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Although natural resource managers are concerned about climate change, many are unable to adequately incorporate climate change science into their adaptation strategies or management plans, and are not always aware of or do not always employ the most current scientific knowledge. One of the most prominent natural resource management agencies in the United States is the Bureau of Land Management (BLM), which is tasked with managing over 248 million acres (>1 million km² ) of public lands for multiple, often conflicting, uses. Climate change will affect the sustainability of many of these land uses and could further increase conflicts between them. As such, the purpose of our study was to determine the extent to which climate change will affect public land uses, and whether the BLM is managing for such predicted effects. To do so, we first conducted a systematic review of peer-reviewed literature that discussed potential impacts of climate change on the multiple land uses the BLM manages in the Intermountain West, USA, and then expanded these results with a synthesis of projected vegetation changes. Finally, we conducted a content analysis of BLM Resource Management Plans in order to determine how climate change is explicitly addressed by BLM managers, and whether such plans reflect changes predicted by the scientific literature. We found that active resource use generally threatens intrinsic values such as conservation and ecosystem services on BLM land, and climate change is expected to exacerbate these threats in numerous ways. Additionally, our synthesis of vegetation modeling suggests substantial changes in vegetation due to climate change. However, BLM plans rarely referred to climate change explicitly and did not reflect the results of the literature review or vegetation model synthesis. Our results suggest there is a disconnect between management of BLM lands and the best available science on climate change. We recommend that the BLM actively integrates such research into on-the-ground management plans and activities, and that researchers studying the effects of climate change make a more robust effort to understand the practices and policies of public land management in order to effectively communicate the management significance of their findings. [ABSTRACT FROM AUTHOR]

Tulip poplar is an important component of the eastern deciduous forest and one of the few diffuse‐porous tree species with indeterminate apical growth in North America for which there are substantial dendroecological data. This dendroecological study evaluated correlations between radial growth of tulip poplar and monthly, seasonal, and annual climate variables and how these correlations varied across time and spatial climate gradients. The strongest and most spatially consistent correlations were with climate variables related to site water balance, especially precipitation. Growth was positively correlated with climate variables related to site water balance during the months of May through July of the year the annual ring forms and during the previous year growing season and autumn. Growth was negatively correlated with prior year growing season maximum temperature, but positively correlated with prior winter minimum temperature. There was some evidence of temporal variation in growth–climate associations between 1900 and 2016, but the climate variables with the strongest associations were consistent across different time periods. Correlations with climate variables related to water stress increased from east to west as precipitation decreased, but there was no spatial trend in correlations with growing season temperature from north to south as temperature increases. Strength of positive correlations with winter temperature increased from north to south. Growth of tulip poplar will likely be adversely affected if drought frequency or severity increases during the twenty‐first century. Increased winter temperature would likely have a positive influence on growth during the subsequent growing season in some parts of the species range. Radial growth of tulip poplar is most affected by climate conditions during a narrow time period early in the growing season, similar to results obtained for multiple oak species and a few other diffuse‐porous species in eastern North America. Simulation modelers might consider the phenology of these correlations to formulate more biologically realistic tree climate response functions. [ABSTRACT FROM AUTHOR]

Impending climate warming is expected to influence plant growth and distribution, and the distribution range limit of tree species is extremely sensitive to climate change. However, synchronous comparisons of responses of different tree species with overlapping ecological niches to climate at their distribution range limit in the same region have received little attention. In the present study, we assessed the discrepancy in radial growth responses of two dominant oak species to climate at their distribution range limit (southern range limit for Quercus mongolica, northern range limit for Quercus variabilis) in Beijing, China. Furthermore, growth-climate relationships were examined using linear mixed-effects models, and growth trends up to the year 2100 were forecast based on future climate scenarios (RCP2.6 and RCP8.5). Our results indicated that there were no significant differences in the growth response to climate between Q. variabilis at its northern limit and Q. mongolica at its southern limit, and the growth of the two tree species was positively correlated with the minimum temperature and negatively correlated with the climatic moisture deficit of autumn. However, the growth response to climate variables varied at different sites. Additionally, the model forecast showed an increase in radial growth of Q. variabilis at its northern limit and Q. mongolica at its southern limit up to the end of the present century. [ABSTRACT FROM AUTHOR]

