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Mobergia calculiformis (W.A. Weber) H. Mayrhofer & Sheard

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Scientific name
Mobergia calculiformis
(W.A. Weber) H. Mayrhofer & Sheard
Common names
Coastal Popcorn Lichen
Palomitas Costeras
IUCN Specialist Group
Assessment status
Assessment date
IUCN Red List Category
IUCN Red List Criteria
A2c+3c+4c; B2ab(i,ii,iii,iv,v)
Herrera-Campos, M., Parrinello, C. & Bungartz, F.
Stone, D.

Assessment Notes

The content on this page is fetched from The IUCN Red List of Threatened Species: https://www.iucnredlist.org/species/175709748/200461142


Mobergia calculiformis is a rock dwelling lichen, from the Pacific Coast of Southern California and the Baja Peninsula. There has been an inferred >50% overall population reduction based on all United States subpopulations having been extirpated, which has led to a reduction in Area of Occupancy (AOO), Extent of Occurrence (EOO), and number of locations. The loss of the species is accompanied by a severe reduction in habitat quality throughout its range due to development and recreation. There is an inferred future reduction of at least 50% as the four remaining locations are all threatened. One location is impacted by tourism, and another one might be affected in the future by the Escalera Náutica (Álvarez Torres 2009; also see websites cited) and is threatened by currently ongoing infrastructure projects (https://www.cielomarbaja.com/%E2%80%8Bescalera-nautica-nautical-ladder/), and the other 50% of extant subpopulations are either minute (Sierra La Giganta) and/or threatened by urbanisation (Sierra La Giganta and south of San Quintín). Although the EOO is large, the AOO is less than 80 km2 and the subpopulations are severely fragmented, plus there is a continuing decline in EOO, AOO, and a projected decline of the number of locations and subpopulations. Therefore, this species is Endangered under criteria: A2c+3c+4c; B2ab(i,ii,iii,iv,v).

Taxonomic notes

Mobergia is a genus in the family Physciaceae with only two species.

Geographic range

Mobergia calculiformis was originally reported from coastal California (U.S.A.) and both Baja California and Baja California Sur (Mexico) (Mayrhofer et al. 1992, Spjut 1995, Mayrhofer and Sheard 2004). All United States locations have been revisited by K. Knudsen (pers. comm.) who confirmed that these subpopulations are now extirpated. The Mexican sites (almost all in Baja California) are the only surviving subpopulations. The sole subpopulation from Baja California Sur has not been confirmed recently. The species also occurs on Guadalupe Island, Baja California. Using the known extant localities from the Baja peninsula the Extent of Occurrence (EOO) is 108,000 km2 and the Area of Occupancy as 72 km2. The relatively large EOO is a result of the specimens from Guadalupe Island, which is far off the coast, almost 250 km away from the mainland peninsula.

Population and Trends

All U.S.A. subpopulations are extirpated. In Mexico, four subpopulations are still extant:

(1) The subpopulation immediately south of San Quintín is very heavily urbanised and the habitat has drastically changed.

(2) The subpopulation near Santa Rosaliíta is still in very good shape, the small fishing village is not much frequented by tourism and the species is relatively abundant according to an informal survey by F. Bungartz and R. Vargas in May 2018. However, this location will drastically change if the Mexican government approves the Escalera Náutica project, which plans to crisscross the peninsula with a network of roads to allow tourists to move their sailing boats from the Pacific to the Sea of Cortés.

 (3) The subpopulation on Guadalupe Island recently became encompassed within a biosphere reserve, and although it is in a protected area, this subpopulation is today heavily impacted by tourism and its accompanying development.

(4) The southernmost subpopulation on the western flanks of Sierra La Giganta near Ciudad Insurgentes (a huge, heavily urbanised area) is not well documented. Nearby, on the Pacific coast near the port of Adolfo López Mateos, a large seashore resort is being built which may impact this population.

