Editing Colorado River (section)

===Wildlife and plants===
{{further|List of flora of the Lower Colorado River Valley}}
[[Image:Topockgorge.jpg|thumb|right|alt=View of a wide river flowing through a forested area, with jagged mountains in the background|Heavily forested banks of the Colorado River near [[Topock, Arizona]]]]

The Colorado River and its tributaries often nourish extensive corridors of [[riparian zone|riparian]] growth as they traverse the arid desert regions of the watershed. Although riparian zones represent a relatively small proportion of the basin and have been affected by engineering projects and river diversion in many places, they have the greatest biodiversity of any habitat in the basin.<ref>{{cite web |url=http://cpluhna.nau.edu/Biota/riparian_communities.htm |title=Biotic Communities of the Colorado Plateau: Riparian Areas |publisher=Northern Arizona University |work=Land Use History of North America |access-date=February 23, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120213105737/http://www.cpluhna.nau.edu/Biota/riparian_communities.htm |archive-date=February 13, 2012}}</ref> The most prominent riparian zones along the river occur along the lower Colorado below Davis Dam,<ref>{{cite web |title=The Ecology of the Lower Colorado River from Davis Dam to the Mexico-United States International Boundary: A Community Profile |url=http://www.nwrc.usgs.gov/techrpt/85-7-19.pdf |publisher=U.S. Fish and Wildlife Service |date=September 1988 |first1=Robert D. |last1=Ohmart |first2=Bertin W. |last2=Anderson |first3=William C. |last3=Hunter |pages=9, 12, 14 |access-date=June 29, 2013 |archive-date=June 3, 2013 |archive-url=https://web.archive.org/web/20130603002626/http://www.nwrc.usgs.gov/techrpt/85-7-19.pdf |url-status=live }}</ref> especially in the Colorado River Delta, where riparian areas support 358 species of birds despite the reduction in freshwater flow and invasive plants such as [[Tamarix|tamarisk]] (salt cedar).<ref>{{cite journal |url=http://www.lvwash.org/assets/pdf/resources_ecoresearch_birds_journal.pdf |title=Restoring Habitat for Riparian Birds in the Lower Colorado River Watershed: An Example from the Las Vegas Wash, Nevada |journal=Journal of Arid Environments |date=2011 |pages=1182–1190 |doi=10.1016/j.jaridenv.2011.06.017 |author1=Shanahan, S.A. |author2=Nelson, S.M. |author3=Van Dooremolen, D.M. |author4=Eckberg, J.R. |volume=75 |issue=11 |bibcode=2011JArEn..75.1182S |access-date=February 24, 2012 |archive-date=January 20, 2013 |archive-url=https://web.archive.org/web/20130120034136/http://www.lvwash.org/assets/pdf/resources_ecoresearch_birds_journal.pdf |url-status=dead}}</ref> Reduction of the delta's size has also threatened animals such as jaguars and the [[vaquita]] porpoise, which is endemic to the gulf.<ref>{{cite web |author=Alles, David L. |url=http://fire.biol.wwu.edu/trent/alles/TheDelta.pdf |title=The Delta of the Colorado River |publisher=Western Washington University |date=August 8, 2007 |access-date=February 23, 2012 |archive-date=June 20, 2012 |archive-url=https://web.archive.org/web/20120620100453/http://fire.biol.wwu.edu/trent/alles/TheDelta.pdf |url-status=live }}</ref> Human development of the Colorado River has also helped to create new riparian zones by smoothing the river's seasonal flow, notably through the Grand Canyon.<ref>{{cite web |author1=Schell, Robert |author2=King, Morgan E. |url=https://www.geology.ucdavis.edu/~shlemonc/html/trips/Grand%20Canyon%20web/html/flogs/PDFs/structuralvegetation.pdf |archive-url=https://wayback.archive-it.org/all/20111206211357/https://www.geology.ucdavis.edu/~shlemonc/html/trips/Grand%20Canyon%20web/html/flogs/PDFs/structuralvegetation.pdf |url-status=dead |archive-date=December 6, 2011 |title=Riparian Vegetation: Structural Diversity Benefits Birds |publisher=University of California, Davis |access-date=February 23, 2012}}</ref>

More than 1,600 species of plants grow in the Colorado River watershed, ranging from the [[creosote bush]], [[saguaro cactus]], and [[Joshua tree]]s of the Sonoran and Mojave Deserts to the forests of the Rocky Mountains and other uplands, composed mainly of [[ponderosa pine]], [[subalpine fir]], [[Douglas-fir]] and [[Engelmann spruce]].{{sfn|Benke|Cushing|p=488|2005}} Before logging in the 19th&nbsp;century, forests were abundant in high elevations as far south as the Mexico–U.S. border, and runoff from these areas nourished abundant grassland communities in river valleys. Some arid regions of the watershed, such as the upper Green River valley in Wyoming, Canyonlands National Park in Utah and the [[San Pedro River (Arizona)|San Pedro River]] valley in Arizona and Sonora, supported extensive reaches of grassland roamed by large mammals such as [[American bison|buffalo]] and [[pronghorn|antelope]] as late as the 1860s. Near Tucson, Arizona, "where now there is only powder-dry desert, the grass once reached as high as the head of a man on horse back".<ref>{{cite web |url=http://www.nps.gov/history/history/online_books/colorado/chap3a.htm |title=Status of Plant and Animal Life |publisher=U.S. National Park Service |work=A Survey of the Recreational Resources of the Colorado River Basin |date=September 6, 2004 |access-date=February 23, 2012 |archive-date=May 1, 2014 |archive-url=https://web.archive.org/web/20140501135622/http://www.nps.gov/history/history/online_books/colorado/chap3a.htm |url-status=live }}</ref>

Rivers and streams in the Colorado basin were once home to 49 species of native fish, of which 42 were [[endemic species|endemic]]. Engineering projects and river regulation have led to the extinction of four species and severe declines in the populations of 40 species.{{sfn|Benke|Cushing|p=493|2005}} [[Bonytail chub]], [[razorback sucker]], [[Colorado pikeminnow]], and [[humpback chub]] are among those considered the most at risk; all are unique to the Colorado River system and well adapted to the river's natural silty conditions and flow variations. Clear, cold water released by dams has significantly changed characteristics of habitat for these and other Colorado River basin fishes.<ref>{{cite web |url=http://www.feow.org/ecoregion_details.php?eco=130 |title=130: Colorado |publisher=Freshwater Ecoregions of the World |date=January 11, 2012 |access-date=February 23, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120618091541/http://www.feow.org/ecoregion_details.php?eco=130 |archive-date=June 18, 2012}}</ref> A further 40 species that occur in the river today, notably the [[brown trout]], were introduced during the 19th and 20th&nbsp;centuries, mainly for sport fishing.<ref>{{cite web |url=http://www.defenders.org/wildlife_and_habitat/wildlife/colorado_river_basin_fish.php |title=Colorado River Basin Fish |publisher=Defenders of Wildlife |archive-url=https://web.archive.org/web/20110406174223/http://www.defenders.org/wildlife_and_habitat/wildlife/colorado_river_basin_fish.php |archive-date=April 6, 2011}}</ref>