Introduction

The Canary Islands lie in the Atlantic Ocean, one hundred kilometers west of the Moroccan coast. They consist of seven larger islands: Tenerife, Fuertenventura, Gran Canaria, Lanzarote, La Palma, La Gomera and Hierro, and four smaller ones: La Graciosa, Alegreza, Lobos and Montafla Clara.

The formation of this archipelago can be attributed to the movements of the African and European plates which, in the middle of the Cretaceous period (about 100 million years ago), caused the raising of the Alps. The rocks connected with these events and therefore representing the most ancient part of the archipelago have been found in Fuertenventura.

The following stages of the formation of the islands resulted from the great volcanic eruptions which took place between the Miocene (19 million years ago) and the Pleistocene (0,5 million years ago) periods. The nearest islands to the African coast have proved to be the most ancient, whilst moving away from the coast and towards the open ocean, the islands become younger and younger. Moreover, if we go from east to west the sounds around the individual islands get deeper - about 1000 metres between the African coasts and Lanzarote and more than 4000 meters around La Palma. In other words the further west we go, the more the islands loose their continental character and take on a more oceanic nature.

The particular geographic position of these islands enabled the conservation of many kinds of tropical and sub-tropical vegetation which in the past could also be found in the Mediterranean basin but has disappeared as a consequence of two great catastrophic events: the desertisation process and a series of glacial cycles.

Geology

The former event took place in the late Miocene period some 8-9 million years ago and was due to the raising of the mountain chain now known as the Atlas Mountains and Sierra Nevada. This occurrence meant a smaller supply of water from the Atlantic Ocean and a consequent drying up and cooling down of the climate in the surrounding areas. The series of glacial cycles took place between the Pliocene and Pleistocene periods about 1 - 1.5 million years ago causing a sudden cooling down of all the northern hemisphere climates as well as the definite disappearance in southern Europe and in the Mediterranean countries, of all the sub-tropical species that survived the Miocene events.

These geological events have also influenced the other Atlantic Ocean islands: Azzorre, Madeira, Salvajes islands and Capoverde. These islands and the Canary Islands form the biogeography region called Macaronesia. The eruptive cycles and the consequent dismantle of the volcanic cones due to erosional agents have given a peculiar aspect to this archipelago. The islands come out from the sea with steep coasts where there are many torrents flowing in deep gorges called "barrancos". These valleys, caused by the repeated action of the waters, are arranged almost in a radial shape around the principal volcanic structure.

At the outlets to the sea of these torrents the coasts are shallow and only very seldom made of sand and more often formed by volcanic rocks. The mountains are often very high as in Tenerife's Mount Teide which reaches a height of 3718 meters making it the highest volcano in Europe. The first men arriving in the waters of the "Lucky Archipelago" saw flames and smoke coming out of Mount Teide and so named Tenerife "Isla del Infierno". Fortunately the name never reached the pages of popular history or geographic maps, and the current name seems to be due to one of Viana's poems, in which the author described the mountain as "tenerife" - the mountain with snow.

Climate

Snow and fire are in fact the two characterising extremes of the whole archipelago, highlighting the almost double nature of the Canary Islands. Moreover, the volcanoes themselves, with their awesome height and dimensions are the origin of the great climatic contrasts on these islands. The humid and fresh air streams coming from the west and northwest are called "Trade winds" and determine a typically oceanic humid and fresh climate in the windward sides resulting in great luxuriance. The effects of these trade winds can be seen especially between 300 and 1500 meters - under this zone the effect can hardly been felt, whereas above it there is an arid climate characterised by very hot dry summers and cold winters.

The sides of the islands that face towards Africa do not get the positive effect of the trade winds and are also influenced by the hot, dry winds blowing from the Sahara. This influence results in a dry and arid climate. These climatic contrasts have spawned the amazing array of vegetative species that can be found on the Canary Islands.

Human Impact

The agricultural exploitation of Canary Islands has been very obviously affected by its geological situation. There is no definite data about the first colonisation of the islands, but is likely that the first inhabitants, called Guanches or Canarios, were north African somatic types. They would have shared much with the Neolithic culture, and would have lived at subsistence level, in harmony with nature thanks to a limited agricultural skill set.

