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362 assessment of climate change in the southwest united statesFigure 16.5 Protected areas in western portion of U.S.-Mexico border region. Source: Laird-Benner and Ingram (2011) reprinted with permission from Taylor & Francis.(woodlands) (Hurd and Coonrod 2008). Native fish, neotropical songbirds, and migratorywaterfowl, including threatened and endangered species, have all declined precipitouslyin recent decades (Lacewell et al. 2010).The Colorado River delta is a significant border ecosystem that is most at risk fromincreasing regional water stress. Lacking a dedicated source of water to maintain ecologicalflows, several wetlands of high resource value are threatened, including the Ciénegade Santa Clara (see case study below) (Glenn et al. 1992; Glenn et al. 1996; Liverman etal. 1999; Pitt and Luecke 2000; Varady et al. 2001; Zamora-Arroyo and Flessa 2009). Twoprincipal vulnerabilities associated with the Lower Colorado River and delta are (1) thelack of dedicated ecological flows to sustain critical wetlands and bird habitat in thedelta; and (2) the over-allocation of Colorado River water and over-reliance of the sevenU.S. basin states and Sonora and Baja California on its water as a principal source of supply.xxvii This latter issue is addressed in the water sector analysis below; the discussionhere is on the Colorado River delta ecosystem.Likely effects of the climate changes described in Table 16.1 are primarily associatedwith increasing temperatures, declining precipitation and streamflows, and increasingextreme events (i.e., droughts). Expected effects include: constraints on available watersupply to major cities reliant on Colorado River water (MacDonald 2010; Woodhouse