogenic climate change has already exacerbated pollen seasons in the past three decades with attendant deleterious effects on respiratory health.
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http://dx.doi.org/10.1073/pnas.2013284118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7896283PMC
February 2021

A climatic dipole drives short- and long-term patterns of postfire forest recovery in the western United States.

Proc Natl Acad Sci U S A 2020 11 9;117(47):29730-29737. Epub 2020 Nov 9.

Department of Ecosystem and Conservation Sciences, College of Forestry and Conservation, University of Montana, Missoula, MT 59812.

Researchers are increasingly examining patterns and drivers of postfire forest recovery amid growing concern that climate change and intensifying fires will trigger ecosystem transformations. Diminished seed availability and postfire drought have emerged as key constraints on conifer recruitment. However, the spatial and temporal extent to which recurring modes of climatic variability shape patterns of postfire recovery remain largely unexplored. Here, we identify a north-south dipole in annual climatic moisture deficit anomalies across the Interior West of the US and characterize its influence on forest recovery from fire. We use annually resolved establishment models from dendrochronological records to correlate this climatic dipole with short-term postfire juvenile recruitment. We also examine longer-term recovery trajectories using Forest Inventory and Analysis data from 989 burned plots. We show that annual postfire ponderosa pine recruitment probabilities in the northern Rocky Mountains (NR) and the southwestern US (SW) track the strength of the dipole, while declining overall due to increasing aridity. This indicates that divergent recovery trajectories may be triggered concurrently across large spatial scales: favorable conditions in the SW can correspond to drought in the NR that inhibits ponderosa pine establishment, and vice versa. The imprint of this climatic dipole is manifest for years postfire, as evidenced by dampened long-term likelihoods of juvenile ponderosa pine presence in areas that experienced postfire drought. These findings underscore the importance of climatic variability at multiple spatiotemporal scales in driving cross-regional patterns of forest recovery and have implications for understanding ecosystem transformations and species range dynamics under global change.
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http://dx.doi.org/10.1073/pnas.2007434117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7703638PMC
November 2020

Record-setting climate enabled the extraordinary 2020 fire season in the western United States.

Glob Chang Biol 2021 Jan 26;27(1):1-2. Epub 2020 Oct 26.

School of Engineering, University of California Merced, Merced, CA, USA.

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http://dx.doi.org/10.1111/gcb.15388DOI Listing
January 2021

Changes in Fire Activity in Africa from 2002 to 2016 and Their Potential Drivers.

Geophys Res Lett 2019 Jul 27;46(13):7643-7653. Epub 2019 Jun 27.

Department of Geographical Sciences, University of Maryland, College Park, MD, USA.

While several studies have reported a recent decline in area burned in Africa, the causes of this decline are still not well understood. In this study, we found that from 2002 to 2016 burned area in Africa declined by 18.5%, with the strongest decline (80% of the area) in the Northern Hemisphere. One third of the reduction in burned area occurred in croplands, suggesting that changes in agricultural practices (including cropland expansion) are not the predominant factor behind recent changes in fire extent. Linear models that considered interannual variability in climate factors directly related to biomass productivity and aridity explained about 70% of the decline in burned area in natural land cover. Our results provide evidence that despite the fact that most fires are human-caused in Africa, increased terrestrial moisture during 2002-2016 facilitated declines in fire activity in Africa.
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http://dx.doi.org/10.1029/2019gl083469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7241591PMC
July 2019

Large contribution from anthropogenic warming to an emerging North American megadrought.

Science 2020 04;368(6488):314-318

Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80302, USA.

Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogenic climate change. We use hydrological modeling and new 1200-year tree-ring reconstructions of summer soil moisture to demonstrate that the 2000-2018 SWNA drought was the second driest 19-year period since 800 CE, exceeded only by a late-1500s megadrought. The megadrought-like trajectory of 2000-2018 soil moisture was driven by natural variability superimposed on drying due to anthropogenic warming. Anthropogenic trends in temperature, relative humidity, and precipitation estimated from 31 climate models account for 47% (model interquartiles of 35 to 105%) of the 2000-2018 drought severity, pushing an otherwise moderate drought onto a trajectory comparable to the worst SWNA megadroughts since 800 CE.
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http://dx.doi.org/10.1126/science.aaz9600DOI Listing
April 2020

Multivariate climate departures have outpaced univariate changes across global lands.

Sci Rep 2020 03 3;10(1):3891. Epub 2020 Mar 3.

