South Coast

Identifying organic contaminants at trespass cannabis grows on federal land in California, USA

Elsevier | September 25th, 2025

Despite the legalization of recreational cannabis in California, USA, illegal cannabis cultivation remains pervasive, partly through the establishment of illegal cult

Despite the legalization of recreational cannabis in California, USA, illegal cannabis cultivation remains pervasive, partly through the establishment of illegal cultivation on public lands (trespass grows). These operations often illegally divert water for irrigation and perform unauthorized applications of chemical fertilizers and pesticides. This work investigates a broad suite of these chemicals, focusing on their persistence in topsoil and presence in water and bed sediment in adjacent streams. Quantitative analyses of pesticides were conducted (183 compounds in water; 176 in topsoil/bed sediment), supplemented by qualitative nontargeted screening at three trespass grows that had no active cultivation for 8 months to 2 years. Targeted multi-residue analysis of topsoil detected the insecticides bifenthrin, cyfluthrin, malathion and imidacloprid (with concentrations up to 38 ng/g dry weight, d.w.), and the fungicides fluopyram, myclobutanil, and triadimefon (concentrations up to 8.1 ng/g d.w.). No pesticides were detected in the companion water or streambed sediment samples from adjacent streams. In addition, no water samples were found to have measurable estrogenic activity. Nontargeted screening uncovered additional pesticides (i.e., spiromesifen, trinexapac) in the topsoil and cannabis-related compounds (i.e., cannabidol, delta9-tetrahydrocannabinol) in both topsoil and streambed sediment suggesting the likelihood of offsite transport of cannabis related compounds. Phthalate plasticizers, rubber-related compounds, pharmaceuticals and personal care product chemicals were detected in topsoil, water, and streambed sediment and may be related to extensive irrigation infrastructure installed at these trespass grows. This work begins to establish a contaminant profile associated with illegal cannabis growing activities, providing a foundation for future research focused on their potential ecological impacts.

Identifying the Amount of Wastewater that is Available and Feasible to Recycle in California

Water Research Foundation (WRF) | July 24th, 2023

Identifying wastewater chemicals in coastal aerosols

American Association for the Advancement of Science (AAAS) | May 28th, 2025

The Tijuana River, at the US-Mexico border, discharges millions of gallons of wastewater daily—sewage, industrial waste, and runoff—into the Pacific Ocean, making it

The Tijuana River, at the US-Mexico border, discharges millions of gallons of wastewater daily—sewage, industrial waste, and runoff—into the Pacific Ocean, making it the dominant source of coastal pollution in this region. This study examines how such wastewater influences coastal aerosols by tracking spatial gradients from near the border northward. Using benzoylecgonine (a nonvolatile cocaine metabolite) as a sewage tracer, we find that wastewater compounds—including a mixture of illicit drugs, drug metabolites, and chemicals from tires and personal care products—become aerosolized and are detectable in both water and air. Spatial analyses confirm that most measured chemicals concentrate in aerosols near the Tijuana River, potentially exposing local populations to tens of nanograms per hour (e.g., octinoxate and methamphetamine) via inhalation. This airborne pathway highlights a largely overlooked source of atmospheric pollution, emphasizing the need to reassess health risks in coastal regions as global water contamination continues to escalate.

Impact of underground storm drain systems on larval ecology of Culex and Aedes species in urban environments of Southern California

Nature Portfolio (Springer Nature) | July 16th, 2021

An extensive network of storm water conveyance systems in urban areas, often referred to as the “underground storm drain system” (USDS), serves as significant product

An extensive network of storm water conveyance systems in urban areas, often referred to as the “underground storm drain system” (USDS), serves as significant production habitats for mosquitoes. Knowledge of whether USDS habitats are suitable for newly introduced dengue vectors Aedes aegypti and Ae. albopictus will help guide surveillance and control efforts. To determine whether the USDS functions as a suitable larval habitat for Culex, Ae. aegypti and Ae. albopictus in southern California, we examined mosquito habitat utilization and larval survivorship using laboratory microcosm studies. The data showed that USDS constituted 4.1% of sampled larval habitats for Ae. aegypti and Ae. albopictus, and 22.0% for Cx. quinquefasciatus. Furthermore, USDS water collected in the summer completely inhibited Aedes larval development, but yielded a 15.0% pupation rate for Cx. quinquefasciatus. Food supplementation in the microcosms suggests that nutrient deficiency, toxins and other factors in the USDS water led to low success or complete failure of larval development. These results suggest that USDS habitats are currently not major productive larval habitats for Aedes mosquitoes in southern California. Our findings prompt inclusion of assessments of pupal productivity in USDS habitats and adult mosquito resting sites in the mosquito surveillance program.

Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming

Wiley | February 21st, 2013

Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, a

Ocean acidification represents a threat to marine species worldwide, and forecasting the ecological impacts of acidification is a high priority for science, management, and policy. As research on the topic expands at an exponential rate, a comprehensive understanding of the variability in organisms' responses and corresponding levels of certainty is necessary to forecast the ecological effects. Here, we perform the most comprehensive meta‐analysis to date by synthesizing the results of 228 studies examining biological responses to ocean acidification. The results reveal decreased survival, calcification, growth, development and abundance in response to acidification when the broad range of marine organisms is pooled together. However, the magnitude of these responses varies among taxonomic groups, suggesting there is some predictable trait‐based variation in sensitivity, despite the investigation of approximately 100 new species in recent research. The results also reveal an enhanced sensitivity of mollusk larvae, but suggest that an enhanced sensitivity of early life history stages is not universal across all taxonomic groups. In addition, the variability in species' responses is enhanced when they are exposed to acidification in multi‐species assemblages, suggesting that it is important to consider indirect effects and exercise caution when forecasting abundance patterns from single‐species laboratory experiments. Furthermore, the results suggest that other factors, such as nutritional status or source population, could cause substantial variation in organisms' responses. Last, the results highlight a trend towards enhanced sensitivity to acidification when taxa are concurrently exposed to elevated seawater temperature.

