Climate change and variability drive increasing exposure of marine heatwaves across US estuaries

Nature Portfolio (Springer Nature) | March 6th, 2025

Marine heatwaves (MHWs) are among the greatest threats to marine ecosystems, and while substantial advances have been made in oceanic MHWs, little is known about estuarin

Marine heatwaves (MHWs) are among the greatest threats to marine ecosystems, and while substantial advances have been made in oceanic MHWs, little is known about estuarine MHWs. Utilizing a temperature dataset spanning over two decades and 54 stations distributed across 20 estuaries in the United States National Estuarine Research Reserve System, we present a comprehensive analysis of estuarine MHW characteristics and trends. Long-term climate-change-driven warming is driving more frequent MHWs along the East Coast, and if trends continue, this region will be in a MHW state for ~ 1/3 of the year by the end of the century. In contrast, the vast majority of the West Coast showed no trends, highlighting the potential for future thermal refugia. The West Coast was more strongly influenced by climate variability through the enhancement/suppression of MHWs during different phases of climate modes, suggesting long-term predictability potential. These results can provide guidance for management actions and planning in these critical environments.

Climate Change Scenarios for Air and Water Temperatures in the Upper San Francisco Estuary: Implications for Thermal Regimes and Delta Smelt

University of California, Davis (UC Davis) | June 10th, 2024

Climate change scenarios forecast increased drought exposure for terrestrial vertebrates in the contiguous United States

Nature Portfolio (Springer Nature) | November 15th, 2024

Climate change vulnerability of native and alien freshwater fishes of California: A systematic assessment approach

PLOS | May 22nd, 2013

Freshwater fishes are highly vulnerable to human-caused climate change. Because quantitative data on status and trends are unavailable for most fish species, a

Freshwater fishes are highly vulnerable to human-caused climate change. Because quantitative data on status and trends are unavailable for most fish species, a systematic assessment approach that incorporates expert knowledge was developed to determine status and future vulnerability to climate change of freshwater fishes in California, USA. The method uses expert knowledge, supported by literature reviews of status and biology of the fishes, to score ten metrics for both (1) current status of each species (baseline vulnerability to extinction) and (2) likely future impacts of climate change (vulnerability to extinction). Baseline and climate change vulnerability scores were derived for 121 native and 43 alien fish species. The two scores were highly correlated and were concordant among different scorers. Native species had both greater baseline and greater climate change vulnerability than did alien species. Fifty percent of California’s native fish fauna was assessed as having critical or high baseline vulnerability to extinction whereas all alien species were classified as being less or least vulnerable. For vulnerability to climate change, 82% of native species were classified as highly vulnerable, compared with only 19% for aliens. Predicted climate change effects on freshwater environments will dramatically change the fish fauna of California. Most native fishes will suffer population declines and become more restricted in their distributions; some will likely be driven to extinction. Fishes requiring cold water (,22uC) are particularly likely to go extinct. In contrast, most alien fishes will thrive, with some species increasing in abundance and range. However, a few alien species will likewise be negatively affected through loss of aquatic habitats during severe droughts and physiologically stressful conditions present in most waterways during summer. Our method has high utility for predicting vulnerability to climate change of diverse fish species. It should be useful for setting conservation priorities in many different regions.

Climate-Altered Wetlands Challenge Waterbird Use and Migratory Connectivity in Arid Landscapes

Nature Portfolio (Springer Nature) | March 15th, 2019

Wetlands in arid landscapes provide critical habitat for millions of migratory waterbirds across the world and throughout their annual cycle. The scope and scale

Wetlands in arid landscapes provide critical habitat for millions of migratory waterbirds across the world and throughout their annual cycle. The scope and scale of understanding avian use of these wetlands in conjunction with changes in climate are daunting yet critical to address lest we lose continent-wide migratory pathways. Here, we assess changes in waterbird use of North America’s Pacific Flyway in the Great Basin by examining water availability and climate trends over the past 100 years. We found recent (1980–2015) climate warming has significantly reduced the amount and shifted seasonality of water flowing into wetlands. Further, we found remarkable changes in waterbird species composition over time. We propose that a reduced hydroperiod and lower water quality from reduction in water level and flow limits sites used by waterbirds. These factors reduce chick survivorship as they cannot metabolize saline water, which makes suitable freshwater conditions a limiting resource. Collectively, climate-induced changes in Great Basin wetlands suggest a major shift in freshwater ecosystems, resulting in degradation of a continental migratory route. This work illustrates the importance of examining multi-scale changes in critical regional resources to understand their impact across a hemispheric flyway and provides a model to examine other flyways.

Climate-driven aerobic habitat loss in the California Current System

American Association for the Advancement of Science (AAAS) | May 15th, 2020

Climate warming is expected to intensify hypoxia in the California Current System (CCS), threatening its diverse and productive marine ecosystem. We analyzed past region

Climate warming is expected to intensify hypoxia in the California Current System (CCS), threatening its diverse and productive marine ecosystem. We analyzed past regional variability and future changes in the Metabolic Index, a species-specific measure of the environment’s capacity to meet temperature-dependent organismal oxygen demand. Across the traits of diverse animals, exhibits strong seasonal to interdecadal variations throughout the CCS, implying that resident species already experience large fluctuations in available aerobic habitat. For a key CCS species, northern anchovy, the long-term biogeographic distribution and decadal fluctuations in abundance are both highly coherent with aerobic habitat volume. Ocean warming and oxygen loss by 2100 are projected to decrease below critical levels in 30 to 50% of anchovies’ present range, including complete loss of aerobic habitat—and thus likely extirpation—from the southern CCS. Aerobic habitat loss will vary widely across the traits of CCS taxa, disrupting ecological interactions throughout the region.

