Patterns of species composition and reserve design for a fragmented estate: Monsoon rainforests in the Northern Territory, Australia Original Research Article

Monsoon rainforests occur as small patches in the extensive Eucalyptus-dominated landscape of northern Australia. This distribution presents formidable conservation problems. On a coarse scale (1 : 1,000,000), monsoon rainforests are currently relatively well represented in the existing reserve network. However, inspection at a finer resolution shows that six of 16 variants are unreserved, and about 18% of plant species have not been captured by the existing reserve system. Inspection of inventory data for 1245 monsoon rainforest patches and 570 associated plant species in the Northern Territory revealed very idiosyncratic species composition for individual patches and a large number of restricted species (e.g. 20% of species are known from five or fewer patches). Vertebrate distributions were less idiosyncratic, although sampling effort was far less intensive (45 patches and 58 associated species). A minimum selection algorithm (CODA) was used to design a reserve system which captures all occurrences of singleton species and at least two representations for all other plant species. This selected 139 patches, with a total area of 6413ha. Inclusion of vertebrate records increased the number of selections only marginally (to 141 patches). However, this solution has profound practical limitations: the number of selected patches is probably politically unacceptable, the management required to protect the patches adequately is beyond the economic allowance for conservation of all existing NT parks, and the solution does not adequately consider the spatial arrangement of patches which is probably critical for the maintenance of ecological processes. It is not possible to design an efficient solution in which patches are clustered together. The conservation of the monsoon rainforest estate will be reliant upon (1) the identification and active intense management of particularly restricted and vulnerable species; and (2) conservation planning for the whole landscape, which integrates monsoon rainforest conservation with that of the surrounding savanna woodlands.