Ashley E. Larsen

Eco-Label Conveys Reliable Information on Fish Stock Health to Seafood Consumers

Concerns over fishing impacts on marine populations and ecosystems have intensified the need to improve ocean management. One increasingly popular market-based instrument for ecological stewardship is the use of certification and eco-labeling programs to highlight sustainable fisheries with low environmental impacts. The Marine Stewardship Council (MSC) is the most prominent of these programs. Despite widespread discussions about the rigor of the MSC standards, no comprehensive analysis of the performance of MSC-certified fish stocks has yet been conducted. We compared status and abundance trends of 45 certified stocks with those of 179 uncertified stocks, finding that 74% of certified fisheries were above biomass levels that would produce maximum sustainable yield, compared with only 44% of uncertified fisheries. On average, the biomass of certified stocks increased by 46% over the past 10 years, whereas uncertified fisheries increased by just 9%. As part of the MSC process, fisheries initially go through a confidential pre-assessment process. When certified fisheries are compared with those that decline to pursue full certification after pre-assessment, certified stocks had much lower mean exploitation rates (67% of the rate producing maximum sustainable yield vs. 92% for those declining to pursue certification), allowing for more sustainable harvesting and in many cases biomass rebuilding. From a consumer’s point of view this means that MSC-certified seafood is 3–5 times less likely to be subject to harmful fishing than uncertified seafood. Thus, MSC-certification accurately identifies healthy fish stocks and conveys reliable information on stock status to seafood consumers.

Agricultural landscape simplification does not consistently drive insecticide use

Significance Increases in agricultural production have greatly altered land-use patterns, often resulting in simplified landscapes composed of large monocultures separated by fragments of natural lands. It is thought that these simplified landscapes enable agricultural insect pests to thrive due to an absence of predators and abundant food, necessitating greater insecticide use. Despite the logic of this theory, empirical support is lacking. Using a multiyear analysis it becomes clear that the presence and direction of the relationship between landscape simplification and insecticide use varies greatly between years. In some years more simplified landscapes have increased pest pressure, whereas in other years there is no relationship or it is reversed. Understanding the nature of this variability is critical for land use policy. The increase in agricultural production over the past 40 y has greatly altered land-use patterns, often resulting in simplified landscapes composed of large swaths of monocultures separated by small fragments of natural lands. These simplified landscapes may be more susceptible to insect pest pressure because of the loss of natural enemies and the increased size and connectivity of crop resources, and a recent analysis from a single year (2007) suggests this increased susceptibility results in increased insecticide use. I broaden the temporal analysis of this connection between landscape simplification and insecticide use by examining cross-sectional and panel data models from multiple decades (US Department of Agriculture Census of Agriculture years 2007, 2002, 1997, 1992, 1987) for seven Midwestern states composed of over 560 counties. I find that although the proportion of county in cropland—my metric for landscape simplification—was positively correlated with insecticide use in 2007, this relationship is absent or reversed in prior census years and when all years are analyzed together. This broader temporal perspective suggests that landscape simplification has inconsistent effects on insecticide use and that multiyear studies will be key to unlocking the true drivers of variation in insecticide application.

Lyme Disease Risk Influences Human Settlement in the Wildland–Urban Interface: Evidence from a Longitudinal Analysis of Counties in the Northeastern United States

The expansion of human settlement into wildland areas, including forests in the eastern United States, has resulted in fragmented forest habitat that has been shown to drive higher entomological risk for Lyme disease. We investigated an alternative pathway between fragmentation and Lyme disease, namely whether increased risk of Lyme disease results in a reduced propensity to settle in high-risk areas at the interface of developed and undeveloped lands. We used longitudinal data analyses at the county level to determine whether Lyme disease incidence (LDI) influences the proportion of the population residing in the wildland-urban interface in 12 high LDI states in the eastern United States. We found robust evidence that a higher LDI reduces the proportion of a countys population residing in the wildland-urban interface in high-LDI states. This study provides some of the first evidence of human behavioral responses to Lyme disease risk via settlement decisions.

