Phenomenological vs. biophysical models of thermal stress in aquatic eggs

Ecology Letters (Wiley) | January 1st, 2017

Predicting species responses to climate change is a central challenge in ecology. These predictions are often based on lab-derived phenomenological relationships between

Predicting species responses to climate change is a central challenge in ecology. These predictions are often based on lab-derived phenomenological relationships between temperature and fitness metrics. We tested one of these relationships using the embryonic stage of a Chinook salmon population. We parameterised the model with laboratory data, applied it to predict survival in the field, and found that it significantly underestimated field-derived estimates of thermal mortality. We used a biophysical model based on mass transfer theory to show that the discrepancy was due to the differences in water flow velocities between the lab and the field. This mechanistic approach provides testable predictions for how the thermal tolerance of embryos depends on egg size and flow velocity of the surrounding water. We found support for these predictions across more than 180 fish species, suggesting that flow and temperature mediated oxygen limitation is a general mechanism underlying the thermal tolerance of embryos.

Piloting a Water Rights Information System for California

Center for Law, Energy, and the Environment (CLEE) | July 15th, 2021

California’s complex water management challenges are growing and intensifying. Systemic stressors like the more frequent and severe droughts and floods driven by climat

California’s complex water management challenges are growing and intensifying. Systemic stressors like the more frequent and severe droughts and floods driven by climate change are only making it harder to respond. Accordingly, California needs to dramatically improve the ability of local, regional, and State entities to make agile and effective water management decisions. We believe doing so will require enhanced understanding of our water resources and how they align with the needs of a range of agencies and stakeholders. Water rights data provide a crucial opportunity for advancing this understanding. We find that modernizing water rights data is feasible, affordable, and can increase transparency and clarity for better decision-making.

Planning and investing for a resilient California: A guidebook for state agencies

Governor's Office of Planning and Research (OPR) | November 17th, 2017

Executive Order (EO) B-30-15 (April 2015; Appendix A) identified three actions to advance adaptation and resilience: 1. Preparation of Implementation Action Plans to id

Executive Order (EO) B-30-15 (April 2015; Appendix A) identified three actions to advance adaptation and resilience: 1. Preparation of Implementation Action Plans to identify the steps that will be taken to realize the goals in Safeguarding California; 2. Direction to all State agencies to consider climate change in all planning and investment, including infrastructure investment; and 3. Direction to the Governor’s Office of Planning and Research (OPR) to establish a Technical Advisory Group (TAG) to provide state agencies with guidance on how to integrate climate change into planning and investment. This document is the product of the Technical Advisory Group (TAG) formed under EO B-30-15. The TAG was comprised of representatives from a majority of agencies, departments, offices and commissions of the Governor’s executive branch, and members of the public, including local and regional governments, non-governmental organizations, and the private sector (see Appendix B). This guidance document is designed to inform planning and investment processes to address the two primary elements of resilience – planning for future conditions and doing planning itself differently. This document introduces a four step process and a set of resilient decision making principles for state agencies.

Plant-water sensitivity regulates wildfire vulnerability

Nature Portfolio (Springer Nature) | February 7th, 2022

Extreme wildfires extensively impact human health and the environment. Increasing vapour pressure deficit (VPD) has led to a chronic increase in wildfire area in the west

Extreme wildfires extensively impact human health and the environment. Increasing vapour pressure deficit (VPD) has led to a chronic increase in wildfire area in the western United States, yet some regions have been more affected than others. Here we show that for the same increase in VPD, burned area increases more in regions where vegetation moisture shows greater sensitivity to water limitation (plant-water sensitivity; R2 = 0.71). This has led to rapid increases in human exposure to wildfire risk, both because the population living in areas with high plant-water sensitivity grew 50% faster during 1990–2010 than in other wildland–urban interfaces and because VPD has risen most rapidly in these vulnerable areas. As plant-water sensitivity is strongly linked to wildfire vulnerability, accounting for ecophysiological controls should improve wildfire forecasts. If recent trends in VPD and demographic shifts continue, human wildfire risk will probably continue to increase.

Plant-water sensitivity regulates wildfire vulnerability

Nature Portfolio (Springer Nature) | February 7th, 2022

Extreme wildfires extensively impact human health and the environment. Increasing vapour pressure deficit (VPD) has led to a chronic increase in wildfire area in the west

Extreme wildfires extensively impact human health and the environment. Increasing vapour pressure deficit (VPD) has led to a chronic increase in wildfire area in the western United States, yet some regions have been more affected than others. Here we show that for the same increase in VPD, burned area increases more in regions where vegetation moisture shows greater sensitivity to water limitation (plant-water sensitivity; R2 = 0.71). This has led to rapid increases in human exposure to wildfire risk, both because the population living in areas with high plant-water sensitivity grew 50% faster during 1990–2010 than in other wildland–urban interfaces and because VPD has risen most rapidly in these vulnerable areas. As plant-water sensitivity is strongly linked to wildfire vulnerability, accounting for ecophysiological controls should improve wildfire forecasts. If recent trends in VPD and demographic shifts continue, human wildfire risk will probably continue to increase.

