Location and General Description
The Canary Archipelago is a group of volcanic islands and rock islets found in the Macronesia region, which also includes Salvajes, Madeira, Azores and Cape Verde Islands. The Canaries are located in the Atlantic Ocean, between 27º 20’ and 29º 25’north and between 13º 20’ and 18º 10’ west (Bacallado et al. 1984, González et al. 1986). They are about 115 km from the northwest coast of Africa (González et al. 1986). This ecoregion includes the five western islands: La Palma, Hierro, Gomera, Tenerife, and Gran Canaria. The western islands are younger than the eastern group and are more mountainous, with well-developed forests (González et al. 1986). The eastern islands are lower are drier and are included here within the Mediterranean Acacia-Argania Dry Woodland and Succulent Thicket ecoregion.
Despite their proximity to Africa (in latitudes similar to those of the Sahara, Egypt and Saudi Arabia), the Canaries show a wide range of different microclimates apart from sub-desert landscapes. This is caused by several factors such as elevation and orientation, but especially because of the influence of northeast to southwest sea winds, called alisios.These relatively hot winds become cooler and more humid as they pass over the sea surface. The seas surrounding the islands are cool because of a current flowing north past the islands from cold southern latitudes. Once the alisios reach the northern parts of the higher Canary Islands, this moisture is trapped by the dense laurisilva and fayal-brezal (heath) vegetation on the mountain slopes. This vegetation acts as a sponge, condensing moisture in drops as large as 3 mm3 and producing a phenomenon called horizontal rain. Most of the water is captured in the north, and the mountains function as natural barriers, so the southern parts of the islands are drier and have proportionally higher temperatures and lower humidity levels throughout the year. Low-lying islands with elevations under 750 m receive no rain from the passing alisios so that habitats and climate here are drier and similar to the southern parts of the higher islands. Sometimes, the Archipielago experiences eastern dry winds from the Sahara. This phenomenon is locally called "calima" or "calina," and dust levels in the air become temporally high (Bacallado et al. 1984, González et al. 1986, Marzol 1998).
Rains are heavier in the autumn and winter months. Precipitation in coastal zones is between 100 and 350 mm per year with air relative humidity levels (ARHL) ranging from 55-65 percent. Annual precipitation levels at elevations from 250 to 600 m are about 650 mm per year with 70-80 percent ARHL. Annual precipitation levels at elevations higher than 600 m average about 400 mm with 35-40 percent ARHL (Bacallado et al. 1984, González et al. 1986, Marzol 1998).
The Canary Island Archipelago was formed by undersea volcanic activity. There have also been eruptions on emergent islands, with the most recent one occurring in La Palma in 1971. La Palma and El Hierro are the youngest islands, only 2-3 million years old. Because of the islands’ origin, all materials in the Canaries are volcanic and, depending on the substances composing the lava, they can be grouped into the following types: Traquitic-fonolitic, basaltic and traquibasaltic rocks, and Piroclastic and slag materials. Different soil types have been produced due to the effects of vegetation, local weather conditions and topography on these volcanic materials (Bacallado et al. 1984, González et al. 1986).
Each of the habitats recognised in the Canaries grows on a specific kind of soil. The following are soil descriptions for dry woodlands and forests. Canarian endemic pine forests grow on two kinds of fertile soil: ancient red lands (the color is produced by high iron oxide content and clay levels) and level, grey, clay lands with low organic material content formed in places with well-defined seasons. Endemic Macronesian heaths are located in humid zones in young soils composed of hydrated aluminic silicates with a high level of organic material. Laurisilva occurs on recent materials in places with well-defined seasons and medium to low organic substance levels which lie above older soil types (like those where Canarian endemic pine forests grow) (González et al. 1986).
The Canary Islands lack river systems. In spite of that and owing to the steep topography of the western islands, they are crossed by complex systems of ravines produced by water erosion over thousands of years. These gullies serve as drainage for winter rainfall and, on the higher islands like Tenerife, water from the thawing snow and ice flows year-round. Other islands become dry in summer. Generally, the northern parts of the islands are steeper than the southern regions, which have bigger plains and more semiarid landscapes.
