The terrestrial environment

D’Arros and the islands of the St Joseph Atoll are flat and sandy. Scattered throughout the interior of the larger islands, a rocky layer of fossilised guano lies beneath the surface of the sand, giving testament to bygone seabird colonies. The beaches consist of uninterrupted soft white sand and are fringed by gentle lapping waves on one side and coconut palms on the other. Although coconuts are indigenous to the region, they are normally restricted to the beach crests of islands as they are unable to penetrate existing tropical forests. However, when the interior is denuded of native vegetation, coconut palms quickly occupy the open space to form a dense jungle devoid of other plant species. Unfortunately, by the late 1900s this fate had overcome most of the outer Seychelles islands. D’Arros and the seven largest islands of the St Joseph Atoll were no exception and today 90 percent of the vegetation on these islands is dominated by coconut. The remaining 10 percent comprises casuarina trees and small patches of indigenous broadleaf forest interspersed along the beach crest and among the coconuts.

While a jungle of coconuts might seem aesthetic­ally pleasing, it is extremely low in biodiversity. This quickly becomes evident when you attempt to slash your way into the dense jungle on D’Arros. Apart from a few skinks, spiders and several million mosquitoes, there is very little life. If the natural forest had been left undisturbed, you would likely have encountered several species of land bird feeding on a diversity of insects and fruits; giant tortoises lumbering around on the open forest floor; crabs and skinks scuttling about and seabirds nesting in the leafy canopy overhead. Fortunately there is a very strong conservation ethic in Seychelles and several vegetation rehabilitation projects are currently underway. D’Arros Island has taken a lead role in this initiative as it facilitates the most extensive forest rehabilitation programme in the region using an innovative, low cost and effective technique that was devised on the island. Encouragingly, large numbers of seabirds have already begun nesting and roosting in the rehabilitated areas, raining down the nutrient rich guano that is required to kick-start natural ecosystem processes.

In the southeast of the atoll along the inner shore of St Joseph Island, there are a series of muddy channels flowing between rocky shelves of fossilised corals. Small stands of mangrove grow in these channels and along the inner rim of most of the other islands in the atoll. In the past, mangroves were heavily exploited for their bark and thus it is believed that they were once far more common in the atoll than they are today. Although these remnant mangrove stands are expanding again, the D’Arros Research Centre is accelerating this process by planting propagated mangrove seedlings in strategic areas. Mangroves are a vital component of lagoon ecosystems as they provide food and shelter for a diversity of marine creatures; act as a nursery for fish, sharks and rays; provide nesting habitat for seabirds; act as a nutrient trap; offer a valuable food source for many species and reduce coastal erosion.

Blacktip reef sharks and sicklefin lemon sharks thrive in the shallow lagoon and reef flat habitats of the atoll. Both species use the lagoon for breeding purposes and shark pups can be seen patrolling the shallows all year round. Other sharks regularly encountered around the islands are whitetip reef, tawny nurse and grey reef sharks. Bull sharks and hammerheads are less common but have been encountered on several occasions. Further out to sea where the Amirantes bank drops off into the deep, silvertip, silky and oceanic whitetip sharks have been seen.

Hundreds of endangered hawksbill and green turtles nest on the beaches of D’Arros and St Joseph every year. While green turtles emerge to nest at night, hawksbills nest in the daytime, a phenomenon that is unique to the Seychelles.

The shallow marine environment at D’Arros and St Joseph provide crucial developmental habitats for juvenile green and hawksbill turtles, the numbers of which probably range in the thousands. Green turtles graze seagrass on the reef flats during the high tide and when the reef flats become exposed on the dropping tide the turtles retreat to the deeper lagoon or the adjoining coral reefs to rest. A leisurely dive along the reef crest during the low tide can yield more than 30 turtle sightings. Hawksbills forage in a variety of habitats seeking out sponges and zoanthids. The most preferred habitat is the shallow silty region in the southeast of the atoll as it is rich with their food. It is a long way to deeper water from there so turtles are forced to sit out the low tide in small stagnant pools on the reef flats, often tolerating water temperatures in excess of 37 degrees. These turtles are clearly distinguishable from others as their lack of contact with the open ocean ensures that they are covered from head to flipper in green algae!

A brief history

The islands were uninhabited when they were officially discovered in 1771 during a French exploratory mission from Mauritius and named after Baron d’Arros, the French Naval Commander at the time. A small community of less than 20 Seychellois settled on the islands in the mid 1800s to establish a coconut plantation. By the early 1900s the community had grown to more than 100 and more than 90 percent of the natural vegetation had been converted to coconut plantation. The community was also extracting guano, logging mangroves and curing fish and turtle meat for the local market. By the 1970s Asia was dominating the coconut oil market and most of the outer island plantations were abandoned. In 1974 D’Arros and St Joseph came under private ownership and soon coconut production ceased and discreet conservation policies were implemented. Today, the population on D’Arros numbers between 30 and 40 while the Islands of the St Joseph Atoll are once again uninhabited.

Of the five land bird species existing on D’Arros and St Joseph today, the turtle dove and the Seychelles fody are believed to be native while the house sparrow, Madagascar fody and the zebra dove were probably introduced by humans. However, once a significant portion of the vegetation has been rehabilitated, certain land bird species that are endemic to the Seychelles will be reintroduced.

Three heron species occur of which the grey heron and green-backed heron are breeding residents. No less than 15 migrant wader species have been recorded with the ruddy turnstone and crab plover being the most common.