Population Trend: decreasing

Habitat and Ecology

The species is saxicolous, attached to pebbles and larger coastal rock, cliffs, and boulders; and thus is not blown about by the wind. It occurs only along the Pacific coast in a heavily fog-induced desert of the Baja peninsula. Before similar habitat in the U.S.A. was replaced by urban and agricultural development, the species presumably was common there too.


The northernmost extant subpopulation, south of San Quintín, is very heavily impacted by agricultural and urban development as well as by tourism (Vanderplank 2011). This subpopulation is currently not protected. It is still very abundant within the subpopulation along the Pacific coast between El Rosario and Santa Rosaliíta and currently may be considered the one best preserved (F. Bungartz pers. obs., and R. Vargas, pers. comm.). These sites are at least in part located in and near the Parque Natural del Desierto Central de Baja California, but the sites are nevertheless projected to be heavily developed as part of the Escalera Náutica project (Álvarez Torres 2009; and websites cited). Like most of the Baja desert sites, an additional threat is the various off-road races (e.g. Baja 1000 Race, http://score-international.com/). A single, isolated site (comprising another subpopulation) in the Sierra La Giganta in Baja California Sur is poorly known and has not been visited since 1989, but the location lies just north of the heavily urbanised Ciudad Insurgentes. The subpopulation inside the Guadalupe Island Biosphere Reserve is healthy, but nevertheless impacted by tourism (Comisión Nacional de Áreas Naturales Protegidas 2013).  

Mobergia calculiformis is a species commonly growing on the ground, interspersed along coastal plains near the foggy Pacific seashore, scattered among pebbles. It typically adheres to the pebbles and thus is not blown about by the wind. Thalli adhering to their saxicolous substrate can also be found growing on fog-drenched boulders and cliffs close to the shore. The unusual thallus growth form (an inflated, three-dimensional "brain-like" structure) make this lichen particularly susceptible to damage. Walking across the coastal pebble fields can inadvertently destroy many of the thalli. Biking and off-roading from motorized vehicles (Baja 100 race: jeeps, motorbikes) will have an even more destructive impact. The specimens growing on cliffs and boulders are necessarily better protected from these impacts, but with large infrastructure construction projects looming (Escaleara Náutica) even these sites may be damaged or even destroyed (bulldozers, construction machines building roads, landing sites for boats, etc.).

Conservation Actions

Most current conservation actions at the known sites focus on the preservation of plant habitat and habitat for birds and small mammals (e.g. Rodríguez-Estrella 2005, Lovich et al. 2009, Harper et al. 2011, Vanderplank 2011, Aguirre-Muñoz et al. 2018), but lichens are still largely ignored. The Comisión Nacional de Áreas Naturales Protegidas (2013), in its management programme for the Isla Guadalupe Biosphere Reserve, highlights the necessity to preserve the enormous lichen diversity on the island, citing Moran (1996), who emphasized that on the Baja mainland and in southern California (USA) comparable ecosystems have largely been destroyed (Comisión Nacional de Áreas Naturales Protegidas (2013, p. 32): "...Esta flora es remanente de la que hubo alguna vez en gran parte del Sur de California y del Norte de Baja California. Prácticamente este ecosistema ha sido destruido por el desarrollo y cambio de uso de suelo en Estados Unidos..."). Raising public awareness for the unique lichen biota of the Baja peninsula is thus critically important. In particular, on the Pacific site, the sensitive fog desert habitat needs to be better protected from a broad range of destructive impacts: tourism, off-road driving (e.g. Baja 1000 race, http://score-international.com/), urbanisation, infrastructure (Aguirre-Muñoz et al. 2018), agriculture (Vanderplank 2011), etc. Further research and conservation planning is also required.

Source and Citation

Herrera-Campos, M., Parrinello, C. & Bungartz, F. 2021. Mobergia calculiformis. The IUCN Red List of Threatened Species 2021: e.T175709748A200461142. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T175709748A200461142.en .Accessed on 6 February 2024

Country occurrence