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Perspectives on bay-delta science and policy

The State of Bay–Delta Science 2008 highlighted seven emerging perspectives on science and management of the Delta. These perspectives had important effects on policy and legislation concerning management of the Delta ecosystem and water exports. From the collection of papers that make up the State of Bay–Delta Science 2016, we derive another seven perspectives that augment those published in 2008. The new perspectives address nutrient and contaminant concentrations in Delta waters, the failure of the Delta food web to support native species, the role of multiple stressors in driving species toward extinction, and the emerging importance of extreme events in driving change in the ecosystem and the water supply. The scientific advances that underpin these new perspectives were made possible by new measurement and analytic tools. We briefly discuss some of these, including miniaturized acoustic fish tags, sensors for monitoring of water quality, analytic techniques for disaggregating complex contaminant mixtures, remote sensing to assess levee vulnerability, and multidimensional hydrodynamic modeling. Despite these new tools and scientific insights, species conservation objectives for the Delta are not being met. We believe that this lack of progress stems in part from the fact that science and policy do not incorporate sufficiently long-term perspectives. Looking forward half a century was central to the Delta Visioning process, but science and policy have not embraced this conceptual breadth. We are also concerned that protection and enhancement of the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place, as required by the Delta Reform Act, has received no critical study and analysis. Adopting wider and longer science and policy perspectives immediately encourages recognition of the need for evaluation, analysis, and public discourse on novel conservation approaches. These longer and wider perspectives also encourage more attention to the opportunities provided by heavily invaded ecosystems. It is past time to turn scientific and policy attention to these issues.

California

Wintering waterfowl respond to Wetlands Reserve Program lands in the Central Valley of California

Daytime use by wintering waterfowl at Wetlands Reserve Program (WRP) sites within the northern Central Valley of California (CVC) increased dramatically after wetland restoration and was sustained for up to 8 years post-restoration. The magnitude of the increase in waterfowl density at WRP sites after wetland restoration was greater with greater densities of birds in the local area before restoration, lower amount of surrounding wetland habitat within a 1.5-km radius, greater increase in flooding after restoration, and closer proximity to flooded rice fields. Estimates of waterfowl distribution within areas sampled by weather surveillance radar suggest that 18 percent of wintering waterfowl use the more than 67,900 acres of restored and unrestored land enrolled in the WRP. Restored wetland habitat within WRP sites made up about 8 percent (30,360 acres) of the total wetland habitat within the CVC in 2007. Waterfowl use of flooded rice fields during the daytime and during wetter winters nearly tripled from 1995 to 2007 relative to use of natural wetland habitats. Recommendations An additional 104,000 acres of seasonal wetland restoration are needed to meet waterfowl conservation objectives in the CVC ( Central Valley Joint Venture 2006). Active restoration of hydrology and moist-soil management on WRP sites can help meet this objective. Waterfowl use of WRP sites can also be improved by locating sites close to flooded rice fields within local landscapes that have high pre-existing waterfowl abundance and relatively little wetland habitat. The assessment team developed spatially explicit decision support tools for prioritizing future WRP enrollments. The tools map the predicted post-restoration magnitude of waterfowl use based on site and local landscape variables.

California

Farm bill conservation programs can help meet the needs of spring-migrating waterfowl in southern Oregon-northeastern California

The Southern Oregon-Northeastern California (SONEC) region is an important migration and breeding area for Pacific Flyway waterfowl. Through a Conservation Effects Assessment Project (CEAP) partnership, the Intermountain West Joint Venture conducted a preliminary analysis of the contribution of SONEC Wetlands Reserve Program (WRP) enrollments in meeting recently established spring migrating waterfowl habitat objectives. Results suggest that WRP wetlands may meet up to 21 percent of the energetic needs for spring-migrating dabbling ducks in SONEC at North American Waterfowl Management Plan goal levels.

