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Guadalupe Island

Coordinates: 29°02′20″N 118°16′41″W / 29.039°N 118.278°W / 29.039; -118.278
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For the French Caribbean archipelago, see Guadeloupe.
Southeast coast of Guadalupe Island

Guadalupe Island, or Isla Guadalupe (29°02′20″N 118°16′41″W / 29.039°N 118.278°W / 29.039; -118.278) is a volcanic island located 241 kilometers (150 statute miles) off the west coast of Mexico's Baja California peninsula and some 400 kilometers (250 statute miles) southwest of the city of Ensenada in Baja California state, in the Pacific Ocean. The two other Mexican island groups in the Pacific Ocean that are not on the continental shelf are Revillagigedo Islands and Rocas Alijos.

Administration and population

The 2008 census recorded a population of 15 persons on the island[1]. Guadalupe is part of Ensenada delegación, one of the 24 delegaciones or subdivisions of Ensenada municipality of the Mexican state of Baja California. Ensenada delegación and Chapultepec delegación together form the city of Ensenada, the municipal seat of the namesake municipality. The postal code of Guadalupe Island is 22997.

Campo Oeste ("West Camp", also called Campo Tepeyác, with 15 buildings) is a small community of abalone and lobster fishermen, located on the western coast, specifically on the north side of West Anchorage, a bay that provides protection from the strong winds and swells that whip the islands during winter. Generators provide electricity, and a military vessel brings 30,000 liters of fresh water. The number of fishermen varies annually depending on the fishing season. Ten months of the year the 30 families of the fishing cooperative "Abuloneros and Langosteros of Guadalupe Island" are present. [2]

Additional temporary fishing camps are Campo Norte ("North Camp", four buildings), Campo Lima (Campo Corrals) (one building) and Arroyitos (four buildings). [3]

An abandoned fishermen community, Campo Este ("East Camp"), is located near a cove on the eastern shore.

At the southern tip, on Melpómene Cove, there is a weather station staffed by a detachment from the Mexican Ministry of the Navy. The site is called Campamento Sur ("South Encampment").

Campo Bosque was established as a temporary camp in 1999 in the cypress forest in the north. The camp houses members of the Cooperative Farming Society "Francisco Javier Maytorena, S.C. of R.L." and removes goats from the island and sells them in the State of Sonora, with permission of SEMARNAT and the support of the Secretariat of the Navy.

Campo Pista is located at the small airport, near the center of the island (29°01′24.04″N 118°16′21.75″W / 29.0233444°N 118.2727083°W / 29.0233444; -118.2727083, elevation:592 m, direction:05/23).[4] At the end of the runway near threshold 23 is the crashed former bomber North American B-25J-30/32 Mitchell, BMM-3501 (c/n 44-86712) which suffered serious damage in trying to take-off overloaded [5](29°01′09.85″N 118°16′41.03″W / 29.0194028°N 118.2780639°W / 29.0194028; -118.2780639).

Airport Isla Guadalupe (IATA Code GUD, ICAO Code MMGD) has a 1200 meter long runway.

Geography and geology

Island map

Guadalupe has a rugged landscape. It consists of two ancient overlapping shield volcanoes, of which the northern and higher volcano is the younger. The island measures 35 km north-south and up to 9.5 km east-west, with a total area of 243.988 km2 (94.204 square miles). It features a chain of high volcanic mountain ridges which rises to a height of 1,298 meters (4,257 ft) at its northern end (Mount Augusta). Its smaller counterpart on the southern end is the 975 m (3,199 ft) El Picacho. The southern part of the island is barren, but there are fertile valleys and trees in the northern part. The coast generally consists of rocky bluffs with detached rocks fronting some of them. Two high and prominent islets are within 3 km of the southwestern end of the island, separated from one another by a gap called Tuna Alley:

Elsewhere, the other islets are very small and close to the shore, all less than one kilometer away:

Climate

The island has two major climate zones: a very arid, semi-hot climate between 0 and 800 meters elevation, with mean annual temperature between 18-22°C, and a very arid, temperate climate above 800 meters elevation with temperatures over 22°C in the hottest month of the year.

Most precipitation occurs over the winter months with strong influence of northwestern winds and cyclones.