Climate-Smart Tools to Protect California’s Freshwater Biodiversity

Public Policy Institute of California (PPIC) | May 28th, 2024

California’s freshwater ecosystems—and the native plants and animals that rely on them—have been in decline for decades. Roughly half of California’s native fresh

California’s freshwater ecosystems—and the native plants and animals that rely on them—have been in decline for decades. Roughly half of California’s native freshwater species are highly vulnerable to extinction within this century. But efforts to protect and recover native species now face an additional serious threat: climate change, which is accelerating and compounding the impacts of past and current land and water management issues. Simply working harder, using the same insufficient approaches to conservation, is unlikely to be successful. New approaches, including some that are experimental or highly controversial, are urgently needed. Although California has recently made important strides in setting goals for salmon, the state lacks a comprehensive approach to protecting native biodiversity in the face of climate change. We have identified a portfolio of actions that can help California rise to this urgent challenge.

Climatic regulation of the neurotoxin domoic acid

National Academy of Sciences (NAS) | January 9th, 2017

Domoic acid is a potent neurotoxin produced by certain marine microalgae that can accumulate in the foodweb, posing a health threat to human seafood consumers a

Domoic acid is a potent neurotoxin produced by certain marine microalgae that can accumulate in the foodweb, posing a health threat to human seafood consumers and wildlife in coastal regions worldwide. Evidence of climatic regulation of domoic acid in shellfish over the past 20 y in the Northern California Current regime is shown. The timing of elevated domoic acid is strongly related to warm phases of the Pacific Decadal Oscillation and the Oceanic Niño Index, an indicator of El Niño events. Ocean conditions in the northeast Pacific that are associated with warm phases of these indices, including changes in prevailing currents and advection of anomalously warm water masses onto the continental shelf, are hypothesized to contribute to increases in this toxin. We present an applied domoic acid risk assessment model for the US West Coast based on combined climatic and local variables. Evidence of regional- to basin-scale controls on domoic acid has not previously been presented. Our findings have implications in coastal zones worldwide that are affected by this toxin and are particularly relevant given the increased frequency of anomalously warm ocean conditions.

Collateral Damage: A citizen’s guide to fish kills and habitat degradation at the state and federal water project pumps in the Delta

Bay Institute | March 1st, 2012

Large-scale fish kills and habitat destruction aren’t an unusual occurrence at the giant federal and state pumps that export water from the Sacramento-San Joaquin Delta

Large-scale fish kills and habitat destruction aren’t an unusual occurrence at the giant federal and state pumps that export water from the Sacramento-San Joaquin Delta to agribusinesses and cities in the southern half of the state. These events are business as usual. • Every day, between 870 and 61,000 fish – including from 200 to 42,000 native and endangered fishes – are “salvaged” at the pumps. Most die in the process. • On average, over 9 million fish – representing the twenty fish species considered in this report – are “salvaged” each year at the pumps. As many as 15 million fish of all species encountered are “salvaged” each year. • Up to 40% of the total population of the endangered delta smelt and 15% of the endangered winter-run population of Chinook salmon are killed at the pumps in some years. In the first half of 2011, over 8.6 million splittail were salvaged. • Salvage estimates drastically underestimate the problem. The numbers do not factor in the results of “indirect” mortality, as high levels of export pumping disrupt fish migration, shrink the amount of non-lethal habitat available to fish species, and remove vast amounts of biomass, including fish eggs and larvae too small to be screened at the pumps. • Export pumping causes the lower San Joaquin River to flow backwards most of the year and removes the equivalent of 170 railroad boxcars of water – and the accompanying fish, other organisms, and nutrients – from the Delta ecosystem every minute. • Large numbers of fish being entrained is a problem even for species that are not currently listed as “endangered.” Killing large numbers of fish year after year cuts off population growth in response to favorable conditions and can start the species on a downward path to extinction. As the species declines, the population impacts of entrainment become proportionately larger. • Entrainment is a real problem. But the same interests in the Delta export community who claim that it isn’t also back constructing expensive new conveyance facilities such as a peripheral canal or tunnel to solve the problem that they say doesn’t exist.

Colorado River Basin Environmental Transfers Scorecard

Stanford University | March 16th, 2017

The Colorado River and its tributaries support more than 35 million people and irrigate more than four million acres of farmland. At the same time, the river supports 30

The Colorado River and its tributaries support more than 35 million people and irrigate more than four million acres of farmland. At the same time, the river supports 30 fish species found nowhere else on earth and inspires millions of visitors and residents alike with its sheer beauty. However, growing water scarcity caused by increased water use, hydrologic variability and climate change loom over all the Colorado River provides. Click here for follow-up report.