Restoration of Amsterdam Island, South Indian Ocean, following control of feral cattle
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Published source details
Micol T. & Jouventin P. (1995) Restoration of Amsterdam Island, South Indian Ocean, following control of feral cattle. Biological Conservation, 73, 199-206.
Published source details Micol T. & Jouventin P. (1995) Restoration of Amsterdam Island, South Indian Ocean, following control of feral cattle. Biological Conservation, 73, 199-206.
Summary
Amsterdam Island (55 km², 37°50'S, 77°31'E) in the southern Indian Ocean, has been drastically modified by anthropogenic influences (fire, direct killing and mammal introductions). Some endemic species persist, and the discovery of a relic Amsterdam albatross Diomedea amsterdamensis population in 1983 prompted a restoration programme, including reduction of feral cattle Bos taurus. Five cattle were introduced in 1871; a census in 1988 estimated a population of about 2,000. Although cattle-induced habitat destruction is the main threat to endangered species, a compromise was reached between the need to prevent further degradation and the scientific interest of the herd (i.e. one of very few feral B.taurus herds in the world).
In 1987, a 4 km long electric barbed-wire fence (running NE-SW) was erected across the eastern side of the island. In March-April 1988 and January-March 1989, 1,059 cattle south of it (1,664 ha) were killed.
North of the fence after the 1988 dry season, 30% of 993 remaining cattle died from starvation. Monthly culling was used to stabilise numbers (580 in July 1989; reducing density from 0.81 to 0.47 individuals/ha). In 1990 and 1991, recruitment exceeded removal; in January 1992 the herd numbered 872. In February-March 1992, 327 cattle were culled and a second fence section (4.5 km long) was erected to complete division of the island into two; 43 cattle south of the fence on the island’s peat-bog (a threat to albatrosses) were shot.
During the programme soils were mapped. Vegetation and invertebrates are being monitored.
Cattle are now confined to the northern area (1,225 ha); 532 cattle (density: 0.43/ha) were recorded in May 1993. They are now in a much better health due to density reduction. It is hoped to maintain low density (< 0.5 individuals/ha) to prevent overgrazing recurrence.
Initially, native plants declined and aliens increased after culling but are now recovering. In 1989, one year after the first cull, vegetation became significantly taller and the native rush Scirpus nodosus was recolonising. In 1992, vegetation in previously short meadows approached 1 m tall. The dense vegetation, whilst preventing erosion, is restricting native flora recovery, but also reducing some invasives, mainly spear thistle Cirsium vulgare.
Methods to improve germination of Phylica (a native tree)seeds were developed and seedlings propagated. From 1989 to 1993, more than 6,000 saplings were planted in areas covered by natural forest 300 years ago. Non-native Cupressus, Eucalyptus, Malus and Acacia trees are being eradicated.
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