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Linking climate change to lemming cycles
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The population cycles of rodents at northern latitudes have puzzled
people for centuries1,2
, and their impact is manifest throughout the
alpine ecosystem2,3
. Climate change is known to be able to drive
animal population dynamics between stable and cyclic phases
4,5
,
and has been suggested to cause the recent changesin cyclic dynamics
of rodents and their predators
3,6–9
. But although predator–rodent
interactions are commonly argued to be the cause of the
Fennoscandian rodent cycles
1,10–13
, the role of the environment in
the modulation of such dynamics is often poorly understood in
natural systems
8,9,14
. Hence, quantitative links between climatedriven
processes and rodent dynamics have so far been lacking.
Here we show that winter weather and snow conditions, together
with density dependence in the net population growth rate, account
for the observed population dynamics of the rodent community
dominated by lemmings (Lemmus lemmus) in an alpine Norwegian
core habitat between 1970 and 1997, and predictthe observed absence
of rodent peak years after 1994. These local rodent dynamics are
coherentwith alpine bird dynamics both locally and over all ofsouthern
Norway, consistent with the influence of large-scale fluctuations
in winter conditions. The relationship between commonly available
meteorological data and snow conditions indicates that changes in
temperature and humidity, and thus conditions in the subnivean
space, seem to markedly affect the dynamics of alpine rodents and
their linked groups. The pattern of less regular rodent peaks, and
corresponding changes in the overall dynamics of the alpine ecosystem,
thusseemslikely to prevail over a growing area under projected
climate change.
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Impact of disturbed desert soils on duration of mountain snow cover
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Snow cover duration in a seasonally snow covered
mountain range (San Juan Mountains, USA) was found to
be shortened by 18 to 35 days during ablation through
surface shortwave radiative forcing by deposition of
disturbed desert dust. Frequency of dust deposition and
radiative forcing doubled when the Colorado Plateau, the
dust source region, experienced intense drought (8 events
and 39–59 Watts per square meter in 2006) versus a year
with near normal precipitation (4 events and 17–34 Watts
per square meter in 2005). It is likely that the current
duration of snow cover and surface radiation budget
represent a dramatic change from those before the
widespread soil disturbance of the western US in the late
1800s that resulted in enhanced dust emission. Moreover,
the projected increases in drought intensity and frequency
and associated increases in dust emission from the desert
southwest US may further reduce snow cover duration
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The Historical Dynamics of Socio-ecological Traps
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Environmental degradation is a typical unintended
outcome of collective human behavior. Hardin’s
metaphor of the ‘‘tragedy of the commons’’ has become a
conceived wisdom that captures the social dynamics leading
to environmental degradation. Recently, ‘‘traps’’ has gained
currency as an alternative concept to explain the rigidity of
social and ecological processes that produce environmental
degradation and livelihood impoverishment. The trap metaphor
is, however, a great deal more complex compared to
Hardin’s insight. This paper takes stock of studies using the
trap metaphor. It argues that the concept includes time and
history in the analysis, but only as background conditions and
not as a factor of causality. From a historical–sociological
perspective this is remarkable since social–ecological traps
are clearly path-dependent processes, which are causally
produced through a conjunction of events. To prove this point
the paper conceptualizes social–ecological traps as a process
instead of a condition, and systematically compares history
and timing in one classic and three recent studies of social–
ecological traps. Based on this comparison it concludes that
conjunction of social and environmental events contributes
profoundly to the production of trap processes. The paper
further discusses the implications of this conclusion for policy
intervention and outlines how future research might generalize
insights from historical–sociological studies of traps.
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The influence of conversion of forest types on carbon sequestration and other ecosystem services in the South Central United States
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This paper develops a forestland management model for the three states in the South Central United States (Arkansas,
Louisiana, and Mississippi). Forest type and land-use shares are estimated to be a function of economic and physical variables.
The results suggest that while historically pine plantations in this region have been established largely on old agricultural land,
in the future pine plantations are likely to occur on converted hardwood-forest lands. This shift in the supply of land for
plantations could have large effects on above-ground carbon storage and other ecosystem services. Subsidies of approximately
$12–27 per ha per year would maintain the area of hardwood forests and reduce carbon emissions from the above-ground and
product pool carbon stocks over the next 30 years. Across the several scenarios considered, results suggest that maintaining
hardwoods could be an efficient carbon sequestration alternative.
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Understanding Soil Time
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Efforts to maintain soils in a sustainable
manner are complicated by interactions among
soil components that respond to perturbation
at vastly different rates.
