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Turning back from the brink: Detecting an impending regime shift in time to avert it: Ecological regime shifts are large, abrupt, long-lasting changes in ecosystems that often have considerable impacts on human econ- omies and societies. Avoiding unintentional regime shifts is widely regarded as desirable, but prediction of ecological regime shifts is notoriously difficult. Recent research indicates that changes in ecological time series (e.g., increased variability and autocorrela- tion) could potentially serve as early warning indicators of im- pending shifts. A critical question, however, is whether such indicators provide sufficient warning to adapt management to avert regime shifts. We examine this question using a fisheries model, with regime shifts driven by angling (amenable to rapid reduction) or shoreline development (only gradual restoration is possible). The model represents key features of a broad class of ecological regime shifts. We find that if drivers can only be manipulated gradually management action is needed substantially before a regime shift to avert it; if drivers can be rapidly altered aversive action may be delayed until a shift is underway. Large increases in the indicators only occur once a regime shift is initiated, often too late for management to avert a shift. To improve usefulness in averting regime shifts, we suggest that research focus on defining critical indicator levels rather than detecting change in the indicators. Ideally, critical indicator levels should be related to switches in ecosystem attractors; we present a new spectral density ratio indicator to this end. Averting ecological regime shifts is also dependent on developing policy pro- cesses that enable society to respond more rapidly to information about impending regime shifts. early warning indicator 􏰆 ecological threshold 􏰆 spectral density ratio

HOW LONG HAVE WE BEEN IN THE ANTHROPOCENE ERA?: Editorial- 1st paragraph: With great interest we have read Ruddiman’s intriguing article which is in favor of placing the start of the Anthropocene at 5–8 millennia BP instead of the late quarter of the 18th century. He shows how land exploitation for agriculture and animal husbandry may have led to enhanced emissions of CO2 and CH4 to the atmosphere, thereby modifying the expected changes in the concentrations of these gases beyond those expected from variations in the Milankovich orbital parameters. Much of his argument depends on the correctness of their projected CH4 concen- tration curve from 7,000 years BP to pre-industrial times showing a decline to about 425 ppb, according to Milankovich, instead of the measured 700 ppb. It appears, however, strange that in Ruddiman’s analysis the proposed increase of CH4 due to anthropogenic activities stopped at about 1000 years BP, because ice core data showed almost constant mixing ratios of CH4 between 1000 years BP and about 200 years ago before the rapid rise of CH4 in the industrial period (IPCC, 2001). A major feature of Ruddiman’s argument is that natural atmospheric CH4 concentrations depend strongly on geological varying summer time insolations in the tropical northern hemisphere, controlling tropical wetlands and methane release from decaying organic matter under anaerobic conditions.

20th-Century doubling in dust archived in an Antarctic Peninsula ice core parallels climate change and desertification in South America: Crustal dust in the atmosphere impacts Earth’s radiative forcing directly by modifying the radiation budget and affecting cloud nucleation and optical properties, and indirectly through ocean fertilization, which alters carbon sequestration. Increased dust in the atmosphere has been linked to decreased global air tempera- ture in past ice core studies of glacial to interglacial transitions. We present a continuous ice core record of aluminum deposition during recent centuries in the northern Antarctic Peninsula, the most rapidly warming region of the Southern Hemisphere; such a record has not been reported previously. This record shows that aluminosilicate dust deposition more than doubled during the 20th century, coincident with the 􏰀1°C Southern Hemisphere warming: a pattern in parallel with increasing air temperatures, decreasing relative humidity, and widespread desertification in Patagonia and northern Argentina. These results have far-reaching implications for understanding the forces driving dust generation and impacts of changing dust levels on climate both in the recent past and future. aluminosilicate dust 􏰆 global warming 􏰆 human impacts 􏰆 Patagonia 􏰆 radiative transfer

The Rescaling of Global Environmental Politics: Key Words governance, international, linked issues, networks, scale Abstract In the past half-century, the practice and study of global environmental politics and governance have been dramatically rescaled. They have be- come increasingly complex and interconnected with respect to the level (between local and global) at which they take place, the range of actors engaged in them, and the linkages between them and nominally nonen- vironmental issues. Global environmental politics and governance have been rescaled vertically down toward provincial and municipal gov- ernments and up toward supranational regimes. They have also been rescaled horizontally across regional and sectoral organizations and net- works and across new issues, such as development, security, and trade among others. This rescaling reflects shifts in the magnitude, complexity, and interconnectedness of the global environmental problems humans face as well as epistemological shifts in how humans understand and respond to these problems, and rescaling has implications for both the practice and study of global environmental politics.

