Assumption Island – a miserable past, an uncertain future

Calm clear water lapping at Assumption’s 5 1/2 km sandy western beach, nesting area of numerous Green Turtles (Photo: Chris Feare/SIF)

11.6 km2 Assumption Island lies about 1100 km south-west of Mahe, Seychelles’ largest and most populous island, and is close to Aldabra atoll, famed for its relatively undisturbed ecosystem that qualified it for World Heritage Site status.

Assumption is a raised coral island and was formerly home to a vast number of seabirds, especially boobies, who left their mark in the form of an accumulation of guano from millennia of years of occupation by the birds. When guano became a valuable resource for expanding global agricultural production at the end of the 19th century, mining of Assumption’s reserves began in the early 20th century and continued until the 1970s. This involved destruction of most of the island’s woodland and removal of its soils for export, resulting in a biodiversity catastrophe. Virtually all of its birds, some of them endemic forms, all of its Giant Tortoises and most of its vegetation were lost. Cats, Black Rats and invasive plants were introduced and in the 1970s four species of land bird were released. Of these, Red-whiskered Bulbuls and Madagascar Fodies posed a direct threat to the integrity of Aldabra’s endemic avifauna, necessitating an expensive eradication programme co-ordinated by Seychelles Islands Foundation (SIF), custodians of Aldabra, and funded by the European Union.

Red-whiskered Bulbul, an invasive bird successfully eradicated by Seychelles Island Foundation (Photo: Chris Feare/SIF)
Relics of the guano era: rusting railway track

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After the exhaustion of the island’s guano reserves the island’s human population fell and fishing, especially for sea cucumbers, became a principal occupation. In 1990 a 1200 m concrete airstrip was built, involving destruction of part of the largest sand dune system in Seychelles to provide sand for the construction. Subsequently, further sand was extracted to build improved accommodation for island staff, whose main task became servicing of the airstrip and associated facilities. The airstrip became and remains an important gateway for visitors to Aldabra.

An old pirogue that had been used to transport guano from the jetty to a waiting cargo ship (Photos: Chris Feare/SIF)

 

An aftermath of these activities has been the  accumulation of large quantities of waste materials, including corroding oil drums and lead-acid batteries, and rusting machinery from the guano era and subsequent construction activities, along with plastic, metal and glass waste associated with human occupation. Much of this has been deposited in solution holes in the limestone, where they can contaminate the underlying sea water, and deprive the affected solution holes of their current roles as refuges for some of the island’s plants and safe havens for nesting Souimanga Sunbirds, the only surviving indigenous land bird.

Corroding machinery on Assumption (Photo: Chris Feare/SIF)

The major trauma now facing the island stems from India’s desire to establish a naval base there. This is leading to much controversy and the emergence of apparently conflicting accounts of the relative roles of Seychelles and India in the base’s construction and operation.

In press coverage I have seen, there is no mention of environmental concerns. Assumption is one of only two significant raised reef islands in Seychelles; the other, St Pierre, was similarly wrecked by guano mining. Assumption’s 5 ½ km western sandy beach is one of the finest in Seychelles and supports a large population of nesting Green Turtles. During the SIF Red-whiskered Bulbul and Madagascar Fody eradications, monitoring of vegetation cover indicated that, despite the loss of soils, some indigenous vegetation was recovering at the expense of introduced plant species. With help, therefore, it seems that Assumption could achieve some level of recovery.

Assumption Island’s concrete airstrip. In the background is the dune system from which sand was extracted for its construction. Giant Tortoises were introduced from Aldabra and now thrive in Assumption (Photo: Chris Feare/SIF)

The construction and subsequent use as a military base comes with some environmental certainties and some unknowns. The presence of a large workforce will necessitate the sustained import of food and generate large quantities of waste packaging and sewage. Inevitable health problems will lead to contamination of sewage with pharmaceuticals. Construction of a deep water berth will create turbulence and opacity in the water, risking coral survival and possibly changing water flow along the western sand beach, with consequences for sedimentation and erosion. This could impact the nesting Green Turtle population, which could be further threatened by illegal capture of adults and eggs for food by the workforce of the base.

Among other things, a naval base will require the offloading and storage of large amounts of fuel, risking spillages at sea and on land, and the use of increased amounts of fuel on the island will create atmospheric pollution. South-east winds prevail for most of the year, as do westerly-flowing currents. These risk spillages at sea reaching Aldabra, only 27 km away and visible from the top of the sand dune. Furthermore, such spillages could impact Aldabra’s large seabird populations while feeding over a much wider area of ocean. Similarly, any contaminants on land that percolate into the sea, such as fuel leaks or sewage, could threaten Aldabra’s marine environment.

Use of Assumption as a military base will certainly be a setback for any meaningful recovery or rehabilitation of the island’s habitats. It further risks the introduction of invasive species if rigid biosecurity measures are not practiced and policed, both at the island and at the sources of the incoming goods. In my opinion, Seychelles should further protect its island by insisting that all waste is removed at regular defined intervals and is safely processed elsewhere where suitable facilities exist.

While accepting that Seychelles needs help in policing and protecting its vast oceanic realm, the country should not lose sight of the fact that its very limited land area is unique and warrants all steps possible to ensure that uses are sustainable and not environmentally damaging. Seychelles’ own record in managing Assumption’s environment leaves much to be desired. The clock cannot be turned back to pre-guano mining days but it should ensure much improved care in future for the sake of this island and that of its showpiece atoll of Aldabra.

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