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Human Impacts on Regional Avian Diversity and Abundance

Authors

  • CHRISTOPHER A. LEPCZYK,

    Corresponding author
    1. Department of Forest Ecology and Management, University of Wisconsin–Madison, Madison, WI 53706, U.S.A.
    2. Center for Systems Integration and Sustainability, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, U.S.A.
      **Current address: Department of Natural Resources and Environmental Management, University of Hawai'i at Mānoa, Honolulu, HI 96822, U.S.A., email lepczyk@hawaii.edu
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  • CURTIS H. FLATHER,

    1. USDA Forest Service, Rocky Mountain Research Station, Fort Collins, CO 80526, U.S.A.
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  • VOLKER C. RADELOFF,

    1. Department of Forest Ecology and Management, University of Wisconsin–Madison, Madison, WI 53706, U.S.A.
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  • ANNA M. PIDGEON,

    1. Department of Forest Ecology and Management, University of Wisconsin–Madison, Madison, WI 53706, U.S.A.
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  • ROGER B. HAMMER,

    Corresponding author
    1. Department of Rural Sociology, University of Wisconsin-Madison, Madison, WI 53706, U.S.A.
      ††Current address: Department of Sociology, Oregon State University, Corvallis, OR 97331, U.S.A.
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  • JIANGUO LIU

    1. Center for Systems Integration and Sustainability, Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 48824, U.S.A.
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**Current address: Department of Natural Resources and Environmental Management, University of Hawai'i at Mānoa, Honolulu, HI 96822, U.S.A., email lepczyk@hawaii.edu

††Current address: Department of Sociology, Oregon State University, Corvallis, OR 97331, U.S.A.

Abstract

Abstract: Patterns of association between humans and biodiversity typically show positive, negative, or negative quadratic relationships and can be described by 3 hypotheses: biologically rich areas that support high human population densities co-occur with areas of high biodiversity (productivity); biodiversity decreases monotonically with increasing human activities (ecosystem stress); and biodiversity peaks at intermediate levels of human influence (intermediate disturbance). To test these hypotheses, we compared anthropogenic land cover and housing units, as indices of human influence, with bird species richness and abundance across the Midwestern United States. We modeled richness of native birds with 12 candidate models of land cover and housing to evaluate the empirical evidence. To assess which species were responsible for observed variation in richness, we repeated our model-selection analysis with relative abundance of each native species as the response and then asked whether natural-history traits were associated with positive, negative, or mixed responses. Native avian richness was highest where anthropogenic land cover was lowest and housing units were intermediate based on model-averaged predictions among a confidence set of candidate models. Eighty-three of 132 species showed some pattern of association with our measures of human influence. Of these species approximately 40% were negatively associated, approximately 6% were positively associated, and approximately 7% showed evidence of an intermediate relationship with human influence measures. Natural-history traits were not closely related to the direction of the relationship between abundance and human influence. Nevertheless, pooling species that exhibited any relationship with human influence and comparing them with unrelated species indicated they were significantly smaller, nested closer to the ground, had shorter incubation and fledging times, and tended to be altricial. Our results support the ecosystem-stress hypothesis for the majority of individual species and for overall species diversity when focusing on anthropogenic land cover. Nevertheless, the great variability in housing units across the land-cover gradient indicates that an intermediate-disturbance relationship is also supported. Our findings suggest preemptive conservation action should be taken, whereby areas with little anthropogenic land cover are given conservation priority. Nevertheless, conservation action should not be limited to pristine landscapes because our results showed that native avian richness and the relative abundance of many species peaked at intermediate housing densities and levels of anthropogenic land cover.

Abstract

Resumen: Los patrones de asociación entre humanos y biodiversidad típicamente muestran relaciones negativas o cuadráticas negativas y pueden ser descritas por 3 hipótesis: áreas biológicamente ricas con densidades humanas altas co-ocurren con áreas de biodiversidad (productividad) alta; la biodiversidad decrece monotónicamente con el incremento de las actividades humanas (estrés del ecosistema); y la biodiversidad alcanza picos en niveles intermedios de influencia humana (perturbación intermedia). Para probar estas hipótesis, comparamos la cobertura de suelo antropogénica y las unidades de vivienda, como índices de la influencia humana, con la riqueza y abundancia de especies de aves en el medio oeste de Estados Unidos. Modelamos la riqueza de aves nativas con 12 modelos de cobertura de suelo y viviendas para evaluar la evidencia empírica. Para evaluar cuales especies eran responsables de la variación observada en la riqueza, repetimos nuestro análisis de selección de modelos con la abundancia relativa de cada especie nativa como la respuesta y luego preguntamos si los atributos de la historia natural estaban asociados con las respuestas positivas, negativas o mixtas. La riqueza de aves nativas fue mayor donde la cobertura de suelo antropogénica fue menor y las unidades de vivienda fueron intermedias con base en predicciones de modelos entre un conjunto de confianza de modelos posibles. Ochenta y tres de 132 especies mostraron algún patrón de asociación con nuestras medidas de influencia humana. De estas especies, approximately 40% se asociaron negativamente, approximately 6% se asociaron positivamente y approximately 7% mostraron evidencias de una relación intermedia con las medidas de influencia humana. Los atributos de historia natural no se relacionaron estrechamente con la dirección de la relación entre la abundancia y la influencia humana. Sin embargo, al combinar especies que mostraron alguna relación con la influencia humana y compararlas con especies no relacionadas encontramos que eran significativamente menores en tamaño, anidaban más cerca del suelo, tenían tiempos de incubación y salida del nido más cortos y tendían a ser altriciales. Nuestros resultados soportan la hipótesis del estrés del ecosistema para la mayoría de las especies individuales y para la diversidad de especies total al considerar la cobertura de suelo antropogénico. Sin embargo, la gran variabilidad en las unidades de vivienda en el gradiente de cobertura de suelo indica que también se soporta una relación de perturbación intermedia. Nuestros resultados sugieren que se deben tomar medidas preventivas de conservación, con lo cual se daría prioridad a áreas con baja cobertura de suelo antropogénica. Sin embargo, las acciones de conservación no se deben limitar a paisajes prístinos porque nuestros resultados mostraron que la riqueza de aves nativas y la abundancia relativa de muchas especies alcanzaron su máximo en densidades intermedias de densidades de viviendas y niveles de cobertura de suelo antropogénica.

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