Constance I. Millar

CLIMATE CHANGE AND FORESTS OF THE FUTURE: MANAGING IN THE FACE OF UNCERTAINTY

We offer a conceptual framework for managing forested ecosystems under an assumption that future environments will be different from present but that we cannot be certain about the specifics of change. We encourage flexible approaches that promote reversible and incremental steps, and that favor ongoing learning and capacity to modify direction as situations change. We suggest that no single solution fits all future challenges, especially in the context of changing climates, and that the best strategy is to mix different approaches for different situations. Resources managers will be challenged to integrate adaptation strategies (actions that help ecosystems accommodate changes adaptively) and mitigation strategies (actions that enable ecosystems to reduce anthropogenic influences on global climate) into overall plans. Adaptive strategies include resistance options (forestall impacts and protect highly valued resources), resilience options (improve the capacity of ecosystems to return to desired conditions after disturbance), and response options (facilitate transition of ecosystems from current to new conditions). Mitigation strategies include options to sequester carbon and reduce overall greenhouse gas emissions. Priority-setting approaches (e.g., triage), appropriate for rapidly changing conditions and for situations where needs are greater than available capacity to respond, will become increasingly important in the future.

Ain't no mountain high enough: plant invasions reaching new elevations

Most studies of invasive species have been in highly modified, lowland environments, with comparatively little attention directed to less disturbed, high-elevation environments. However, increasing evidence indicates that plant invasions do occur in these environments, which often have high conservation value and provide important ecosystem services. Over a thousand non-native species have become established in natural areas at high elevations worldwide, and although many of these are not invasive, some may pose a considerable threat to native mountain ecosystems. Here, we discuss four main drivers that shape plant invasions into high-elevation habitats: (1) the (pre-)adaptation of non-native species to abiotic conditions, (2) natural and anthropogenic disturbances, (3) biotic resistance of the established communities, and (4) propagule pressure. We propose a comprehensive research agenda for tackling the problem of plant invasions into mountain ecosystems, including documentation of mountain invasion patterns at multiple scales, experimental studies, and an assessment of the impacts of non-native species in these systems. The threat posed to high-elevation biodiversity by invasive plant species is likely to increase because of globalization and climate change. However, the higher mountains harbor ecosystems where invasion by non-native species has scarcely begun, and where science and management have the opportunity to respond in time.

Restoring diversity: strategies for reintroduction of endangered plants.

The reintroduction of rare and endangered species to their natural habitats is becoming an increasingly important tool in ecosystem management. This book seeks to unify concepts in the field of restoration, and fill significant technical and policy gaps.

Distribution and Climatic Relationships of the American Pika (Ochotona princeps) in the Sierra Nevada and Western Great Basin, U.S.A.; Periglacial Landforms as Refugia in Warming Climates

Abstract We used a rapid assessment to survey American pika (Ochotona princeps) populations and documented 420 pika site occurrences in southwestern U.S.A. These included 329 sites from the Sierra Nevada (SN), California; 67 from six southwestern Great Basin (swGB) ranges, California and Nevada; 16 from three central Great Basin ranges, Nevada; and 8 from the central Oregon Cascades. Of these, 67% were currently occupied, 27% modern (indirectly scored active), and 6% old. Sites were grouped into 148 demes, 88 regions, and 11 mountain ranges. Current elevations ranged from 1645 m (1827 m excluding Oregon) to 3887 m, extending the lower elevational range of the species at the study latitude. Sites were distributed on all slope aspects with a preference for north to easterly aspects, and without preference for substrate. Rock-ice-feature (RIF) till, notably rock-glacier and boulder-stream landforms, accounted for 83% of the sites. Climatic relationships from the PRISM model for the SN and swGB sites showed wide tolerance, with average precipitation 910 mm, average minimum temperature −3.9 °C, and average maximum temperature 8.7 °C. Average minimum temperatures for old sites were not significantly different from recent sites, whereas average maximum temperatures were significantly higher in old sites. Unusual features of RIF landforms make them important refugia for pikas as climates warm. In contrast to studies that document species vulnerability elsewhere, pikas in the SN and swGB appear to be thriving and tolerating a wide range of thermal environments.