California;Nevada;Oregon

Maximizing the water quality benefits of wetlands in croplands

Key Takeaways Nutrient loads from croplands continue to negatively affect surface water quality, despite considerable investments in and adoption of agricultural conservation practices aimed at reducing nutrient losses. Numerous studies indicate that effective restoration and management of wetlands in and adjacent to cultivated croplands could reduce surface and subsurface nutrient loads to downstream waters. Current drainage basin-scale models do not effectively account for the local-scale processes that are important in understanding the functional variability of wetlands and their potential as conservation practices across different spatial and temporal scales. Findings presented here from a literature review and simulation modeling study help inform bottom-up field-scale modeling of nitrogen and phosphorus dynamics and improve our understanding of the capacity for wetlands to provide nutrient retention services in agricultural drainage basins to inform strategic agricultural wetland restoration

Conservation Insight

The disappearance of Guam's wildlife: New insights for herpetology, evolutionary ecology, and conservation

The wealth of data generated from intensive study of the brown tree snake as a result of the need to control introduced populations of this pest species allow several important conclusions. First, that the snakes on Guam are extraordinary in terms of their absolute abundance and in terms of their ability to exploit a broad prey base. Our data suggest an exceptionally high reproductive success on Guam for a snake with an otherwise unnoteworthy reproductive capability and life history (i.e. small clutch size, typical ontogenetic shift from small heterothermic prey to larger homeotherms). Especially important was the snakes versatility in taking advantage of extremely common prey on islands; population expansion was slow but survival was maximal, ultimately leading to high population levels. The brown tree snake shares many attributes with other snakes that could cause similar biodiversity crises in a wide variety of contexts in which they lack coevolutionary histories (especially formerly snake-free island environments). As opposed to their relatively poor history as over-water dispersers, snakes may be especially problematic as travelers in increasing ship and air traffic between widely separated geographic regions of the world.

BioScience

A typology of time-scale mismatches and behavioral interventions to diagnose and solve conservation problems

Ecological systems often operate on time scales significantly longer or shorter than the time scales typical of human decision making, which causes substantial difficulty for conservation and management in socioecological systems. For example, invasive species may move faster than humans can diagnose problems and initiate solutions, and climate systems may exhibit long-term inertia and short-term fluctuations that obscure learning about the efficacy of management efforts in many ecological systems. We adopted a management-decision framework that distinguishes decision makers within public institutions from individual actors within the social system, calls attention to the ways socioecological systems respond to decision makers’ actions, and notes institutional learning that accrues from observing these responses. We used this framework, along with insights from bedeviling conservation problems, to create a typology that identifies problematic time-scale mismatches occurring between individual decision makers in public institutions and between individual actors in the social or ecological system. We also considered solutions that involve modifying human perception and behavior at the individual level as a means of resolving these problematic mismatches. The potential solutions are derived from the behavioral economics and psychology literature on temporal challenges in decision making, such as the human tendency to discount future outcomes at irrationally high rates. These solutions range from framing environmental decisions to enhance the salience of long-term consequences, to using structured decision processes that make time scales of actions and consequences more explicit, to structural solutions aimed at altering the consequences of short-sighted behavior to make it less appealing. Additional application of these tools and long-term evaluation measures that assess not just behavioral changes but also associated changes in ecological systems are needed.

Conservation Biology

Managing American Oystercatcher ( Haematopus palliatus ) population qrowth by targeting nesting season vital rates

In populations of long-lived species, adult survival typically has a relatively high influence on population growth. From a management perspective, however, adult survival can be difficult to increase in some instances, so other component rates must be considered to reverse population declines. In North Carolina, USA, management to conserve the American Oystercatcher ( Haematopus palliatus ) targets component vital rates related to fecundity, specifically nest and chick survival. The effectiveness of such a management approach in North Carolina was assessed by creating a three-stage female-based deterministic matrix model. Isoclines were produced from the matrix model to evaluate minimum nest and chick survival rates necessary to reverse population decline, assuming all other vital rates remained stable at mean values. Assuming accurate vital rates, breeding populations within North Carolina appear to be declining. To reverse this decline, combined nest and chick survival would need to increase from 0.14 to ≤ 0.27, a rate that appears to be attainable based on historical estimates. Results are heavily dependent on assumptions of other vital rates, most notably adult survival, revealing the need for accurate estimates of all vital rates to inform management actions. This approach provides valuable insights for evaluating conservation goals for species of concern.

