Editing Yosemite National Park (section)

===Management issues===
[[File:YosemiteBlackBearTagged wb.jpg|thumb|A [[American black bear|black bear]] with an ear tag in Yosemite Valley]]
The black bears of Yosemite were once famous for breaking into parked cars to steal food. They were an encouraged tourist sight for many years at the park's garbage dumps, where they congregated to eat garbage, and tourists gathered to photograph them. Increasing bear/human encounters and increasing property damage led to an aggressive campaign to discourage bears from interacting with people and their stuff. The open-air dumps were closed; trash receptacles were replaced with [[bear-resistant food storage container|bear-proof]] receptacles; campgrounds were equipped with bear-proof food lockers so that people would not leave food in their vehicles. Because bears who show aggression towards people usually are destroyed, park personnel have come up with innovative ways to lead bears to associate humans and their property with experiences such as getting hit with a [[rubber bullet]]. {{as of|2001}}, about 30 bears a year were captured and [[ear tag|ear-tagged]] and their [[DNA]] sampled so that, when bear damage occurs, rangers can ascertain which bear was causing the problem.<ref>{{cite magazine | url= http://news.nationalgeographic.com/news/2001/04/0423_wirebears.html | archive-url= https://web.archive.org/web/20010430063837/http://news.nationalgeographic.com/news/2001/04/0423_wirebears.html | url-status= dead | archive-date= April 30, 2001 | title= DNA to Help Identify "Problem" Bears at Yosemite | magazine= National Geographic | date = April 23, 2001 | access-date=January 4, 2007}}</ref>{{update inline|date=November 2020}}

Despite the richness of high-quality habitats in Yosemite, the [[brown bear]], [[California condor]], and [[least Bell's vireo]] have become extinct in the park within historical time,<ref name = "snepTerrestrialVertebrates">{{Cite book | first = David M. | last = Graber | chapter = 25: Status of Terrestrial Vertebrates | year = 1996 | pages = 709–34 | title = Sierra Nevada Ecosystem Project. Final Report to Congress. Status of the Sierra Nevada Volume II: Assessments and Scientific Basis for Management Options | publisher = Centers for Water and Wildland Resources, University of California | url = http://pubs.usgs.gov/dds/dds-43/VOL_II/VII_C25.PDF | isbn = 1887673016 | access-date = December 10, 2014 | archive-date = June 20, 2020 | archive-url = https://web.archive.org/web/20200620143941/https://pubs.usgs.gov/dds/dds-43/VOL_II/VII_C25.PDF | url-status = live }}</ref> and another 37 species currently have special status under either California or federal [[endangered species]] legislation. The most serious current threats include loss of a natural fire regime, [[exotic species]], air pollution, [[habitat fragmentation]], and climate change. On a more local basis, factors such as [[road kill]]s and the availability of human food have affected some wildlife species.<ref>{{Cite web |last=Stephens |first=Tim |title=Yosemite bears and human food: Study reveals changing diets over past century |url=https://news.ucsc.edu/2014/03/yosemite-bears.html |access-date=2022-06-27 |website=UC Santa Cruz News |language=en |archive-date=June 18, 2022 |archive-url=https://web.archive.org/web/20220618204900/https://news.ucsc.edu/2014/03/yosemite-bears.html |url-status=live }}</ref><ref>{{Cite web |last=Hughes |first=Trevor |title=National park visitors leave roadkill in their wake |url=https://www.usatoday.com/story/news/nation/2013/07/27/national-park-road-kill/2587753/ |access-date=2022-06-27 |website=USA TODAY |language=en-US |archive-date=June 27, 2022 |archive-url=https://web.archive.org/web/20220627011811/https://www.usatoday.com/story/news/nation/2013/07/27/national-park-road-kill/2587753/ |url-status=live }}</ref>

[[File:Yellow star thistle.jpg|thumb|left|upright=0.6|The [[Centaurea solstitialis|yellow star thistle]] competes with Yosemite's native plants.<ref name = "exotic"/>]]
Yosemite National Park has documented the presence of more than 130 non-native plant species within park boundaries. They were introduced into Yosemite following the migration of early [[European colonization of the Americas|Euro-American]] settlers in the late 1850s. Natural and human-caused disturbances, such as wildland fires and construction activities, have contributed to a rapid increase in the spread of non-native plants. Some of these species invade and displace the native plant communities, impacting park resources. Non-native plants can bring about significant ecosystem changes by altering native plant communities and the processes that support them. Some non-native species may cause an increase in fire frequency or increase the available soil nitrogen that allow other non-native plants to establish. Many non-native species, such as [[Centaurea solstitialis|yellow star thistle]] (''Centaurea solstitialis''), are able to produce a long [[tap root]] that allows them to out-compete the native plants for available water.<ref name = "exotic">{{cite web | url= http://www.nps.gov/archive/yose/nature/veg_exotics.htm | archive-url=https://web.archive.org/web/20070102234435/http://www.nps.gov/archive/yose/nature/veg_exotics.htm|archive-date=January 2, 2007 | title= Exotic Plants | date = December 22, 2004| publisher= National Park Service: Yosemite National Park | access-date= January 4, 2007 }}</ref>

Bull thistle (''[[Cirsium vulgare]]''), common mullein (''[[Verbascum thapsus]]''), and Klamath weed (''[[Hypericum perforatum]]'') have been identified as noxious [[pest (organism)|pests]] in Yosemite since the 1940s. More recently recognized species are yellow star thistle (''Centaurea solstitialis''), sweet clover (''[[Melilot]]'' spp.), Himalayan blackberry (''[[Rubus armeniacus]]''), cut-leaved blackberry (''[[Rubus laciniatus]]'') and large periwinkle (''[[Vinca major]]'').<ref name = "exotic"/>

Increasing [[ozone]] pollution causes tissue damage to sequoia trees, making them more vulnerable to insect infestation and disease. Since the [[conifer cone|cones]] of these trees require fire-touched soil to [[germination|germinate]], historic [[Wildfire#Suppression|fire suppression]] has reduced their ability to reproduce. Planned [[prescribed fire]]s may help the germination issue.<ref>{{Cite web|title=Giant Sequoias and Fire – Sequoia & Kings Canyon National Parks (U.S. National Park Service)|url=https://www.nps.gov/seki/learn/nature/giant-sequoias-and-fire.htm|access-date=2021-04-08|website=www.nps.gov|language=en|archive-date=August 24, 2021|archive-url=https://web.archive.org/web/20210824004759/https://www.nps.gov/seki/learn/nature/giant-sequoias-and-fire.htm|url-status=live}}</ref>