Response of Subalpine Conifers in the Sierra Nevada, California, U.S.A., to 20th-Century Warming and Decadal Climate Variability

Abstract Four independent studies of conifer growth between 1880 and 2002 in upper elevation forests of the central Sierra Nevada, California, U.S.A., showed correlated multidecadal and century-long responses associated with climate. Using tree-ring and ecological plot analysis, we studied annual branch growth of krummholz Pinus albicaulis; invasion by P. albicaulis and Pinus monticola into formerly persistent snowfields; dates of vertical branch emergence in krummholz P. albicaulis; and invasion by Pinus contorta into subalpine meadows. Mean annual branch growth at six treeline sites increased significantly over the 20th century (range 130–400%), with significant accelerations in rate from 1920 to 1945 and after 1980. Growth stabilized from 1945 to 1980. Similarly, invasion of six snowfield slopes began in the early 1900s and continued into snowfield centers throughout the 20th century, with significantly accelerated mean invasion from 1925 to 1940 and after 1980. Rate of snowfield invasion decreased between 1950 and 1975. Meadow invasion and vertical leader emergence showed synchronous, episodic responses. Pinus contorta invaded each of ten subalpine meadows in a distinct multidecadal pulse between 1945 and 1976 (87% of all trees) and vertical release in five krummholz P. albicaulis sites also occurred in one pulse between 1945 and 1976 (86% of all branches). These synchronies and lack of effect of local environments implicate regional climate control. Composite weather records indicated significant century-long increases in minimum monthly temperature and multidecadal variability in minimum temperature and precipitation. All ecological responses were significantly correlated with minimum temperature. Significant interactions among temperature, precipitation, Pacific Decadal Oscillation (PDO) indices, and multiyear variability in moisture availability further explained episodic ecological responses. Four multidecadal periods of the 20th century that are defined by ecological response (<1925; 1925–1944; 1945–1976; >1976) correlate with positive and negative PDO phases, as well as with steps in the rate of temperature increase. These diverse factors in spatially distributed upper-montane and treeline ecosystems respond directionally to century-long climate trends, and also exhibit abrupt and reversible effects as a consequence of interdecadal climate variability and complex interactions of temperature and moisture.

Operational approaches to managing forests of the future in Mediterranean regions within a context of changing climates

Many US forest managers have used historical ecology information to assist in the development of desired conditions. While there are many important lessons to learn from the past, we believe that we cannot rely on past forest conditions to provide us with blueprints for future management. To respond to this uncertainty, managers will be challenged to integrate adaptation strategies into plans in response to changing climates. Adaptive strategies include resistance options, resilience options, response options, and realignment options. Our objectives are to present ideas that could be useful in developing plans under changing climates that could be applicable to forests with Mediterranean climates. We believe that managing for species persistence at the broad ecoregion scale is the most appropriate goal when considering the effects of changing climates. Such a goal relaxes expectations that current species ranges will remain constant, or that population abundances, distribution, species compositions and dominances should remain stable. Allowing fundamental ecosystem processes to operate within forested landscapes will be critical. Management and political institutions will have to acknowledge and embrace uncertainty in the future since we are moving into a time period with few analogs and inevitably, there will be surprises.

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 conservation today is the maintenance and restoration of biodiversity, but a broader range of values are also likely to be considered important, including ecological integrity, resilience, historical fidelity (ie the ecosystem appears and functions much as it did in the past), and autonomy of nature. Until recently, the concept of “naturalness” was the guiding principle when making conservation-related decisions in park and wilderness ecosystems. However, this concept is multifaceted and often means different things to different people, including notions of historical fidelity and autonomy from human influence. Achieving the goal of nature conservation intended for such...