Waterbirds

Full-service hotels, convenience stores, or fire escapes? Evaluating the functional role of stopover sites for Neotropical migrants following passage across the Gulf of Mexico in autumn

Nearctic Neotropical migratory songbirds incur the highest mortality during migration. En-route, songbirds rely on a network of stopover sites to rest, refuel, and/or seek refuge during poor weather. Conservation strategies prioritize protection of sites that best meet these needs. However, the specific function of a stopover site is expected to vary in relation to factors, such as geographic location, surrounding landscape, and weather. To identify sites with the highest conservation value for migratory songbirds, a conceptual framework was independently developed to classify sites into three functional categories based on their geographic and landscape features: fire escapes, convenience stores, and full-service hotels. The few attempts to empirically validate this framework have focused on temperate stopover sites. We evaluated the framework by testing the hypothesis that a site’s geographic and landscape characteristics can predict its function. We used capture and radio-tracking data at an island and mainland site in the Yucatan Peninsula, Mexico to quantify mean and variance in daily capture rate, body condition, stopover duration, and departure behavior during autumn, with a focus on four species: Swainson’s Thrush (Catharus ustulatus), Red-eyed Vireo (Vireo olivaceus), Gray Catbird (Dumetella carolinensis), and Prothonotary Warbler (Protonotaria citrea). Our results supported our predictions that the island functions as a fire escape, providing refuge for very high numbers of birds after encountering crosswinds or headwinds over the Gulf of Mexico, and the mainland forest site serves as a full-service hotel. The framework provides valuable insight for strategic conservation planning and management of stopover sites for songbirds. We suggest future studies evaluate the framework’s application to non-forest bird species. Additionally, we encourage collaborative efforts to consolidate and integrate tracking data, capture data from migration banding stations, and radar-based bird density estimates across a broad geography to test the framework’s ability to inform conservation planning across species’ full migratory range.

Avian Conservation and Ecology

Palila Restoration: Lessons from Long-term Research

BACKGROUND The palila (Loxioides bailleui) is a member of the Hawaiian honeycreeper family of birds (Drepanidinae), which is renowned for the profusion of species - many with bizarre bills and specialized feeding habits - that radiated from a single ancestral type. Most of the 57 or so honeycreeper species are extinct, and the palila is endangered because of its high degree of dependence on the mamane tree (Sophora chrysophylla) (Figure 1) and its restricted distribution on the upper slopes of Mauna Kea (Figure 2). Three decades of research have revealed many important facts about palila, providing the foundation and impetus for conservation programs in the wild and captivity. Additionally, an ambitious public conservation campaign arose due to the land-use conflicts on Mauna Kea. Here we summarize progress in palila conservation biology and outline steps that might overcome the remaining major challenges to its recovery. We also highlight lessons learned from palila research that may help the recovery of other Hawaiian forest birds. Palila and two closely-related species on the tiny islands of Nihoa and Laysan are the last of the seed-eating honeycreeper species in the Hawaiian Islands. About a quarter of the honeycreeper species known from living and fossil specimens had finch-like bills suited mainly for eating seeds and fruits. Because of their dietary specialization, palila are vulnerable to changes in forest size and quality, as was also likely the case for extinct species of seed specialists. Palila and many other forest bird species were once distributed in dry, lowland forests. Fossil records indicate that palila also occurred in the lowlands of O`ahu and Kaua`i until human settlement of those islands. However, because lowland habitats have been highly modified by humans and because mamane occurs today primarily at high elevation, palila are the only native bird species found exclusively in dry, subalpine habitat (2000?2850 m). Similar to other feeding specialists, palila lay few eggs, raise few young each year, and take a relatively long time to complete the nesting cycle. Low rates of reproduction result in low rates of population growth and low potential for recovery from disturbances. Long-term studies of palila offer important insights into the conservation biology of all Hawaiian forest bird species, particularly feeding specialists like the palila. Palila face many challenges common to both generalist and specialist Hawaiian honeycreeper species. Habitat loss and degradation, as well as introduced avian diseases, have reduced their numbers and limited their distribution to a very small portion of their historic range. Introduced mammals prey on palila, while alien insects reduce caterpillars that are particularly important in the diet of nestlings. Securing legal protection and funding for palila restoration has been challenging. Understanding how the palila has avoided extinction can help managers plan its recovery, and better design recovery plans for species with different feeding strategies in other habitats.

