Aldabra, One of the Great Wonders of the World
an open ocean birds begin to flock circling high above in the clouds. The water
turns in cycles bringing schools of baitfish and shrimp to the surface. A pod of
bottlenose dolphins feeds on the sandy bottom of the fringing reef, a passing
Wahoo. From the water you cast your eyes upon a shore in the distance. Turtles
wander up the beach to nest; sunbirds jump from branch to branch. Mangroves feed
of the tides and crabs scavenge at night. The cold wind comes with the southerly
breeze; the clouds are turquoise and the lagoon vast and magnificent. Welcome to
has the title of being the worlds largest atoll and a refuge for rare forms
of fauna. Oval the coral
atoll is 31 km (19 mi) long and 13 km (8 mi) wide, and consists of four main
islands Picard, Grande Terre (Main), Polymnie, and Malbar that together surround
a large lagoon as well as several smaller coral islands. Aldabra is a dependency
of the Seychelles in the Indian Ocean.
isolation that has allowed Aldabra to develop in such a magnificent manner is so
extreme, with much of the coral atoll being covered by masses of jaggered, sharp
outcropping. It is possibly this factor more than any other that has helped save
it. Situated about
1,100 km (684 mi) southwest of Mahé and 420 km (260 mi) northwest of
Madagascar. The islands are volcanic in origin and rise from a seabed about
4,000 m (13,120 ft) deep to no more than 10 m (33 ft) above sea level.
one of the great wonders of the planet; it has become so due to its isolation
and remoteness. This isolation has allowed the development of a unique
environment harbouring a diverse range of both plant and animal species. One of
its feats of nature is to host an undisturbed ecosystem. It is the last
remaining habitat of both the Aldabran giant land tortoise and the
white-throated rail, a flightless bird. Aldabra is also the sole breeding
habitat for greater and lesser frigate birds.
It is also a nesting ground to a great number of seabirds such as the
boobies and tropicbirds. Regularly throughout the year a spectacular event of
nesting sea turtles grace the white sand beaches and swim amongst the
tranquillity of the lagoon. Among
the 200 species of plants found on Aldabra, some 20% are endemic.
Portuguese visited Aldabra (then uninhabited) in 1511 but did not settle. It
became a French dependency in the 18th century, and then was held by the British
in 1810 during the Napoleonic Wars. Aldabra was part of the British Indian Ocean
Territory from 1965 to 1976 During this time there were controversial but
unrealized plans to develop the atoll as a military base, this was condemned by
conversationalist who saw the development as being catastrophic to the survival
of the islands species.
was fortunate that in this case nature won and later in 1976 the island was
handed over to the Seychelles, with the Seychelles Island Foundation (SIF) as
its protector. The SIF was established primarily to protect, conserve and
monitor the atoll. As an independent organization the SIF is mainly
self-financing and prides itself in putting nature at the top of the list and
not the other way around.
P 0 Box 853,
Tel : (+248) 321 735
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foundation was established as a public trust in 1979, with the President of
Seychelles as patron. The Board of trustees, appointed by the President, has 14
members, including not less than five representing organizations concerned with
the conservation of wildlife and natural history or national academics of
science. In 1982 the
atoll was declared a World Heritage listed site and further protection of its
existence has occurred. There are no permanent residents, and the fragility of
the ecosystem has meant that few visitors are permitted.
on Aldabra relies on the change of the tides. Twice a day the water surges
through the narrow channels with tremendous force, it breathes new life into the
lagoon, bringing with it a host of fish and other sea creature, humpbacks have
been seen basking in the mouth of main channel, dolphins regularly parade the
outer reef. Virtually un-spoilt by man the environment has become one of total
inspiration. It is a virgin land where plants and animals can live in harmony on
a fragile yet present equilibrium. We could easily upset this balance if we
didnt monitor the effects human impact is having on the daily life of the
order to maintain the balance the SIF has introduced a management team of
rangers, research officers, boat staff and a warden. It is there job to watch,
or act as guardians to the atoll and its inhabitants. Monitoring of the
islands species occurs on monthly bases, controlled tourist access to limited
parts of the environment also aid in its protection. Zones are defined by the
access allowed due to the ecological sensitivity of nature. Breeding, nesting,
and critical habitat areas are included in the zone management.