Rainfall averages 133 mm near sea level at the south end but appears to be much more at the high north end. An estimate for the rainfall in the northern highlands is possible by way of taking the Pinis radiata as an indicator, which is native to that area of the island. Other places where Pinis radiata is native, it grows best with about 750 mm of rainfall but under some conditions can survive with as little as half that much. The effective moisture, of course, is much greater because of fog drip.[2]

Ecology

NASA satellite image

Guadalupe shares the California chaparral and woodlands ecoregion with the Channel Islands of California in the United States, but the island was at one time been practically denuded of all plants higher than a few centimeters by the up to 100,000[3] feral goats.

Originally brought there in the early 19th century by primarily Russian whalers and sealers for provisions when stopping over, the population eventually eliminated most vegetation; the number of goats declined to a few thousand. The main impact of the goat population was before this collapse, about the turn of the 19th/20th century. Naturalist A.W. Anthony wrote in 1901:

"It is directly due to the despised Billy-goat that many interesting species of plants formerly abundant are now extinct, and also that one or more of the birds peculiar to the island has disappeared, and others are following rapidly."[4]

After the crash, the goat population once again grew, this time more slowly, until it had reached the new, lower carrying capacity at maybe 10,000–20,000 in modern times. The island had been a nature conservancy area since August 16, 1928, making it one of the oldest reserves in Mexico. Eradication of the goats was long envisioned, but logistical difficulties such as island size and lack of suitable spots for landing and encamping hunters and material prevented this. As of June 2005, after many years of false starts, the Mexican government has almost completed a round-up and evacuation of the remaining goat population and Guadalupe has been designated a biosphere reserve.

Of the large tree species on Guadalupe Island (Guadalupe Palm, Guadalupe Cypress, Island Oak, and Guadalupe Pine), there were only old individuals left; California Juniper had entirely disappeared. As the goats ate any seedlings that managed to germinate, no regeneration of trees was possible. Water, formerly plentiful as the common fogs condensed in the forests of the northern end of the island, today only occurs in a few scattered pools and springs. Because the springs were a critical emergency water supply for the human inhabitants, protective measures including goat fences were installed beginning in 2000, allowing new seedlings of many species to survive for the first time in 150 years. Seacology, a non-profit environmental group located in Berkeley, CA, provided funding to the Island Conservation & Ecology Group for the construction of ten fenced exclosures to keep goats out of the most sensitive areas of Guadalupe Island.

Many island or marine species that reside on or near Guadalupe also frequent the Channel Islands, and vice-versa. In stark contrast to the rampant extinction of terrestrial life that happened at the same time, Guadalupe was the last refuge for the Northern Elephant Seal (Mirounga angustirostris) and the Guadalupe Fur Seal (Arctocephalus townsendi) in the 1890s. The island has been a pinniped sanctuary since 1975.

Great white off Isla Guadalupe
Great white off Isla Guadalupe
Great white off Isla Guadalupe

Guadalupe is considered one of the best spots in the world for sightings of the Great White Shark, possibly because of its large population of pinnipeds. A joint team from the USA and Mexico (UC Davis and CICIMAR) are working in tandem with eco-tour operators Horizon Charters, Islander Charters and Shark Diver to tag and study these sharks.

Habitat types

Before the removal of goats, surveys found eight major land habitats on Guadalupe:[5]