Vegetation can be described according to elevation zones. At the lowest elevation, coastal vegetation grows, including types typical of cliffs and sandy regions. Endemic palm groves (Phoenix canariensis), and semiarid vegetation.are present. Generally, these vegetation types occur from sea level to 600 m in the north and up to 1,000 m in the south, and include many endemic taxa. Endemics are mainly found to be from the Euphorbiaceae, for example, Euphorbia canariensis, and E. balsamifera . Other important endemic species are Ceropegia fusca, Plocama pendula, Salvia canariensis, Argyranthemum frutescens, Rumex lunaria, Convolvulus floridus, and Messerschmidia fruticosa (Bramwell and Bramwell 1983, González et al. 1986 , Strasburger et al. 1986).
Along the transition zone from 50 to 500m, between the sea level coastal community and giving way to laurisilva vegetation, there are thermophiles and pre-steppe bush The species found here are common to both the lower and higher vegetation formations. This zone has been damaged for decades because of its good potential for crops. Some of the endemic and representative species are Bosea yervamora, Echium strictum, Greenovia aurea, Aeonium sp., Monanthes laxiflora, Campylanthus salsoloides, Forsskaolea angustifolia, and Dracaena draco (Bramwell and Bramwell 1983, González et al. 1986).
Humid and shady laurisilva forest grows between 500 and 1400 m in elevation, with some species reaching more than 20 m in height. Some 20 million years ago, this evergreen forest covered large areas of the world. However, because of the dramatic weather changes experienced in the Quaternary, it has only survived in a few places. This is one of the jewels of vegetation biodiversity in the Canary Islands; the best conserved of all Macronesian laurel forest can be found here. Even though laurisilva is formed by several taxa grouped in different families, there are four representative speciesfrom all of Lauraceae. They are: Ocotea foetens, Apollonias barbujana, Laurus azorica, and Persea indica. Other Macronesian endemic species found in laurisilva are Arbutus canariensis, Ilex canariensis, Visnea mocanera, Picconia excelsa, Heberdenia excelsa, Salix canariensis, and Viburnum tinus (Bramwell and Bramwell 1983, González et al. 1986).
Endemic Macronesian heaths, also known as fayal-brezal, grow from 500 to 1,700 m, as transition vegetation between laurisilva and Canarian endemic pine forests, with which they share some species (Ilex canariensis, I. perado, Larus azorica, and Picconia excelsa). There are three distinctive species Myrica faya, Erica arborea and E. scoparia. Three different patterns of distribution can be seen. The first one is the contact zone with laurisilva, where Myrica spp. are dominant, with some Erica spp.; the second one is the typical fayal-brezal association (Myrica-Erica); and finally the third one is the contact zone with pine forests where Erica spp. are more common than Myrica spp. (González et al.1986).
Canarian endemic pine forests (Pinus canariensis) are found almost at sea level in southern areas but in the northern parts of the islands are found from 1,200 to 2,400 m in elevation. Previously widespread in southern Europe, they disappeared from the continent with the last glaciations (Pliocene). In their limited range they are mixed with Adenocarpus spp., Myrica-Erica associations, or even with laurisilva forest (northern), or with Chamaecytisus spp., Spartocytisus spp., and Ephedera spp., or Cistus spp. or Micromeria spp. (southern). Pines can also be found mixed with Juniperus cedrus and J. phoenicea at higher elevations. Although Canarian endemic pine forests contain a lower number of species compared with other vegetation formations in the Canaries, they have a large number of endemics in all plant groups, including fungi and lichens. Some of these Canarian endemic plants are Bystropogon plumosus, Aeonium spathulatum, Asparagus plocamoides,Tolpis laciniata and Teline sp. (Bramwell and Bramwell 1983, González et al. 1986).
Finally, vegetation grows in the high mountains above 2,000 m on La Palma and Tenerife. Some of the typical species of this vegetation can also be found occasionally on other high islands of the archipelago that hold the following climatic attributes: very low humidity level, scarce rainfalls, very cool winters (-16ºC occasionally registered), warm summers (sometimes more than 46ºC), high isolation year-round, and big contrasts of day/night temperatures. Both endemic species and genera are found and these include Spartocytisus supranubius, Erysimum scoparium, Nepeta teydea, Plantago webbii, Senecio palmensis, Juniperus cedrus, Polycarpaea tenuis, and Echium sp.(Bramwell and Bramwell 1983, González et al.1986, Marzol 1998).
