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Geography and Geology
Terrestrial Biodiversity
Marine Biodiversity
Biodiversity Research
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The Azores

flag_coatofarms_azoresNumber of islands: 9 main islands
Capital: Ponta Delgada
Area: 2314 km2
Population: 241,700 inhabitants (2004)
Population density: 106 inhabitants/km²
GDP/inhabitant: 17 800€ (2005)
Climate: humid and cool oceanic
Economic activities: agriculture, fisheries and tourism
Official language: Portuguese
Status: Portuguese Autonomous Region, EU Outermost Region (OR)
Climate: maritime sub-tropical

General Information

The Azores is composed of 9 main islands that stretch across the mid-Atlantic Ocean for over 600 km in a northwest-southeast direction, making it possible for the archipelago to have an exclusive economic zone of nearly 1.1 million km2. At a distance of about 1500 km from mainland Portugal and 3900 km from the east coast of North America, the archipelago forms the Autonomous Region of the Azores, one of the two autonomous regions of Portugal (the other being the archipelago of Madeira).


The Azores economy is based mainly on agriculture, fisheries and tourism.

In the agriculture sector, cattle-raising occupies a major role, while some crops deserve mentioning, as is the case of pineapples, vine plantations, potatoes, tobacco and tea.

Fig 1_Fisheries are an important economic activity on all islands. Fishing methods are highly traditional among Azorean fishermen, hook and line still being the major fishing gear used. This has allowed for a sustainable exploration of resources over centuries.
Not surprisingly, industry in the Azores is based mainly on the production of dairy products (milk, cheese) and transformation of fisheries products, such as tuna.
It is tourism, however, that has been gaining most terrain in the economic scenario in recent years. It is far less developed than those industries of its Macaronesian neighbours, Madeira and Canary Islands, and its focus is mainly on the archipelago’s natural heritage. On the reverse side of the coin, the sector has seen great development and important investments are a result of this. Fig 2_Over the past decade tourist infrastructure has grown markedly and, also as a measure to combat isolation, the frequency and diversity of air routes within the islands and to the exterior has risen. There is a growing interest in the construction of ports and harbours and in coastal development, altogether.

Despite these recent developments, and partly because tourism in the Azores is greatly based on the islands’ cultural diversity, quality of life and natural beauty, in 2008 they were ranked 2nd best islands (or group of islands) in the world for sustainable tourism by National Geographic Traveler.

Geography and Geology

The islands of the Azores are located along the mid-Atlantic ridge system, atop an active triple junction between three large tectonic plates: the North American Plate, the Eurasian Plate and the African Plate. The two westernmost Azorean islands (Flores and Corvo) actually lie on the North American plate. All of the islands have volcanic origins, although one, Santa Maria, also has some reef contribution and an abundance of sediments where marine fossils have been discovered.

Fig 3_Volcanism associated with the formation of the islands arises from the fact that the Azores Triple Junction involves rifting, a process whereby the crust is spreading along three ridge legs radiating out from the triple junction. The volcanism is also related to the Azores hotspot. Geologically, the Azores comprise a 20–36-million-year old volcanic plateau; the oldest rocks (composing Santa Maria Island) emerged 8.120 million years ago, whereas the youngest (forming Pico Island) are about 250,000 years old.

Fig 4_Due to their volcanic origin, the islands are by nature rugged, with high peaks contrasting with calderas (large depressions resulting from the collapse of the centre of volcanic systems) that host interesting lagoon systems. As a result of several recent historical lava flows, there is a great concentration of lava tube caves and pits in the Azores. A total of 250 underground cavities, including lava tubes, volcanic pits, pit-caves, and sea-erosion caves, are known to exist in the Azores, creating many kilometres of cave passages, extraordinary geological formations, and unique fauna adapted to caves. The relatively recent volcanism of the Azores results in the occurrence of numerous associated phenomena, such as thermal springs, geisers and hot springs, as well as high seismic activity.
Fig 5 (coming soon)
The last volcano to erupt in the archipelago was the Capelinhos Volcano in 1957, in the western part of Faial Island, increasing the size of the island by 2.4 km, but it's estimated that the great part of it will be washed away in next 20 years.


