Geography of Gran Canaria

Few islands justify a nickname as fully as Gran Canaria does that of 'miniature continent'. Within some 1,560 square kilometres of almost circular outline coexist climates, reliefs and ways of life that on the mainland would require travelling enormous distances: coasts of dunes and cliffs, agricultural midlands, pine-clad summits and an urban shoreline of Atlantic vocation. The island's roof is Pico de las Nieves, which at 1,949 metres crowns the central massif from which the whole territory descends towards the sea. This concentric arrangement —summit, midlands and coast— has long ordered island life and explains why, within a few kilometres, one passes from the sea of clouds to the sands of the south.

The most powerful structural feature of the relief is the radial network of ravines radiating from the summit towards the coast in every direction, conditioning settlement and communications. On the right bank of the Guiniguada ravine, the Real de Las Palmas was founded in 1478, origin of the present capital; the lower course of the Tirajana ravine crosses the Sardina plain in the southeast, where the ancient Canarians already irrigated their lands; towards the south open the Fataga ravine and those descending from the Tirajana and Mogán calderas, and towards the west the great Tejeda-La Aldea basin. In the north, ravines such as Azuaje, La Virgen and Oscuro shelter humid corners, while Guayadeque, one of the longest inhabited ravines on the island, preserves troglodyte hamlets and a remarkable density of natural and cultural heritage.

The geological reading of this relief points to an island of great antiquity, deeply shaped by erosion. Tirajana and Tejeda are considered erosion calderas, enormous basins carved out by water over millions of years, and the surfaces of the southwest are among the most worn-down in the archipelago. Standing out among these materials is the so-called Roque Nublo agglomerate, a rock that produces highly characteristic erosion forms: from it emerge monoliths such as Roque Nublo itself, which at 1,813 metres is, together with the crags of Tejeda and Artenara, the visual icon of the Gran Canarian summit. On the west coast, the Andén Verde cliff and the Dedo de Dios at Agaete complete a catalogue of spectacular landforms.

The climate assigns its roles according to orientation. The trade winds load the northern, windward slopes with moisture, forming the characteristic sea of clouds, while the southern, leeward slopes lie under pronounced aridity. On the coastal strip average temperatures hover around 20-22 degrees and rainfall barely reaches 200-300 millimetres a year; between 400 and 1,500 metres on the northern slope, by contrast, the mist condensing on the trees generates the so-called 'horizontal precipitation', whose contribution multiplies that of conventional rain. From this arises the island's essential contrast: a humid, agricultural north facing an arid south that today concentrates tourism.

Upon this climatic gradient, the vegetation arranges itself in curious altitudinal rings around the central peak: coastal and sand communities, thermophile forest of junipers, mastic trees and wild olives, cardón-tabaiba scrub, laurel forest —present only on the northern slope—, pine forest and summit vegetation of brooms. Gran Canaria belongs to the Macaronesian region and harbours numerous endemic genera, such as Argyranthemum, Echium, Aeonium and Sideritis, the fruit of adaptive radiation and vicariance processes that make the island a natural laboratory of insular evolution. In 2005 UNESCO declared it a Biosphere Reserve, recognition of that value and of the urgency of protecting its living landscapes.

The forests tell the island's environmental history. On the summits and western crests the Canary pine forest endures, with Tamadaba as its most celebrated enclave and refuge of the Gran Canaria blue chaffinch, of which barely a hundred pairs breed in the southwestern pine woods. The laurel forest had its central sector in the Montaña de Doramas, which the first Spaniards described as a fertile grove with abundant water, great springs and such thickness that the sun could hardly be seen; the agricultural economy implanted after the conquest in the sixteenth century —sugar cane, vineyards, timber, charcoal-making and pasture— caused an intense regression of that forest. Today only redoubts remain, such as Los Tilos de Moya, Barranco Oscuro, Barranco de Azuaje and the Brezal del Palmital, small but decisive for soil protection and aquifer recharge.

Water is the other geographical key. Gran Canaria was, by far, the island with the most surface water in the archipelago: around 1850 its irrigation flow per square kilometre was several times that of Tenerife or La Palma, and at that date some 300 'maretas' were counted, waterproofed reservoirs of indigenous tradition. The land distributions after the conquest mention irrigation channels 'from the time of the Canarians' and aboriginal ponds reused to water the cane fields, proof of a hydraulic culture predating colonisation. Upon that heritage, the island developed a dense catchment network: dams impounding the waters of the ravines and, in the face of growing scarcity, seawater desalination plants such as those operating on Gran Canaria since the twentieth century.

Human geography reproduces the physical contrasts. Las Palmas de Gran Canaria, founded beside the Guiniguada and later extended towards the bay of La Isleta, is today the most populous city in the Canaries, with nearly 400,000 inhabitants concentrated along some ten kilometres of coastline between La Isleta and Jinámar, beside the urban beach of Las Canteras and the Puerto de la Luz. The plains and midlands of the north and the interior sustain the agricultural tradition, from Gáldar to the Sardina plain in Tirajana, while the arid south has concentrated tourist development since the 1960s around the dunes and lagoon of Maspalomas, a singular ecosystem under strong human pressure and today the object of recovery plans. Altogether, the island approaches 860,000 inhabitants: a small continent in demographic terms as well.