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Changes in the Asian monsoon climate during 1700 –1850 induced by preindustrial cultivation
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Preindustrial changes in the Asian summer monsoon climate from the 1700s to the 1850s were estimated with an atmospheric general circulation model (AGCM) using historical global land cover/use change data reconstructed for the last 300 years. Extended cultivation resulted in a decrease in monsoon rainfall over the Indian subcontinent and southeastern China and an associated weakening of the Asian summer monsoon circulation. The precipitation decrease in India was marked and was consistent with the observational changes derived from examining the Himalayan ice cores for the concurrent period. Between the 1700s and the 1850s, the anthropogenic increases in greenhouse gases and aerosols were still minor; also, no long-term trends in natural climate variations, such as those caused by the ocean, solar activity, or volcanoes, were reported. Thus, we propose that the land cover/ use change was the major source of disturbances to the climate during that period. This report will set forward quantitative ex-amination of the actual impacts of land cover/use changes on Asian monsoons, relative to the impact of greenhouse gases and aerosols, viewed in the context of global warming on the interannual, decadal, and centennial time scales.
atmospheric water balance climate change historical land-cover change monsoon rainfall
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Domesticated Nature: Shaping Landscapes and Ecosystems for Human Welfare
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Like all species, humans have exercised their impulse to perpetuate and propagate themselves. In doing so, we have domesticated landscapes and ecosystems in ways that enhance our food supplies, reduce exposure to predators and natural dangers, and promote commerce. On average, the net benefits to humankind of domesticated nature have been positive. We have, of course, made mistakes, causing unforeseen changes in ecosystem attributes, while leaving few, if any, truly wild places on Earth. Going into the future, scientists can help humanity to domesticate nature more wisely by quantifying the tradeoffs among ecosystem services, such as how increasing the provision of one service may decrease ecosystem resilience and the provision of other services.
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Climate change and the ecologist
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The evidence for rapid climate change now seems overwhelming. Global temperatures are predicted to rise by up to 4 °C by 2100, with associated alterations in precipitation patterns. Assessing the consequences for biodiversity, and how they might be mitigated, is a Grand Challenge in ecology.
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Temporal dynamics of a commensal network of cavity-nesting vertebrates: increased diversity during an insect outbreak
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Network analysis offers insight into the structure and function of ecological
communities, but little is known about how empirical networks change over time during
perturbations. ‘‘Nest webs’’ are commensal networks that link secondary cavity-nesting
vertebrates (e.g., bluebirds, ducks, and squirrels, which depend on tree cavities for nesting)
with the excavators (e.g., woodpeckers) that produce cavities. In central British Columbia,
Canada, Northern Flicker (Colaptes auratus) is considered a keystone excavator, providing
most cavities for secondary cavity-nesters. However, roles of species in the network, and
overall network architecture, are expected to vary with population fluctuations. Many
excavator species increased in abundance in association with a pulse of food (adult and larval
beetles) during an outbreak of mountain pine beetle (Dendroctonus ponderosae), which peaked
in 2003–2004. We studied nest-web dynamics from 1998 to 2011 to determine how network
architecture changed during this resource pulse.Cavity availability increased at the onset of the beetle outbreak and peaked in 2005. During and after the outbreak, secondary cavity-nesters increased their use of cavities made by five species of beetle-eating excavators, and decreased their use of flicker cavities. We found low link turnover, with 74% of links conserved from year to year. Nevertheless, the network
increased in evenness and diversity of interactions, and declined slightly in nestedness and
niche overlap. These patterns remained evident seven years after the beetle outbreak,
suggesting a legacy effect. In contrast to previous snapshot studies of nest webs, our dynamic approach reveals how the role of each cavity producer, and thus quantitative network architecture, can vary over
time. The increase in interaction diversity with the beetle outbreak adds to growing evidence
that insect outbreaks can increase components of biodiversity in forest ecosystems at various
temporal scales. The observed changes in (quantitative) network architecture contrast with the
relatively stable (qualitative) architecture of empirical mutualistic networks that have been
studied to date. However, they are consistent with recent theory on the importance of
population fluctuations in driving network architecture. Our results support the view that
models should allow for the possibility of rewiring (species switching partners) to avoid
overestimation of secondary extinction risk.
