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Aim: As climate change increases the frequency and severity of droughts in many regions, conservation during drought is becoming a major challenge for ecologists. Droughts are multidimensional climate events whose impacts may be moderated by changes in temperature, water availability or food availability, or some combination of these. Simultaneously, other stressors such as extensive anthropogenic landscape modification may synergize with drought. Useful observational models for guiding conservation decision‐making during drought require multidimensional, dynamic representations to disentangle possible drought impacts, and consequently, they will require large, highly resolved data sets. In this paper, we develop a two‐stage predictive framework for assessing how drought impacts vary with species, habitats and climate pathways. Location: Central Valley, California, USA. Methods: We used a two‐stage counterfactual analysis combining predictive linear mixed models and N‐mixture models to characterize the multidimensional impacts of drought on 66 bird species. We analysed counts from the eBird participatory science data set between 2010 and 2019 and produced species‐ and habitat‐specific estimates of the impact of drought on relative abundance. Results: We found that while fewer than a quarter (16/66) of species experienced abundance declines during drought, nearly half of all species (27/66) changed their habitat associations during drought. Among species that shifted their habitat associations, the use of natural habitats declined during drought while use of developed habitat and perennial agricultural habitat increased. Main Conclusions: Our findings suggest that birds take advantage of agricultural and developed land with artificial irrigation and heat‐buffering microhabitat structure, such as in orchards or parks, to buffer drought impacts. A working lands approach that promotes biodiversity and mitigates stressors across a human‐induced water gradient will be critical for conserving birds during drought. [ABSTRACT FROM AUTHOR]

The spatial heterogeneity related to complex topography in California demands high-resolution (< 5 km) modeling, but global convection-permitting climate models are computationally too expensive to run multi-decadal simulations. We developed a 3.25 km California climate modeling framework by leveraging regional mesh refinement (CARRM) using the U.S. Department of Energy (DOE)'s global Simple Cloud-Resolving E3SM Atmosphere Model (SCREAM) version 0. Four 5-year time periods (2015–2020, 2029–2034, 2044–2049, and 2094–2099) were simulated by nudging CARRM outside California to 1° coupled simulation of E3SMv1 under the Shared Socioeconomic Pathways (SSP)5-8.5 future scenario. The 3.25 km grid spacing adds considerable value to the prediction of the California climate changes, including more realistic high temperatures in the Central Valley and much improved spatial distributions of precipitation and snowpack in the Sierra Nevada and coastal stratocumulus. Under the SSP5-8.5 scenario, CARRM simulation predicts widespread warming of 6–10 °C over most of California, a 38 % increase in statewide average 30 d winter–spring precipitation, a near-complete loss of the alpine snowpack, and a sharp reduction in shortwave cloud radiative forcing associated with marine stratocumulus by the end of the 21st century. We note a climatological wet precipitation bias for the CARRM and discuss possible reasons. We conclude that SCREAM RRM is a technically feasible and scientifically valid tool for climate simulations in regions of interest, providing an excellent bridge to global convection-permitting simulations. [ABSTRACT FROM AUTHOR]

A three‐dimensional variably saturated flow model was developed for assessing future global water resources and parameterized for groundwater pumping. We applied this model to an actual watershed to verify its validity as an Earth System Model. For global applicability, the parameterization method for multi‐layered groundwater pumping was developed and verified through comparison with observations and MODFLOW results. The parameterization proposed in this study is applicable even when multiple groundwater pumping wells are present within one horizontal computational grid and when the well spans multiple vertical grids. This method can be applied at the global scale without parameters such as the well radius, for which data may be difficult to obtain. The parameterization recreated seasonal and annual variations in the observed values. Furthermore, the results were comparable to those of MODFLOW. However, the calculation results were overestimated relative to the observed values. This overestimation was likely to be due to active groundwater pumping in the Central Valley before the start of the unsteady‐state calculation. Therefore, the groundwater level at the beginning of the unsteady‐state calculation was calculated using observed values, improving reproducibility. Furthermore, as observed groundwater levels are unlikely to be available at the global scale, steady‐state calculations were conducted over 15 and 60 years considering groundwater pumping. However, the results were not as reproducible as those obtained using observed groundwater levels. These results suggest that the groundwater level set at the beginning of the calculation is important for global‐scale groundwater flow calculation. Plain Language Summary: Water resources are expected to become strained in the future due to climate change and population growth. The main focus of water resource assessments conducted to date has been on river water. Although groundwater is an important component of water resources, it has generally not been considered. This is largely due to the lack of groundwater models that can be applied at a global scale. Therefore, we developed a new groundwater model that was parameterized for groundwater pumping and validated in plains. The results of this study indicate that parameterization of groundwater pumping can produce reasonable results relative to observed values, and that the groundwater level set at the beginning of the calculation is important for the evaluation and prediction of global water resources. In particular, collection of observed groundwater levels or estimation of groundwater pumping are key steps toward more realistic prediction. Key Points: A three‐dimensional variably saturated flow model for use as an Earth System Model was developed and parameterized for groundwater pumpingThe validation results reproduced observations to some extent and were comparable to those of MODFLOW in the Central ValleyThe results show that setting the groundwater level at the beginning of the unsteady‐state simulation is important for global‐scale [ABSTRACT FROM AUTHOR]