Located in the Atlantic Ocean at a mean latitude of 38°30? N, the Azores enjoy a very humid cool-oceanic climate with fairly minor annual variations. The sea exerts a tampon effect on the Azorean climate, with temperature and precipitation varying little throughout the year: temperatures range from 16°C (60°F) in winter to a comfortable 26°C (79°F) in summer. The sea is warmed by the Gulf Stream and sea water temperature varies from 14ºC to 22ºC. The influence of the anticiclone (which goes by the name of Azorian anticiclone due to its permanent position over the archipelago), the western wind action and the disturbance of the polar front are the principal factors conditioning the climate of the islands. 

Terrestrial Biodiversity

The fact that the Azores is composed of islands (i.e isolated regions) contributes to the emergence of endemic species that constitute a unique natural heritage of global importance. Of the 4467 species and subspecies of terrestrial plants and animals known to inhabit this archipelago, 420 are endemic, some of which are confined to few or only one location!

Fig 6 Notwithstanding this significant percentage of terrestrial endemism, the native fauna and flora of the Azores is impoverished when compared to the other Macaronesian archipelagos (Madeira and the Canary Islands). Given the isolation of the Azores, the ancestors of all the terrestrial endemic species found in the archipelago had to travel over a significant water distance (more than 1200 km) from neighbouring Europe and about 800 km from Madeira Island. Additionally, the Azores archipelago is geologically young and colonization by flora and fauna occurred over a short geological period. Accordingly, it is of no surprise that the only indigenous terrestrial vertebrates are bats (two species) and birds (16 species) (Borges et al., in press). Among these is the Azores bullfinch (Pyrrhula murina), an endangered bird species with a population of about 250, included in the IUCN Red List, whose population is restricted to the cloud forest on the east of the Island of São Miguel (McGinley, 2007).

Table I: Number of currently known terrestrial species and subspecies in the fauna and flora of the Azores (based on the catalogue of Borges et al., 2005 in Borges et al., in press).
Algicolous fungi 1 0
Lichenicolous fungi 22 0

Regarding native plant communities, laurisilva - a humid evergreen broadleaf laurel forest – was considered up until recently to be one of the predominant vegetation forms in the Azores. The Azorean laurisilva differs from that found on Madeira and on the Canary Islands, in terms of species composition. Today, only 2% of the original Laurel forest cover has been spared from deforestation.

Fig 7
Fig 8
In contrast to other Macaronesian archipelagos, the Azores only has one endemic genus of vascular plants (Azorina). After human settlement, other types of vegetation cover became progressively dominant. Presently, they include pastureland, production forest (mostly with Cryptomeria japonica), mixed woodland (dominated by non-indigenous taxa), field crops and orchards, vineyards, hedgerows, and gardens.

Fig 9_These islands were discovered in the fifteenth century, and more than 500 years of human settlement have taken their toll on the local fauna and flora. The indigenous flora and fauna have been under severe pressure from deforestation, agriculture and the introduction of invasive species. Approximately 70% of the vascular plants and 58% of the arthropods found in the Azores are exotic, many of them invasive.

Marine Biodiversity

The most outstanding detail of the global picture of the marine fauna and flora is the low number of endemic species. In fact, evidence of endemism among the Azorean marine and maritime biota is sparse and clearly apparent only with regard to the supralittoral, maritime vegetation. Most of the organisms now present probably reached the Azores in the last 17 thousand years - a too short period of time for species differentiation. This “late arrival” provides an explanation for the existence of fewer species - 2100 fauna species and over 300 species of algae - and the low amount of endemisms in the Azores. The lack of extensive margins of shallow water also obstructs colonization of the islands by littoral organisms and the uniformity of shore types limits recruitment, even of successful immigrants, and coastal diversity and sources of primary productivity are only enriched in a few significant wetlands. The greater distance from continental coasts is another important factor contributing to the low number of shore fishes in the Azores.

The majority of the Azorean coastal and marine biota is very modem and comprises species that have arrived predominantly from the eastern Atlantic, especially the area between southern Europe (Lusitanian Region) and northwest Africa (Mauretanian Region), including the Mediterranean, but also contains species from other Atlantic sources. The picture that emerges is that the Azores is at a ‘cross-roads’ where shallow marine fauna and flora of different origins meet. Regardless of their geographic origin, most representatives of the coastal Azorean marine biota are chance survivors of recent chance immigrants probably delivered to these shores in a variety of ways, but predominantly through currents. Some marine colonisers have received human assistance, particularly the maritime vegetation and other well known exotics.