All the Canary Islands are like small isolated continents. They are unique for their high level of endemic taxa. Not only species, but even many genera are exclusive to this ecoregion. Every family of plants found in the Canary Islands has endemic representatives, often including endemic genera. Endemism levels are especially high in invertebrates, vascular plants and vertebrates (100% of native terrestrial reptiles). Over a quarter of the 1,992 vascular plants found on the Canary Islands are endemic to these islands (Machado 1998). Endemicity in non-migratory vertebrates is 17.2%, or 21 out of 122 species (Machado 1998). Among arthropod invertebrates, 44.4% of the 6,378 species are endemic (Machado 1998). For non-arthropod invertebrates, endemism is 28.8% out of 774 species (Machado 1998). The figures for terrestrial endemic vertebrates only include those animals restricted to this ecoregion but there are other species and subspecies with small distributions, endemic to all of the Canaries, or shared exclusively with other Macronesian Archipelagos.
Atlantic Islands Pipistrelle (Pipistrellus maderensis, VU) and Canary Big-eared bat (Plecotus teneriffae, VU) are considered near-endemic to this ecoregion (but endemic to the Archipelago) (Bacallado et al. 1984, Trujillo 1991). Four birds are endemic to the ecoregion, Bolle's pigeon (Columba bollii), Laurel pigeon (Columba junoniae, VU), Canary Islands finch (Fringilla teydea), and Canary Islands kinglet (Regulus teneriffae) (Bacallado et al. 1984, Heinzel et al. 1992, Moreno 1988). Berthelot's pipit (Anthus berthelotii), plain swift (Apus unicolor), and common canary (Serinus canaria) are near-endemic to the Canary Islands Dry Woodlands and Forests (Bacallado et al. 1984, Heinzel et al. 1992, Moreno 1988). The Canary Island oystercatcher (Haematopus meadewaldoi) was formerly present but is now considered extinct (Hilton-Taylor 2000).
Bird subspecies restricted to the Canary Islands include a subspecies of kestrel (Falco tinnunculus teneriffae), a grey wagtail (Motacilla cinerea canariensis), a long-eared owl (Asio otus canariensis), three subspecies of chaffinches (Fringilla coelebs tintillon, F.c. ombriosa, F.c. palmae), a Chiffchaff (Phylloscopus canariensis) and two subspecies of great spotted woodpeckers (Dendrocopos major canariensis, D. m. thanneri) (Bacallado et al. 1984, Helbig et al. 1996, Heinzel et al. 1992, Moreno 1988).
Vertebrates, especially reptiles, went through an evolutionary radiation as species adapted to the varied island habitats. As a result, each island has its own species or subspecies of lizard, skink or gecko; there are even island endemic representatives of these three families. In the recent past (decades in some cases) the Canaries were inhabited by giant lizards (near 150 cm long), now extinct. Smaller relatives of these extinct reptiles are still living in cliffs and crevices of islands like El Hierro, La Gomera, Tenerife and probably La Palma. On Gran Canaria, larger than average lizards can also be seen all around the island. A similar process of radiation, has occurred in many birds, such as the blue tit Parus caeruleus (Paridae) that has evolved into three different subspecies: P. c. teneriffae in Gran Canaria, Tenerife and La Gomera, P.c. ombriosus in El Hierro and P.c. palmensis in La Palma (Moreno 1988). Island specific endemicity is even more spectacular in invertebrates, such as beetles and butterflies (Machado 1998). The Geometridae family (Lepidoptera) contains approximately 50 percent endemicity (García et al. 1992). Other groups like Orthoptera and Diptera species are almost 45 percent and 40 percent endemic respectively (García et al. 1992, Machado 1998).
Because of the short distance to Africa, the Canary Islands are visited every year by many migratory bird species that fly south in autumn in search of warmer places and go back to Europe in the spring. Others, mainly marine birds, use the archipelago as a nesting point only in the breeding season and after that return to the sea. This is the case with species of shearwater, such as Puffinus puffinus (Procellariidae), which nest in gullies of laurisilva (Martín 1987).
Apart from terrestrial species, there are important populations of cetaceans living year-round in Canarian seas. Loggerhead (Caretta caretta) (EN), green (Chelonia mydas) (EN) and leatherback (Dermochelys coriacea) (CR) turtles are common, and Kemp’s ridley (Lepidochelys kempi) (CR), olive ridley (L. olivacea) (EN) and hawksbill turtles (Eretmochelys imbricata) (CR) are also sighted occasionally. (Hilton-Taylor 2000).
