A Climate Change Vulnerability Assessment of California's At-Risk Birds. Gardali, Thomas; Seavy, Nathaniel E.; DiGaudio, Ryan T. & Comrack, Lyann A..
http://dx.doi.org/10.1371%2Fjournal.pone.0029507 DOI: 10.1371%2Fjournal.pone.0029507
Conservationists must develop new strategies and adapt existing tools to address the consequences of anthropogenic climate change. To support statewide climate change adaptation, we developed a framework for assessing climate change vulnerability of California's at-risk birds and integrating it into the existing California Bird Species of Special Concern list. We defined climate vulnerability as the amount of evidence that climate change will negatively impact a population. We quantified climate vulnerability by scoring sensitivity (intrinsic characteristics of an organism that make it vulnerable) and exposure (the magnitude of climate change expected) for each taxon. Using the combined sensitivity and exposure scores as an index, we ranked 358 avian taxa, and classified 128 as vulnerable to climate change. Birds associated with wetlands had the largest representation on the list relative to other habitat groups. Of the 29 state or federally listed taxa, 21 were also classified as climate vulnerable, further raising their conservation concern. Integrating climate vulnerability and California's Bird Species of Special Concern list resulted in the addition of five taxa and an increase in priority rank for ten. Our process illustrates a simple, immediate action that can be taken to inform climate change adaptation strategies for wildlife.
Climate change and the future of California's endemic flora. Loarie, Scott R.; Carter, Benjamin E.; Hayhoe, Katharine; McMahon, Sean; Moe, Richard; Knight, Charles A. & Ackerly, David D..
The flora of California, a global biodiversity hotspot, includes 2387 endemic plant taxa. With anticipated climate change, we project that up to 66% will experience >80% reductions in range size within a century. These results are comparable with other studies of fewer species or just samples of a region's endemics. Projected reductions depend on the magnitude of future emissions and on the ability of species to disperse from their current locations. California's varied terrain could cause species to move in very different directions, breaking up present-day floras. However, our projections also identify regions where species undergoing severe range reductions may persist. Protecting these potential future refugia and facilitating species dispersal will be essential to maintain biodiversity in the face of climate change.
Climate Change and the Future of California's Endemic Flora. Loarie S.R., Carter B.E., Hayhoe K., McMahon S., Moe R., Knight C. A. & Ackerly D.D..
The flora of California, a global biodiversity hotspot, includes 2387 endemic plant taxa. With anticipated climate change, we project that up to 66% will experience .80% reductions in range size within a century. These results are comparable with other studies of fewer species or just samples of a region's endemics. Projected reductions depend on the magnitude of future emissions and on the ability of species to disperse from their current locations. California's varied terrain could cause species to move in very different directions, breaking up present-day floras. However, our projections also identify regions where species undergoing severe range reductions may persist. Protecting these potential future refugia and facilitating species dispersal will be essential to maintain biodiversity in the face of climate change.
Climatic Changes Lead to Declining Winter Chill for Fruit and Nut Trees in California during 1950-2099. Eike Luedeling, Minghua Zhang, Evan H. Girvetz.
http://dx.doi.org/10.1371/journal.pone.0006166 DOI: 10.1371/journal.pone.0006166
Background: Winter chill is one of the defining characteristics of a location's suitability for the production of many tree crops. We mapped and investigated observed historic and projected future changes in winter chill in California, quantified with two different chilling models (Chilling Hours, Dynamic Model). Methodology/Principal Findings: Based on hourly and daily temperature records, winter chill was modeled for two past temperature scenarios (1950 and 2000), and 18 future scenarios (average conditions during 2041-2060 and 2080-2099 under each of the B1, A1B and A2 IPCC greenhouse gas emissions scenarios, for the CSIRO-MK3, HadCM3 and MIROC climate models). For each scenario, 100 replications of the yearly temperature record were produced, using a stochastic weather generator. We then introduced and mapped a novel climatic statistic, ''safe winter chill'', the 10% quantile of the resulting chilling distributions. This metric can be interpreted as the amount of chilling that growers can safely expect u der each scenario. Winter chill declined substantially for all emissions scenarios, with the area of safe winter chill for many tree species or cultivars decreasing 50-75% by mid-21st century, and 90-100% by late century. Conclusions/Significance: Both chilling models consistently projected climatic conditions by the middle to end of the 21st century that will no longer support some of the main tree crops currently grown in California, with the Chilling Hours Model projecting greater changes than the Dynamic Model. The tree crop industry in California will likely need to develop agricultural adaptation measures (e.g. low-chill varieties and dormancy-breaking chemicals) to cope with these projected changes. For some crops, production might no longer be possible.