In 1994, Neto reported the existence of 256 species of algae for the archipelago but on-going work with this group of flora led to the current number of approximately 400 species identified (Tittley et al., 2009). Schmidt (1931 in Neto, 1994) listed 8 species as endemic, but most of these were never confirmed in posterior work. The only exception is the green algae Codium elisabethae, which lost the status of Azorean endemism when it was reported for Madeira (Neto et al., 2001).
In terms of marine invertebrates, the shallow subtidal fauna is diverse and abundant, but taxonomic knowledge of this group is only relatively adequate for the larger-size species. Possibly more than 1000 species are reported, but inventories are incomplete and scattered (Cardoso et al., 2008). Endemisms are lacking in demosponges and hydroids (Santos et al., 1995), but there are clear signs of endemism in molluscs and amphipods. This lack of endemism (or of confirmation) is probably a result of the reduced knowledge of the greater part of the taxa (e.g. Lopes et al., 1993; Ávila, 2005 in Cardoso et al., 2008), as marine invertebrate taxonomy has not been a priority research area in the Region. This should be cause of major concern as these species are threatened by over-exploitation and some even of local extinction, which allied to ignorance, can result in species depletion (Cardoso et al., 2008).   
Fig 10_Endemic marine fishes are almost absent in the Azores. Scorpaena azorica described by Eschmeyer in 1969 (Santos et al., 1995) and Centrolabrus caeruleus described in Azevedo, 1999 - and more recently considered as to belonging to the genus Symphodus (Symphodus caeruleus) by Almada et al. (2002) – are the only two species of marine littoral fish confirmed to date. However, it is thought that an important component (possibly circa 15%) of the coastal fish species of the Azores is endemic of Macaronesia.

Fig 11
Sites of the Azores archipelago are considered as important areas for several species of marine birds (at least 10), some of which are included in Annex I of the EU Birds Directive and Annex 2 of Bern Convention and considered as Species of Conservation Concern in Europe. However, many populations are now confined to the steep cliffs or small islets due to, among other factors, the introduction of rats. The archipelago concentrates around 70% of the world population of the Cory’s shearwater Calonectris diomedea borealis during the species’ breeding season and for this reason, since 1995 the Region promotes a campaign for the protection of juveniles that abandon their nests for their first trans-oceanic flight. The Azores counts with one endemic marine bird species only recently described: Monteiro’s Storm-petrel (Oceanodroma monteiroi).

As for reptiles, there are 5 known species of marine turtles to occur in the Azores. In terms of marine mammals, the region is a privileged location for sighting whales and dolphins, with over 20 species commonly observed in the Azorean waters near the coasts of most islands.


The relatively high level of endemism in the Azores (terrestrial) gives to the archipelago’s biota great conservation relevance. Its preservation has also been recognized by the local government through the establishment of protected areas for conservation purposes since the early 1980s. The Azorean Protected Areas Network is currently being reformulated according to IUCN criteria and integrates 23 Sites of Community Importance and 15 Special Areas of Conservation, which are part of the NATURA 2000 network of nature protection areas. Besides the creation of 9 Island Nature Parks, the Azores Marine Park will incorporate all classified marine areas that fall outside the territorial sea, therefore including areas currently classified under international instruments such as the OSPAR Convention (7 sites currently inscribed for the Azores, 1 proposed), as is the case of the Lucky Strike and Menez Gwen hydrothermal vent fields.
The Azores hold also a series of areas classified under UNESCO programmes. Currently the Region counts with 12 Ramsar sites and 3 islands – Graciosa, Corvo and Flores – have been adopted as Biosphere Reserves. In progress is a transnational application of sites of outstanding natural value along the Mid-Atlantic Ridge for inscription in UNESCO’s World Heritage List.

Biodiversity Research

The nine islands of the Azores, isolated in the middle of the Atlantic, with different geological histories, are wonderful ecological and evolutionary laboratories.

