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Projections of Future Drought in the Continental United States and Mexico
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Using the Palmer drought severity index, the ability of 19 state-of-the-art climate models to reproduce ob- served statistics of drought over North America is examined. It is found that correction of substantial biases in the models’ surface air temperature and precipitation fields is necessary. However, even after a bias correction, there are significant differences in the models’ ability to reproduce observations. Using metrics based on the ability to reproduce observed temporal and spatial patterns of drought, the relationship between model per- formance in simulating present-day drought characteristics and their differences in projections of future drought changes is investigated. It is found that all models project increases in future drought frequency and severity. However, using the metrics presented here to increase confidence in the multimodel projection is complicated by a correlation between models’ drought metric skill and climate sensitivity. The effect of this sampling error can be removed by changing how the projection is presented, from a projection based on a specific time interval to a projection based on a specified temperature change. This modified class of projections has reduced intermodel uncertainty and could be suitable for a wide range of climate change impacts projections.
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This space contains information on projects to increase information sharing within the community of practice working on Wildland Fire and Prescribed Burning.
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This space contains information on projects to increase information sharing within the community of practice working on Wildland Fire and Prescribed Burning.
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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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prosperity_without_growth_report.pdf
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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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Protected areas facilitate species’ range expansions
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The benefits of protected areas (PAs) for biodiversity have been questioned in the context of climate change because PAs are static, whereas the distributions of species are dynamic. Current PAs may, however, continue to be important if they provide suitable locations for species to colonize at their leading-edge range boundaries, thereby enabling spread into new regions. Here, we present an empirical assessment of the role of PAs as targets for coloniza- tion during recent range expansions. Records from intensive sur- veys revealed that seven bird and butterfly species have colonized PAs 4.2 (median) times more frequently than expected from the availability of PAs in the landscapes colonized. Records of an additional 256 invertebrate species with less-intensive surveys supported these findings and showed that 98% of species are disproportionately associated with PAs in newly colonized parts of their ranges. Although colonizing species favor PAs in general, species vary greatly in their reliance on PAs, reflecting differences in the dependence of individual species on particular habitats and other conditions that are available only in PAs. These findings highlight the importance of current PAs for facilitating range expansions and show that a small subset of the landscape receives a high proportion of colonizations by range-expanding species.
conservation | climate change adaptation | nature reserves
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Protected areas in Borneo may fail to conserve tropical forest biodiversity under climate change
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Protected areas (PAs) are key for conserving rainforest species, but many PAs are becoming increasingly
isolated within agricultural landscapes, which may have detrimental consequences for the forest biota
they contain. We examined the vulnerability of PA networks to climate change by examining connectivity
of PAs along elevation gradients. We used the PA network on Borneo as a model system, and examined
changes in the spatial distribution of climate conditions in future. A large proportion of PAs will not
contain analogous climates in future (based on temperature projections for 2061–2080), potentially
requiring organisms to move to cooler PAs at higher elevation, if they are to track climate changes. For
the highest warming scenario (RCP8.5), few (11–12.5%; 27–30/240) PAs were sufficiently topographically
diverse for analogous climate conditions (present-day equivalent or cooler) to remain in situ. For the
remaining 87.5–89% (210–213/240) of PAs, which were often situated at low elevation, analogous climate
will only be available in higher elevation PAs. However, over half (60–82%) of all PAs on Borneo are too
isolated for poor dispersers (<1 km per generation) to reach cooler PAs, because there is a lack of connecting
forest habitat. Even under the lowest warming scenario (RCP2.6), analogous climate conditions will
disappear from 61% (146/240) of PAs, and a large proportion of these are too isolated for poor dispersers
to reach cooler PAs. Our results suggest that low elevation PAs are particularly vulnerable to climate
change, and management to improve linkage of PAs along elevation gradients should be a conservation
priority
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Protecting the Tennessee River Gorge
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A video documenting why the Tennessee River Gorge Trust's work is necessary.
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