Fact Sheet

Genomics-informed delineation of conservation units in a desert amphibian

Delineating conservation units (CUs, e.g., evolutionarily significant units, ESUs, and management units, MUs) is critical to the recovery of declining species because CUs inform both listing status and management actions. Genomic data have strengths and limitations in informing CU delineation and related management questions in natural systems. We illustrate the value of using genomic data in combination with landscape, dispersal, and occupancy data, to inform CU delineation in Nevada populations of the Great Basin Distinct Population Segment of the Columbia spotted frog ( Rana luteiventris ). R. luteiventris occupies naturally fragmented aquatic habitats in this xeric region, but beaver removal, climate change, and other factors have put many of these populations at high risk of extirpation without management intervention. We addressed three objectives: (1) assessing support for ESUs within Nevada; (2) evaluating and revising, if warranted, the current delineation of MUs; and (3) evaluating genetic diversity, effective population size, adaptive differentiation, and functional connectivity to inform ongoing management actions. We found little support for ESUs within Nevada but did identify potential revisions to MUs based on unique landscape drivers of connectivity that distinguish these desert populations from those in the northern portion of the species range. Effective sizes were uniformly small, with low genetic diversity and weak signatures of adaptive differentiation. Our findings suggest that management actions, including translocations and genetic rescue, might be warranted. Our study illustrates how a carefully planned genetic study, designed to address priority management goals that include CU delineation, can provide multiple insights to inform conservation action.

Molecular Ecology

A strategy for recovering continuous behavioral telemetry data from Pacific walruses

Tracking animal behavior and movement with telemetry sensors can offer substantial insights required for conservation. Yet, the value of data collected by animal-borne telemetry systems is limited by bandwidth constraints. To understand the response of Pacific walruses ( Odobenus rosmarus divergens ) to rapid changes in sea ice availability, we required continuous geospatial chronologies of foraging behavior. Satellite telemetry offered the only practical means to systematically collect such data; however, data transmission constraints of satellite data-collection systems limited the data volume that could be acquired. Although algorithms exist for reducing sensor data volumes for efficient transmission, none could meet our requirements. Consequently, we developed an algorithm for classifying hourly foraging behavior status aboard a tag with limited processing power. We found a 98% correspondence of our algorithm's classification with a test classification based on time–depth data recovered and characterized through multivariate analysis in a separate study. We then applied our algorithm within a telemetry system that relied on remotely deployed satellite tags. Data collected by these tags from Pacific walruses across their range during 2007–2015 demonstrated the consistency of foraging behavior collected by this strategy with data collected by data logging tags; and demonstrated the ability to collect geospatial behavioral chronologies with minimal missing data where recovery of data logging tags is precluded. Our strategy for developing a telemetry system may be applicable to any study requiring intelligent algorithms to continuously monitor behavior, and then compress those data into meaningful information that can be efficiently transmitted.

Wildlife Society Bulletin

Distribution and dynamics of mangrove forests of South Asia

Mangrove forests in South Asia occur along the tidal sea edge of Bangladesh, India, Pakistan, and Sri Lanka. These forests provide important ecosystem goods and services to the region's dense coastal populations and support important functions of the biosphere. Mangroves are under threat from both natural and anthropogenic stressors; however the current status and dynamics of the region's mangroves are poorly understood. We mapped the current extent of mangrove forests in South Asia and identified mangrove forest cover change (gain and loss) from 2000 to 2012 using Landsat satellite data. We also conducted three case studies in Indus Delta (Pakistan), Goa (India), and Sundarbans (Bangladesh and India) to identify rates, patterns, and causes of change in greater spatial and thematic details compared to regional assessment of mangrove forests. Our findings revealed that the areal extent of mangrove forests in South Asia is approximately 1,187,476 ha representing ∼7% of the global total. Our results showed that from 2000 to 2012, 92,135 ha of mangroves were deforested and 80,461 ha were reforested with a net loss of 11,673 ha. In all three case studies, mangrove areas have remained the same or increased slightly, however, the turnover was greater than the net change. Both, natural and anthropogenic factors are responsible for the change and turnover. The major causes of forest cover change are similar throughout the region; however, specific factors may be dominant in specific areas. Major causes of deforestation in South Asia include (i) conversion to other land use (e.g. conversion to agriculture, shrimp farms, development, and human settlement), (ii) over-harvesting (e.g. grazing, browsing and lopping, and fishing), (iii) pollution, (iv) decline in freshwater availability, (v) floodings, (vi) reduction of silt deposition, (vii) coastal erosion, and (viii) disturbances from tropical cyclones and tsunamis. Our analysis in the region's diverse socio-economic and environmental conditions highlights complex patterns of mangrove distribution and change. Results from this study provide important insight to the conservation and management of the important and threatened South Asian mangrove ecosystem.