parts of the island have been classified as restricted zones which limits the
visitors in one area at any given time extreme caution is taken at all time to
limit the interaction and impact visits to these zones have. In the restricted
zones people numbers are limited to 6 at any given moment. This hopefully plays
a role in limiting the impact of people on the island. In reality people will
still visit Aldabra and to accommodate this zones have been set aside
particularly for this use. The areas are selected for their richness in
biodiversity and scenic value but most importantly their ability to support
limited, well-managed nature conservation and educational tourism. Due to the
physical limitations of the environment these areas can only support low numbers
of people. It is therefore even more of an amazing experience if you receive the
chance or opportunity to visit this wilderness.
the zones of the atoll much monitoring occurs ranging from rainfall to species
distribution. There are six base camps on Aldabra which act as stations from
which more in-depth study can occur over the period of a couple of days.
Rainfall monitoring for example provides extremely important data in all aspects
of science and conservation on Aldabra. It can help explain population cycles,
patterns and more of the dynamics of life on Aldabra. The island has 13 rain
gauges from which manual readings can be taken.
time Aldabra did have a higher rainfall and plants species developed endemic to
the island. Today some of these species are restricted to small parts of the
atoll due to the lower precipitation levels recorded recently. These species are
quite unique in that nowhere else will you find them, many of them stem from
other species and what you find are now subspecies. Atolls, and isolated Island
groups have long been realized to host a microcosm of evolution; the giant land
tortoise is a prime example.
early as the 70s studies began on the land tortoise delving into their
history and their evolution cycles, including their survival as a species today.
Aldabra host the healthiest population of giant land tortoises in the numbers of
around 113,000. In 1997 The ERGO (Environmental Research Group Oxford) conducted
a survey of the population and reviewed the monitoring process, the primary goal
being the protection and survival of the species.
Conclusions were made that the monitoring techniques being used were
satisfactory and providing a stable amount of information.
population faces many predators birds preying on the young, lack of food and
water. Although there is a more immediate threat to the population on Grande
Terre. At the end of the nineteenth century goats where introduced to the
Aldabran Islands to breed and create a source of meat. It is undeniable that
this once introduced species is now having a detrimental impact on the ecosystem
on Grande Terre. This is the only of the four islands in the toll that they
land tortoise forages on the leaves of trees that have fallen to the ground.
Initially the threat of the goats was not apparent, yet know it is becoming
visible that the increase in the goat population is linked with the decline in
available food because goats choose to cause destruction of anything in their
path. Some parts of the vegetation show clear lines of destruction at their
maximum feeding height of 2m. Eradication of the species and thus removing the
threat on the giant land tortoise is essential to return the balance to that of
which nature intended.
is not only the giant tortoise which relies on the habitat for survival an
entangled niche exists and provides homes for many other species. Land birds are
particular special on Aldabra in particular the Flightless rail the last of
its species in the Indian Ocean. There are 13 species of land birds and 6
shore birds. The lack of interference by man and the predators is one of the
reasons these species are so unique to the island. The Rail is now only found in
four places on the Atoll, it is believed that in the past feral cats another
introduction could be responsible for the limited distribution. Where in the
past there was no natural predator the species thrived and became specifically
land based, thus easy prey for the introduced cats. Fortunately they have since
been controlled and the population is able to slowly increase and return to
normal. This species is yet another aspect of the atolls importance.
Darwin noted that remote islands and atolls are prime examples of subspecies
development and he viewed such occurrences on Galapagos, an environment similar
to Aldabra in its isolation and development of unique species. Each bird species
contribute to the food web in a particular way, which possibly a conclusion to
the equilibrium found within the species, as they are not all competing for the
same food source. The blue pigeons feed on fruit trees while the nightjar and
the brush warbler are insect eater, and of course the flamingo which draws its
fabulous colouration from feeding on plankton. The balance is an essential part
of the ecosystems survival. Lets not forget the significance birds play in
relation to plant pollination and seed dispersal.
is also one of the most important breeding sites in the Indian Ocean for five
species of sea birds. Great and lesser frigates red-tailed and white-tailed
tropicbirds, and the red-footed bobby. The lagoon provides a sheltered and
protected breeding site away from predators. This is important in Species like
the frigates and bobbies whom feed and harbour their young for up to a year.