Although the Canary Islands base their economy on tourism and local crops, there are still some small areas that contain intact habitats, and consequently they display more or less complete biotas. These habitats are located in difficult-to-reach places like cliffs, steep mountains or rocky isles that tourists rarely frequent. Most of those places are included within protected areas. A complex net of natural protected areas has been developed throughout the islands. Through the UNESCO program MaB (Man and Biosphere) three reserves have been declared in the Canaries: Los Tiles (in La Palma), Lanzarote and El Hierro (both complete islands). La Gomera, La Palma and El Hierro are the islands with best-conserved habitats and biotas, probably due to smaller size and lower deforestation. Some reduced natural areas could also be found in Tenerife and fewer in Gran Canaria (Gobierno de Canarias 1995).
Although partially or severely affected by human activities, some of these protected areas are especially important because of the habitat found here. These include the ‘Frontera’ Rural Park, ‘Roques de Salmor’ Integral Natural Reserve and ‘Tibataje’ Special Nature Reserve in El Hierro; ‘La Caldera de Taburiente’ National Park and ‘El Pinar de Garafía’ Integral Natural Reserve in La Palma; ‘Garajonay’ National Park and ‘Valle Gran Rey’ Rural Park in La Gomera; ‘Teide’ National Park, ‘Anaga’ Rural Park, ‘Teno’ Rural Park, Corona ‘Forestal’ Natural Park and ‘Las Palomas’ Natural Reserve in Tenerife; and Doramas’ Rural Park, ‘Los Tilos de Moya’ Special Natural Reserve and ‘El Brezal’ Special Natural Reserve in Gran Canaria (Gobierno de Canarias 1995).
The Canarian government together with European Community authorities have made a significant effort to preserve and protect the natural habitats and biota in the archipelago. Canary Islands Conservation Projects have been financed by the European Community (LIFE Funds). Accomplishments thus far include recovery plans and the reintroduction of the giant lizard of El Hierro (Gallotia simonyi machadoi); the conservation of Chiroptera and invertebrates in volcanic cavities; the conservation of five priority species of the Canarian sub-humid montane layer (monteverde); and the conservation of endemic birds, such as the Gran Canaria blue chaffinch (Fringilla teydea polatzeki), dark and white tailed laurel pigeons (Columba bolli, C. junoniae), and others. A number of marine projects have been conducted including measures for the recovery of the monk seal (Monachus monachus) in the Atlantic and support projects for the conservation of the loggerhead turtle (Caretta caretta) and the bottlenose dolphin (Tursiops truncatus) (Biodiversidad 2001).
Types and Severity of Threats
A variety of factors can be identified as threatening problems for Canarian biota and habitats, causing habitat loss and directly or indirectly menacing local species. First, tourist resorts and illegal building destroys habitats. In the last several years the tourist boom has increased. Many local and foreign enterprises have overdeveloped different areas of the islands, causing enormous habitat destruction. The illegal construction of houses inside protected areas is also a large threat. Fires are another significant threat. Accidentally and intentionally set for livestock grazing, crop planting, timber and real estate speculation, fires have dramatically reduced forests in the last decades. Pollution and uncontrolled dump sites are further concerns, despite some success by local authorities in regulating them.
The illegal capture and hunting of wild taxa are other threats to some species such as endemic laurel pigeons hunted for sport. Other bird species, such as canaries, goldfinches and warblers, among others, are trapped for the pet trade. Finally, one of the most dangerous factors is the introduction of alien species, which threaten local taxa with foreign diseases, hybridization risks, competition and predatory effects. The most significant introduced predators are feral cats and rats. Recent exotic pet fever has led to many established aliens like Psittacula krameri and Myiopsitta monachus. Even snakes, caiman turtles, red swamp crayfish and green iguanas have been found in the wild recently, some of them with breeding populations (Urioste 1999, Rodríguez and Urioste 2000).
Justification of Ecoregion Delineation
The Canary Islands are a volcanic archipelago rising up to 3,700m. The higher elevation islands in the Canary Islands archipelago form their own ecoregion because the moist climate here permits the development of distinctive vegetation types (including Macronesian laurel forests) containing many endemic species. The islands in this ecoregion are La Palma, El Hierro, Gomera, Tenerife, and Gran Canaria. The lower and drier Canary Islands of Fuerteventura and Lanzarote do not contain any wetter forest habitats and are placed within the mainland Acacia-Argania woodland ecoregion.
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Museo de Ciencias Naturales de Tenerife.
Prepared by: Jaime A. de Urioste, Maria Jose Bethencourt Linares
Reviewed by: In progress