Implementing Climate-Smart Conservation

Public Policy Institute of California (PPIC) | March 4th, 2025

In our first report, Climate-Smart Tools to Protect California’s Freshwater Biodiversity (Sommer et al. 2024), we reviewed a broad suite of tools available to a

In our first report, Climate-Smart Tools to Protect California’s Freshwater Biodiversity (Sommer et al. 2024), we reviewed a broad suite of tools available to address the urgent problem of safeguarding California’s freshwater biodiversity in the changing climate. This toolbox includes some familiar approaches—such as various ways to improve freshwater habitat—as well as approaches that may be less familiar, more experimental, and more controversial. We also recommended the adoption of a climate-smart conservation planning process, involving a broad range of stakeholders, to prioritize the selection of tools within watersheds and to adaptively implement those tools. In this follow-up report, we explore the feasibility of implementing these tools and climate-smart planning in light of legal, policy, and institutional factors.2 Our analysis draws on an extensive review of the legal literature on ecosystem and protected species management, as well as interviews and small workshops with a wide-ranging set of 45 experts from all over the state. These experts are working on the frontlines of ecosystem policy and management; they include state and federal regulators, members of the environmental conservation community, legal professionals, and representatives of many entities involved in water and land management.

Implications of projected climate change for groundwater recharge in the western United States

Journal of Hydrology (Elsevier) | March 1st, 2016

Existing studies on the impacts of climate change on groundwater recharge are either global or basin/location-specific. The global studies lack the specificity to inform

Existing studies on the impacts of climate change on groundwater recharge are either global or basin/location-specific. The global studies lack the specificity to inform decision making, while the local studies do little to clarify potential changes over large regions (major river basins, states, or groups of states), a scale often important in the development of water policy. An analysis of the potential impact of climate change on groundwater recharge across the western United States (west of 100 longitude) is presented synthesizing existing studies and applying current knowledge of recharge processes and amounts. Eight representative aquifers located across the region were evaluated. For each aquifer published recharge budget components were converted into four standard recharge mechanisms: diffuse, focused, irrigation, and mountain-systems recharge. Future changes in individual recharge mechanisms and total recharge were then estimated for each aquifer. Model-based studies of projected climate-change effects on recharge were available and utilized for half of the aquifers. For the remainder, forecasted changes in temperature and precipitation were logically propagated through each recharge mechanism producing qualitative estimates of direction of changes in recharge only (not magnitude). Several key patterns emerge from the analysis. First, the available estimates indicate average declines of 10–20% in total recharge across the southern aquifers, but with a wide range of uncertainty that includes no change. Second, the northern set of aquifers will likely incur little change to slight increases in total recharge. Third, mountain system recharge is expected to decline across much of the region due to decreased snowpack, with that impact lessening with higher elevation and latitude. Factors contributing the greatest uncertainty in the estimates include: (1) limited studies quantitatively coupling climate projections to recharge estimation methods using detailed, process-based numerical models; (2) a generally poor understanding of hydrologic flowpaths and processes in mountain systems; (3) difficulty predicting the response of focused recharge to potential changes in the frequency and intensity of extreme precipitation events; and (4) unconstrained feedbacks between climate, irrigation practices, and recharge in highly developed aquifer systems.

Importance of subsurface water for hydrological response during storms in a post-wildfire bedrock landscape

Nature Portfolio (Springer Nature) | June 29th, 2023

Improving Groundwater Security in the United States

The White House | December 14th, 2024

The U.S. is facing a serious and unprecedented groundwater challenge. In many aquifers, groundwater withdrawal has outpaced natural recharge, which is exacerbated by the

The U.S. is facing a serious and unprecedented groundwater challenge. In many aquifers, groundwater withdrawal has outpaced natural recharge, which is exacerbated by the changing climate and precipitation variability. Much of the water in the major aquifers in the U.S. is fossil water, recharged over 10,000 years ago, and will not be replaced naturally on human timescales. In the western U.S., groundwater resources are being depleted at alarming rates, mostly from agricultural withdrawal. The depletion has caused land subsidence and earth fissures as well as permanent reduction of storage capacity. The depletion has national and global consequences as non-renewable groundwater in the west is embedded in agricultural products transported to the rest of the U. S. and in agricultural commodities exported globally. Many federal agencies have programs to measure the quality and quantity of groundwater, as well as conservation programs for sustainable use of groundwater. PCAST applauds and endorses their efforts as well as those by state governments, non-governmental organizations, professional organizations, local communities, private citizens, and others, to manage their groundwater resources. To ensure the sustainability of this indispensable resource and mitigate risks from its depletion, it is imperative that we enhance our understanding and management of groundwater resources.

Inaction’s Economic Cost for California’s Water Supply Challenges

University of California, Davis (UC Davis) | May 14th, 2025

California’s water system is in for challenges in coming decades as climate, groundwater policy, and environmental regulations reduce availability and increase variabil

California’s water system is in for challenges in coming decades as climate, groundwater policy, and environmental regulations reduce availability and increase variability in water supplies for agricultural and urban uses. A previous report estimated 4 to 9 million acre-feet (maf) per year of unavoidable reductions in existing water supplies, 12% to 25% of today’s water use (Lund et al. 2024). This report estimates the economic costs of not responding to these reductions in water availability.