Tenerife: Visit to Las Canadas National Park

One of the most dramatic and rewarding experiences in Tenerife is a visit to Las Canadas National Park. This wonderful area is designated as a World Heritage Site. The whole park is a caldera that consists of the remains of a super volcano that collapsed nearly two hundred thousand years ago. Today, we think of the massive volcanic cone of Teide as being impressive; it is the highest mountain in Spain, but it is nothing compared to the original volcano that stood on this site.

A visit to Las Canadas National Park from Puerto de la Cruz starts with a drive through a large amount of suburbia. However, this can be interesting for the botanist. On a wall beside a suburban road, we found the Canarian endemic member of the stonecrop family, Aichryson parlatorei in excellent flower. Entering the edges of Aguamanza, and before reaching the pine forest, on the roadside verge were fine examples of the beautiful, purple flowered endemic Pericallis echinata and on the same verge was the endemic figwort, Scrophularia smithii.

Aichryson parlatorei

Pericallis echinata

On leaving the suburbs, the terrain begins to rise up towards the caldera through a zone of Canarian Pine Forest. The species of pine making up the woodland is Pinus canariensis and is endemic to the Canary Islands. Especially on Tenerife, it produces large areas of forest. Amongst other things, this habitat is home to the delightful and endemic Blue Chaffinch. As lichens are a group that I am particularly interested in, I was delighted to see a range of species that would never grow on pine in Britain, but are doing exceptionally well on the trees here. Species included the hairlike Alectoria sarmentosa and Usnea articulata which were surprisingly difficult to separate when growing together in Tenerife. Perhaps the greatest surprises were great cabbage-like bushes of Common Lungwort Lobaria pulmonaria and the delightful, bright yellow lichen Teloschistes flavicans. This latter is particularly rare in Britain, and is particularly pollution sensitive.

Canary Island Pine Forest
(Photograph: Amanda Davey)

Lobaria pulmonaria

Teloschistes flavicans – photographed on the Anaga Ridge

At lower levels, the flowering plant flora of the woodland is not rich, but as it opens out higher up, the verges especially support a wide range of species. These include the almost white endemic Sideritis oroteneriffae which seems to be restricted to a particular altitude zone in the higher part of the forest. Sideritis is another of those genera that has many endemic relatives in the Canary islands. Also seen here are Aeonium sedifolium and areas where the beautiful, if introduced, Californian Poppy makes a striking show. Another rather scarce little plant from this zone is Helianthemum juliae. The distinctive black triangular shapes at the base of the petals help to distinguish it from other rock roses. It grows amongst its much taller relative Cistus symphytifolius with its large pink flowers. In this same area, the close relative of Cistus symphytifolius occurs, but is rare and differs only slightly. This is Cistus osbeckifolius, a species that I looked out for hard, but failed to find.

Sideritis oroteneriffae

Aeonium spathulatum

Helianthemum juliae

Cistus symphytifolius

Once out into the open and arid countryside of Las Canadas Country Park, the main features are the dotted, bushy clumps of species such as the white Spartocytisus supranubius, the yellow Tolpis webbii and Adenocarpus viscosus. The white flowered Argyranthemum teneriffae is abundant, especially by the road, as is the scabious relative Pterocephalus lasiospermus. These are the main components of much of the flora of Las Canadas.

Teide

Road through Las Canadas
(Photograph: Amanda Davey)

Las Canadas Vegetation
(Photograph: Amanda Davey)

Argyranthemum  teneriffae

Pterocephalus lasiospermus

Spartocytisus supranubius

It is on approaching the base of Teide and the Parador that the most dramatic species of the area becomes such a feature. This is the endemic bugloss Echium wildpretii that is virtually restricted to Las Canadas in the world. Outside Las Canadas, and entering it from the south, it can be encountered just above Viraflor where Lotus bertelotii can be seen so well. Close to the base of Teide is the real home of Echium wildpretii, where its tall spikes can dominate the arid volcanic landscape.

Echium wildpretii
(Photograph: Amanda Davey)

One species I had particularly hoped to find is the endemic Viola cheiranthifolia. This delightful little plant grows amongst stones on the slopes of Mount Teide itself. Although I was given directions to a relatively low altitude spot where it was supposed to be, even scanning with binoculars I failed to find it. I had also hoped perhaps to see it in one of the gardens I visited, but this plant eluded me. Perhaps May is the wrong time of year for it.

