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‘As Earth’s testimonies tell’: wilderness conservation in a changing world
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Too often, wilderness conservation ignores a temporal perspective greater than the past
50 years, yet a long-term perspective (centuries to millennia) reveals the dynamic nature
of many ecosystems. Analysis of fossil pollen, charcoal and stable isotopes, combined
with historical analyses and archaeology can reveal how ongoing interactions between
climatic change, human activities and other disturbances have shaped today’s landscapes
over thousands of years. This interdisciplinary approach can inform wilderness
conservation and also contribute to interpreting current trends and predicting how
ecosystems might respond to future climate change. In this paper, we review literature
that reveals how increasing collaboration among palaeoecologists, archaeologists,
historians, anthropologists and ecologists is improving understanding of ecological
complexity. Drawing on case studies from forested and non-forested ecosystems in
Europe, the Americas, Africa and Australia, we discuss how this integrated approach can
inform wilderness conservation and ecosystem management.
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A century of climate and ecosystem change in Western Montana: what do temperature trends portend?
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Abstract The physical science linking human-induced increases ingreenhouse gasses to the warming of the global climate system is well established, but the implications of this warming for ecosystem processes and services at regional scales is still poorly understood. Thus, the objectives of this work were to: (1) describe rates of change in temperature averages and extremes for western Montana, a region containing sensitive resources and ecosystems, (2) investigate associations between Montana temperature change to hemispheric and global temperature change, (3) provide climate analysis tools for land and resource managers responsible for researching and maintaining renewable resources, habitat, and threatened/endangered species and (4) integrate our findings into a more general assessment of climate impacts on ecosystem processes and services over the past century. Over 100 years of daily and monthly temperature data collected in western Montana, USA are analyzed for long-term changes in seasonal averages and daily extremes. In particular, variability and trends in temperature above or below ecologically and socially meaningful thresholds within this region (e.g., −17.8◦C (0◦F), 0◦C (32◦F), and 32.2◦C (90◦F)) are assessed. The daily temperature time series reveal extremely cold days (≤ −17.8◦C) terminate on average 20 days earlier and decline in number, whereas extremely hot days (≥32◦C) show a three-fold increase in number and a 24-day increase in seasonal window during which they occur. Results show that regionally important thresholds have been exceeded, the most recent of which include the timing and number of the 0◦C freeze/thaw temperatures during spring and fall. Finally, we close with a discussion on the implications for Montana’s ecosystems. Special attention is given to critical processes that respond non-linearly as temperatures exceed critical thresholds, and have positive feedbacks that amplify the changes.
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A Changing Climate for Prediction
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Standard climate model projections, which have shown the significance of global warming, must be redesigned to inform climate change adaptation and mitigation policy.
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A Chinese cave links climate change, social impacts, and human adaptation over the last 500 years
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The collapse of some pre-historical and historical cultures, including Chinese dynasties were presumably linked to widespread droughts, on the basis of synchronicities of societal crises and proxy-based climate events. Here, we present a comparison of ancient inscriptions in Dayu Cave from Qinling Mountains, central China, which described accurate times and detailed impacts of seven drought events during the period of 1520–1920 CE, with high-resolution speleothem records from the same cave. The comparable results provide unique and robust tests on relationships among speleothem δ18O changes, drought events, and societal unrest. With direct historical evidences, our results suggest that droughts and even modest events interrupting otherwise wet intervals can cause serious social crises. Modeling results of speleothem δ18O series suggest that future precipitation in central China may be below the average of the past 500 years. As Qinling Mountain is the main recharge area of two large water transfer projects and habitats of many endangered species, it is imperative to explore an adaptive strategy for the decline in precipitation and/or drought events.
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A Complex Landscape has both Vulnerabilities and Resilience to Climate Change
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Central Appalachian forests have been experiencing the effects of a changing climate for decades, and effects such as more heavy rainfall events, more drought, and more hot days are likely to continue, according to a new vulnerability assessment for the region by the U.S. Forest Service and many partners.
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A Determination of the Cloud Feedback from Climate Variations over the Past Decade
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Estimates of Earth's climate sensitivity are uncertain, largely because of uncertainty in the
long-term cloud feedback. I estimated the magnitude of the cloud feedback in response to short-term
climate variations by analyzing the top-of-atmosphere radiation budget from March 2000 to February
2010. Over this period, the short-term cloud feedback had a magnitude of 0.54 T 0.74 (2s) watts
per square meter per kelvin, meaning that it is likely positive. A small negative feedback is possible,
but one large enough to cancel the climate’s positive feedbacks is not supported by these observations.
Both long- and short-wave components of short-term cloud feedback are also likely positive.
Calculations of short-term cloud feedback in climate models yield a similar feedback. I find no
correlation in the models between the short- and long-term cloud feedbacks.