USDA Forest Service, Rocky Mountain Research Station, Aldo Leopold Wilderness Research Institute, Missoula, USA.

Changes in individual climate variables have been widely documented over the past century. However, assessments that consider changes in the collective interaction amongst multiple climate variables are relevant for understanding climate impacts on ecological and human systems yet are less well documented than univariate changes. We calculate annual multivariate climate departures during 1958-2017 relative to a baseline 1958-1987 period that account for covariance among four variables important to Earth's biota and associated systems: annual climatic water deficit, annual evapotranspiration, average minimum temperature of the coldest month, and average maximum temperature of the warmest month. Results show positive trends in multivariate climate departures that were nearly three times that of univariate climate departures across global lands. Annual multivariate climate departures exceeded two standard deviations over the past decade for approximately 30% of global lands. Positive trends in climate departures over the last six decades were found to be primarily the result of changes in mean climate conditions consistent with the modeled effects of anthropogenic climate change rather than changes in variability. These results highlight the increasing novelty of annual climatic conditions viewed through a multivariate lens and suggest that changes in multivariate climate departures have generally outpaced univariate departures in recent decades.
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http://dx.doi.org/10.1038/s41598-020-60270-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054431PMC
March 2020

A dataset on human perception of and response to wildfire smoke.

Sci Data 2019 10 24;6(1):229. Epub 2019 Oct 24.

Department of Civil Engineering, Boise State University, Boise, Idaho, 73725, US.

Wildfire smoke presents a growing threat in the Western U.S.; and human health, transportation, and economic systems in growing western communities suffer due to increasingly severe and widespread fires. While modelling wildfire activity and associated wildfire smoke distributions have substantially improved, understanding how people perceive and respond to emerging smoke hazards has received little attention. Understanding and incorporating human perceptions of threats from wildfire smoke is critical, as decision-makers need such information to mitigate smoke-related hazards. We surveyed 614 randomly selected people (in-person) across the Boise Metropolitan Area in Idaho and 1,623 Boise State University affiliates (online), collecting information about their level of outside activity during smoke event(s), knowledge about the source of air quality information and effective messaging preference, perception of wildfire smoke as a hazard, and smoke-related health experiences. This relatively large dataset provides a novel perspective of people's perception of smoke hazards, and provides crucial policy-relevant information to decision-makers. Dataset is available to the public and can be used to address a wide range of research questions.
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http://dx.doi.org/10.1038/s41597-019-0251-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6813346PMC
October 2019

Spatiotemporal prediction of wildfire size extremes with Bayesian finite sample maxima.

Ecol Appl 2019 09 20;29(6):e01898. Epub 2019 Jun 20.

Earth Lab, University of Colorado Boulder, 4001 Discovery Drive, Suite S348 611 UCB, Boulder, Colorado, 80303, USA.

Wildfires are becoming more frequent in parts of the globe, but predicting where and when wildfires occur remains difficult. To predict wildfire extremes across the contiguous United States, we integrate a 30-yr wildfire record with meteorological and housing data in spatiotemporal Bayesian statistical models with spatially varying nonlinear effects. We compared different distributions for the number and sizes of large fires to generate a posterior predictive distribution based on finite sample maxima for extreme events (the largest fires over bounded spatiotemporal domains). A zero-inflated negative binomial model for fire counts and a lognormal model for burned areas provided the best performance. This model attains 99% interval coverage for the number of fires and 93% coverage for fire sizes over a six year withheld data set. Dryness and air temperature strongly predict extreme wildfire probabilities. Housing density has a hump-shaped relationship with fire occurrence, with more fires occurring at intermediate housing densities. Statistically, these drivers affect the chance of an extreme wildfire in two ways: by altering fire size distributions, and by altering fire frequency, which influences sampling from the tails of fire size distributions. We conclude that recent extremes should not be surprising, and that the contiguous United States may be on the verge of even larger wildfire extremes.
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http://dx.doi.org/10.1002/eap.1898DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6851762PMC
September 2019

Human-environmental drivers and impacts of the globally extreme 2017 Chilean fires.

Ambio 2019 Apr 20;48(4):350-362. Epub 2018 Aug 20.

Menzies Institute for Medical Research, University of Tasmania, Private Bag 23, Hobart, TAS, 7001, Australia.