An extreme precipitation event produced catastrophic debris flows in central Chile during 29–31 January 2021 (austral summer). Our study focuses on the triggering factors and dynamic behavior of hail-debris flows affecting the small commune of Malloa (Central Valley), which caused 200 injured individuals and 73 damaged houses. We carried out a post-event detailed field mapping of the local geology, the erosional features on the ravines, and its related hail-debris flow deposits. In parallel, the study involved a socio-cultural analysis of vulnerability to debris flows, with a particular focus on the disaster experience of the local community. Our results indicate that these hail-debris flows were likely conditioned by extended drought, local geomorphology, bedrock weathering/alteration, and water-oversaturated soil by two antecedent precipitation pulses. Soil erosion triggered by a hailstorm during a third precipitation pulse initiated hail-debris flows from small basins (< 1.2 km2). Basin concentration times were estimated in 6–8 min, while hail reduced flow resistance by interparticle lubrication, promoting peak flow velocities near 2.4 to 5.5 m/s. Debris flow risk management should focus on developing suitable infrastructure and installing capacities at the local level as an essential condition for implementing subsequent inter-sectoral actions (for prevention, mitigation, and design risk scenarios). [ABSTRACT FROM AUTHOR]

People seek reliable natural resources despite climate change. Diverse habitats and biologies stabilize productivity against disturbances like climate, prompting arguments to promote climate‐resilient resources by prioritizing complex, less‐modified ecosystems. These arguments hinge on the hypothesis that simplifying and degrading ecosystems will reduce resources' climate resilience, a process liable to be cryptically evolving across landscapes and human generations, but rarely documented. Here, we examined the industrial era (post 1848) of California's Central Valley, chronicling the decline of a diversified, functional portfolio of salmon habitats and life histories and investigating for empirical evidence of lost climate resilience in its fishery. Present perspectives indicate that California's dynamic, warming climate overlaid onto its truncated, degraded habitat mosaic severely constrains its salmon fishery. We indeed found substantial climate constraints on today's fishery, but this reflected a shifted ecological baseline. During the early stages of a stressor legacy that transformed the landscape and ‐‐ often consequently ‐‐ compressed salmon life history expression, the fishery diffused impacts of dry years across a greater number of fishing years and depended less on cool spring‐summer transitions. The latter are important given today's salmon habitats, salmon life histories, and resource management practices, but are vanishing with climate change while year‐to‐year variation in fishery performance is rising. These findings give empirical weight to the idea that human legacies influence ecosystems' climate resilience across landscapes and boundaries (e.g., land/sea). They also raise the question of whether some contemporary climate effects are recent and attributable not only to increasing climate stress, but to past and present human actions that erode resilience. In general, it is thus worth considering that management approaches that prioritize complex, less‐modified ecosystems may stabilize productivity despite increasing climate stress and such protective actions may be required for some ecological services to persist into uncertain climate futures. [ABSTRACT FROM AUTHOR]

Groundwater depletion is a major threat to agricultural and municipal water supply in California's Central Valley. Recent droughts during 2007–2009 and 2012–2016 exacerbated chronic groundwater depletion. However, it is unclear how much groundwater storage recovered from drought‐related overdrafts during post‐drought years, and how climatic conditions and water management affected recovery times. We estimated groundwater storage change in the Central Valley for April 2002 through September 2019 using four methods: GRACE satellite data, a water balance approach, a hydrologic simulation model, and monitoring wells. We also evaluated the sensitivity of drought recovery to different climate scenarios (recent climate ± droughts and future climate change scenarios: 20 GCMs and 2 RCPs) using water balance method and statistical sampling of historical climate data. Estimated Central Valley groundwater loss during the two droughts ranged from 19 km3 (2007–2009) to 28 km3 (2012–2016) (median of four methods). Median aquifer storage recovery was 34% and 19% of the overdraft during the 2010–2011 and 2017–2019 post‐drought years, respectively. Numerical experiments show that recovery times are sensitive to climate forcing, with longer recovery times for a future climate scenario that replicate historical climatology relative to historical forcing with no droughts. Overdraft recovery times decrease by ∼2× with implementation of pumping restrictions (30th to 50th percentiles of historical groundwater depletion) to constrain groundwater depletion relative to no restrictions with a no‐drought future climatology. This study highlights the importance of considering water management implications for future drought recoveries within the context of climate change scenarios. Plain Language Summary: California's Central Valley has experienced chronic groundwater depletion over the past few decades, the rate of which was amplified by droughts in 2007–2009 and 2012–2016. There is limited knowledge as to how much of the drought‐caused groundwater depletion has recovered during post‐drought years and how climate and water management affect overdraft recovery times. We address these issues by estimating groundwater storage changes using four methods and conducting numerical experiments with varying climatic conditions and water management options. We find that less than one‐third of the groundwater overdraft from the most recent droughts was recovered during post‐drought years. Projected overdraft recovery times vary greatly depending on the climate scenarios and water management strategies, and future droughts are likely to cause overdrafts from which recovery is unlikely given the current level of groundwater extractions. However, management measures such as capping groundwater pumping could reduce recovery times by a factor of two or more depending on the groundwater extraction cap and post‐drought climate. Key Points: Groundwater storage recovery during post‐drought periods ranged from 34% (2007–2009 drought) to 19% (2012–2016 drought)Projected drought recovery times decrease by a factor of 3.6–7.8 with post‐drought periods containing no drought years or wet years onlyOverdraft recovery time decreased by a factor of 2 with implementation of modest pumping restrictions under no‐drought post‐drought climate [ABSTRACT FROM AUTHOR]