This is also one of the reasons why the birds do not often breed every year, as
they require time to recover. This results in the population of breeding birds
being only a portion of the entire population of each species.
the breeding sites of the frigates and the Boobies only two are open to visitors
and monitoring of the disturbance is recorded each time a boat enters the site.
The rangers look at how many birds are disturbed from their nest, not including
those already in the air. This gives them and idea of the impact of the visits.
With frigates once they leave the nest you will notice they each scavenge twigs
from the others nest or inhabit the nest themselves. So by influencing the birds
to fly we are possibly changing the natural cycle of their selection.
is yet another unique element to life on Aldabra the sea turtles. In the past
sea turtles in particular Hawksbills and Greens fell to the hands of poaches
after thee meat and shell of the delicate animal with no stringent control the
impact on the population began to show and numbers of green turtles dropped as
low as 200. Today Aldabra is the refugee and home to a flourishing population of
turtles and an indication of the increase is the number of untagged individuals
that have begun making it ashore in the last few years.
Aldabra turtle monitoring covers a ranges of beaches both inside and outside the
lagoon. The lagoon has been observed to be a more preferred nesting site of the
hawksbills as well as a haven and growing habitat for juvenile of both species.
The greens are noted to nest on the beaches on the outside of the atoll. Whether
it has been by choice or selection, the two species have developed to be able to
share the habitat and both prosper from it.
to Aldabra they have also been recorded to mate the whole year round. More
common is a mating season of approximately 3 months with variables, although
this seems irrelevant to the turtle population on Aldabra, yet a peek season is
evident between June and Oct with hatchlings in November.
from the thriving population of turtles Aldabra also host a teeming biodiversity
of marine life and studies of the coral reef ecosystem are beginning to follow
in the footsteps of the land tortoises. In 1999 a survey of benthic and reef
fish communities and coral diversity and abundance with a side-glance at the
improvements since a survey was taken just after the bleaching in 1998. Results
from the survey showed a high diversity of reef fish at the atoll an indication
that the overall productivity of the ecosystem has not yet been significantly
affected from the bleaching. Although there is a correlation between the reef
fish species and the live coral habitats remaining suggesting distribution and
numbers will be effected by the further loss of coral habitats. On a positive
note regardless of the fact that shallow coral reefs suffered a great deal, the
deeper water habitats have shown substantial regeneration. This is a positive
sign for the future and another of the reasons why preservation of the atoll is
focus is not only on the animal life but the ecosystem on a whole, which
includes an extensive range of flora endemic to the islands. The first
collection of plant specimens was carried out in the late 19th
century. It wasnt however until the 1960s that an extensive study was
carried out. It still lacked a little, in the access to some parts of the atoll
were near impossible considering some of the more treacherous terrain, some data
was collected from aerial photographs. Many species of plants found on the
island once relied on a suitable source of plant material for dispersal and
plant life is extremely diverse and rich for such a remote area. There are three
major types that exist. The mangroves around the edge of the lagoon, grasslands
covering much of the coastal areas as well as dense woodlands around the main
island. The unique aspect of all of these areas is the role that their existence
plays in the survival of many of the animal species. A prime example is in the
land tortoises diet and well as providing shelter in the dry season when water
such an extreme diversity of species which appear to prosper in the some what
uninhabitable environment, it is difficult not to assume in man ways it is
nature way of marking the atoll and one of the main reasons why the SIF is
working to ensure its ultimate survival as one of natures untouched wonders.
Untouched and untarnished is how this pristine environment should remain as a symbol of biodiversity existing in such perfect harmony. If there has ever been such a place that offers just the slightest glimpse of paradise Aldabra is such a place. It is one of Nature masterpieces and a perfect example of life the way Mother Nature intended. It allows people the opportunity to learn about the pure essence of a natural environment and the ability it has to shine, today tomorrow and forever.
Anna Liljevik, Research Officer, Aldabra station
Brian Betsy, Ranger, Aldabra Station
A.J. Seaton, K.Beaver and M.Afif, Editors (1991) A Focus on Aldabra, Seychelles Island Foundation (SIF), Ministry of Education, Seychelles No 3.