Contributed Paper Effect of Widespread Agricultural Chemical Use on Butterfly Diversity across Turkish Provinces BURAK K. PEKIN Institute for Conservation Research, San Diego Zoo Global, 15600 San Pasqual Valley Road, Escondido, CA 92027, U.S.A., email bpekin@sandiegozoo.org Abstract: Although agricultural intensification is thought to pose a significant threat to species, little is known about its role in driving biodiversity loss at regional scales. I assessed the effects of a major component of agricultural intensification, agricultural chemical use, and land-cover and climatic variables on butterfly diversity across 81 provinces in Turkey, where agriculture is practiced extensively but with varying degrees of intensity. I determined butterfly species presence in each province from data on known butterfly distributions and calculated agricultural chemical use as the proportion of agricultural households that use chemical fertil- izers and pesticides. I used constrained correspondence analyses and regression-based multimodel inference to determine the effect of environmental variables on species composition and richness, respectively. The variation in butterfly species composition across the provinces was largely explained (78%) by the combi- nation of agricultural chemical use, particularly pesticides, and climatic and land-cover variables. Although overall butterfly richness was primarily explained by climatic and land-cover variables, such as the area of natural vegetation cover, threatened butterfly richness and the relative number of threatened butterfly species decreased substantially as the proportion of agricultural households using pesticides increased. These findings suggest that widespread use of agricultural chemicals, or other components of agricultural intensification that may be collinear with pesticide use, pose an imminent threat to the biodiversity of Turkey. Accordingly, policies that mitigate agricultural intensification and promote low-input farming practices are crucial for protecting threatened species from extinction in rapidly industrializing nations such as Turkey. Keywords: agricultural intensification, biodiversity loss, hierarchical partitioning, industrializing nations, Mediterranean basin, multimodel inference, pesticide use Efectos del Uso Extensivo de Agroqu´ ımicos sobre la Diversidad de Mariposas en Provincias Turcas Resumen: Aunque se piensa que la intensificaci´ on agr´ ıcola representa una amenaza significativa para las especies, se sabe poco sobre su papel en la p´erdida de biodiversidad en escalas regionales. Evalu´ e los efectos de un componente principal de la intensificaci´ on agr´ ıcola, el uso de agroqu´ ımicos, la cobertura de suelo y variables clim´ aticas sobre la diversidad de mariposas en 81 provincias de Turqu´ ıa, donde la agricultura se practica extensivamente pero con diferentes niveles de intensidad. Determin´e la presencia de especies de mariposas en cada provincia a partir de datos de las distribuciones conocidas y med´ ı el uso de agroqu´ ımicos como la proporci´ on de agricultores que utilizan fertilizantes y pesticidas qu´ ımicos. Utilic´ e an´ alisis de correspondencia constre˜ nida e inferencia con multimodelos basados en regresiones para determinar el efecto de las variables ambientales sobre la composici´ on y riqueza de especies, respectivamente. La variaci´ on en la composici´ on de especies de mariposas en las provincias fue explicada principalmente (86%) por la combinaci´ on del uso de agroqu´ ımicos, particularmente pesticidas, y las variables clim´ aticas y de cobertura de suelo. Aunque la riqueza total de mariposas fue explicada primariamente por variables clim´ aticas y de cobertura de suelo, como la superficie de cubierta vegetal natural, la riqueza de mariposas amenazadas y el n´ umero relativo de especies de mariposas amenazadas disminuy´ o sustancialmente a medida que increment´ o la proporci´ on de agricultores que utilizan pesticidas. Estos resultados sugieren que el uso extensivo de agroqu´ ımicos, u otros componentes de la intensificaci´ on agr´ ıcola que pueden utilizados con pesticidas, representan una amenaza para la biodiversidad de Turqu´ ıa. En consecuencia, las pol´ ıticas que Paper submitted August 30, 2012; revised manuscript accepted March 11, 2013. 1439 Conservation Biology, Volume 27, No. 6, 1439–1448 C  2013 Society for Conservation Biology DOI: 10.1111/cobi.12103