0 m ▁above ▁the ▁sh or eline , ▁and ▁are ▁rarely ▁found ▁on ▁the ▁vertical ▁surfaces ▁of ▁highly ▁exposed ▁rocks . ▁C occ ot re ma ▁mar it imum ▁anchor ▁only ▁to ▁rock y ▁surfaces . ▁ ▁Range ▁ ▁C occ ot re ma ▁mar it imum ▁have ▁a ▁very ▁limited ▁range ; ▁they ▁are ▁only ▁seen ▁in ▁coast al ▁British ▁Columbia , ▁Canada . ▁They ▁are ▁abund ant ▁in ▁the ▁Queen ▁Charlotte ▁Islands , ▁which ▁are ▁located ▁roughly ▁ 8 0   km ▁off ▁main land ▁British ▁Columbia , ▁north ▁of ▁V ancouver ▁Island . ▁ ▁Import ance ▁to ▁humans ▁ ▁L ich ens ▁in ▁general ▁are ▁important ▁bio - ind ic ators ▁as ▁they ▁are ▁highly ▁sensitive ▁to ▁any ▁changes ▁in ▁the ▁environment ; ▁this ▁sens itivity ▁is ▁a ▁result ▁of ▁their ▁reli ance ▁on ▁atmos pher ic ▁mo ist ure ▁and ▁nut ri ents , ▁in ▁combination ▁with ▁their ▁limited ▁ability ▁to ▁rid ▁themselves ▁of ▁to x ins . ▁Through ▁observation ▁of ▁their ▁physical ▁appearance ▁and ▁monitoring ▁of ▁their ▁chemical ▁composition ▁l ich ens ▁are ▁used ▁to ▁indicate ▁the ▁health ▁of ▁environments ▁world wide . ▁C occ ot re ma ▁mar it imum ▁and ▁other ▁species ▁may ▁be ▁effective ▁indic ators ▁of ▁air ▁quality ▁and ▁the ▁effects ▁of ▁oil ▁sp ills ▁and ▁post ▁sp ill ▁clean - up . ▁This ▁may ▁be ▁a ▁particularly ▁relevant ▁usage ▁in ▁the ▁Queen ▁Charlotte ▁Islands , ▁as ▁there ▁is ▁an ▁increasing ▁probability ▁of ▁oil ▁and ▁gas ▁development ▁between ▁the ▁Islands ▁and ▁the ▁BC ▁main