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Impacts of mountaintop mining on terrestrial ecosystem integrity: identifying landscape thresholds for avian species in the central Appalachians, United States
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Reclaimed mine-dominated landscapes (less forest and more grassland/shrubland cover) elicited more negative (57 %) than positive (39 %) species responses. Negative thresholds for each landscape metric generally occurred at lower values than positive thresholds, thus negatively responding species were
detrimentally affected before positively responding species benefitted. Forest interior birds generally
responded negatively to landscape metric thresholds, interior edge species responses were mixed, and early
successional birds responded positively. The forest interior guild declined most at 4 % forest loss, while
the shrubland guild increased greatest after 52 % loss
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A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests
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Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the
future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with
climate change could fundamentally alter the composition, structure, and biogeography of forests in
many regions. Of particular concern are potential increases in tree mortality associated with climateinduced
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.
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Scaling up from gardens: biodiversity conservation in urban environments
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As urbanisation increases globally and the natural environment becomes increasingly fragmented, the
importance of urban green spaces for biodiversity conservation grows. In many countries, private gardens area major component of urban green space and can provideconsiderable biodiversity benefits. Gardens and
adjacent habitats form interconnected networks and a landscape ecology framework is necessary to understand the relationship between the spatial configuration of garden patches and their constituent biodiversity. A scale-dependent tension is apparent in garden management, whereby the individual garden is much smaller than the unit of management needed to retain viable populations. To overcome this, here we suggest mechanisms for encouraging ‘wildlife-friendly’ management of collections of gardens across scales from the neighbourhood to the city.
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Scenarios of future land use change around United States’ protected areas
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Land use change around protected areas can diminish their conservation value, making it important to
predict future land use changes nearby. Our goal was to evaluate future land use changes around protected
areas of different types in the United States under different socioeconomic scenarios. We analyzed
econometric-based projections of future land use change to capture changes around 1260 protected
areas, including National Forests, Parks, Refuges, and Wilderness Areas, from 2001 to 2051, under different
land use policies and crop prices. Our results showed that urban expansion around protected areas
will continue to be a major threat, and expand by 67% under business-as-usual conditions.
Concomitantly, a substantial number of protected areas will lose natural vegetation in their surroundings.
National land-use policies or changes in crop prices are not likely to affect the overall pattern of land use,
but can have effects in certain regions. Discouraging urbanization through zoning, for example, can
reduce future urban pressures around National Forests and Refuges in the East, while the implementation
of an afforestation policy can increase the amount of natural vegetation around some Refuges throughout
the U.S. On the other hand, increases in crop prices can increase crop/pasture cover around some protected
areas, and limit the potential recovery of natural vegetation. Overall, our results highlight that future
land-use change around protected areas is likely to be substantial but variable among regions and
protected area types. Safeguarding the conservation value of protected areas may require serious consideration of threats and opportunities arising from future land use.
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Invited Review: Quantifying surface albedo and other direct biogeophysical climate forcings of forestry activities
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By altering fluxes of heat, momentum, and moisture exchanges between the land surface and atmosphere, forestry and other land-use activities affect climate. Although long recognized scientifically as being important, these so-called biogeophysical forcings are rarely included in climate policies for forestry and other land management projects due to the many challenges associated with their quantification. Here, we review the scientific literature in the fields of atmospheric science and terrestrial ecology in light of three main objectives: (i) to elucidate the challenges associated with quantifying biogeophysical climate forcings connected to land use and land management, with a focus on the forestry sector; (ii) to identify and describe scientific approaches and/or metrics facilitating the quantification and interpretation of direct biogeophysical climate forcings; and (iii) to identify and recommend research priorities that can help overcome the challenges of their attribution to specific land-use activities, bridging the knowledge gap between the climate modeling, forest ecology, and resource management communities. We find that ignoring surface
biogeophysics may mislead climate mitigation policies, yet existing metrics are unlikely to be sufficient. Successful metrics ought to (i) include both radiative and nonradiative climate forcings; (ii) reconcile disparities between biogeophysical and biogeochemical forcings, and (iii) acknowledge trade-offs between global and local climate benefits. We call for more coordinated research among terrestrial ecologists, resource managers, and coupled climate modelers to harmonize datasets, refine analytical techniques, and corroborate and validate metrics that are more amenable to analyses at the scale of an individual site or region.
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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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