Preserve A Living Laboratory
Last stand, The Old World species of giant land tortoise once inhabited most of the islands of the southwest Zndian Ocean. Today it is found only here on Aldabra Island. Its closest living relative is the famous tortoise of Galapagos Islands, on the other side of the world from Aldabra
Zoological curiosity shop, living natural history museum, biological treasure house, living laboratory-all have been used to describe Aldabra Island, a 60-square-mile coral atoll 260 miles northwest of Madagascar. Aldabra is home to about 7000 land tortoises. Along with the 3000-4000 on the Galapagos Islands made famous by Charles Darwin, they constitute the total natural population of this giant reptile that once ranged over much of the southwest Indian Ocean. Aldabra is also home to the flightless rail and the pink-footed booby. Its unique ecosystem includes 12 endemic species or subspecies of birds and more than 18 of higher plants. All this unique system is endangered by a proposal of the British Government to locate an airfield, a BBC transmitting station, and supporting facilities on the island. Britain’s Royal Society has protested the proposal, pointing out how human intrusions have damaged other unspoiled escosystems like Aldabra’s. The United States’ National Academy of Sciences issued a formal statement calling the plan ‘ia threat of incalculable damage to one of the world’s unique resources for scientific investigations.” The Smithsonian Institution has also voiced concern over the plan. Oceanic island
Aldabra is an oceanic island, possibly created by volcanic action followed by ages of coral growth. It has never been linked to continental masses. Un-
778 Environmental Science and Technology
OUTLOOK less man interferes, oceanic islands get their flora and fauna by immigration across the sea. However, many forms of life are poorly adapted for such immigration. So, except for bats, few land mammals have reached oceanic islands. Amphibia, freshwater fishes, and many orders of insects never appear. An oceanic island may provide a haven for a species in trouble on the mainland from competitors or predators. It may develop its own plants and animals: flightless birds and insects may evolve, for example, if flying out to sea is dangerous. Oceanic islands provide models or natural laboratories for the study of ecological and evolutionary problems. Indeed, Charles Darwin developed many of his fundamental ideas on natural selection from his observations of the simplified ecosystem of the Galapagos Islands. Even among oceanic islands, Aldabra has special attributes: It is only 400 miles from Africa and so has had greater opportunity for animal and plant colonization than a more isolated island. It is an elevated atoll and so has a wider range of habitats than a sea-level atoll. It is relatively untouched by man. Lacking guano and phosphate rock, it has not been industrialized as have many other Indian Ocean islands. The terrain is difficult and has never been considered suitable for cultivation. Apart from rain, there is little drinking water. Sporadic attempts have been made to develop the island. Currently, less than 100 contract laborers are on West Island: they live by cutting mangroves and coconuts, by fishing, and by turtling. Why, then, put an airfield on this scientific treasure? The only reason, say the critics. is strictly economic. Aldabra is larger than other islands in the vicinity, Thus, it provides a cheaper site for building an airfield in what is considered a strategic location. Conservation won’t help
In trying to save Aldabra, the Royal Society is against half-way measures;
Sea bird. Great numbers of pink-footed boobies nest in the mangroves of Aldabra’s Middle Island. The area also serves as the breeding grounds for the frigate population of the entire Indian Ocean area
“No amount of conservation planning and foresight could avoid the loss of the major contribution which the study of Aldabra can make to science-a contribution that can be made only by total preservation of the island for long-term studies.” The proposed development would affect the island community in several ways. The planned runway is slated for the breeding and browsing grounds of the tortoise, The large-scale clearing of vegetation would kill off some species of animals. The lagoon that makes up the central part of the island would be dammed, affecting the ecology of the lagoon mangroves and the birds which now feed on the lagoon at low water. The frigate bird, with its penchant for hovering at low altitudes, would pose the same problem for aircraft as the albatross does on Midway. A road will be built connecting the four main islands, When Aldabra was first colonized, various mammals, including goats, cats, and dogs, were introduced. They are now confined largely to the South and West Islands. The road will permit them to spread to Middle Island, with its large bird population. The flightless rail will be particularly vulnerable to the cats, and goats could mean the end of the vege-
tation on which tortoises depend. Modern man also brings with him the problems of sewage disposal, insecticides, oil wastes, and aircraft noise. The result, the Royal Society feels, would be ecological chaos in what was once an unspoiled island ecosystem. The final decision on Aldabra will be reached by May of 1968. Meanwhile, the Royal Society has mounted an expedition to gather as much information on the island as possible before the threatened construction starts. In the first part of the expedition, seven scientists spent five weeks on the island making a preliminary survey of numbers and distribution of animals and plants. They came back more convinced than ever that Aldabra should be preserved. The studies, which will continue to March 1968, will cover both terrestrial and marine ecology and will span both wet and dry seasons. This is not the first time scientists have had to take up the cudgels in defense of Aldabra. In the 1870’s, Charles Darwin and other scientists successfully opposed, at least for a while, a scheme to settle laborers on the island to harvest mangrove. Perhaps scientists again will be able to keep one small part of man’s environment the way nature made it.
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