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A dispersal-induced paradox: synchrony and stability in stochastic metapopulations
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Understanding how dispersal influences the dynamics of spatially distributed populations is a major priority of both basic and applied ecologists. Two well-known effects of dispersal are spatial synchrony (positively correlated population dynamics at different points in space) and dispersal-induced stability (the phenomenon whereby populations have simpler or less extinction-prone dynamics when they are linked by dispersal than when they are isolated). Although both these effects of dispersal should occur simultaneously, they have primarily been studied separately. Herein, I summarise evidence from the literature that these effects are expected to interact, and I use a series of models to characterise that interaction. In particular, I explore the observation that although dispersal can promote both synchrony and stability singly, it is widely held that synchrony paradoxically prevents dispersal-induced stability. I show here that in many realistic scenarios, dispersal is expected to promote both synchrony and stability at once despite this apparent destabilising influence of synchrony. This work demonstrates that studying the spatial and temporal impacts of dispersal together will be vital for the conservation and management of the many communities for which human activities are altering natural dispersal rates.
Keywords
Autoregressive model, correlated environmental stochasticity, dispersal, dispersal-induced stability, metapopulation, negative binomial model, Ricker model, spatial heterogeneity, synchrony.
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A drought-induced pervasive increase in tree mortality across Canada’s boreal forests
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Drought-induced tree mortality is expected to increase worldwide under projected future climate changes (1–4). The Canadian boreal forests, which occupy about 30% of the boreal forests worldwide and 77% of Canada’s total forested land, play a critical role in the albedo of Earth’s surface (5) and in its global carbon budget (6). Many of the previously reported regional-scale impacts of drought on tree mortality have affected low- and middle-latitude tropical regions (2) and the temperate forests of the western United States (3), but no study has examined high-latitude boreal regions with multiple species at a regional scale using long-term forest permanent sampling plots (7–9). Here, we estimated tree mortality in natural stands throughout Canada’s boreal forests using data from the permanent sampling plots and statistical models. We found that tree mortality rates increased by an overall average of 4.7%yr−1 from 1963 to 2008, with higher mortality rate increases in western regions than in eastern regions (about 4.9 and 1.9% yr−1 ,respectively).The water stress created by regional drought may be the dominant contributor to these widespread increases in tree mortality rates across tree species, sizes, elevations, longitudes and latitudes. Western Canada seems to have been more sensitive to drought than eastern Canada.
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A framework for generating and analyzing movement paths on ecological landscapes
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The movement paths of individuals over landscapes are basically represented by sequences of points (xi, yi) occurring at times ti. Theoretically, these points can be viewed as being generated by stochastic processes that in the simplest cases are Gaussian random walks on featureless landscapes. Generalizations have been made of walks that (i) take place on landscapes with features, (ii) have correlated distributions of velocity and direction of movement in each time interval, (iii) are Le ́ vy processes in which distance or waiting-time (time-between steps) distributions have infinite moments, or (iv) have paths bounded in space and time. We begin by demonstrating that rather mild truncations of fat-tailed step-size distributions have a dramatic effect on dispersion of organisms, where such truncations naturally arise in real walks of organisms bounded by space and, more generally, influenced by the interactions of physiological, behavioral, and ecological factors with landscape features. These generalizations permit not only increased realism and hence greater accuracy in constructing movement pathways, but also provide a biogeographically detailed epistemological framework for interpreting movement patterns in all organisms, whether tossed in the wind or willfully driven. We illustrate the utility of our framework by demonstrating how fission–fusion herding behavior arises among individuals endeavoring to satisfy both nutritional and safety demands in heterogeneous environments. We conclude with a brief discussion of potential methods that can be used to solve the inverse problem of identifying putative causal factors driving movement behavior on known landscapes, leaving details to references in the literature.
fission–fusion GPS landscape matrices random and Levy walks dispersal movement ecology
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A general integrative model for scaling plant growth, carbon flux, and functional trait spectra
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Linking functional traits to plant growth is critical for scaling attributes of organisms to the dynamics of ecosystems (1,2) and for understanding how selection shapes integrated botanical phenotypes (3). However, a general mechanistic theory showing how traits specifically influence carbon and biomass flux within and across plants is needed. Building on foundational work on relative growth rate (4–6), recent work on functional trait spectra (7–9), and metabolic scaling theory (10,11), here we derive a generalized trait-based model of plant growth. In agreement with a wide variety of empirical data, our model uniquely predicts how key functional traits interact to regulate variation in relative growth rate, the allometric growth normalizations for both angiosperms and gymnosperms, and the quantitative form of several functional trait spectra relationships. The model also provides a general quantitative framework to incorporate additional leaf-level trait scaling relationships (7,8) and hence to unite functional trait spectra with theories of relative growth rate, and metabolic scaling. We apply the model to calculate carbon use efficiency. This often ignored trait, which may influence variation in relative growth rate, appears to vary directionally across geographic gradients. Together, our results show how both quantitative plant traits and the geometry of vascular transport networks can be merged into a common scaling theory. Our model provides a framework for predicting not only how traits covary within an integrated allometric phenotype but also how trait variation mechanistically influences plant growth and carbon flux within and across diverse ecosystems.
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