Insect Responses to Major Landscape-Level Disturbance: Keywords tolerance, dispersal, succession, local extinction, outbreak, population dynamics Abstract Disturbances are abrupt events that dramatically alter habitat conditions and resource distribution for populations and communities. Terrestrial land- scapes are subject to various disturbance events that create a matrix of patches with different histories of disturbance and recovery. Species tolerances to ex- treme conditions during disturbance or to altered habitat or resource condi- tions following disturbances determine responses to disturbance. Intolerant populations may become locally extinct, whereas other species respond posi- tively to the creation of new habitat or resource conditions. Local extinction represents a challenge for conservation biologists. On the other hand, out- breaks of herbivorous species often are triggered by abundant or stressed hosts and relaxation of predation following disturbances. These insect re- sponses can cause further changes in ecosystem conditions and predispose communities to future disturbances. Improved understanding of insect re- sponses to disturbance will improve prediction of population and community dynamics, as well as ecosystem and global changes.

Climate Change, Aboveground-Belowground Interactions, and Species’ Range Shifts: Changes in climate, land use, fire incidence, and ecological connections all may contribute to current species’ range shifts. Species shift range individually, and not all species shift range at the same time and rate. This variation causes community reorganization in both the old and new ranges. In terrestrial ecosystems, range shifts alter aboveground-belowground interactions, influencing species abundance, community composition, ecosystem processes and services, and feedbacks within communities and ecosystems. Thus, range shifts may result in no-analog communities where foundation species and community genetics play unprecedented roles, possibly leading to novel ecosystems. Long-distance dispersal can enhance the disruption of aboveground-belowground interactions of plants, herbivores, pathogens, symbiotic mutualists, and decomposer organisms. These effects are most likely stronger for latitudinal than for altitudinal range shifts. Disrupted aboveground-belowground interactions may have influenced historical postglacial range shifts as well. Assisted migration without considering aboveground-belowground interactions could enhance risks of such range shift–induced invasions.

Global Cooling by Grassland Soils of the Geological Past and Near Future: Keywords grass, mammal, coevolution, paleosol, paleoclimate, carbon sequestration, albedo Abstract Major innovations in the evolution of vegetation such as the Devonian ori- gin of forests created new weathering regimes and soils (Alfisols, Histosols) that increased carbon consumption and sequestration and ushered in the Permian-Carboniferous Ice Age. Similarly, global expansion of grasslands and their newly evolved, carbon-rich soils (Mollisols) over the past 40 mil- lion years may have induced global cooling and ushered in Pleistocene glacia- tion. Grassland evolution has been considered a consequence of mountain uplift and tectonic reorganization of ocean currents, but it can also be viewed as a biological force for global change through coevolution of grasses and grazers. Organisms in such coevolutionary trajectories adapt to each other rather than to their environment, and so can be forces for global change. Some past farming practices have aided greenhouse gas release. However, modern grassland agroecosystems are a potential carbon sink already under intensive human management, and carbon farming techniques may be useful in curbing anthropogenic global warming.

Evolution of Grasses and Grassland Ecosystems: The evolution and subsequent ecological expansion of grasses (Poaceae) since the Late Cretaceous have resulted in the establishment of one of Earth’s dominant biomes, the temperate and tropical grasslands, at the expense of forests. In the past decades, several new approaches have been applied to the fossil record of grasses to elucidate the patterns and processes of this ecosystem transformation. The data indicate that the development of grassland ecosystems on most continents was a multistage process involving the Pale- ogene appearance of (C3 and C4) open-habitat grasses, the mid-late Cenozoic spread of C3 grass-dominated habitats, and, finally, the Late Neogene expansion of C4 grasses at tropical-subtropical latitudes. The evolution of herbivores adapted to grasslands did not necessarily coincide with the spread of open-habitat grasses. In addition, the timing of these evolutionary and ecological events varied between regions. Consequently, region-by-region investigations using both direct (plant fossils) and indirect (e.g., stable carbon isotopes, faunas) evidence are required for a full understanding of the tempo and mode of grass and grassland evolution.