In January 2017, hundreds of fires in Mediterranean Chile burnt more than 5000 km, an area nearly 14 times the 40-year mean. We contextualize these fires in terms of estimates of global fire intensity using MODIS satellite record, and provide an overview of the climatic factors and recent changes in land use that led to the active fire season and estimate the impact of fire emissions to human health. The primary fire activity in late January coincided with extreme fire weather conditions including all-time (1979-2017) daily records for the Fire Weather Index (FWI) and maximum temperature, producing some of the most energetically intense fire events on Earth in the last 15-years. Fire activity was further enabled by a warm moist growing season in 2016 that interrupted an intense drought that started in 2010. The land cover in this region had been extensively modified, with less than 20% of the original native vegetation remaining, and extensive plantations of highly flammable exotic Pinus and Eucalyptus species established since the 1970s. These plantations were disproportionally burnt (44% of the burned area) in 2017, and associated with the highest fire severities, as part of an increasing trend of fire extent in plantations over the past three decades. Smoke from the fires exposed over 9.5 million people to increased concentrations of particulate air pollution, causing an estimated 76 premature deaths and 209 additional admissions to hospital for respiratory and cardiovascular conditions. This study highlights that Mediterranean biogeographic regions with expansive Pinus and Eucalyptus plantations and associated rural depopulation are vulnerable to intense wildfires with wide ranging social, economic, and environmental impacts, which are likely to become more frequent due to longer and more extreme wildfire seasons.
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http://dx.doi.org/10.1007/s13280-018-1084-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6411810PMC
April 2019

Natural and managed watersheds show similar responses to recent climate change.

Proc Natl Acad Sci U S A 2018 08 6;115(34):8553-8557. Epub 2018 Aug 6.

Department of Biology, Saint Louis University, St. Louis, MO 63103.

Changes in climate are driving an intensification of the hydrologic cycle and leading to alterations of natural streamflow regimes. Human disturbances such as dams, land-cover change, and water diversions are thought to obscure climate signals in hydrologic systems. As a result, most studies of changing hydroclimatic conditions are limited to areas with natural streamflow. Here, we compare trends in observed streamflow from natural and human-modified watersheds in the United States and Canada for the 1981-2015 water years to evaluate whether comparable responses to climate change are present in both systems. We find that patterns and magnitudes of trends in median daily streamflow, daily streamflow variability, and daily extremes in human-modified watersheds are similar to those from nearby natural watersheds. Streamflow in both systems show negative trends throughout the southern and western United States and positive trends throughout the northeastern United States, the northern Great Plains, and southern prairies of Canada. The trends in both natural and human-modified watersheds are linked to local trends in precipitation and reference evapotranspiration, demonstrating that water management and land-cover change have not substantially altered the effects of climate change on human-modified watersheds compared with nearby natural watersheds.
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http://dx.doi.org/10.1073/pnas.1801026115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6112693PMC
August 2018

Global patterns of interannual climate-fire relationships.

Glob Chang Biol 2018 11 24;24(11):5164-5175. Epub 2018 Aug 24.

Department of Forest, Range and Fire Sciences, University of Idaho, Moscow, Idaho.

Climate shapes geographic and seasonal patterns in global fire activity by mediating vegetation composition, productivity, and desiccation in conjunction with land-use and anthropogenic factors. Yet, the degree to which climate variability affects interannual variability in burned area across Earth is less understood. Two decades of satellite-derived burned area records across forested and nonforested areas were used to examine global interannual climate-fire relationships at ecoregion scales. Measures of fuel aridity exhibited strong positive correlations with forested burned area, with weaker relationships in climatologically drier regions. By contrast, cumulative precipitation antecedent to the fire season exhibited positive correlations to nonforested burned area, with stronger relationships in climatologically drier regions. Climate variability explained roughly one-third of the interannual variability in burned area across global ecoregions. These results highlight the importance of climate variability in enabling fire activity globally, but also identify regions where anthropogenic and other influences may facilitate weaker relationships. Empirical fire modeling efforts can complement process-based global fire models to elucidate how fire activity is likely to change amidst complex interactions among climatic, vegetation, and human factors.
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http://dx.doi.org/10.1111/gcb.14405DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7134822PMC
November 2018

TerraClimate, a high-resolution global dataset of monthly climate and climatic water balance from 1958-2015.

Sci Data 2018 Jan 9;5:170191. Epub 2018 Jan 9.

University of Idaho, Department of Geography, 875 Perimeter Dr, Moscow, ID 83844, USA.