Spatiotemporal variation in the relationship between landscape simplification and insecticide use

Agrochemicals have numerous negative impacts on human health, ecosystem services, and ecological communities. Thus, their efficient use is an economic and ecological priority. Simplified landscapes may enhance insecticide use by reducing natural enemies and increasing connectivity of crops, but empirical tests of this theory are inconclusive. We explored the relationship between landscape simplification and insecticide use using longitudinal data from USDA Census of Agriculture spanning six censuses and 25 years (1987, 1992, 1997, 2002, 2007, 2012) for nearly 3000 counties across the continental United States. The effect of landscape simplification was highly variable spatially and temporally. Landscape simplification was consistently correlated with increased insecticide use in some regions, but not in others. Our results indicate that the landscape-simplification-insecticide-use relationship is dynamic, and that national land use policy would benefit from actions that adequately reflect the spatial differences in the importance of landscape complexity to insecticide use.

Agricultural pesticide use and adverse birth outcomes in the San Joaquin Valley of California

Virtually all agricultural communities worldwide are exposed to agricultural pesticides. Yet, the health consequences of such exposure are poorly understood, and the scientific literature remains ambiguous. Using individual birth and demographic characteristics for over 500 000 birth observations between 1997–2011 in the agriculturally dominated San Joaquin Valley, California, we statistically investigate if residential agricultural pesticide exposure during gestation, by trimester, and by toxicity influences birth weight, gestational length, or birth abnormalities. Overall, our analysis indicates that agricultural pesticide exposure increases adverse birth outcomes by 5–9%, but only among the population exposed to very high quantities of pesticides (e.g., top 5th percentile, i.e., ~4200 kg applied over gestation). Thus, policies and interventions targeting the extreme right tail of the pesticide distribution near human habitation could largely eliminate the adverse birth outcomes associated with agricultural pesticide exposure documented in this study.The health consequences of exposure to pesticides are uncertain and subject to much debate. Here, the effect of exposure during pregnancy is investigated in an agriculturally dominated residential area, showing that an increase in adverse birth outcomes is observed with very high levels of pesticide exposure.

Identifying the landscape drivers of agricultural insecticide use leveraging evidence from 100,000 fields

Significance Ecological theory predicts simplified agricultural landscapes composed of large-scale, homogeneous cropland will have increased pest problems due to fewer natural enemies and concentrated host plants, which will result in increased pesticide use and associated environmental degradation. Using detailed data from Kern County, California, for 100,000 field-year observations, we parse apart how different components of landscape simplification affect insecticide use. We find insecticide use decreases with increases in crop diversity and increases with field size, whereas the effect of cropland extent depends on the spatial scale. This refined spatial perspective provides unique understanding of how different components of landscape simplification influence insecticide use, and indicates that neither the traditionally conceived “simplified” nor “complex” agricultural landscape is most beneficial to pest control. Agricultural landscape intensification has enabled food production to meet growing demand. However, there are concerns that more simplified cropland with lower crop diversity, less noncrop habitat, and larger fields results in increased use of pesticides due to a lack of natural pest control and more homogeneous crop resources. Here, we use data on crop production and insecticide use from over 100,000 field-level observations from Kern County, California, encompassing the years 2005–2013 to test if crop diversity, field size, and cropland extent affect insecticide use in practice. Overall, we find that higher crop diversity does reduce insecticide use, but the relationship is strongly influenced by the differences in crop types between diverse and less diverse landscapes. Further, we find insecticide use increases with increasing field size. The effect of cropland extent is distance-dependent, with nearby cropland decreasing insecticide use, whereas cropland further away increases insecticide use. This refined spatial perspective provides unique understanding of how different components of landscape simplification influence insecticide use over space and for different crops. Our results indicate that neither the traditionally conceived “simplified” nor “complex” agricultural landscape is most beneficial to reducing insecticide inputs; reality is far more complex.