Phoenicians, Persians and Carthaginians probably landed on the islands about 500 years BC, but Pliny the Elder seems to be the first person to tell about an expedition to the Lucky Islands led by Juba, Prince of Mauritania, at the time of the Emperor Augustus. In the late Middle Ages, ships from Genoa and Majorca arrived at the islands and by the end of 1496 the Spanish, led by Fernandez de Lugo of "Catholic Kings", comprehensively conquered the Canaries. They annexed the islands under the Crown of Castilla, dividing them between themselves and beginning the transformation of the vegetated landscape of the archipelago.

They began a massive deforestation to make room for crops - especially cereals, sugar cane, vineyards and orchards which found ideal conditions on the humid sides of the islands. On the higher altitudes, sheep farming replaced agriculture causing a strong pressure on the native vegetable patrimony. When the international trade increased, the Canary Islands became a major stopping off point for the ships coming and going to Spain from South America. Many species of exotic, edible and ornamental plants were introduced to the archipelago, which became a kind of special garden to acclimatise them. As a consequence of this system, many species coming from central and South America entered the local flora community and in some cases completely overwhelmed it.

At present, the exotic flora of the Canary Islands consists of about five hundred species, many of which very often live in areas drastically altered by their human residents. In recent years, the abandonment of traditional agriculture, combined with the increase in artificial spaces and the expansion of urban and industrial areas to accommodate the rising demographic pressure of tourism, has brought about a considerable deterioration of the environment.

This encroachment of human activity on the natural surroundings, like the construction of roads, has reduced the original ecosystems to only 20% of the total area. A representative case is that of Argyranthemum coronopifolium, an endemic plant condensed in a small area on the Teno peak (Tenerife): the construction of an asphalt road has divided the individual plants of the same population making them unable to fertilise one another. In such conditions, the number of seeds, and therefore the number of new plants, tends to decrease more and more, and as a consequence the species is due to become extinct.

Classification and Habitat

The different kinds of volcanic material that composes the land surface combined with the great variety of the climate and the human activity, has determined a varied and characteristic landscape that is home to a great number of different species. One significant contribution to our knowledge of this rich heritage of wildlife is Webb & Berthelot's monumental work Histoire Naturelle de Isle Canaries. PB. Webb (b. 1793-d. 1854) was a rich English gentleman traveling around the world and indulging his love of botany. In the course of his travel from Madeira to Brazil in 1828 he stopped in Tenerife where he met S. Berthelot (b. 1794-d. 1880) who for some years had already been collecting plants and insects from the islands. Mr. Berthelot kindled in him such a deep love for Canary Island nature that Mr. Webb remained in Tenerife for two more years, giving up his journey to Brazil. Over the next twenty years, Mr. Webb and Mr. Berthelot devoted themselves to the drawing up their grand work which was eventually published in Paris in one hundred and six installments between 1835 and 1850.

This work, to which two hundred and eighty seven lithographic prints were added, consisted of three volumes dedicated to the ethnography, geography, zoology and botany of both the Canary Islands and of the other islands that compose the Macaronesia. In this work the vast majority of plants found in the archipelago are registered, two hundred and thirty two of which for the first time. The huge amount of the material that was collected during this exploration is now kept at the herbarium in the University of Florence to which it was donated after Webb's death. The herbarium in Florence is of primary historical and biological importance for all scholars interested in the flora of the Canary Islands.

At present, the flora of the islands consists of about two thousand species, five hundred and twenty of which are to be considered endemic, and as many as five hundred and ninety three that are rare or becoming extinct. Many of these species are geneses or sub-geneses that are impossible to find outside the Canary Islands. Such great variety might in future be an important genetic resource for new plants of agricultural, horticultural or medical interest, provided the environment is protected from the often thoughtless action of man.

The aim of this short guide is to get in contact with some of the species most characteristic of the great bio-variety enjoyed by these islands. To do this, we have catagorised every species according to the surroundings where they are mostly found, including a brief introduction concerning the typical habitat followed by the description of the individual plants. To all this organised research a vast series of pictures has been added to help spread of the knowledge concerning this great scientific and naturalistic heritage. We have also added pertinent news about the surroundings as well as noting the species considered by the European Community of great value and therefore deserving protection.

We have identified several different habitats in the Canaries every one of which contains its own typical species. The following are those habitats we have singled out for closer inspection:

• Coastal
• Arid
• Laurel-like Trees
• Pine Forest
• High Mountain
• Rocky
• Ruin
• Artificial

Every one of these ecosystems has been described by its principle characteristics to enable the reader to easily recognise it. This description is followed by one related to the most interesting plants that best represent the habitat with descriptions following the same order in which the plants are named in the text. In the part concerning the artificial habitat, the name of the plants will be in strict alphabetical order.