Toward an Era of Restoration in Ecology: Successes, Failures, and Opportunities Ahead: Keywords resilience, ecosystem restoration, restoration ecology, recovery, degradation, ecosystem services, environmental change, novel ecosystems Abstract As an inevitable consequence of increased environmental degradation and anticipated future environmental change, societal demand for ecosystem restoration is rapidly increasing. Here, I evaluate successes and failures in restoration, how science is informing these efforts, and ways to better ad- dress decision-making and policy needs. Despite the multitude of restora- tion projects and wide agreement that evaluation is a key to future progress, comprehensive evaluations are rare. Based on the limited available infor- mation, restoration outcomes vary widely. Cases of complete recovery are frequently characterized by the persistence of species and abiotic processes that permit natural regeneration. Incomplete recovery is often attributed to a mixture of local and landscape constraints, including shifts in species distributions and legacies of past land use. Lastly, strong species feedbacks and regional shifts in species pools and climate can result in little to no recovery. More forward-looking paradigms, such as enhancing ecosystem services and increasing resilience to future change, are exciting new direc- tions that need more assessment. Increased evidence-based evaluation and cross-disciplinary knowledge transfer will better inform a wide range of critical restoration issues such as how to prioritize sites and interventions, include uncertainty in decision making, incorporate temporal and spatial dependen- cies, and standardize outcome assessments. As environmental policy increasingly embraces restoration, the opportunities have never been greater.

Drought’s legacy: multiyear hydraulic deterioration underlies widespread aspen forest die-off and portends increased future risk: Forest mortality constitutes a major uncertainty in projections of climate impacts on terrestrial ecosystems and car- bon-cycle feedbacks. Recent drought-induced, widespread forest die-offs highlight that climate change could acceler- ate forest mortality with its diverse and potentially severe consequences for the global carbon cycle, ecosystem services, and biodiversity. How trees die during drought over multiple years remains largely unknown and pre- cludes mechanistic modeling and prediction of forest die-off with climate change. Here, we examine the physiological basis of a recent multiyear widespread die-off of trembling aspen (Populus tremuloides) across much of western North America. Using observations from both native trees while they are dying and a rainfall exclusion experiment on mature trees, we measure hydraulic performance over multiple seasons and years and assess pathways of accumu- lated hydraulic damage. We test whether accumulated hydraulic damage can predict the probability of tree survival over 2 years. We find that hydraulic damage persisted and increased in dying trees over multiple years and exhibited few signs of repair. This accumulated hydraulic deterioration is largely mediated by increased vulnerability to cavita- tion, a process known as cavitation fatigue. Furthermore, this hydraulic damage predicts the probability of interyear stem mortality. Contrary to the expectation that surviving trees have weathered severe drought, the hydraulic deteri- oration demonstrated here reveals that surviving regions of these forests are actually more vulnerable to future droughts due to accumulated xylem damage. As the most widespread tree species in North America, increasing vul- nerability to drought in these forests has important ramifications for ecosystem stability, biodiversity, and ecosystem carbon balance. Our results provide a foundation for incorporating accumulated drought impacts into climate–vege- tation models. Finally, our findings highlight the critical role of drought stress accumulation and repair of stress- induced damage for avoiding plant mortality, presenting a dynamic and contingent framework for drought impacts on forest ecosystems. Keywords: biosphere–atmosphere interactions, climate change, ecosystem shift, forest mortality, vegetation model, xylem cavitation, dieoff

Are we in the midst of the sixth mass extinction? A view from the world of amphibians: Many scientists argue that we are either entering or in the midst of the sixth great mass extinction. Intense human pressure, both direct and indirect, is having profound effects on natural environ- ments. The amphibians—frogs, salamanders, and caecilians—may be the only major group currently at risk globally. A detailed worldwide assessment and subsequent updates show that one- third or more of the 6,300 species are threatened with extinction. This trend is likely to accelerate because most amphibians occur in the tropics and have small geographic ranges that make them susceptible to extinction. The increasing pressure from habitat destruction and climate change is likely to have major impacts on narrowly adapted and distributed species. We show that salamanders on tropical mountains are particularly at risk. A new and significant threat to amphibians is a virulent, emerging infec- tious disease, chytridiomycosis, which appears to be globally distributed, and its effects may be exacerbated by global warming. This disease, which is caused by a fungal pathogen and implicated in serious declines and extinctions of >200 species of amphibians, poses the greatest threat to biodiversity of any known disease. Our data for frogs in the Sierra Nevada of California show that the fungus is having a devastating impact on native species, already weakened by the effects of pollution and introduced predators. A general message from amphibians is that we may have little time to stave off a potential mass extinction. chytridiomycosis 􏰎 climate change 􏰎 population declines 􏰎 Batrachochytrium dendrobatidis 􏰎 emerging disease

