Aldabra Atoll in the Indian Ocean
Friday, 18 March 2022 - 11:00 am (CET/MEZ) Berlin | Author/Destination: Around the World / Rund um die WeltCategory/Kategorie: General, Environment, UNESCO World Heritage Reading Time: 14 minutes Aldabra is the world’s second-largest coral atoll. It is situated in the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands of the Seychelles, with a distance of 1,120 km (700 mi) southwest of the capital, Victoria, on Mahé Island. Aldabra atoll has, besides the four larger islands, some 40 smaller islands and rocks, all inside the lagoon, as well as a few very small islets at the West Channels between Grand Terre Island and Picard Islands, the largest of those being Îlot Magnan. A small scientific research station of the SIF is based on La Gigi village on Picard Island. The permanent staff (currently 12) conduct research to study Aldabra’s biodiversity. Aldabra is not easily accessed. No airstrips, helipads or landing jetties have been permitted to be built on the atoll. The nearest airfield on Assumption is 50 kilometres (31 mi) south-east of Picard Island. Supply ships operating from Mahé provide food and other essentials once every two months to the scientists and staff at the research station. Cruises are operated by several companies along with dive boats which may visit the atoll on expedition tours. Visits to the island by people other than the scientists and staff of the SIF are strictly controlled and only guided tours are provided with prior permission., an average of 900 tourists visit the atoll a year. Within the atoll, paved walking paths exist from the village of La Gigi, which leads to a promontory from where scenic views of the large lagoon (during low tides) and the mangrove species are seen.
Aldabra is situated in the dry zone of the south-west Indian Ocean. The northwest monsoon is from November to March and brings the heaviest rainfall. In the remaining months, the south-easterly trade winds are recorded. Aldabra receives an average of 960 millimetres (38 in) rainfall per year. Cyclones are rare in the Seychelles on account of its nearness to the Equator. Tides in the coastal zone rise to 3 metres (9.8 ft) height, causing channel currents, and a huge influx of water; the main channel drains 60% flow into the lagoon. The reported monthly mean maximum temperature recorded in December is 31 °C (88 °F). The mean minimum temperature recorded in August is 22 °C (72 °F).
The earliest study of the flora and fauna, and also the geomorphological structure is dated to 1910. There are 307 species of animals and plants on Aldabra. Reptiles are the prominent terrestrial fauna. Sir David Attenborough called Aldabra “One of the wonders of the world”, and it is also known as one of “crown jewels” of the Indian Ocean.
The higher areas of Aldabra are covered in pemphis, a thick coastal shrub, while the lower areas, which are home to the giant tortoises, are a mixture of trees, shrubs, herbs and grasses. There have been recorded 273 species of flowering plants, shrubs, and ferns on the atoll. There are dense thickets of Pemphis acidula, and a mixture of grasses and herbs called “tortoise turf” in many areas. This flora includes 19 endemic species and 22 species that are only common to neighboring islands, and several of these species are on the IUCN Red List. The tropicbird orchid (Angraecum seychellarum) is the national flower of Seychelles and is found in the dry craggy limestone champignon of Aldabra. Other endemic plants such as Pandanus aldabrensis, the Aldabra lily (Lomatophyllum aldebrense) and a sub-species of tropicbird orchid, Angraecum eburneum. The lagoon is bordered by mangrove forests, and has large inland seagrass meadows as well as areas of coral reef and sand flats. The mangroves, which thrive in tidal mudflat areas and saline conditions, are seen on the shores of the lagoon and are integral to the coastal ecosystem. There are seven species of mangrove occurring on Aldabra, three of which are rarely occurring species. These include ‘Mangliye blan’ or white mangrove (Avicennia marina) which grows to 12 metres (39 ft), ‘Mangliye lat’ or black mangrove (Bruguiera gymnorhiza) which grows to 18 metres (59 ft) in a conical shape, ‘Mangliye zonn’ (Ceriops tagal) which grows to 7 metres (23 ft) with a buttressed trunk, and ‘Mangliye rouz’ or red mangrove (Rhizophora mucronata) which is the tallest species up to 20 metres (66 ft) in height.