In the past, there were gardens surrounding the Park Visitor Centre, where a number of the endemic species of Las Canadas could be seen. This included the rare Cheirolophus teydis with its pale yellow flowers. Cheirolophus is another important genus with several Canarian endemic species, and most are rather rare, and restricted in range. I have only ever seen this one in flower in September and October. This time I could not even see it in seed.

Cheirolophus teydis

Another blue flowered endemic with a very restricted range is Nepeta teydea. My experience is that it is restricted to a small area to the south west of Teide itself where it is easy to see on the roadside verge. Also growing in this area is the ordinary, but endemic Arrhenatherum calderae, a relative of our very common false oat grass. This one, however is extremely restricted in occurrence.

Nepeta teydea

Arrhenatherum calderae

No visit to Las Canadas would be complete without a chance to marvel at its volcanic splendour. At 3718 metres (12198 feet) Mount Teide is a high, and impressive mountain. At this altitude, it frequently retains snow on its upper reaches well into May. It is possible to ascend the mountain by cable car. More often than not, the view, although majestic, is a sea of white cloud far below, out of which emerge other members of the Canarian archipelago. Beneath the summit can be seen Teide’s Nostrils. These are the result of an eruption that was witnessed by Columbus as he sailed past Tenerife in the 16th century. The last eruption took place in 1909, and during one eighteenth-century eruption, the harbour of a fishing village (Garachico) on the north coast was dramatically filled with larva.

Teide’s Nostrils

Landscape dominated by volcanic lava
(Photograph: Amanda Davey)

Solidified lava flow near the base of Mount Teide

Banded volcanic ash near the edge of Las Canadas National Park

La Palma rising above surrounding cloud

Two features of particular importance are the dramatic lava flow that can be seen from the road close to the base of Mount Teide. A convenient car park allows the visitor to enjoy fine views of it. On leaving Las Canadas on one of the major access roads that heads to La Laguna, the road passes by a spectacular series of layers of ash ranging from white to almost black. Once again, there is a convenient car park here, and in suitable weather, which is frequent, the island of La Palma to the west can be seen rising from the surrounding cloud bank. One feature of Canarian weather seems to be that the Anaga Ridge, and Puerto de la Cruz are frequently smothered in cloud while Las Canadas National Park rises majestically above it.

Woodland Continuity

Common Lungwort - Lobaria pulmonaria

It was Francis Rose who, way back in 1974, first recognised the value of lichens in assessing ecological continuity in woodland. A list of seventy species was compiled by the British Lichen Society which were found to be most closely associated with ecological continuity and lack of disturbance. This list was used to arrive at the New Index of Ecological Continuity (NIEC). Added to this, a list of rarer, bonus species could be used to calculate a second index. These indices work well for much of Britain, however further indices were formulated for areas where other lichens were found to indicate continuity. Where the large and showy common lungwort Lobaria pulmonaria works well as an indicator throughout much of England, it is a common species in Western Scotland, and its presence there cannot be used as an indicator of continuity. For upland England and Wales, as well as in Western Scotland, the Eu-Oceanic Calcifuge Woodland Index is used. Further indices are used in Scotland and Western Ireland.

Heterodermia japonica growing amongst a form of
Hypnum cupressiforme

It was noticed while undertaking a survey in Eastern Cornwall in a nature reserve known to consist of ancient woodland, that the nationally scarce lichen Heterodermia japonica occurring on a beech branch was fertile, and supported a number of small, disc like fruits or apothecia. A day or two later, there was a depression in the lichen where the fruits had been. It seemed most probable that a slug had browsed them off. Some six months later, the site was revisited, and small daughter colonies of the lichen were found up to six feet away from the parent lichen. If, as seems probably the main vector for spreading the spores of ancient woodland indicator lichens is the digestive system of slugs, then distribution is going to be very slow indeed. No slug will ever take the trouble to cross a major road simply to spread a particular species of lichen.  Slugs are also ideal as vectors as the spores are conveniently attached to the substrate in their slime trail. It would be interesting to experiment by collecting slugs from known ancient woodland sites and introduce them to more recent sites to see if indicators of continuity became established.