The 1980’s saw an upsurge in scientific research in the Azores. With the creation of the University of the Azores in 1976, scientists based on the islands initiated research on different aspects of the archipelago’s natural history. In the last 20 years, several research groups from the University of the Azores contributed decisively to the knowledge of the evolutionary history and biodiversity of the archipelago. The first list of Azorean terrestrial biodiversity and a Web Portal dedicated to Azorean biodiversity and its distribution across the islands is now available (www.azoresbioportal.angra.uac.pt). Also, marine biodiversity is well studied and documented (www.intradop.info), with a growing interest in off-shore, deep-sea habitats, such as seamounts and hydrothermal vent fields.




Almada, V., Almada, F., Henriques, M., Santos, R.S., Brito, A. (2002). On the phylogenetic affinities of Centrolabrus trutta and Centrolabrus caeruleus (Perciformes: Labridae) to the genus Symphodus: molecular, meristic and behavioural evidences. Arquipélago: Ciências Biológicas e Marinhas. ISSN 0873-4704. Nº 19A (2002), pp. 85-92. Available online: http://hdl.handle.net/10400.3/34

Amat, J.N., Cardigos, F., Santos, R.S. (2008). The recent northern introduction of the seaweed Caulerpa webbiana (Caulerpales, Chlorophyta) in Faial, Azores Islands (North-Eastern Atlantic). Aquatic Invasions (2002), vol. 3, issue 4, pp. 429-434.

Azevedo, J.M.N. (1999). Centrolabrus caeruleus sp. nov., a long unrecognized species of marine fish (Teleostei: Labridae) from the Azores. Bocagiana. ISSN 0523-7904. 196(1999): 11 p. Available online: http://repositorio.uac.pt/handle/10400.3/34

Borges, P.A.V., Cunha, R., Gabriel, R., Martins, A.F., Silva, L., Vieira, V. (eds.) (2005). A list of the terrestrial fauna (Mollusca and Arthropoda) and flora (Bryophita, Pteridophyta and Spermatophyta) from the Azores. Direcção Regional do Ambiente and Universidade dos Açores, Horta, Angra do Heroísma and Ponta Delgada, 317 pp.

Borges, P.A.V., Amorim, I.R., Cunha, R., Gabriel, R., Martins, A. F., Silva, L., Costa, A. & Vieira, V. (in press). Azores – Biology. In: R. Gillespie & D. Clagu (Eds.), Encyclopedia of Islands, pp ??. University of California Press, Califórnia.

Cardoso, P., Borges, P.A.V., Costa, A.C., Cunha, R.T., Gabriel, R., Martins, A.M.F., Silva, L., Homem, N., Martins, M., Rodrigues, P., Martins, B., Mendonça, E. (2008). A perspectiva arquipelágica: Açores. En: Martín, J.L., Arechavaleta, M., Borges, P.A.V., Faria, B. (eds.). TOP 100: Las 100 especies amenazadas prioritarias de gestión en la región europea biogeográfica de la Macaronesia. Consejería de Media Ambiente y Ordenación Territorial, Gobierno de Canarias, pp. 421-449.

McGinley, M. (2007). Azores temperate mixed forests. The Encyclopedia of Earthavailable online

Morton, B., Britton, J.C. (2000). The origins of the coastal and marine flora and fauna of the Azores. Oceanography and Marine Biology (2000), vol. 38, pp. 13-84.

Neto, A. I. (1994). Checklist of the benthic marine algae of the Azores. Arquipélago: Ciências Biológicas e Marinhas, Nº 12A, pp. 15-34.

Neto, A.I., Cravo, D.C., Haroun, R.T. (2001). Checklist of the benthic marine plants of Madeira Archipelago. Botanica Marina, Nº 44, pp. 391-414.

Tittley, I., Neto, A.I., Parente, M.I. (2009). The Marine Algal (Seaweed) Flora of the Azores: additions and amendments 3. Botanica Marina, Nº 5, pp. 7-14.

Santos, R.S., Hawkins, S., Monteiro, L.R., Alves, M., Isidro, E.J. (1995). Marine research and conservation in the Azores. Aquatic Conservation: Marine and Freshwater Ecosystems, vol. 5, pp. 311-354.