Slow Recovery from Perturbations as a Generic Indicator of a Nearby Catastrophic Shift: The size of the basin of attraction in ecosystems with alternative stable states is often referred to as “ecological resilience.” Ecosystems with a low ecological resilience may easily be tipped into an alternative basin of attraction by a stochastic event. Unfortunately, it is very difficult to measure ecological resilience in practice. Here we show that the rate of recovery from small perturbations (some- times called “engineering resilience”) is a remarkably good indicator of ecological resilience. Such recovery rates decrease as a catastrophic regime shift is approached, a phenomenon known in physics as “crit- ical slowing down.” We demonstrate the robust occurrence of critical slowing down in six ecological models and outline a possible ex- perimental approach to quantify differences in recovery rates. In all the models we analyzed, critical slowing down becomes apparent quite far from a threshold point, suggesting that it may indeed be of practical use as an early warning signal. Despite the fact that critical slowing down could also indicate other critical transitions, such as a stable system becoming oscillatory, the robustness of the phenom- enon makes it a promising indicator of loss of resilience and the risk of upcoming regime shifts in a system. Keywords: alternative stable states, catastrophic bifurcations, critical slowing down, early warning signals, resilience, return time.

A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests: Of particular concern are potential increases in tree mortality associated with climate- induced physiological stress and interactions with other climate-mediated processes such as insect outbreaks and wildfire. Despite this risk, existing projections of tree mortality are based on models that lack functionally realistic mortality mechanisms, and there has been no attempt to track observations of climate-driven tree mortality globally. Here we present the first global assessment of recent tree mortality attributed to drought and heat stress. Although episodic mortality occurs in the absence of climate change, studies compiled here suggest that at least some of the world’s forested ecosystems already may be responding to climate change and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited. This further suggests risks to ecosystem services, including the loss of sequestered forest carbon and associated atmospheric feedbacks. Our review also identifies key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system. Overall, our review reveals the potential for amplified tree mortality due to drought and heat in forests worldwide. heat, temperature, drought, tree mortality, forest dieoff

AGU: Human-induced climate change requires urgent action.: 1st paragraph: concentrations of carbon dioxide and other heat-trapping greenhouse gases have increased sharply since the Industrial Revolution. Fossil fuel burning dominates this increase. Human-caused increases in greenhouse gases are responsible for most of the observed global average surface warming of roughly 0.8°C (1.5°F) over the past 140 years.

Trees on farms: Tackling the triple challenge of 07 mitigation, adaptation and food security: Policy recommendations ␣␣Increased adoption of agroforestry should be supported through finance for agricultural development and adaptation as well as mitigation. ␣␣Payments for environmental services – including carbon finance – should be geared towards increasing the extent of trees on farms ␣ More support is needed to increase the contribution of tree-based crops to smallholder incomes, thus diversifying income sources and increasing food security in the face of climate change.

Afforestation Effects on Soil Carbon Storage in the United States: A Synthesis: Afforestation (tree establishment on nonforested land) is a management option for increasing terrestrial C sequestration and mitigating rising atmo- spheric carbon dioxide because, compared to nonforested land uses, afforestation increases C storage in aboveground pools. However, because terrestrial ecosystems typically store most of their C in soils, afforestation impacts on soil organic carbon (SOC) storage are critical components of eco- system C budgets. We applied synthesis methods to identify the magnitude and drivers of afforestation impacts on SOC, and the temporal and verti- cal distributions of SOC change during afforestation in the United States. Meta-analysis of 39 papers from 1957 to 2010 indicated that previous land use drives afforestation impacts on SOC in mineral soils (overall average = +21%), but mined and other industrial lands (+173%) and wildlands (+31%) were the only groups that specifically showed categorically significant increases. Temporal patterns of SOC increase were statistically significant on former industrial and agricultural lands (assessed by continuous meta- analysis), and suggested that meaningful SOC increases require ≥15 and 30 yr of afforestation, respectively. Meta-analysis of 13C data demonstrated the greatest SOC changes occur at the surface soil of the profile, although par- tial replacement of C stocks derived from previous land uses was frequently detectable below 1 m. A geospatial analysis of 409 profiles from the National Soil Carbon Network database supported 13C meta-analysis results, indicating that transition from cultivation to forest increased A horizon SOC by 32%. In sum, our findings demonstrate that afforestation has significant, positive effects on SOC sequestration in the United States, although these effects require decades to manifest and primarily occur in the uppermost (and per- haps most vulnerable) portion of the mineral soil profile. Abbreviations: BD, bulk density; CI, confidence interval; MAP, mean annual precipitation; MAT, mean annual temperature; SOC, soil organic carbon.