Journal of Environmental Management

Bridging remote sensing advances and management needs for small Prairie Pothole waterbodies using a multiscale accuracy assessment

Remote sensing of surface water provides a powerful tool to inform the management of waterfowl habitat, but there is little information available to directly assess the relative accuracy of different remote sensing datasets. Our objective was to understand how the characteristics of remotely sensed inundation datasets inform dataset accuracy, the reliable detection of small waterbodies, the distribution of surface water, observation frequency and completeness of data: all attributes relevant to the management of waterfowl habitat. We compared surface water composites from 10 remotely sensed surface water datasets from 2016 to 2021 to in-situ surface water data for three complexes of small waterbodies in the U.S. Prairie Pothole Region and evaluated their accuracy at the pixel, waterbody and local landscape scales. While all products had high per-pixel balanced accuracies (>0.75), we found distinct differences in waterbody area and landscape distribution estimates among datasets. Sentinel-1-based datasets provided a more complete set of observations over time and were more sensitive in detecting water presence in smaller waterbodies but were less accurate at identifying waterbody area than other datasets evaluated. Landsat datasets, alternatively, produced simpler landscape distributions that largely omitted the smallest waterbodies. While the datasets that either fused Sentinel-1 and −2 data collections or utilized local training data had the highest performances (e.g. balanced accuracy = 0.92), all datasets had use-case scenarios for which they may be informative. Our comparisons revealed differences that were not evident in traditional pixel-scale accuracy assessment, such as an 18-fold difference in the number of inundated waterbodies identified across remote sensing datasets. These findings provide novel insights for waterfowl conservation management on howremote sensing datasets may differ in their ability to monitor annual spring surface water presence within landscapes dominated by small waterbodies, such as the Prairie Pothole Region.

Minnesota, North Dakota

Estimating occupancy and abundance using aerial images with imperfect detection

Species distribution and abundance are critical population characteristics for efficient management, conservation, and ecological insight. Point process models are a powerful tool for modelling distribution and abundance, and can incorporate many data types, including count data, presence-absence data, and presence-only data. Aerial photographic images are a natural tool for collecting data to fit point process models, but aerial images do not always capture all animals that are present at a site. Methods for estimating detection probability for aerial surveys usually include collecting auxiliary data to estimate the proportion of time animals are available to be detected. We developed an approach for fitting point process models using an N -mixture model framework to estimate detection probability for aerial occupancy and abundance surveys. Our method uses multiple aerial images taken of animals at the same spatial location to provide temporal replication of sample sites. The intersection of the images provide multiple counts of individuals at different times. We examined this approach using both simulated and real data of sea otters ( Enhydra lutris kenyoni ) in Glacier Bay National Park, southeastern Alaska. Using our proposed methods, we estimated detection probability of sea otters to be 0.76, the same as visual aerial surveys that have been used in the past. Further, simulations demonstrated that our approach is a promising tool for estimating occupancy, abundance, and detection probability from aerial photographic surveys. Our methods can be readily extended to data collected using unmanned aerial vehicles, as technology and regulations permit. The generality of our methods for other aerial surveys depends on how well surveys can be designed to meet the assumptions of N -mixture models.

Methods in Ecology and Evolution

Do lake-specific characteristics mediate the temporal relationship between walleye growth and warming water temperatures?

