Editing Lichen (section)

=== Life span ===
Lichens may be [[longevity|long-lived]], with some considered to be among the oldest living organisms.<ref name=LNA/><ref name="Morris2007"/> Lifespan is difficult to measure because what defines the "same" individual lichen is not precise.<ref name=ELNGDL>{{cite web|url=http://www.earthlife.net/lichens/growth.html|title=The Earth Life Web, Growth and Development in Lichens|publisher=earthlife.net|access-date=12 October 2014|archive-url=https://web.archive.org/web/20150528035845/http://www.earthlife.net/lichens/growth.html|archive-date=28 May 2015|url-status=dead}}</ref> Lichens grow by vegetatively breaking off a piece, which may or may not be defined as the "same" lichen, and two lichens can merge, then becoming the "same" lichen.<ref name=ELNGDL/> One specimen of ''[[Rhizocarpon geographicum]]'' on East [[Baffin Island]] has an estimated age of 9500 years.<ref>{{Cite journal |last1=Rosenwinkel |first1=Swenja |last2=Korup |first2=Oliver |last3=Landgraf |first3=Angela |last4=Dzhumabaeva |first4=Atyrgul |date=2015 |title=Limits to lichenometry |url=https://www.sciencedirect.com/science/article/abs/pii/S0277379115301529 |journal=Quaternary Science Reviews |volume=129 |pages=229–238 |doi=10.1016/j.quascirev.2015.10.031|bibcode=2015QSRv..129..229R }}</ref><ref>{{Cite journal |last1=Miller |first1=G. H. |last2=Andrews |first2=J. T. |date=April 1972 |title=Quaternary History of Northern Cumberland Peninsula, East Baffin Island, N.W.T., Canada Part VI: Preliminary Lichen Growth Curve for Rhizocarpon geographicum |url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/83/4/1133/7545/Quaternary-History-of-Northern-Cumberland |journal=GSA Bulletin |volume=83 |issue=4 |pages=1133–1138 |doi=10.1130/0016-7606(1972)83[1133:QHONCP]2.0.CO;2}}</ref> [[Thallus|Thalli]] of ''Rhizocarpon geographicum'' and ''[[Rhizocarpon]] eupetraeoides''/''inarense'' in the central [[Brooks Range]] of northern Alaska have been given a maximum possible age of 10,000–11,500 years.<ref>{{Cite journal |last1=Haworth |first1=Leah A. |last2=Calkin |first2=Parker E. |last3=Ellis |first3=James M. |date=1986 |title=Direct Measurement of Lichen Growth in the Central Brooks Range, Alaska, U.S.A., and Its Application to Lichenometric Dating, Arctic and Alpine Research |url=https://www.tandfonline.com/doi/abs/10.1080/00040851.1986.12004090 |journal=Arctic and Alpine Research |volume=18 |issue=3 |pages=289–296 |doi=10.2307/1550886|jstor=1550886 }}</ref><ref>{{Cite journal |last=Benedict |first=James B. |date=January 2009 |title=A Review of Lichenometric Dating and Its Applications to Archaeology |url=https://www.cambridge.org/core/journals/american-antiquity/article/abs/review-of-lichenometric-dating-and-its-applications-to-archaeology/21C29EAAF0361CCE2B98793DC3CB9F5F |journal=American Antiquity |volume=74 |issue=1 |pages=143–172 |doi=10.1017/S0002731600047545|s2cid=83108496 }}</ref>