The Canary Islands
Montelongo, F.G.; Romero, C.D.; Tena, R.C. (2000). The Canary Islands, in: Sheppard, C.R.C. (Ed.) Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. pp. 185-199
In: Sheppard, C.R.C. (Ed.) (2000). Seas at the millennium: an environmental evaluation: 1. Regional chapters: Europe, The Americas and West Africa. Pergamon: Amsterdam. ISBN 0-08-043207-7. XXI, 934 pp., meer
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Documenttype: Revisie
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| Auteurs | | Top |
- Montelongo, F.G.
- Romero, C.D.
- Tena, R.C.
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| Abstract |
The Canary Islands of Spain are of volcanic origin, situated in the north Atlantic between 39°45' and 14°49'N, and between 31°17' and 13°20'W. They are markedly different from the nearest part of the continent of Africa in spite of their proximity to it, with rugged shorelines surrounded by an irregular oceanic seabed. Their sublittoral slopes are steep and great depths are found not far from the shoreline. Thus, the area for primary producers is small and production capacity is limited. Rocky seabeds are found everywhere, while sandy, clay or shell sediments are rare though they are more common in the eastern islands. The rocky bottoms are very uneven and craggy , with many shallows, cliffs and underwater caves. Their position in a subtropical area near the west of Africa has resulted in a unique climate. They are alternatively under the influence of the subtropical hot high pressures causing a stable climate, and of less frequent polar low pressures, which bring unstable rainy weather. The Azores anticyclone is the primary factor resulting in the Trade Winds and stable weather, but when high pressure moves towards the west, outbreaks of colder air masses from the north and, less frequently, hotter outbreaks from the Sahara may reach the islands. This climate together with the influence of the Canary Island Stream gives the islands their mild temperatures and low daily variation which are so favoured by visitors. The pelagic system is affected by the presence of different oceanic species from tropical and from temperate seas. This brings a relatively large marine biomass to the islands. The pelagic coastal system may also be classified into a group of species living nearer the coast, and another belonging to oceanic waters which go to coastal waters to reproduce and grow. Another unique feature of the Canarian coastal ecosystem is that many deep-water species live very close to the coast and rise to surface at night. These usually deep species have become an integral part of this shallow ecosystem. This phenomenon is almost unique in calm waters. The most common communities in this area are those of rocky shores which are adapted to extremes of moisture, salinity, abrasion and light intensity. Production per unit area is high, though the total area is low. Fishing resources are made up of a great variety of species, most of them endemic, but low in number. Fishing for shellfish is a traditional activity even though production is relatively low. In some places this resource is over-fished, but most of these species reproduce in the winter and grow quickly, so that this over-exploitation may be replenished fairly quickly. Development in the last decades has favoured intensive and indiscriminate use of the limited marine resources of these islands. Only in 1986 did the Local Government of the Canary Islands establish rules to protect and recover marine resources. However, after ten years, only a few protective actions are well established and results are scarce so far. Another important problem for the coastal ecosystem comes from displacement of the population due to the increasing demands and pressures of tourism in coastal tourist resorts. Sewage disposal occurs by outfalls into coastal waters, though in the last few years public opinion has demanded action to overcome often severe pollution of bathing beaches, so that the main cities such as Santa Cruz de Tenerife now have large coastal sewage treatment plants, whose treated waters are also used for agricultural purposes. |
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