Pluvial flood impacts and policyholder responses throughout the United States

Nature Portfolio (Springer Nature) | January 24th, 2025

Poleward shift of the major ocean gyres detected in a warming climate

American Geophysical Union (AGU) | February 24th, 2020

Recent evidence shows that wind‐driven ocean currents, like the western boundary currents, are strongly affected by global warming. However, due to insufficient observa

Recent evidence shows that wind‐driven ocean currents, like the western boundary currents, are strongly affected by global warming. However, due to insufficient observations both on temporal and spatial scales, the impact of climate change on large‐scale ocean gyres is still not clear. Here, based on satellite observations of sea surface height and sea surface temperature, we find a consistent poleward shift of the major ocean gyres. Due to strong natural variability, most of the observed ocean gyre shifts are not statistically significant, implying that natural variations may contribute to the observed trends. However, climate model simulations forced with increasing greenhouse gases suggest that the observed shift is most likely to be a response of global warming. The displacement of ocean gyres, which is coupled with the poleward shift of extratropical atmospheric circulation, has broad impacts on ocean heat transport, regional sea level rise and coastal ocean circulation.

Population exposure to pre-emptive de-energization aimed at averting wildfires in Northern California

Environmental Research Letters (IOP) | August 26th, 2020

Recent extreme fire seasons in California have prompted utilities such as Pacific Gas and Electric to pre-emptively de-energize portions of the electrical grid during per

Recent extreme fire seasons in California have prompted utilities such as Pacific Gas and Electric to pre-emptively de-energize portions of the electrical grid during periods of extreme fire weather to reduce the risk of powerline-related fire ignitions. The policy was deployed in 2019, resulting in 12 million person-days of power outages and widespread societal disruption. Retrospective weather and vegetation moisture data highlight hotspots of historical risk across northern California. We estimate an average of 1.6 million person-days of de-energization per year, based on recent historical climate conditions and assuming publicly stated utility de-energization thresholds. We further estimate an additional 70% increase in the population affected by de-energization when vegetation remains abnormally dry later into autumn—suggesting that climate change will likely increase population vulnerable to de-energization. Adaptation efforts to curtail fire risk can be beneficial, but efforts to prepare affected populations, modernize the grid, and refine decision-making surrounding such policies have high potential to reduce the magnitude of negative externalities experienced during the 2019 de-energization events.

Potential evapotranspiration and continental drying

Nature Portfolio (Springer Nature) | June 6th, 2016

By various measures (drought area and intensity, climatic aridity index, and climatic water deficits), some observational analyses have suggested that much of the Earth�

By various measures (drought area and intensity, climatic aridity index, and climatic water deficits), some observational analyses have suggested that much of the Earth’s land has been drying during recent decades, but such drying seems inconsistent with observations of dryland greening and decreasing pan evaporation. ‘Offline’ analyses of climate-model outputs from anthropogenic climate change (ACC) experiments portend continuation of putative drying through the twenty-first century, despite an expected increase in global land precipitation. A ubiquitous increase in estimates of potential evapotranspiration (PET), driven by atmospheric warming, underlies the drying trends, but may be a methodological artefact. Here we show that the PET estimator commonly used (the Penman–Monteith PET for either an open-water surface or a reference crop) severely overpredicts the changes in non-water-stressed evapotranspiration computed in the climate models themselves in ACC experiments. This overprediction is partially due to neglect of stomatal conductance reductions commonly induced by increasing atmospheric CO2 concentrations in climate models. Our findings imply that historical and future tendencies towards continental drying, as characterized by offline-computed runoff, as well as other PET-dependent metrics, may be considerably weaker and less extensive than previously thought.

Potential Impacts of Climate Change on Biodiversity and Ecosystem Services in the San Francisco Bay Area

California Energy Commission (CEC) | July 31st, 2012

The San Francisco Bay Area contains a rich array of plant and animal biodiversity and an extensive open space network, embedded within a major metropolitan area. Terrestr

The San Francisco Bay Area contains a rich array of plant and animal biodiversity and an extensive open space network, embedded within a major metropolitan area. Terrestrial habitats in the San Francisco Bay Area support a wide range of ecosystem services, including carbon storage, forage production, enhanced water supply and quality, crop pollination, and outdoor recreation. The distribution of habitats and plant and animal species is strongly influenced by spatial variation in climate, and is thus expected to change in response to changes in regional and global climate. Current research suggests that most vegetation types will shift toward the coast, especially under scenarios with warmer and drier conditions; range contractions and reduced diversity are projected for California endemic plants in the Bay Area. Bird communities are projected to undergo significant reorganization, leading to altered interactions and community structure. Improved modeling at fine spatial scales represents an important priority to reduce uncertainty in these projections. Climate change is expected to strongly affect ecosystem services. Carbon storage in soils and vegetation could contribute to California’s carbon emissions reduction strategy, but current models project reduced carbon storage in trees due to climate change. Altered agricultural management strategies, including conversion to perennial crops, have the potential to increase soil carbon storage. Climate change impacts on vegetation, hydrology and habitat integrity may negatively affect fire regimes, forage production, water supplies, crop pollination services, and outdoor recreation and quality of life in the San Francisco Bay Area, but few specific projections are available. Strategic conservation planning in the Bay Area is under way to enhance biodiversity conservation through continued open space acquisition. Conservation of heterogeneous landscapes will provide resilience in the face of climate change. Improved understanding of projected climate change impacts on natural habitats will contribute to the development of regional adaptation strategies.