Pages

Friday, 7 March 2014

Quest for the Wild Canary Part 2: Plants and habitats



Tricholaena sp, Teneriffe
The Canaries are famous for their flowers, and although as our visit was in February there was not a great number in bloom, the endemic plants are of great interest to botanists. One might expect the plants to be the same as you would find in Spain or North Africa, but when the islands first appeared above the sea the Mediterranean did not yet exist. Instead, the western end of the ancient Tethys Ocean still separated Africa and Eurasia, and the Atlantic was much narrower. The native flora of the islands, or at least the oldest elements of it, trace their origin to the vegetation that once grew on the northern and southern shores of the Tethys, which has since been obliterated by the northward movement of Africa and India.
Map of Miocene Europe as the Tethys was closing
In the isolation since then many of the plants have undergone radiation into numerous species, each confined to a separate island or part of one, depending on the local microclimate. Especially prominent groups are the succulent Aonium, a wide variety of shrubby or succulent Euphorbia, and most spectacularly the giant Echium species.
Rosette Aonium, laurasilva forest, La Gomera

Shrubby Aonium, Teneriffe
Euphorbia sp, Teneriffe
On Teneriffe and the other high islands there is a series of well defined habitats as you travel up the mountains. At sea level there is a band of scrub and grassland with shrubby Euphorbia, with more lush vegetation on the northern sides where they get more rain. Also living at sea level is the famous Canary Island Palm, which can now be seen planted as an ornamental palm tree all over the world.  Dryer areas have more succulent vegetation.

Phoenix canariensis
Laurasilva forest, La Gomera
Higher up the climate turns cooler and wetter with the most characteristic forest type, the laurasilva forest. This has dense growth of Laurus novocanariensis (a local relative of the Sweet Bay Laurus nobilis) and other trees, which in clearings and at the upper and lower limits have stands of Tree Heather Erica arborea, which can grow to over 4m tall. This forest type is found in other parts of the world as well, and is a survival of the lush subtropical forests of the Miocene.
Erica arborea
Where it is too high and cool for laurasilva forest, it is replaced by the coniferous forests of Canary Pine and Cistus.
Canary Pine forest
Above 2400m the climate grows too extreme for trees to survive, and an alpine flora replaces it. Most prominent here is the tree Echium, E.wildpretii, a spectacular biennial that can be grown in the south of England in the right spot.
E.wildpretii
On Fuerteventura and the other eastern islands, erosion has reduced the height of the islands to the point where only the highest points trap enough water for trees, and a combination of this and the proximity of the Sahara means that the islands are essentially desert surrounded by sea. There is no laurasilva forest present on the islands now, and the habitat is dominated by drought resistant and succulent shrubs and grasses, and even these have a hard time surviving.
drought-resistant sub-shrub, Fuerteventura
So much for the native vegetation. Unfortunately, as well as gardens and such much of the dry areas on Teneriffe at least are now covered with invasive Opuntia, which crowds out the native vegetation. The cacti were originally introduced to the islands to host the cochineal insect, a scale insect that produces carminic acid as a deterrent to predators. The insects are collected and processed to produce the famous red dye. When chemically synthesized dyes became available the industry collapsed, and now Opuntia appears to be running wild on the islands. Clearing it may prove difficult, although a similar problem in Australia was resolved by importing a cactus-easting moth, Cactoblastis cactorum, which destroyed the pads of the plant.

Opuntia with cochineal scale
Next time, insects and other invertebrates.

 

(images from Wikipedia, cpgeosystems.com, and my own photographs

No comments:

Post a comment