We present TerraClimate, a dataset of high-spatial resolution (1/24°, ~4-km) monthly climate and climatic water balance for global terrestrial surfaces from 1958-2015. TerraClimate uses climatically aided interpolation, combining high-spatial resolution climatological normals from the WorldClim dataset, with coarser resolution time varying (i.e., monthly) data from other sources to produce a monthly dataset of precipitation, maximum and minimum temperature, wind speed, vapor pressure, and solar radiation. TerraClimate additionally produces monthly surface water balance datasets using a water balance model that incorporates reference evapotranspiration, precipitation, temperature, and interpolated plant extractable soil water capacity. These data provide important inputs for ecological and hydrological studies at global scales that require high spatial resolution and time varying climate and climatic water balance data. We validated spatiotemporal aspects of TerraClimate using annual temperature, precipitation, and calculated reference evapotranspiration from station data, as well as annual runoff from streamflow gauges. TerraClimate datasets showed noted improvement in overall mean absolute error and increased spatial realism relative to coarser resolution gridded datasets.
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http://dx.doi.org/10.1038/sdata.2017.191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5759372PMC
January 2018

Human exposure and sensitivity to globally extreme wildfire events.

Nat Ecol Evol 2017 Feb 6;1(3):58. Epub 2017 Feb 6.

College of Natural Resources, University of Idaho, Moscow, Idaho 83844-1133, USA.

Extreme wildfires have substantial economic, social and environmental impacts, but there is uncertainty whether such events are inevitable features of the Earth's fire ecology or a legacy of poor management and planning. We identify 478 extreme wildfire events defined as the daily clusters of fire radiative power from MODIS, within a global 10 × 10 km lattice, between 2002 and 2013, which exceeded the 99.997th percentile of over 23 million cases of the ΣFRP 100 km in the MODIS record. These events are globally distributed across all flammable biomes, and are strongly associated with extreme fire weather conditions. Extreme wildfire events reported as being economically or socially disastrous (n = 144) were concentrated in suburban areas in flammable-forested biomes of the western United States and southeastern Australia, noting potential biases in reporting and the absence of globally comprehensive data of fire disasters. Climate change projections suggest an increase in days conducive to extreme wildfire events by 20 to 50% in these disaster-prone landscapes, with sharper increases in the subtropical Southern Hemisphere and European Mediterranean Basin.
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http://dx.doi.org/10.1038/s41559-016-0058DOI Listing
February 2017

Comparing mechanistic and empirical approaches to modeling the thermal niche of almond.

Int J Biometeorol 2017 Sep 12;61(9):1593-1606. Epub 2017 Apr 12.

Department of Geography, University of Idaho, 875 Perimeter Drive, MS 3021, Moscow, ID, 83844-3021, USA.

Delineating locations that are thermally viable for cultivating high-value crops can help to guide land use planning, agronomics, and water management. Three modeling approaches were used to identify the potential distribution and key thermal constraints on on almond cultivation across the southwestern United States (US), including two empirical species distribution models (SDMs)-one using commonly used bioclimatic variables (traditional SDM) and the other using more physiologically relevant climate variables (nontraditional SDM)-and a mechanistic model (MM) developed using published thermal limitations from field studies. While models showed comparable results over the majority of the domain, including over existing croplands with high almond density, the MM suggested the greatest potential for the geographic expansion of almond cultivation, with frost susceptibility and insufficient heat accumulation being the primary thermal constraints in the southwestern US. The traditional SDM over-predicted almond suitability in locations shown by the MM to be limited by frost, whereas the nontraditional SDM showed greater agreement with the MM in these locations, indicating that incorporating physiologically relevant variables in SDMs can improve predictions. Finally, opportunities for geographic expansion of almond cultivation under current climatic conditions in the region may be limited, suggesting that increasing production may rely on agronomical advances and densifying current almond plantations in existing locations.
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http://dx.doi.org/10.1007/s00484-017-1338-9DOI Listing
September 2017

Human-started wildfires expand the fire niche across the United States.

Proc Natl Acad Sci U S A 2017 03 27;114(11):2946-2951. Epub 2017 Feb 27.

Earth Lab, University of Colorado, Boulder, CO 80309.