The Himalaya, the world's largest mountain chain, spans a wide variety of climates. Further, different locations have historically experienced climatic perturbations to different degrees. This makes it the ideal region to assess roles of contemporary climate, diversification (speciation minus extinction), and dispersal barriers in affecting local species richness. Based on a review of all available Himalayan floras, we determined that 8765 native angiosperm species are presently documented and recorded their location and elevational distributions. We compared species richness and measures of phylogenetic structure in 100-m elevational bands for all species combined and for three major life-forms separately (trees, shrubs, and herbs) across the Himalaya. Species richness declines threefold from the east to the northwest of the Himalaya. Along elevational gradients, tree richness monotonically declines in the northwest, but peaks at ~1000 m in the east. Shrubs and herbs peak in richness at mid-elevations (~2000 m). Mean temperature and annual precipitation together explain ~60% of the variation in species richness. The general phylogenetic pattern observed in this study is that phylogenetic clustering (i.e., more closely related species on fewer long branches) increases from low to high elevations, but with a dip at mid-elevations (2000- 3000 m), which may result from a mixing of distinct floras, but is not associated with exceptionally high richness. High clustering at higher elevations (3000-4500 m) and in the drier northwest suggests ongoing diversification dynamics limit richness in these harsher environments. The effects of diversification dynamics appear to be smaller than those of contemporary climate in limiting buildup of species numbers. [ABSTRACT FROM AUTHOR]

The impacts of different emission levels and climate change conditions to landscape-scale natural vegetation could have large repercussions for ecosystem services and environmental health. We forecast the risk-reduction benefits to natural landscapes of lowering business-as-usual greenhouse gas emissions by comparing the extent and spatial patterns of climate exposure to dominant vegetation under current emissions trajectories (Representative Concentration Pathway, RCP8.5) and envisioned Paris Accord target emissions (RCP4.5). This comparison allows us to assess the ecosystem value of reaching targets to keep global temperature warming under 2°C. Using 350,719 km2 of natural lands in California, USA and the mapped extents of 30 vegetation types, we identify each type's current bioclimatic envelope by the frequency with which it occupies current climate conditions. We then map the trajectory of each pixel's climate under the four climate futures to quantify areas expected to fall within, become marginal to (outside a 95% probability contour), or move beyond their current climate conditions by the end of the 21st century. In California, these four future climates represent temperature increases of 1.9-4.5°C and a -24.8 to +22.9% change in annual precipitation by 2100. From 158,481 to 196,493 km2 (45-56%) of California's natural vegetation is predicted to become highly climatically stressed under current emission levels (RCP8.5) under the drier and wetter global climate models, respectively. Vegetation in three California ecoregions critical to human welfare, southwestern CA, the Great Valley and the Sierra Nevada Mountains, becomes >50% impacted, including 68% of the lands around Los Angeles and San Diego. However, reducing emissions to RCP4.5 levels reduces statewide climate exposure risk by 86,382-99,726 km2. These projections are conservative baseline estimates because they do not account for amplified drought-related mortality, fires and beetle outbreaks that have been observed during the current five-year drought. However, these results point to the landscape benefits of emission reductions. [ABSTRACT FROM AUTHOR]

Forests around the world are experiencing increasingly severe droughts and elevated competitive intensity due to increased tree density. However, the influence of interactions between drought and competition on forest growth remains poorly understood. Using a unique dataset of stand-scale dendrochronology sampled from 6405 trees, we quantified how annual growth of entire tree populations responds to drought and competition in eight, long-term (multi-decadal), experiments with replicated levels of density (e.g., competitive intensity) arrayed across a broad climatic and compositional gradient. Forest growth (cumulative individual tree growth within a stand) declined during drought, especially during more severe drought in drier climates. Forest growth declines were exacerbated by high density at all sites but one, particularly during periods of more severe drought. Surprisingly, the influence of forest density was persistent overall, but these density impacts were greater in the humid sites than in more arid sites. Significant density impacts occurred during periods of more extreme drought, and during warmer temperatures in the semi-arid sites but during periods of cooler temperatures in the humid sites. Because competition has a consistent influence over growth response to drought, maintaining forests at lower density may enhance resilience to drought in all climates. [ABSTRACT FROM AUTHOR]

Macroscale studies of ecological phenomena are increasingly common because stressors such as climate and land-use change operate at large spatial and temporal scales. Cross-scale interactions (CSIs), where ecological processes operating at one spatial or temporal scale interact with processes operating at another scale, have been documented in a variety of ecosystems and contribute to complex system dynamics. However, studies investigating CSIs are often dependent on compiling multiple data sets from different sources to create multithematic, multiscaled data sets, which results in structurally complex, and sometimes incomplete data sets. The statistical power to detect CSIs needs to be evaluated because of their importance and the challenge of quantifying CSIs using data sets with complex structures and missing observations. We studied this problem using a spatially hierarchical model that measures CSIs between regional agriculture and its effects on the relationship between lake nutrients and lake productivity. We used an existing large multithematic, multiscaled database, LAke multiscaled GeOSpatial, and temporal database (LAGOS), to parameterize the power analysis simulations. We found that the power to detect CSIs was more strongly related to the number of regions in the study rather than the number of lakes nested within each region. CSI power analyses will not only help ecologists design large-scale studies aimed at detecting CSIs, but will also focus attention on CSI effect sizes and the degree to which they are ecologically relevant and detectable with large data sets. [ABSTRACT FROM AUTHOR]