Francis Rose, and Richard Hornby of the then Nature Conservancy Council, made a list of higher plants reckoned to be associated with ancient woodland. While the clear felling of a wood totally removes the corticolous lichen flora, higher plants are more robust, and are therefore useful in assessing ancient woodland sites. It is most important to remember that the higher plant list consists of common species, and that it is the total of species present that is significant. The absence of rarer species lacks significance just as does the presence of one or two of the common indicators. Higher plant indicators are all photosynthetic, and therefore need adequate light levels. In many ancient woodlands, due to the current lack of grazing, the ancient woodland flora is confined to rides, or to the roadside banks of the edge of woods.


The British Bryological Society have also made a list of mosses and liverworts most closely associated with woodland continuity that works well and I understand that in the insect world, similar lists of beetles and hoverflies have been made. It would be most interesting to know if there are correlations between all ancient woodland indicator lists.

Barnacle Lichen - Thelotrema lepadinum

One of the difficulties of using lichens, and to a lesser extent bryophytes as indicators of ecological continuity is their sensitivity to air pollution. Throughout most of Central and South-eastern England until some thirty years ago, acid rain and industrial pollution all but destroyed the lichen flora totally, and with it the information it could give. It is lucky that the Barnacle Lichen, Thelotrema lepadinum, which is a most useful indicator, is relatively tolerant of sulphur dioxide in the atmosphere, and it has been found, as would be expected due to the ecological continuity of the sites, in both Epping Forest and Hatfield Park. Even low lichen indices of continuity in these areas can be treated as significant.

Most of the early work that related lichen richness with ecological continuity took place in the deciduous woodlands of England, Wales and North-western Scotland. In Central and Eastern Scotland there are pine forests of great ecological importance and continuity. The lichen flora associated with these trees is very different, as are the habitats they provide. Dr Brian Coppins, the foremost Scottish lichenologist, is known to say that the only good pine tree [for lichens] is a dead pine tree. He points out that a pine provides habitat for lichens for a longer period as a standing dead tree than it does when alive. While coppice woodlands with hazel or hornbeam in England can be important for lichens, and the coppice poles can support a rich flora, this is nothing compared with the incredible richness found in a few very important and ancient hazel woodlands in western Scotland and in the Hebrides.

A further index using lichens is also used, but these days only occasionally. This is the Revised Index of Ecological Continuity (RIEC). In this case thirty species are used, and by multiplying the number of species by 5, a figure for the index is found as a percentage. A score of 100% is reckoned to equate to a wood with perfect ecological continuity. However scores higher than a hundred are possible such as Glen Shira in Scotland with a score of 130%. Using the New Index of Ecological Continuity, a total of thirty or more species that includes bonus species is thought to indicate a wood of high conservation value. Parham Park which is arguably the best example of ancient woodland in Sussex has a total of 27 NIEC species added to which should be 3 bonus species bringing a total score of 30. In other parts of Britain, much higher totals are found.

Francis Rose was never keen to indicate the meaning that should be given to higher plant indicator totals. However, he told me he was of the opinion that a score below twenty species indicated a wood of low conservation interest. Similarly a score of twenty bryophytes indicate conservation value, though this is reduced to fifteen throughout South-eastern England.

Hoverfly - Calliprobola speciosa

Beetle - Helops caeruleus

Some groups of insects also contain species that are good as indicators of ecological continuity. Two groups certainly spring to mind which are  hoverflies and beetles. Two illustrated here are the rare New Forest hoverfly Calliprobola speciosa which could be used, as could the beetle Helops caeruleus. There are many more hoverflies and beetles that could be used as indicators of ecological continuity.

This account has been to do with ancient woodland with continuous canopy cover. This type of woodland is not rich in butterflies. For butterfly richness, it is the woodland rides and their floristic richness that are important.  Woods such as Bernwood in Oxfordshire are soft wood plantations, but the richness of the rides make them outstanding for insects such as butterflies. Beautiful bluebell woods are not examples of woodland with long continuity, but are none the less very important. Similarly, it is coppiced woodland that generally provides habitat for greatest flowering plant biodiversity. It is a balance that is required as well as the importance that is given to woodland with a long history.