The economic and ecological costs of wildfire in the United States have risen substantially in recent decades. Although climate change has likely enabled a portion of the increase in wildfire activity, the direct role of people in increasing wildfire activity has been largely overlooked. We evaluate over 1.5 million government records of wildfires that had to be extinguished or managed by state or federal agencies from 1992 to 2012, and examined geographic and seasonal extents of human-ignited wildfires relative to lightning-ignited wildfires. Humans have vastly expanded the spatial and seasonal "fire niche" in the coterminous United States, accounting for 84% of all wildfires and 44% of total area burned. During the 21-y time period, the human-caused fire season was three times longer than the lightning-caused fire season and added an average of 40,000 wildfires per year across the United States. Human-started wildfires disproportionally occurred where fuel moisture was higher than lightning-started fires, thereby helping expand the geographic and seasonal niche of wildfire. Human-started wildfires were dominant (>80% of ignitions) in over 5.1 million km, the vast majority of the United States, whereas lightning-started fires were dominant in only 0.7 million km, primarily in sparsely populated areas of the mountainous western United States. Ignitions caused by human activities are a substantial driver of overall fire risk to ecosystems and economies. Actions to raise awareness and increase management in regions prone to human-started wildfires should be a focus of United States policy to reduce fire risk and associated hazards.
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http://dx.doi.org/10.1073/pnas.1617394114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5358354PMC
March 2017

Designing ecological climate change impact assessments to reflect key climatic drivers.

Glob Chang Biol 2017 07 6;23(7):2537-2553. Epub 2017 Mar 6.

U.S. Geological Survey, Department of the Interior North Central Climate Science Center, Fort Collins, CO, 80523, USA.

Identifying the climatic drivers of an ecological system is a key step in assessing its vulnerability to climate change. The climatic dimensions to which a species or system is most sensitive - such as means or extremes - can guide methodological decisions for projections of ecological impacts and vulnerabilities. However, scientific workflows for combining climate projections with ecological models have received little explicit attention. We review Global Climate Model (GCM) performance along different dimensions of change and compare frameworks for integrating GCM output into ecological models. In systems sensitive to climatological means, it is straightforward to base ecological impact assessments on mean projected changes from several GCMs. Ecological systems sensitive to climatic extremes may benefit from what we term the 'model space' approach: a comparison of ecological projections based on simulated climate from historical and future time periods. This approach leverages the experimental framework used in climate modeling, in which historical climate simulations serve as controls for future projections. Moreover, it can capture projected changes in the intensity and frequency of climatic extremes, rather than assuming that future means will determine future extremes. Given the recent emphasis on the ecological impacts of climatic extremes, the strategies we describe will be applicable across species and systems. We also highlight practical considerations for the selection of climate models and data products, emphasizing that the spatial resolution of the climate change signal is generally coarser than the grid cell size of downscaled climate model output. Our review illustrates how an understanding of how climate model outputs are derived and downscaled can improve the selection and application of climatic data used in ecological modeling.
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http://dx.doi.org/10.1111/gcb.13653DOI Listing
July 2017

Quantifying the human influence on fire ignition across the western USA.

Ecol Appl 2016 Dec 30;26(8):2388-2399. Epub 2016 Sep 30.

Organismic and Evolutionary Biology Program, University of Massachusetts-Amherst, Amherst, Massachusetts, 01003, USA.

Humans have a profound effect on fire regimes by increasing the frequency of ignitions. Although ignition is an integral component of understanding and predicting fire, to date fire models have not been able to isolate the ignition location, leading to inconsistent use of anthropogenic ignition proxies. Here, we identified fire ignitions from the Moderate Resolution Imaging Spectrometer (MODIS) Burned Area Product (2000-2012) to create the first remotely sensed, consistently derived, and regionally comprehensive fire ignition data set for the western United States. We quantified the spatial relationships between several anthropogenic land-use/disturbance features and ignition for ecoregions within the study area and used hierarchical partitioning to test how the anthropogenic predictors of fire ignition vary among ecoregions. The degree to which anthropogenic features predicted ignition varied considerably by ecoregion, with the strongest relationships found in the Marine West Coast Forest and North American Desert ecoregions. Similarly, the contribution of individual anthropogenic predictors varied greatly among ecoregions. Railroad corridors and agricultural presence tended to be the most important predictors of anthropogenic ignition, while population density and roads were generally poor predictors. Although human population has often been used as a proxy for ignitions at global scales, it is less important at regional scales when more specific land uses (e.g., agriculture) can be identified. The variability of ignition predictors among ecoregions suggests that human activities have heterogeneous impacts in altering fire regimes within different vegetation types and geographies.
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http://dx.doi.org/10.1002/eap.1395DOI Listing
December 2016

Climate influences on whitebark pine mortality from mountain pine beetle in the Greater Yellowstone Ecosystem.

Ecol Appl 2016 Dec 30;26(8):2505-2522. Epub 2016 Sep 30.

USDA Forest Service, Emigrant, Montana, 59027, USA.