Adaptive management of biological systems: A review: Adaptive Management (AM) is widely considered to be the best available approach for managing biolog- ical systems in the presence of uncertainty. But AM has arguably only rarely succeeded in improving bio- diversity outcomes. There is therefore an urgent need for reflection regarding how practitioners might overcome key problems hindering greater implementation of AM. In this paper, we present the first structured review of the AM literature that relates to biodiversity and ecosystem management, with the aim of quantifying how rare AM projects actually are. We also investigated whether AM practitioners in terrestrial and aquatic systems described the same problems; the degree of consistency in how the term ‘adaptive management’ was applied; the extent to which AM projects were sustained over time; and whether articles describing AM projects were more highly cited than comparable non-AM articles. We found that despite the large number of articles identified through the ISI web of knowledge (n = 1336), only 61 articles (<5%) explicitly claimed to enact AM. These 61 articles cumulatively described 54 separate projects, but only 13 projects were supported by published monitoring data. The extent to which these 13 projects applied key aspects of the AM philosophy – such as referring to an underlying conceptual model, enacting ongoing monitoring, and comparing alternative management actions – varied enormously. Further, most AM projects were of short duration; terrestrial studies discussed biodiversity conservation significantly more frequently than aquatic studies; and empirical studies were no more highly cited than qualitative articles. Our review highlights that excessive use of the term ‘adaptive man- agement’ is rife in the peer-reviewed literature. However, a small but increasing number of projects have been able to effectively apply AM to complex problems. We suggest that attempts to apply AM may be improved by: (1) Better collaboration between scientists and representatives from resource-extracting industries. (2) Better communication of the risks of not doing AM. (3) Ensuring AM projects ‘‘pass the test of management relevance’’.

TOO EARLY TO TELL, OR TOO LATE TO RESCUE? ADAPTIVE MANAGEMENT UNDER SCRUTINY: “The Forest Service’s definition of adaptive management does not emphasize experimentation but rather rational planning coupled with trial and error learning. Here ‘adaptive’ management has become a buzzword, a fash- ionable label that means less than it seems to promise.” Kai Lee, 1999 KEY FINDINGS 􏰣 • A new approach to the research-management relations is required.The natural tension between the two arenas can produce strengthened relations and improved learning, particularly with focussed input from lead scientists and AMA coordinators. • The AMA research effort is an important complement to PNW Research Station direction and priorities.The AMAs represent an additional research setting, one that offers important opportunities to test, validate, and possibly revise standards and guides contained within the NWFP. • The AMA research must be grounded in a local sense of priority and need, established by strong links between management and research.At the same time, designing research to maximize its applicability across the whole AMA system is also productive.

Integrated assessment of global water scarcity over the 21st century under multiple climate change mitigation policies: Water scarcity conditions over the 21st century both globally and regionally are assessed in the context of climate change and climate mitigation policies, by estimating both water availability and water demand within the Global Change Assessment Model (GCAM), a leading community- integrated assessment model of energy, agriculture, climate, and water. To quantify changes in future water availabil- ity, a new gridded water-balance global hydrologic model – namely, the Global Water Availability Model (GWAM) – is developed and evaluated. Global water demands for six ma- jor demand sectors (irrigation, livestock, domestic, electricity generation, primary energy production, and manufacturing) are modeled in GCAM at the regional scale (14 geopolitical regions, 151 sub-regions) and then spatially downscaled to 0.5◦ × 0.5◦ resolution to match the scale of GWAM. Using a baseline scenario (i.e., no climate change mitigation pol- icy) with radiative forcing reaching 8.8 W m−2 (equivalent to the SRES A1Fi emission scenario) and three climate pol- icy scenarios with increasing mitigation stringency of 7.7, 5.5, and 4.2 W m−2 (equivalent to the SRES A2, B2, and B1 emission scenarios, respectively), we investigate the ef- fects of emission mitigation policies on water scarcity. Two carbon tax regimes (a universal carbon tax (UCT) which in- cludes land use change emissions, and a fossil fuel and in- dustrial emissions carbon tax (FFICT) which excludes land use change emissions) are analyzed. The baseline scenario results in more than half of the world population living un- der extreme water scarcity by the end of the 21st century. Additionally, in years 2050 and 2095, 36 % (28 %) and 44 % (39 %) of the global population, respectively, is projected to live in grid cells (in basins) that will experience greater water demands than the amount of available water in a year (i.e., the water scarcity index (WSI) > 1.0). When comparing the climate policy scenarios to the baseline scenario while main- taining the same baseline socioeconomic assumptions, water scarcity declines under a UCT mitigation policy but increases with a FFICT mitigation scenario by the year 2095, particu- larly with more stringent climate mitigation targets. Under the FFICT scenario, water scarcity is projected to increase, driven by higher water demands for bio-energy crops. water: supply; demand; tax; scarcity

The timing of climate change: An innovative assessment of climate change calculates the year in which ongoing warming will surpass the limits of historical climate variability. Three experts explain this calculation’s significance compared with conventional approaches, and its relevance to Earth’s biodiversity.

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