Investigating the (Mis)Match between Natural Pest Control Knowledge and the Intensity of Pesticide Use

Transforming modern agriculture towards both higher yields and greater sustainability is critical for preserving biodiversity in an increasingly populous and variable world. However, the intensity of agricultural practices varies strongly between crop systems. Given limited research capacity, it is crucial to focus efforts to increase sustainability in the crop systems that need it most. In this study, we investigate the match (or mismatch) between the intensity of pesticide use and the availability of knowledge on the ecosystem service of natural pest control across various crop systems. Using a systematic literature search on pest control and publicly available pesticide data, we find that pest control literature is not more abundant in crops where insecticide input per hectare is highest. Instead, pest control literature is most abundant, with the highest number of studies published, in crops with comparatively low insecticide input per hectare but with high world harvested area. These results suggest that a major increase of interest in agroecological research towards crops with high insecticide input, particularly cotton and horticultural crops such as citrus and high value-added vegetables, would help meet knowledge needs for a timely ecointensification of agriculture.

High highs and low lows: Elucidating striking seasonal variability in pesticide use and its environmental implications

Despite substantial public and scientific concern regarding unintended environmental and health consequences of agricultural pesticide use, identifying when and where high levels of use occur is stymied by a dearth of data at biologically relevant spatial or temporal scales. Here we investigate intra-annual patterns in pesticide use by crop and by pesticide type using unique pesticide use data from agriculturally diverse croplands of California, USA. We find that timing and type of pesticide use is strongly crop-dependent, and that for many high pesticide use crops, monthly application rates are highly consistent from year-to-year. Further, while pesticide use hotspots are concentrated in early summer, regions with very high use occur throughout the year with spatial distributions varying therein. The enormity of intra-annual variation in pesticide use, as well as the consistency in those patterns through time, suggests opportunities for crop-specific pest management and region-specific mitigation approaches to limit environmental and human health hazards from agricultural pesticide use.

Missing the people for the trees: Identifying coupled natural‐human system feedbacks driving the ecology of Lyme disease

Infectious diseases are rapidly emerging and many are increasing in incidence across the globe. Processes of land‐use change, notably habitat loss and fragmentation, have been widely implicated in the emergence and spread of zoonoses such as Lyme disease, yet evidence remains equivocal. Here, we discuss and apply an innovative approach from the social sciences; instrumental variables, which seeks to tease out causality from observational data. Using this approach, we revisit the effect of forest fragmentation on Lyme disease incidence, focusing on human interaction with fragmented landscapes. Although human interaction with infected ticks is of clear and fundamental importance to human disease incidence, human activities that influence exposure have been largely overlooked in ecology literature. Using county‐level land‐use and Lyme disease incidence data for ~800 counties from the northeastern United States over the span of a decade, we illustrate (a) that human interaction with fragmented forest landscapes reliably predicts Lyme disease incidence, while ecological measures of forest fragmentation alone are unreliable predictors and (b) that identifying the effect of forest fragmentation on human disease entails addressing the feedback between Lyme disease risk and human decisions to avoid interaction with high‐risk landscapes. Synthesis and applications. Our innovative approach and novel results help to clarify the equivocal literature on the effects of forest fragmentation on Lyme disease and illustrate the key role that human behaviour may be playing in the ecology of Lyme disease in North America. Accounting for human activity and behaviour in the ecology of disease more broadly may result in improved understanding of both the ecological drivers of disease, as well as actionable intervention strategies to reduce disease burden in a changing world. For example, our model results indicate that forest fragmentation by human settlement increases Lyme disease incidence, which has practical implications for land‐use policy aimed at disease reduction. Specifically, our model suggests land‐use regulations that reduce parcel size would be an actionable approach to reduce Lyme disease transmission for policymakers concerned about increasing Lyme disease incidence in the northeastern United States.