Extensive mortality of whitebark pine, beginning in the early to mid-2000s, occurred in the Greater Yellowstone Ecosystem (GYE) of the western USA, primarily from mountain pine beetle but also from other threats such as white pine blister rust. The climatic drivers of this recent mortality and the potential for future whitebark pine mortality from mountain pine beetle are not well understood, yet are important considerations in whether to list whitebark pine as a threatened or endangered species. We sought to increase the understanding of climate influences on mountain pine beetle outbreaks in whitebark pine forests, which are less well understood than in lodgepole pine, by quantifying climate-beetle relationships, analyzing climate influences during the recent outbreak, and estimating the suitability of future climate for beetle outbreaks. We developed a statistical model of the probability of whitebark pine mortality in the GYE that included temperature effects on beetle development and survival, precipitation effects on host tree condition, beetle population size, and stand characteristics. Estimated probability of whitebark pine mortality increased with higher winter minimum temperature, indicating greater beetle winter survival; higher fall temperature, indicating synchronous beetle emergence; lower two-year summer precipitation, indicating increased potential for host tree stress; increasing beetle populations; stand age; and increasing percent composition of whitebark pine within a stand. The recent outbreak occurred during a period of higher-than-normal regional winter temperatures, suitable fall temperatures, and low summer precipitation. In contrast to lodgepole pine systems, area with mortality was linked to precipitation variability even at high beetle populations. Projections from climate models indicate future climate conditions will likely provide favorable conditions for beetle outbreaks within nearly all current whitebark pine habitat in the GYE by the middle of this century. Therefore, when surviving and regenerating trees reach ages suitable for beetle attack, there is strong potential for continued whitebark pine mortality due to mountain pine beetle.
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http://dx.doi.org/10.1002/eap.1396DOI Listing
December 2016

Impact of anthropogenic climate change on wildfire across western US forests.

Proc Natl Acad Sci U S A 2016 10 10;113(42):11770-11775. Epub 2016 Oct 10.

Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964.

Increased forest fire activity across the western continental United States (US) in recent decades has likely been enabled by a number of factors, including the legacy of fire suppression and human settlement, natural climate variability, and human-caused climate change. We use modeled climate projections to estimate the contribution of anthropogenic climate change to observed increases in eight fuel aridity metrics and forest fire area across the western United States. Anthropogenic increases in temperature and vapor pressure deficit significantly enhanced fuel aridity across western US forests over the past several decades and, during 2000-2015, contributed to 75% more forested area experiencing high (>1 σ) fire-season fuel aridity and an average of nine additional days per year of high fire potential. Anthropogenic climate change accounted for ∼55% of observed increases in fuel aridity from 1979 to 2015 across western US forests, highlighting both anthropogenic climate change and natural climate variability as important contributors to increased wildfire potential in recent decades. We estimate that human-caused climate change contributed to an additional 4.2 million ha of forest fire area during 1984-2015, nearly doubling the forest fire area expected in its absence. Natural climate variability will continue to alternate between modulating and compounding anthropogenic increases in fuel aridity, but anthropogenic climate change has emerged as a driver of increased forest fire activity and should continue to do so while fuels are not limiting.
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http://dx.doi.org/10.1073/pnas.1607171113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5081637PMC
October 2016

The Science of Firescapes: Achieving Fire-Resilient Communities.

Bioscience 2016 Feb 3;66(2):130-146. Epub 2016 Feb 3.