Managing for Multiple Resources Under Climate Change: National Forests

This study explores potential adaptation approaches in planning and management that the United States Forest Service might adopt to help achieve its goals and objectives in the face of climate change. Availability of information, vulnerability of ecological and socio-economic systems, and uncertainties associated with climate change, as well as the interacting non-climatic changes, influence selection of the adaptation approach. Resource assessments are opportunities to develop strategic information that could be used to identify and link adaptation strategies across planning levels. Within a National Forest, planning must incorporate the opportunity to identify vulnerabilities to climate change as well as incorporate approaches that allow management adjustments as the effects of climate change become apparent. The nature of environmental variability, the inevitability of novelty and surprise, and the range of management objectives and situations across the National Forest System implies that no single approach will fit all situations. A toolbox of management options would include practices focused on forestalling climate change effects by building resistance and resilience into current ecosystems, and on managing for change by enabling plants, animals, and ecosystems to adapt to climate change. Better and more widespread implementation of already known practices that reduce the impact of existing stressors represents an important “no regrets” strategy. These management opportunities will require agency consideration of its adaptive capacity, and ways to overcome potential barriers to these adaptation options.

Allozyme differentiation and biosystematics of the Californian closed-cone pines ( Pinus subsect. Oocarpae )

Allozyme differentiation at 32 loci was studied in the three Californian species of Pinus subsect. Oocarpae: P. attenuata, P. muricata, and P. radiata, and in a small sample of a Latin American species of the subsection, P. oocarpa. The Californian species were previously known to comprise highly differentiated, disjunct populations, but with uncertain phylogenetic relationships among several populations and species. All populations had clear affinities for single species. The controversial Channel Islands (Santa Cruz Island) population of P. muricata and the Mexican Island (Guadalupe and Cedros islands) populations of P. radiata were distinct within their respective species, but clearly fell within each species complex. Con- to evidence from other traits, the Californian species were equally differentiated from one another allozymically, with no evidence of close relationships among pairwise comparisons of the three species. Pinus oocorpa, the putative ancestral species, was about two times more variable, and at substantial and approximately equal genetic distance from each of the three Californian species. Divergence of populations within species was generally clinal. The initial radiation of P. attenuata was in the Sierra Nevada, and subsequent divergence was toward the coast in the Siskiyou Mountains, and then south through the coast range to southern California. Divergence in both P. muricata and P. radiata occurred northward along the coast, with the southern island populations retaining ancestral alleles, and differentiation from P. oocarpa increasing northward within species. Genetic differentiation among species was twice that among populations within species.

U.S. National Forests adapt to climate change through Science–Management partnerships

Developing appropriate management options for adapting to climate change is a new challenge for land managers, and integration of climate change concepts into operational management and planning on United States national forests is just starting. We established science–management partnerships on the Olympic National Forest (Washington) and Tahoe National Forest (California) in the first effort to develop adaptation options for specific national forests. We employed a focus group process in order to establish the scientific context necessary for understanding climate change and its anticipated effects, and to develop specific options for adapting to a warmer climate. Climate change scientists provided the scientific knowledge base on which adaptations could be based, and resource managers developed adaptation options based on their understanding of ecosystem structure, function, and management. General adaptation strategies developed by national forest managers include: (1) reduce vulnerability to anticipated climate-induced stress by increasing resilience at large spatial scales, (2) consider tradeoffs and conflicts that may affect adaptation success, (3) manage for realistic outcomes and prioritize treatments that facilitate adaptation to a warmer climate, (4) manage dynamically and experimentally, and (5) manage for structure and composition. Specific adaptation options include: (1) increase landscape diversity, (2) maintain biological diversity, (3) implement early detection/rapid response for exotic species and undesirable resource conditions, (4) treat large-scale disturbance as a management opportunity and integrate it in planning, (5) implement treatments that confer resilience at large spatial scales, (6) match engineering of infrastructure to expected future conditions, (7) promote education and awareness about climate change among resource staff and local publics, and (8) collaborate with a variety of partners on adaptation strategies and to promote ecoregional management. The process described here can quickly elicit a large amount of information relevant for adaptation to climate change, and can be emulated for other national forests, groups of national forests with similar resources, and other public lands. As adaptation options are iteratively generated for additional administrative units on public lands, management options can be compared, tested, and integrated into adaptive management. Science-based adaptation is imperative because increasing certainty about climate impacts and management outcomes may take decades.