Giant Coreopsis (Coreopsis gigantea)
Cylindropuntia prolifera
Perityle emoryi
Pinus radiata cone
  1. Flora of the coastal lowlands and rocky cliffs: mainly up to 200 m above mean sea level (ASL), but higher on the steep cliffs. Largely unresearched due to difficult access, the cliffs might even harbor remnant specimens of the presumably extinct plants.
  2. Succulent perennial herbs: 200-400 m ASL, chiefly on the southern end and on the offshore islets, and in less steep areas towards sea level. Here, the highest number of endemic plants exist. Baeriopsis guadalupensis, Cistanthe guadalupensis, Dudleya guadalupensis, Hemizonia greeneana ssp. greeneana, H. palmeri, Perityle incana and Stephanomeria guadalupensis are dominant endemics, and Giant Coreopsis (Coreopsis gigantea), a non-endemic native species, is also abundant.
  3. Arid maritime shrubland: 400-600 m ASL. Mainly in the southern portion around El Picacho. Native species occurring here include Ambrosia camphorata, Atriplex barclayana, Cylindropuntia prolifera and California Boxthorn (Lycium californicum); none of these is endemic.
  4. Herbland dominated by introduced plants: 600-800m ASL, mainly on the central plateau. This habitat is almost entirely a consequence of overgrazing; hardly anything of the original ecosystem remains. Dominant introduced plants are Avena barbata, Bromus berteroanus, Great Brome (B. diandrus), Soft Brome (B. hordeaceus sspp. hordaceus and mollis), Red Brome (B. madritensis ssp. rubens), tocalote (Centaurea melitensis), Nettle-leaved Goosefoot (Chenopodium murale), Filago californica, Wall Barley (Hordeum murinum sspp. glaucum and leporinum), Crystalline Iceplant (Mesembryanthemum crystallinum), M. nodiflorum, Polypogon monspeliensis and Sisymbrium orientale. The non-endemic natives Dwarf Coastweed (Amblyopappus pusillus), Island False Bindweed (Calystegia macrostegia ssp. macrostegia), Cryptantha maritima var. maritima, Filago arizonica, Gilia nevinii, California Goldfields (Lasthenia californica), Pectocarya palmeri and Perityle emoryi as well as the endemics Cryptantha foliosa and Sphaeralcea palmeri can be found here also; some still are numerous. This probably was a mesic shrub/herbland before the goats destroyed the upland forest, upsetting the water supply. Native plants still found on Guadalupe, like Crossosoma californicum, Laurel Sumac (Malosma laurina) and the endemic Camissonia guadalupensis ssp. guadalupensis, presumably thrived here in former times, as would have such taxa as the native Hoary-leaved Ceanothus (Ceanothus crassifolius), Wedge-leaved Ceanothus (C. cuneatus) – and possibly also Felt-leaved Ceanothus (C. arboreus), which was found in 2001-2003 surveys[6] –, Cammisonia robusta, Red-flowering Currant (Ribes sanguineum) and the endemic Hesperalea palmeri, which have now disappeared from the island.
  5. Guadalupe Palm groves: 400-900 m ASL on the NW side of the island. There are hundreds of palm trees remaining, mainly in a single patch of this habitat. At least one other major palm forest, at the W coast, existed; it was still present in 1906[7] As reproduction is presumably still ongoing, the species will likely recover in due time.
  6. Guadalupe Cypress forest: 800–1000 m ASL. Presently some 4000 of old trees, essentially limited to the central northern part. Other cypress forests, such as a major stand NE of the present patch which was still extant in 1906[8], have been destroyed by the goats early in the 20th century. There is still reproduction, but the water table appears to have declined to below the level required by the cypresses, and mortality of the old trees is high and can be expected to continue even after removal of the goats.
  7. Guadalupe Palm - Island Oak - Guadalupe Pine woodland: 900–1000 m ASL. This habitat has all but disappeared during the 20th century[8], due to the decline in numbers of the oaks and pines.
  8. Guadalupe Pine cloud forest with some Island Oak: restricted to above 1000 m ASL on the N-NE point of the island. The population of the pine has declined by about two-thirds during the last 35 years; it presently stands at about 130 old trees in the main population and about the same number scattered elsewhere. Reproduction is ongoing, with several hundred seedlings having successfully established themselves since 2000[6], and with the elimination of goat browsing, the pines will likely make a full recovery. The situation of the oak is more dire; there are only 20 trees or so remaining (by about 1950, there were 100) and they appear past reproductive age. Not being restricted to Guadalupe, seedlings could be imported from elsewhere.

A ninth habitat type, California Juniper woodland and extending on the central plateau below the cypress forest, was entirely gone by 1906[8]. What other endemic lifeforms underwent coextinction with it will forever remain unknown.

Endemism

Animals:

Guadalupe Fur Seal (Arctocephalus townsendi)

Plants:[5]

Extinctions

Guadalupe Caracara (Polyborus lutosus), painted by John James Audubon

Numerous taxa have gone extinct due to the habitat destruction by the goats, which in turn rendered the endemic fauna vulnerable to predation by introduced cats and to adverse weather by depriving them of shelter.