VOL 321 SCIENCE
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An Uncertain Future for Soil Carbon
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Predictions of how rapidly the large amounts of carbon stored as soil organic matter will respond to warming
are highly uncertain (1). Organic matter plays a key role in determining the physical and chemical properties of soils and is a major reservoir for plant nutrients. Understanding how fast organic matter in soils can be built up and lost is thus critical not just for its net effect on the atmospheric CO2 concentration but for
sustaining other soil functions, such as soil fertility, on which societies and ecosystems rely. Recent analytic advances are rapidly improving our understanding of the complex and interacting factors that control the age
and form of organic matter in soils, but the processes that destabilize organic matter in response to disturbances (such as warming or land use change) are poorly understood
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Impact of terrestrial biosphere carbon exchanges on the anomalous CO2 increase in 2002–2003
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Understanding the carbon dynamics of the terrestrial
biosphere during climate fluctuations is a prerequisite for
any reliable modeling of the climate-carbon cycle feedback.
We drive a terrestrial vegetation model with observed
climate data to show that most of the fluctuations in
atmospheric CO2 are consistent with the modeled shift in
the balance between carbon uptake by terrestrial plants and
carbon loss through soil and plant respiration. Simulated
anomalies of the Fraction of Absorbed Photosynthetically
Active Radiation (FAPAR) during the last two El Nin˜o
events also agree well with satellite observations. Our
model results suggest that changes in net primary
productivity (NPP) are mainly responsible for the
observed anomalies in the atmospheric CO2 growth rate.
Changes in heterotrophic respiration (Rh) mostly happen in
the same direction, but with smaller amplitude. We attribute
the unusual acceleration of the atmospheric CO2 growth rate
during 2002–2003 to a coincidence of moderate El Nin˜o
conditions in the tropics with a strong NPP decrease at
northern mid latitudes, only partially compensated by
decreased
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Emerging Techniques for Soil Carbon measurements
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Soil carbon sequestration is one approach to mitigate greenhouse gases. However, to reliably
assess the quantities sequestered as well as the chemical structure of the soil carbon, new
methods and equipment are needed. These methods and equipment must allow large scale
measurements and the construction of dynamic maps. This paper presents results from some
emerging techniques to measure carbon quantity and stability. Each methodology has specific
capabilities and their combined use along with other analytical tools will improve soil organic
matter research. New opportunities arise with the development and application of portable
equipment, based on spectroscopic methods, as laser-induced fluorescence, laser-induced
breakdown spectroscopy and near infrared, for in situ carbon measurements in different
ecosystems. These apparatus could provide faster and lower cost field analyses thus
improving soil carbon contents and quality databases. Improved databases are essential to
model carbon balance, thus reducing the uncertainties generated through the extrapolation of
limited data.
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Protected Areas as Frontiers for Human Migration
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Causes of human population growth near protected areas have been much debated. We conducted
821 interviews in 16 villages around Budongo Forest Reserve, Masindi district, Uganda, to explore the causes of
human migration to protected areas and to identify differences in forest use between migrant and nonmigrant
communities. We asked subjects for information about birthplace, migration, household assets, household
activities, and forest use. Interview subjects were categorized as nonmigrants (born in one of the interview
villages), socioeconomic migrants (chose to emigrate for economic or social reasons) from within Masindi
district (i.e., local migrants) and from outside the Masindi district (i.e., regional migrants), or forced migrants
(i.e., refugees or internally displaced individuals who emigrated as a result of conflict, human rights abuses,
or natural disaster). Only 198 respondents were born in interview villages, indicating high rates of migration
between 1998 and 2008. Migrants were drawn to Budongo Forest because they thought land was available
(268 individuals) or had family in the area (161 individuals). A greater number of regional migrants settled
in villages near Lake Albert than did forced and local migrants. Migration category was also associated with
differences in sources of livelihood. Of forced migrants 40.5% earned wages through labor, whereas 25.5% of
local and 14.5% of regional migrants engaged in wage labor. Migrant groups appeared to have different effects
on the environment. Of respondents that hunted, 72.7% were regional migrants. Principal component analyses
indicated households of regional migrants were more likely to be associated with deforestation. Our results
revealed gaps in current models of human population growth around protected areas. By highlighting the
importance of social networks and livelihood choices, our results contribute to a more nuanced understanding
of causes of migration and of the environmental effects of different migrant groups.
Conservation Biology, Volume 26, No. 3, 547–556
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Barking up the Wrong Tree? Forest Sustainability in the wake of Emerging Bioenergy Policies
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The spotted owl controversy revealed that federal forest management policies alone could not guarantee functioning forest ecosystems. At the same time as the owl’s listing, agreements made at the 1992 Rio Earth Summit highlighted the mounting pressures on natural systems, thus unofficially marking the advent of sustainable forestry management (SFM).2 While threats to forest ecosystems from traditional logging practices certainly remain,3 developed and developing countries have shifted generally toward more sustainable forest management, at least on paper, including codifying various sustainability indicators in public laws.4 Nevertheless, dark policy clouds are gathering on the forest management horizon. Scientific consensus has grown in recent years around a new and arguably more onerous threat to all of the world’s ecosystems—climate change. Governments’ responses have focused on bioenergy policies aimed
at curtailing anthropogenic greenhouse gas (GHG) emissions, and mandatesfor renewables in energy supplies now abound worldwide.
[Vol. 37:000
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