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Tangled Trends for Temperate Rain Forests as Temperatures Tick Up
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Climate change is altering growing
conditions in the temperate rain forest
region that extends from northern California
to the Gulf of Alaska. Longer,
warmer growing seasons are generally
increasing the overall potential for
forest growth in the region. However,
species differ in their ability to adapt
to changing conditions. For example,
researchers with Pacific Northwest
Research Station examined forest
trends for southeastern and southcentral
Alaska and found that, in 13
years, western redcedar showed a
4.2-percent increase in live-tree biomass,
while shore pine showed a
4.6-percent decrease. In general, the
researchers found that the amount of
live-tree biomass in extensive areas
of unmanaged, higher elevation forest
in southern Alaska increased by
as much as 8 percent over the 13-year
period, contributing to significant
carbon storage.
Hemlock dwarf mistletoe is another species
expected to fare well under warmer
conditions in Alaska. Model projections
indicate that habitat for this parasitic
species could increase 374 to 757 percent
over the next 100 years. This could
temper the prospects for western hemlock—a
tree species otherwise expected
to do well under future climate conditions
projected for southern Alaska.
In coastal forests of Washington and
Oregon, water availability may be a
limiting factor in future productivity,
with gains at higher elevations
but declines at lower elevations.
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The Role of Local Governance and Institutions in Livelihoods Adaptation to Climate Change
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The most important implications of climate change from the perspective of the
World Bank concern its potentially disastrous impacts on the prospects for development,
especially for poorer populations in the global South. Earlier writings on climate change
had tended to focus more on its links with biodiversity loss, spread of pathogens and
diseases, land use planning, ecosystem change, and insurance markets, rather than its
connections with development (Easterling and Apps 2005, Harvell et al. 2002, Tompkins
and Adger 2004). But as the Social Development Department of the World Bank recently
noted, “Climate change is the defining development challenge of our generation” (SDV,
2007: 2). These words echo the World Bank President Robert Zoellick’s statement at the
United Nations Climate Change Conference in 2007 in Bali where he called climate
change a “development, economic, and investment challenge.” Indeed, understanding the
relationship between climate change, the human responses it necessitates, and how
institutions shape such responses is an increasingly urgent need. This report directs
attention towards a subset of such relationships, focusing on rural institutions and poor
populations in the context of climate variability and change-induced adaptations.
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Temperature control of larval dispersal and the implications for marine ecology, evolution, and conservation
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Temperature controls the rate of fundamental biochemical processes
and thereby regulates organismal attributes including development
rate and survival. The increase in metabolic rate with
temperature explains substantial among-species variation in lifehistory
traits, population dynamics, and ecosystem processes.
Temperature can also cause variability in metabolic rate within
species. Here, we compare the effect of temperature on a key
component of marine life cycles among a geographically and
taxonomically diverse group of marine fish and invertebrates.
Although innumerable lab studies document the negative effect of
temperature on larval development time, little is known about the
generality versus taxon-dependence of this relationship. We
present a unified, parameterized model for the temperature dependence
of larval development in marine animals. Because the
duration of the larval period is known to influence larval dispersal
distance and survival, changes in ocean temperature could have
a direct and predictable influence on population connectivity,
community structure, and regional-to-global scale patterns of
biodiversity.
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Politics for the day after tomorrow: The logic of apocalypse in global climate politics
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The recent global climate change discourse is a prominent example of a securitization of environmental
issues. While the problem is often framed in the language of existentialism, crisis or even apocalypse, climate
discourses rarely result in exceptional or extraordinary measures, but rather put forth a governmental
scheme of piecemeal and technocratic solutions often associated with risk management. This article argues
that this seeming paradox is no accident but follows from a politics of apocalypse that combines two logics
– those of security and risk – which in critical security studies are often treated as two different animals.
Drawing on the hegemony theory of Ernesto Laclau and Chantal Mouffe, however, this article shows
that the two are inherently connected. In the same way as the Christian pastorate could not do without
apocalyptic imageries, today’s micro-politics of risk depends on a series of macro-securitizations that
enable and legitimize the governmental machinery. This claim is backed up by an inquiry into current global
discourses of global climate change regarding mitigation, adaptation and security implications. Although
these discourses are often framed through the use of apocalyptic images, they rarely result in exceptional
or extraordinary measures, but rather advance a governmental scheme of risk management. Tracing the
relationship between security and risk in these discourses, we use the case of climate change to highlight
the relevance of our theoretical argument.