There have been 5-6 extinctions of birds:

  • Guadalupe Bewick's Wren (Thryomanes bewickii brevicauda), late 1890s[14]? A date of 1903 is often given, but this seems to be in error.
  • Guadalupe Spotted Towhee (Pipilo maculatus consobrinus), late 1890s
  • The Guadalupe Caracara (Polyborus lutosus) was intentionally made extinct by humans around 1901, ironically because it occasionally preyed on young goats.
  • Guadalupe Flicker (Colaptes cafer rufipileus), c.1910 - the island was later recolonized by individuals of the nominate subspecies
  • Guadalupe Storm Petrel (Oceanodroma macrodactyla), 1910s
  • The Guadalupe Ruby-crowned Kinglet (Regulus calendula obscurus) is close to extinction, if it indeed still exists. It was not observed in 2000 despite thorough searches.

Globally extinct plant taxa from Guadalupe Island are:[15]

and one species of plant incertae sedis

Footnotes

  1. ^ INEGI (2007)
  2. ^ [1]THE FLORA OF GUADALUPE ISLAND, MEXICO By Reid Moran
  3. ^ Maximum population that was reached in the late 19th century; nearly 2 goats per acre/more than 4/ha: León de la Luz et al. (2003)
  4. ^ Anthony (1901)
  5. ^ a b León de la Luz et al. (2003), CMICD (2007)
  6. ^ a b c Junak et al. (2003)
  7. ^ At "Steamer Point" (= opposite Steamboat Rock?): Thayer & Bangs (1908)
  8. ^ a b c Thayer & Bangs (1908)
  9. ^ Often considered a distinct species
  10. ^ Jiménez & Aguilar (1994)
  11. ^ Some naturalized populations exist in California
  12. ^ Depending whether this population belongs to Marah macrocarpus var. major or not
  13. ^ Depending on taxonomic status of Cedros Island population: CMICD (2007)
  14. ^ Anthony (1901), Kaeding (1905)
  15. ^ Junak et al. (2003), León de la Luz et al. (2003), CMICD (2007)

References

  • Anthony, A.W. (1901): The Guadalupe Wren. Condor 3(3): 73. PDF fulltext
  • California/Mexico Island Conservation Database (CMICD) (2007): Plant accounts: Guadalupe Island. Retrieved 2007-OCT-10.
  • Instituto Nacional de Estadística, Geografía e Informática (INEGI) (2007): Principales resultados por localidad 2005 (ITER) ["Principal results of the 2005 census by locality"] [in Spanish]. Retrieved 2007-OCT-10.
  • Jimenez, Maria Luisa & Aguilar, Ricardo (1994): Notas sobre las arañas de las islas Guadalupe y Cedros, Baja California, Mexico (Arachnida, Araneae) ["Notes on the spiders of Guadalupe and Cedros islands, Baja California, Mexico"]. Journal of Arachnology 22(2): 173-175. [in Spanish] PDF fulltext
  • Junak, S.; Keitt, B.; Tershy, B.; Croll, D. & Sánchez, J.A. (2003): Recent conservation efforts and current status of the flora of Guadalupe Island, Baja California, Mexico. Presentation at Taller sobre la Restauración y Conservación de Isla Guadalupe ["Workshop on restauration and conservation of Guadalupe Island"]. Instituto Nacional de Ecología, November 13-14, 2003. HTML abstract.
  • Kaeding, Henry B. (1905): Birds from the West Coast of Lower California and Adjacent Islands (Part II). Condor 7(4): 134-138. PDF fulltext
  • León de la Luz, José Luis; Rebman, Jon P. & Oberbauer, Thomas (2003): On the urgency of conservation on Guadalupe Island, Mexico: is it a lost paradise? Biodiversity and Conservation 12(5): 1073–1082. doi:10.1023/A:1022854211166 (HTML abstract)
  • Thayer, John E.& Bangs, Outram (1908): The Present State of the Ornis of Guadaloupe Island. Condor 10(3): 101-106. doi:10.2307/1360977 PDF fulltext
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