Future frequencies of extreme weather events in the National Wildlife Refuges of the conterminous U.S. Sebastián Martinuzzi a, ⁎, Andrew J. Allstadt a , Brooke L. Bateman a , Patricia J. Heglund b , Anna M. Pidgeon a , Wayne E. Thogmartin c , Stephen J. Vavrus d , Volker C. Radeloff a a SILVIS Lab, Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, 1630 Linden Drive, Madison, WI 53706, USA b U.S. Fish and Wildlife Service, NWRS, Region 3, 2630 Fanta Reed Road, La Crosse, WI 54603, USA c U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, WI 54603, USA d Nelson Institute Center for Climatic Research, University of Wisconsin-Madison, 1225 W. Dayton St, Madison, WI 53706, USA abstract article info Article history: Received 1 March 2016 Received in revised form 3 July 2016 Accepted 6 July 2016 Available online 1 August 2016 Climate change is a major challenge for managers of protected areas world-wide, and managers need information about future climate conditions within protected areas. Prior studies of climate change effects in protected areas have largely focused on average climatic conditions. However, extreme weather may have stronger effects on wildlife populations and habitats than changes in averages. Our goal was to quantify future changes in the fre- quency of extreme heat, drought, and false springs, during the avian breeding season, in 415 National Wildlife Refuges in the conterminous United States. We analyzed spatially detailed data on extreme weather frequencies during the historical period (1950–2005) and under different scenarios of future climate change by mid- and late-21st century. We found that all wildlife refuges will likely experience substantial changes in the frequencies of extreme weather, but the types of projected changes differed among refuges. Extreme heat is projected to in- crease dramatically in all wildlife refuges, whereas changes in droughts and false springs are projected to increase or decrease on a regional basis. Half of all wildlife refuges are projected to see increases in frequency (N 20% higher than the current rate) in at least two types of weather extremes by mid-century. Wildlife refuges in the South- west and Pacific Southwest are projected to exhibit the fastest rates of change, and may deserve extra attention. Climate change adaptation strategies in protected areas, such as the U.S. wildlife refuges, may need to seriously consider future changes in extreme weather, including the considerable spatial variation of these changes. © 2016 Elsevier Ltd. All rights reserved. Keywords: Protected areas Climate change Conservation planning Droughts Extreme heat False springs 1. Introduction Protected areas are a cornerstone for biodiversity conservation, and climate change represents one of the major challenges for managers of protected areas globally (Hole et al., 2009; Lawler, 2009). As climate changes, conditions within protected areas are also expected to change, potentially triggering shifts in species and changing ecosystem proper- ties (Langdon and Lawler, 2015; Wiens et al., 2011). Conserving biodi- versity into the future therefore, requires understanding future climatic conditions in protected areas (Hannah, 2008). Most studies assessing effects of climate change on biodiversity and protected areas have focused on climate averages, e.g. changes in mean temperature or precipitation, rather than potential changes in the fre- quency of extreme weather such as prolonged droughts, extreme heat, or unseasonable cold periods (Garcia et al., 2014; Loarie et al., 2009; Scriven et al., 2015; Wiens et al., 2011). However, studying the changes in extremes explicitly allows for better interpretation of the consequences for protected area managers, because extreme weather events can pose stronger threats to species and ecosystems, and make habitat management more challenging, than shifts in average condi- tions (Reyer et al., 2013). Increased frequency or intensity of extreme heat and droughts can facilitate plant invasions (Jiménez et al., 2011), increase tree mortality (Allen et al., 2010), reduce avian breeding suc- cess and survival (Jenouvrier, 2013), and trigger species movement and range shifts, potentially changing community composition, re- source availability, and ecosystem properties (Parmesan et al., 2000). For example, the Dickcissel (Spiza americana), a grassland bird species of the U.S. Midwest, exhibits strong abundance shifts at its range edges during drought events compared to years of average precipitation (Bateman et al., 2015). In Mediterranean forests, droughts can trigger widespread tree defoliation that disrupts insect and fungal communities and alters food webs (Carnicer et al., 2011). At times when managers are trying to initiate a restoration, flood a wetland management unit, or perform some other management action, droughts may prevent implementing the desired management action at the most beneficial time (Dale et al., 2001; Thurow and Taylor, 1999). In general, extreme heat and drought are projected to become more frequent in some Biological Conservation 201 (2016) 327–335 ⁎ Corresponding author. E-mail address: martinuzzi@wisc.edu (S. Martinuzzi). http://dx.doi.org/10.1016/j.biocon.2016.07.007 0006-3207/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/bioc