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Prolonged suppression of ecosystem carbon dioxide uptake after an anomalously warm year
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Terrestrial ecosystems control carbon dioxide fluxes to and from
the atmosphere1,2 through photosynthesis and respiration, a balance
between net primary productivity and heterotrophic respiration,
that determines whether an ecosystem issequestering carbon
or releasing it to the atmosphere. Global1,3–5 and site-specific6 data
sets have demonstrated that climate and climate variability influence
biogeochemical processes that determine net ecosystem carbon
dioxide exchange (NEE) at multiple timescales. Experimental
data necessary to quantify impacts of a single climate variable,
such as temperature anomalies, on NEE and carbon sequestration
of ecosystems at interannual timescales have been lacking. This
derives from an inability of field studies to avoid the confounding
effects of natural intra-annual and interannual variability in temperature
and precipitation. Here we present results from a fouryear
study using replicate 12,000-kg intact tallgrass prairie monoliths
located in four 184-m3 enclosed lysimeters7
. We exposed 6 of
12 monoliths to an anomalously warm year in the second year of
the study8 and continuously quantified rates of ecosystem processes,
including NEE. We find that warming decreases NEE in
both the extreme year and the following year by inducing drought
that suppresses net primary productivity in the extreme year and
by stimulating heterotrophic respiration of soil biota in the subsequent
year. Our data indicate thattwo years are required for NEE
in the previously warmed experimental ecosystems to recover to
levels measured in the control ecosystems. Thistime lag caused net
ecosystem carbon sequestration in previously warmed ecosystems
to be decreased threefold over the study period, compared with
control ecosystems. Our findings suggest that more frequent
anomalously warm years9
, a possible consequence of increasing
anthropogenic carbon dioxide levels10, may lead to a sustained
decrease in carbon dioxide uptake by terrestrial ecosystems.
Vol 455| 18 September 2008
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Aeolian process effects on vegetation communities in an arid grassland ecosystem
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Many arid grassland communities are changing from grass dominance to shrub
dominance, but the mechanisms involved in this conversion process are not completely
understood. Aeolian processes likely contribute to this conversion from
grassland to shrubland. The purpose of this research is to provide information
regarding how vegetation changes occur in an arid grassland as a result of aeolian
sediment transport. The experimental design included three treatment blocks, each
with a 25 × 50 m area where all grasses, semi-shrubs, and perennial forbs were
hand removed, a 25 × 50 m control area with no manipulation of vegetation cover,
and two 10 × 25 m plots immediately downwind of the grass-removal and control
areas in the prevailing wind direction, 19◦ north of east, for measuring vegetation
cover. Aeolian sediment flux, soil nutrients, and soil seed bank were monitored on
each treatment area and downwind plot. Grass and shrub cover were measured on
each grass-removal, control, and downwind plot along continuous line transects as
well as on 5 × 10 m subplots within each downwind area over four years following
grass removal. On grass-removal areas, sediment flux increased significantly, soil
nutrients and seed bank were depleted, and Prosopis glandulosa shrub cover increased
compared to controls. Additionally, differential changes for grass and shrub
cover were observed for plots downwind of vegetation-removal and control areas.
Grass cover on plots downwind of vegetation-removal areas decreased over time
(2004–2007) despite above average rainfall throughout the period of observation,
while grass cover increased downwind of control areas; P. glandulosa cover increased
on plots downwind of vegetation-removal areas, while decreasing on plots downwind
of control areas. The relationships between vegetation changes and aeolian
sediment flux were significant and were best described by a logarithmic function,
with decreases in grass cover and increases in shrub cover occurring with small
increases in aeolian sediment flux
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Coupling of Vegetation Growing Season Anomalies and Fire Activity with Hemispheric and Regional-Scale Climate Patterns in Central and East Siberia
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An 18-yr time series of the fraction of absorbed photosynthetically active radiation (fAPAR) taken in by
the green parts of vegetation data from the NOAA Advanced Very High Resolution Radiometer
(AVHRR) instrument series was analyzed for interannual variations in the start, peak, end, and length of
the season of vegetation photosynthetic activity in central and east Siberia. Variations in these indicators of
seasonality can give important information on interactions between the biosphere and atmosphere. A
second-order local moving window regression model called the “camelback method” was developed to
determine the dates of phenological events at subcontinental scale. The algorithm was validated by comparing
the estimated dates to phenological field observations. Using spatial correlations with temperature
and precipitation data and climatic oscillation indices, two geographically distinct mechanisms in the system
of climatic controls of the biosphere in Siberia are postulated: central Siberia is controlled by an “Arctic
Oscillation–temperature mechanism,” while east Siberia is controlled by an “El Niño–precipitation mechanism.”