Alistair M.S. Smith is an environmental biophysicist at the University of Idaho, in Moscow, and is affiliated with the College of Natural Resources and the Idaho Fire Initiative for Research and Education (IFIRE). Travis B. Paveglio is a natural resource sociologist who focuses on wildfires and is affiliated with the Department of Natural Resources and Society at the University of Idaho, in Moscow. Andrew D. Kliskey, Luigi Boschetti, Kara M. Yedinak, and Eva K. Strand are each affiliated with the College of Natural Resources at the University of Idaho, in Moscow. Crystal A Kolden is a pyrogeographer affiliated with the College of Science at the University of Idaho, Moscow. Mark A Cochrane is an ecologist affiliated with Geospatial Sciences Center of Excellence at South Dakota State University, Brookings. David M.J.S. Bowman is an environmental change biologist and pyrogeographer affiliated with the University of Tasmania, in Sandy Bay. Max A. Moritz is a cooperative extension specialist in fire ecology and management and is affiliated with the College of Natural Resources at the University of California, Berkeley. Lilian Alessa is a biologist from the University of Idaho, Moscow, and is affiliated with the Center for Resilient Communities, Alaska EPSCoR, and the International Arctic Research Center. Andrew T. Hudak is a research forester affiliated with the USDA Forest Service Rocky Mountain Research Station, in Moscow. Chad M. Hoffman is a forester affiliated with Colorado State University and the Western Forest Fire Research (WESTFIRE) Center, in Fort Collins. James A. Lutz is an ecologist affiliated with Utah State University, Logan, and is affiliated with the Yosemite, Utah, and Wind River Forest Dynamics Plots. Lloyd P. Queen is a remote sensing scientist affiliated with the University of Montana and the FireCenter, Missoula. Scott J. Goetz is a geographer affiliated with Woods Hole Research Center, Falmouth, and is affiliated with the Arctic Boreal Vulnerability Experiment (ABoVE). Philip E. Higuera is an ecologist affiliated with the University of Montana, Missoula. Mike Flannigan is a fire researcher affiliated with the University of Alberta, Edmonton, and is affiliated with the Western Partnership for Western Fire Science. Adam C. Watts is a fire ecologist affiliated with the Desert Research Institute, Reno. Jan W. van Wagtendonk is a research forester emeritus affiliated with the National Park Service, Yosemite National Park, Yosemite Field Station. John W. Anderson is a virtual architect affiliated with Virtual Technology and Design at the University of Idaho, in Moscow. Brian J. Stocks is a forester and is affiliated with BJ Stocks Wildfire Investigations. John T. Abatzoglou is a climatologist and is affiliated with the Department of Geography at the University of Idaho.

Wildland fire management has reached a crossroads. Current perspectives are not capable of answering interdisciplinary adaptation and mitigation challenges posed by increases in wildfire risk to human populations and the need to reintegrate fire as a vital landscape process. Fire science has been, and continues to be, performed in isolated "silos," including institutions (e.g., agencies versus universities), organizational structures (e.g., federal agency mandates versus local and state procedures for responding to fire), and research foci (e.g., physical science, natural science, and social science). These silos tend to promote research, management, and policy that focus only on targeted aspects of the "wicked" wildfire problem. In this article, we provide guiding principles to bridge diverse fire science efforts to advance an integrated agenda of wildfire research that can help overcome disciplinary silos and provide insight on how to build fire-resilient communities.
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http://dx.doi.org/10.1093/biosci/biv182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5865631PMC
February 2016

The Changing Strength and Nature of Fire-Climate Relationships in the Northern Rocky Mountains, U.S.A., 1902-2008.

PLoS One 2015 26;10(6):e0127563. Epub 2015 Jun 26.

College of Natural Resources, University of Idaho, Moscow, Idaho, United States of America.

Time-varying fire-climate relationships may represent an important component of fire-regime variability, relevant for understanding the controls of fire and projecting fire activity under global-change scenarios. We used time-varying statistical models to evaluate if and how fire-climate relationships varied from 1902-2008, in one of the most flammable forested regions of the western U.S.A. Fire-danger and water-balance metrics yielded the best combination of calibration accuracy and predictive skill in modeling annual area burned. The strength of fire-climate relationships varied markedly at multi-decadal scales, with models explaining < 40% to 88% of the variation in annual area burned. The early 20th century (1902-1942) and the most recent two decades (1985-2008) exhibited strong fire-climate relationships, with weaker relationships for much of the mid 20th century (1943-1984), coincident with diminished burning, less fire-conducive climate, and the initiation of modern fire fighting. Area burned and the strength of fire-climate relationships increased sharply in the mid 1980s, associated with increased temperatures and longer potential fire seasons. Unlike decades with high burning in the early 20th century, models developed using fire-climate relationships from recent decades overpredicted area burned when applied to earlier periods. This amplified response of fire to climate is a signature of altered fire-climate-relationships, and it implicates non-climatic factors in this recent shift. Changes in fuel structure and availability following 40+ yr of unusually low fire activity, and possibly land use, may have resulted in increased fire vulnerability beyond expectations from climatic factors alone. Our results highlight the potential for non-climatic factors to alter fire-climate relationships, and the need to account for such dynamics, through adaptable statistical or processes-based models, for accurately predicting future fire activity.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0127563PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4482589PMC
April 2016

Questionable evidence of natural warming of the northwestern United States.

Proc Natl Acad Sci U S A 2014 Dec 19;111(52):E5605-6. Epub 2014 Dec 19.