Climatic Correlates of Tree Mortality in Water- and Energy-Limited Forests. Adrian J. Das, Nathan L. Stephenson, Alan Flint, Tapash Das, Phillip J. van Mantgem.
<p><span style="font-family: AdvP403A40; font-size: xx-small;"><span style="font-family: AdvP403A40; font-size: xx-small;">
<p>Recent increases in tree mortality rates across the western USA are correlated with increasing temperatures, but</p>
<p>mechanisms remain unresolved. Specifically, increasing mortality could predominantly be a consequence of temperatureinduced</p>
<p>increases in either (1) drought stress, or (2) the effectiveness of tree-killing insects and pathogens. Using long-term</p>
<p>data from California’s Sierra Nevada mountain range, we found that in water-limited (low-elevation) forests mortality was</p>
<p>unambiguously best modeled by climatic water deficit, consistent with the first mechanism. In energy-limited (highelevation)</p>
<p>forests deficit models were only equivocally better than temperature models, suggesting that the second</p>
<p>mechanism is increasingly important in these forests. We could not distinguish between models predicting mortality using</p>
<p>absolute versus relative changes in water deficit, and these two model types led to different forecasts of mortality</p>
<p>vulnerability under future climate scenarios. Our results provide evidence for differing climatic controls of tree mortality in</p>
<p>water- and energy-limited forests, while highlighting the need for an improved understanding of tree mortality processes.</p>
Hydrologic Response and Watershed Sensitivity to Climate Warming in California's Sierra Nevada. Sarah E. Null, Joshua H. Viers, Jeffrey F. Mount.
Projected Evolution of California's San Francisco Bay-Delta-River System in a Century of Climate Change. James E. Cloern, Noah Knowles, Larry R. Brown, Daniel Cayan, Michael D. Dettinger, Tara L. Morgan, David H. Schoellhamer, Mark T. Stacey, Mick van der Wegen, R. Wayne Wagner, and Alan D. Jassby.
Background: Accumulating evidence shows that the planet is warming as a response to human emissions of greenhouse gases. Strategies of adaptation to climate change will require quantitative projections of how altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing risks of coastal flooding, and growing challenges to sustainability of native species. Methodology/Principal Findings: We linked a series of models to investigate responses of California's San Francisco Estuary-Watershed (SFEW) system to two contrasting scenarios of climate change. Model outputs for scenarios of fast and moderate warming are presented as 2010-2099 projections of nine indicators of changing climate, hydrology and habitat quality. Trends of these indicators measure rates of: increasing air and water temperatures, salinity and sea level; decreasing precipitation, runoff, snowmelt contribution to runoff, and suspended sediment concentrations; and increasing frequency of extreme environmental conditions such as water temperatures and sea level beyond the ranges of historical observations. Conclusions/Significance: Most of these environmental indicators change substantially over the 21st century, and many would present challenges to natural and managed systems. Adaptations to these changes will require flexible planning to cope with growing risks to humans and the challenges of meeting demands for fresh water and sustaining native biota. Programs of ecosystem rehabilitation and biodiversity conservation in coastal landscapes will be most likely to meet their objectives if they are designed from considerations that include: (1) an integrated perspective that river-estuary systems are influenced by effects of climate change operating on both watersheds and oceans; (2) varying sensitivity among environmental indicators to the uncertainty of future climates; (3) inevitability of biological community changes as responses to cumulative effects of climate change and other drivers of habitat transformations; and (4) anticipation and adaptation to the growing probability of ecosystem regime shifts.