Conservationists feared a major threat to the atoll’s biodiversity in the 1960s when, as part of the British Indian Ocean Territory, the British made plans to set up a military establishment on the atoll. Due to national and international opposition this plan was cancelled in 1967. This incident became known as the ‘Aldabra Affair’ in England. Invasive alien species such as rats, cats and goats that were introduced in the past threaten the native biodiversity of the atoll. Goats were eradicated from the atoll in 2012 after a long-term eradication program. Cats have been removed from all of the islands except Grande Terre Island, which allowed for the reintroduction of the Aldabra rail to Picard Island. Research into a feasibility study to eradicate rats from the atoll has been undertaken. Aldabra was until recently free of introduced birds, but the introduced Foudia madagascariensis that was introduced to Assumption Island now occurs on Aldabra. An eradication program for this bird on both Assumption and Aldabra is almost done. Due to the limited space of its habitat, extreme weather conditions, epidemic and limited range could also pose serious threats to the entire ecology of the atoll.
Aldabra atoll was designated a UNESCO World Heritage Site on 19 November 1982. it is one of the two UNESCO World Heritage Sites in the Seychelles and is managed and protected by the Seychelles Islands Foundation (SIF). The marine protected area extends 1 kilometre (0.62 mi) into the sea to ensure preservation of its marine fauna. Eco tourism is controlled and introduction of invasive species is restricted. Based on the evaluation process, UNESCO inscribed the site, a legally protected special reserve of 35,000 hectares (86,000 acres), on the list of World Heritage Sites under three criteria: Criterion (vii): Aldabra Atoll encompasses a large expanse of relatively untouched natural beauty where a number of important animal species and some plant species thrive, along with remarkable land formations, and its process provides a unique spectacle of natural phenomena; Criterion (ix): The atoll is a superlative example of an oceanic island ecosystem in which evolutionary processes are active within a rich biota. The size and morphological diversity of the atoll has permitted the development of a variety of discrete insular communities with a high incidence of endemicity among the constituent species that are typical of island ecosystems. The natural processes take place with minimal human interference and can be clearly demonstrated in their full complexity; and Criterion (x): Aldabra provides a natural laboratory for the study of the process of evolutionary ecology and is a platform for key scientific discovery. The atoll constitutes a refuge harboring viable populations of a range of rare and endangered species of plants and animals. These include the last giant tortoise and flightless bird populations of the Western Indian Ocean, a substantial marine turtle breeding population, and large seabird colonies which number in the tens of thousands. The substantial tortoise population is self-sustaining and all the elements of its inter-relationship with the terrestrial environment are evident. BirdLife International declared Aldabra as an Important Endemic Bird Area (IBA) in 2001 on account of its large seabird colonies under categories A1, A2, A4i, A4ii and A4iii, covering an area of 33,180 hectares (82,000 acres) overlapping with the special reserve area of 35,000 hectares (86,000 acres) of Aldabra Atoll. Aldabra became a Ramsar Wetland Site of International Importance in 2010. Covering 25,100 ha (over half the area of the whole atoll) the wetland ecosystem of Aldabra include the extensive shallow lagoon inside the atoll, which is carpeted with lush seagrass beds and patchy coral reefs, the intertidal mud flats, the coral reefs outside the lagoon, freshwater pools, beaches, and 2000 ha of mangrove stands. These wetlands support several endangered species including the increasing number of turtles at the atoll, dugongs and many other bird, fish and invertebrate species. Aldabra was designated as a site under the Indian Ocean South East Asia (IOSEA) turtle network, in their 2014 convention.
Read more on Aldabra Marine Programme, unesco.org – Aldabra Atoll and Wikipedia Aldabra (Smart Traveler App by U.S. Department of State - Weather report by weather.com - Global Passport Power Rank - Travel Risk Map - Democracy Index - GDP according to IMF, UN, and World Bank - Global Competitiveness Report - Corruption Perceptions Index - Press Freedom Index - World Justice Project - Rule of Law Index - UN Human Development Index - Global Peace Index - Travel & Tourism Competitiveness Index). Photos by Wikimedia Commons. If you have a suggestion, critique, review or comment to this blog entry, we are looking forward to receive your e-mail at comment@wingsch.net. Please name the headline of the blog post to which your e-mail refers to in the subject line.
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