College of Earth, Ocean, and Atmospheric Sciences, Oregon Climate Change Research Institute, Oregon State University, Corvallis, OR 97331.

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http://dx.doi.org/10.1073/pnas.1421311112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4284571PMC
December 2014

Agroecological factors correlated to soil DNA concentrations of Rhizoctonia in dryland wheat production zones of Washington state, USA.

Phytopathology 2014 Jul;104(7):683-91

The necrotrophic soilborne fungal pathogens Rhizoctonia solani AG8 and R. oryzae are principal causal agents of Rhizoctonia root rot and bare patch of wheat in dryland cropping systems of the Pacific Northwest. A 3-year survey of 33 parcels at 11 growers' sites and 60 trial plots at 12 Washington State University cereal variety test locations was undertaken to understand the distribution of these pathogens. Pathogen DNA concentrations in soils, quantified using real-time polymerase chain reaction, were correlated with precipitation, temperature maxima and minima, and soil texture factors in a pathogen-specific manner. Specifically, R. solani AG8 DNA concentration was negatively correlated with precipitation and not correlated with temperature minima, whereas R. oryzae concentration was correlated with temperature minima but not with precipitation. However, both pathogens were more abundant in soils with higher sand and lower clay content. Principal component analysis also indicated that unique groups of meteorological and soil factors were associated with each pathogen. Furthermore, tillage did not affect R. oryzae but affected R. solani AG8 at P = 0.06. Lower soil concentrations of R. solani AG8 but not R. oryzae occurred when the previously planted crop was a broadleaf (P < 0.05). Our findings showed that R. solani AG8 concentrations were consistent with the general distribution of bare patch symptoms, based on field observations and surveys of other pathogens, but was present at many sites in which bare patch symptoms were not evident. Management of Rhizoctonia root rot and bare patch should account for the likelihood that each pathogen is affected by a unique group of agroecological variables.
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http://dx.doi.org/10.1094/PHYTO-09-13-0269-RDOI Listing
July 2014

Camouflage mismatch in seasonal coat color due to decreased snow duration.

Proc Natl Acad Sci U S A 2013 Apr 15;110(18):7360-5. Epub 2013 Apr 15.

Wildlife Biology Program, Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT 59812, USA.

Most examples of seasonal mismatches in phenology span multiple trophic levels, with timing of animal reproduction, hibernation, or migration becoming detached from peak food supply. The consequences of such mismatches are difficult to link to specific future climate change scenarios because the responses across trophic levels have complex underlying climate drivers often confounded by other stressors. In contrast, seasonal coat color polyphenism creating camouflage against snow is a direct and potentially severe type of seasonal mismatch if crypsis becomes compromised by the animal being white when snow is absent. It is unknown whether plasticity in the initiation or rate of coat color change will be able to reduce mismatch between the seasonal coat color and an increasingly snow-free background. We find that natural populations of snowshoe hares exposed to 3 y of widely varying snowpack have plasticity in the rate of the spring white-to-brown molt, but not in either the initiation dates of color change or the rate of the fall brown-to-white molt. Using an ensemble of locally downscaled climate projections, we also show that annual average duration of snowpack is forecast to decrease by 29-35 d by midcentury and 40-69 d by the end of the century. Without evolution in coat color phenology, the reduced snow duration will increase the number of days that white hares will be mismatched on a snowless background by four- to eightfold by the end of the century. This novel and visually compelling climate change-induced stressor likely applies to >9 widely distributed mammals with seasonal coat color.
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http://dx.doi.org/10.1073/pnas.1222724110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3645584PMC
April 2013

Changes in climatic water balance drive downhill shifts in plant species' optimum elevations.

Science 2011 Jan;331(6015):324-7

Department of Forest Management, College of Forestry and Conservation, University of Montana, Missoula, MT 59812, USA.

Uphill shifts of species' distributions in response to historical warming are well documented, which leads to widespread expectations of continued uphill shifts under future warming. Conversely, downhill shifts are often considered anomalous and unrelated to climate change. By comparing the altitudinal distributions of 64 plant species between the 1930s and the present day within California, we show that climate changes have resulted in a significant downward shift in species' optimum elevations. This downhill shift is counter to what would be expected given 20th-century warming but is readily explained by species' niche tracking of regional changes in climatic water balance rather than temperature. Similar downhill shifts can be expected to occur where future climate change scenarios project increases in water availability that outpace evaporative demand.
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http://dx.doi.org/10.1126/science.1199040DOI Listing
January 2011