Mid‐latitude climate extremes are projected to increase in frequency under global climate change. How this may affect migratory bird populations is not well understood. The mid‐latitudes of North America experienced an extreme warming event during March 2012 that advanced the spring phenology of ecological productivity, resulting in lower levels of productivity during the summer. Here, we test the predictions that: (1) short‐distance migratory birds, due to geographic proximity and more flexible migratory behavior, should advance their spring migration phenology; and (2) breeding populations, due to lower summer productivity, should have reduced occurrences. We used occurrence data for 353 bird species from the eBird database to calculate weekly occurrence anomalies for 2012 relative to the 2010–2014 average. We identified species having unusually large positive occurrence anomalies during March 2012 and species having unusually large negative occurrence anomalies during July–August 2012. For each category, we summarized migration strategies, geographic distributions, and annual associations with temperature and ecological productivity. Short‐distance migrants whose winter and breeding ranges intersect the mid‐latitudes advanced their spring migration phenology during March (n = 21). Long‐distance migrants whose winter and breeding distributions were weakly associated with the mid‐latitudes had lower occurrences during the summer (n = 32). Five species were shared between the two categories. Within species’ winter ranges, temperature and ecological productivity were higher than expected during March; within species’ breeding ranges, ecological productivity was lower than expected during the summer. These differences were strongest for the 21 short‐distance migrants. Following our expectations, mid‐latitude climate extremes and associated ecological consequences broadly affected avian migration and breeding activities within the region. Our findings suggest short‐distance migrants are more flexible and resilient, whereas populations of long‐distance migrants are at a distinct disadvantage, which may intensify if the frequency of these events increases. [ABSTRACT FROM AUTHOR]

Land managers require information about the ongoing and potential effects of future climate to coordinate responses for ecosystems, species, and human communities at scales that are operationally meaningful. Our study focused on the vulnerability for all upland ecosystem types of Arizona and New Mexico in the southwestern United States. Local vulnerability across the two‐state area was represented by the level of departure for late 21st‐century climate from the characteristic pre‐1990 climate envelope of the ecosystem type at each given location, resulting in a probability surface of climate impacts for the two‐state area and an uncertainty assessment based on agreement in results among multiple global climate models. Though the results varied from one ecosystem type to the next, the majority of lands were forecast as high vulnerability and low uncertainty, reflecting significant agreement among climate model projections for the southwestern United States. We then tested our results in relation to ongoing ecological processes that have both regional and global change implications and discovered significant relationships with wildfire severity, upward tree species recruitment, and the encroachment of scrub into semidesert grassland. The testing helped determine the efficacy of the vulnerability surface, as a product of relatively high spatial and thematic resolution, in supporting local planning and management decisions. Most important, this study links climate and changes in vegetation by ecosystem processes that are already ongoing. The results affirm the value of climate model downscaling and show that this portable approach to correlative modeling has value in determining the location and magnitude of potential climate‐related impacts. [ABSTRACT FROM AUTHOR]

Although uncertainty is an integral part of any science, it raises doubts in public perception about scientific evidence, is exploited by denialists, and therefore potentially hinders the implementation of management actions. As a relatively young field of study, invasion science contains many uncertainties. This may explain why, despite international policies aimed at mitigating biological invasions, the implementation of national‐ and regional‐scale measures to prevent or control alien species has done little to slow the increase in extent of invasions and the magnitude of impacts. Uncertainty is therefore a critical aspect of invasion science that should be addressed to enable the field to progress further. To improve how uncertainties in invasion science are captured and characterized, we propose a framework, which is also applicable to other applied research fields such as climate and conservation science, divided into four components: the need (1) to clearly circumscribe the phenomenon, (2) to measure and provide evidence for the phenomenon (i.e., confirmation), (3) to understand the mechanisms that cause the phenomenon, and (4) to understand the mechanisms through which the phenomenon results in consequences. We link these issues to three major types of uncertainty: linguistic, psychological, and epistemic. The application of this framework shows that the four components tend to be characterized by different types of uncertainty in invasion science. We explain how these uncertainties can be detrimental to the implementation of management measures and propose ways to reduce them. Since biological invasions are increasingly tightly embedded in complex socio‐ecological systems, many problems associated with these uncertainties have convoluted solutions. They demand the consensus of many stakeholders to define and frame the dimensions of the phenomenon, and to decide on appropriate actions. While many of the uncertainties cannot be eliminated completely, we believe that using this framework to explicitly identify and communicate them will help to improve collaboration between researchers and managers, increase scientific, political, and public support for invasion research, and provide a stronger foundation for sustainable management strategies. [ABSTRACT FROM AUTHOR]