While the analysis of data from 1982 to 1991 indicates a slight increase in the length of the growing
season for some land-cover types due to an earlier beginning of the growing season, the overall trend from
1982 to 1999 is toward a slightly shorter season for some land-cover types caused by an earlier end of season.
The Arctic Oscillation tended toward a more positive phase in the 1980s leading to enhanced high pressure
system prevalence but toward a less positive phase in the 1990s. The results suggest that the two mechanisms
also control the fire regimes in central and east Siberia. Several extreme fire years in central Siberia were
associated with a highly positive Arctic Oscillation phase, while several years with high fire damage in east
Siberia occurred in El Niño years. An analysis of remote sensing data of forest fire partially supports this
hypothesis
VOLUME 20
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Illuminating the Modern Dance of Climate and CO2
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Records of Earth’s past climate imply higher atmospheric carbon dioxide concentrations in the future
19 SEPTEMBER 2008 VOL 321 SCIENCE
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Soil Temperature following Logging-Debris Manipulation and Aspen Regrowth in Minnesota: Implications for Sampling Depth and Alteration of Soil Processes
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Soil temperature is a fundamental controller of processes influencing the
transformation and flux of soil C and nutrients following forest harvest. Soil
temperature response to harvesting is influenced by the amount of logging
debris (biomass) removal that occurs, but the duration, magnitude, and depth
of influence is unclear. Logging debris manipulations (none, moderate, and
heavy amounts) were applied following clearcut harvesting at four aspendominated
(Populus tremuloides Michx.) sites in northeastern Minnesota, and
temperature was measured at 10-, 30-, and 50-cm depths for two growing
seasons. Across sites, soil temperature was significantly greater at all sample
depths relative to uncut forest in some periods of each year, but the increase
was reduced with increasing logging-debris retention. When logging debris
was removed compared to when it was retained in the first growing season,
mean growing season soil temperatures were 0.9, 1.0, and 0.8°C greater at
10-, 30-, and 50-cm depths, respectively. These patterns were also observed
early in the second growing season, but there was no discernible difference
among treatments later in the growing season due to the modifying effect of
rapid aspen regrowth. Where vegetation establishment and growth occurs
quickly, effects of logging debris removal on soil temperature and the processes
influenced by it will likely be short-lived. The significant increase in
soil temperature that occurred in deep soil for at least 2 yr after harvest
supports an argument for deeper soil sampling than commonly occurs in
experimental studies.
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Climate-induced changes in the small mammal communities of the Northern Great Lakes Region
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We use museum and other collection records to document large and extraordinarily rapid
changes in the ranges and relative abundance of nine species of mammals in the northern
Great Lakes region (white-footed mice, woodland deer mice, southern red-backed voles,
woodland jumping mice, eastern chipmunks, least chipmunks, southern flying squirrels,
northern flying squirrels, common opossums). These species reach either the southern or
the northern limit of their distributions in this region. Changes consistently reflect
increases in species of primarily southern distribution (white-footed mice, eastern
chipmunks, southern flying squirrels, common opossums) and declines by northern
species (woodland deer mice, southern red-backed voles, woodland jumping mice, least
chipmunks, northern flying squirrels). White-footed mice and southern flying squirrels
have extended their ranges over 225 km since 1980, and at particularly well-studied sites
in Michigan’s Upper Peninsula, small mammal assemblages have shifted from numerical
domination by northern species to domination by southern species. Repeated resampling
at some sites suggests that southern species are replacing northern ones rather than
simply being added to the fauna. Observed changes are consistent with predictions from
climatic warming but not with predictions based on recovery from logging or changes in
human populations. Because of the abundance of these focal species (the eight rodent
species make up 96.5% of capture records of all forest-dwelling rodents in the region and
70% of capture records of all forest-dwelling small mammals) and the dominating
ecological roles they play, these changes substantially affect the composition and
structure of forest communities. They also provide an unusually clear example of change
that is likely to be the result of climatic warming in communities that are experienced by
large numbers of people.
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