Walleye ( Sander vitreus ) population declines have been linked to climate change, but it is unclear how the growth of this cool-water species may be affected by warming water temperatures. Because warming rates vary among lakes, it is uncertain whether lake characteristics may mediate the temperature effects on walleye growth or may vary as a result of differences in lake habitat or productivity. In this study, we ( i ) quantified walleye annual growth from 1983 to 2015 in 61 lakes in midwestern United States; ( ii ) estimated the relationship between annual early life growth ( ω ; mm·year –1 ) and water growing degree days (GDD); and ( iii ) identified lake characteristics affecting log e ( ω )–GDD relationships. On average, ω estimates significantly increased with increasing GDD; however, this relationship varied in direction and magnitude among lakes. We estimated an 84% posterior probability of a negative effect of water clarity on the log e ( ω )–GDD relationship, suggesting that water clarity may mediate the effect of warming water temperatures by affecting the magnitude and direction of the log e ( ω )–GDD relationship. Our results provide insights into the conservation of cool-water species in a changing environment and identify lakes characteristics in which walleye growth may be more resilient to climate change.

Minnesota, Wisconsin

Land conversion and pesticide use degrade forage areas for honey bees in America’s beekeeping epicenter

A diverse range of threats have been associated with managed bee declines globally. Recent increases of two known threats, land-use change and pesticide use, have resulted from agricultural expansion and intensification notably in the top honey producing state in the United States (U.S.): North Dakota. This study investigated the dual threat from land conversion and pesticide use surrounding ~14,000 registered apiaries in North Dakota from 2001 to 2014. We estimated the annual total insecticide use (kg) on major crops within 1.6 km of apiary sites. Of the eight insecticides, six showed significant increasing trends over the time period. Specifically, applications of the newly established neonicotinoids Chlothianidin, Imidacloprid and Thiamethoxam, increased annually by 1329 kg, 686 kg, 795 kg, respectively. Also, the use of Chlorpyrifos, which was well-established by 2001 and is highly toxic to honey bees, increased by ~8,800 kg annually from 6,500 kg in 2001 to 115,000 kg in 2014 on corn, soybeans and wheat. We further evaluated the relative quality changes of natural/semi-natural land covers surrounding apiaries in 2006, 2010 and 2014, a period of significant increases in cropland area. In areas surrounding apiaries, we observed changes in multiple indices of forage quality that reflect the deteriorating landscape surrounding registered apiary sites due to land-use change and pesticide-use increases. Overall, our results suggest that the application of foliar-applied insecticides, including pyrethroids and one organophosphate, increased surrounding apiaries when the use of neonicotinoid seed treatment surged and the area for producing corn and soybeans expanded. Spatially, these threats were most pronounced in southeastern North Dakota, a region hosting a high density of apiary sites that has recently experienced corn and soybean expansion. Our results highlight the values of natural and semi-natural land covers as sources of pollinator forage and providing refugia for bees against pesticide exposure. Our study provides insights for targeting conservation efforts to improve forage quality for benefiting managed pollinators.

North Dakota

Migrating whooping crane activity near U.S. Air Force bases and airfields in Oklahoma

The Aransas-Wood Buffalo population of Grus americana (Linnaeus, 1758; whooping cranes) migrates through the U.S. Great Plains, encountering places substantially altered by human activity. Using telemetry data from 2017 to 2022, we investigated whooping crane migration behavior around U.S. Air Force bases in Oklahoma. Our study focused on potential collision risks between whooping cranes and aircraft, a substantial concern for aviation safety. We determined that activity was greatest at Kegelman Air Force Auxiliary Airfield, near whooping crane critical habitat. On average, 61 percent of marked whooping cranes used locations west of Kegelman Air Force Auxiliary Airfield and Vance Air Force Base during autumn migration and 55 percent during spring migration, and few cranes approached within 5 kilometers of airfields. Flight characteristics revealed seasonal variations in altitude and timing; cranes flew at lower altitudes in autumn and had distinct flight patterns. Additionally, we assessed temporal aspects of migration, identifying average arrival and departure dates for spring and autumn migrations. Cranes indicated consistency in seasonal presence, which may aid in risk assessments. Our findings underscore the importance of monitoring potential interactions between whooping cranes and aircraft, particularly around whooping crane critical habitat like the Salt Plains National Wildlife Refuge in Oklahoma. Detailed summaries of migration patterns and flight behavior can be used to assist the U.S. Air Force in assessing collision risks and developing mitigation strategies. Furthermore, these summaries can provide insights for the conservation efforts of this endangered species managed by the U.S. Fish and Wildlife Service and serve as a step towards mitigating risks to aviation safety and the recovery of whooping cranes.

Oklahoma