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7Savanna Links May/June 1998 Flora & Fauna A three-year study by the Parks& Wildlife Commission of theNT, in collaboration with Northern Territory University, has recommended a new network of land reserves to preserve the plants and animals of the Top Ends rainforest patches. Through integrating a series of projects, scientists Owen Price, Christine Bach, Alison Shapcott and Carol Palmer uncovered a delicate natural balance in which the rainforest patches and their animals, particularly those that move between patches, are reliant on one another for survival. Rainforest patches occupy 2700 square km of the NT only 0.2 per cent of the land area and are made up of 15,000 small patches with an average size of 3.6 hectares. Despite their scattered and small nature, these patches include 13 per cent of the NTs known plant species, many of them rare, said Mr Price. Our research has found that protecting these rainforest patches must take into consideration the needs of the animals that use them because without the animals the patches themselves will decline and vice versa. This is because each rainforest patch does not provide all the resources some of these animals require, fruit-eating birds and flying foxes in particular. These animals must move between patches, while also seeking food from other surrounding habitats, during times when few rainforest plants are fruiting. In moving between these patches and across the surrounding landscape, these animals are dispersing seeds, providing new plants to maintain the diversity of species existing in rainforests, said Mr Price. The projects research focused on several species of fruiteating birds including Pied Imperial-pigeons (Torres Strait Pigeon), Rose-crowned Fruit-doves, Figbirds, Yellow Orioles, Common Koel and Great Bowerbirds, along with the Black Flying Fox. As an example of the integral part these animals play in the survival of rainforest patches, our research found that flying foxes deposit about 350 seeds each night into an average sized rainforest patch at Gunn Point and birds about 190 seeds a day, explained Mr Price. The research suggests that in dense areas of rainforest such as between Darwin and Kakadu National Park the loss of about half to two-thirds of rainforest patches would likely result in the extinction of frugivore (fruit-eating) species from remaining patches. The gradual extinction of plant species would then be an inevitable consequence. In recognising this inter-dependence and studying the threshold at which the ecological equilibrium is maintained, the study recommends a number of guidelines for the design of reserves aimed at protecting rainforest and the animals that use them. This includes a suggestion that clusters of rainforest patches be reserved. Each cluster should be made up of all of the rainforest patches (with a minimum area of 32 square km) and a variety of other habitats in a circle of up to 50 km radius. The report says about seven clusters would be needed across NT to protect all flora and fauna species associated with rainforest patches. Mr Price said these suggestions had been made for inclusion in PWCNT strategies, in particular a Parks Master Plan for the Darwin region currently under development. However, he said that all landholders could assist in protecting the delicate balance of nature across the Top End. Remember, when you cut down that tree or clear that patch, however small, the loss from the landscape could trigger a cascading decline among plants and animals in nearby rainforest patches that previously relied on your piece of bush remaining in the network, he said. C ou rt es y of P ar ks & W il dl if e C om m is si on o f t he N T Interdependence of plants and animals: This figure shows NTs rainforest patches and the movement of one Torres Strait Pigeon, TSP22, captured on October 1, 1996. The lines show its pattern of movement between rainforest patches: over 78 days it flew 65.5 km dropping about 10-20 seeds in each rainforest patch. Rainforest patches provide the link For more information contact: Owen Price, PCWNT, Tel: (08) 8944 8467