Based on an September 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden holds 5 accessions of Heuchera maxima in orthodox seed collection. There are as many as 4150 seeds of this species in their collection - although some may have been used for curation testing or sent to back up.
Based on an August 2020 extract of the California Plant Rescue Database, Santa Barbara Botanic Garden has collected 5 seed accessions of Heuchera maxima from 3 plant occurrences listed in the California Natural Diversity Database. These collections together emcompass 95 maternal plants
Endemic to three of the northern Channel Islands (Santa Cruz, Santa Rosa, West Anacapa) off the southern California coast. Recently described as ""widespread in clumps of several to many plants each, throughout its potential habitats"" on Santa Cruz and Santa Rosa (Anacapa has not been resurveyed for decades). Nevertheless, it requires a fairly specific habitat (shaded moist north-facing locations, incl. canyon bottoms and walls, shaded slopes, rock ledges, sea cliffs) and known occurrences sizes are not large (largest 150-170+ plants); total known population on Santa Cruz and Santa Rosa probab ly not more than 2,500 plants. Approximately 34 occurrences are believed extant; an additional 14-20 historical occurrences are known. Although all three islands are now within the Channel Islands National Park, their ecological condition has been degraded due to non-native ungulates, with associated loss of soil and increases in non-native plants. However, this species has been spared the worst of these impacts since it occurs in relatively inaccessible locations. Most ungulates have now been removed from the islands within its range, and all will be removed by 2011. This species exhibited a a documented increase between 1991-1992 and 1995-1996 following feral sheep removal on Santa Cruz Island. However, increases in non-native plants following ungulate removal may pose an increased threat of competition.
Although intensive grazing by sheep, goats and pigs has posed significant threats to other plant species endemic to the Channel Islands, most of Heuchera maxima occurs out of the reach of negative effects of most grazing mammals (USFWS 1997).
This species is currently known from Santa Rosa Island, Santa Cruz Island and West Anacapa Island that support approximately 60 populations (USFWS 1997).
There is currently no implemented management plan for Heuchera maxima. Habitat conservation for the Channel Islands is being implemented by the U.S. Fish and Wildlife Service, the U.S. Navy, U.S. Park Service and the Nature Conservancy.
Population monitoring should be conducted to protect against population declines.
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