|
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
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