Invertebrates and the Restoration of a Forest Ecosystem: 30 Years of Research following Bauxite Mining in Western Australia Jonathan D. Majer, 1,2 Karl E. C. Brennan, 3 and Melinda L. Moir 4 Abstract Restoration needs to consider more than just soils and plants. The role of terrestrial invertebrates in the restora- tion of Alcoa’s bauxite mines in the Jarrah (Eucalyptus marginata) forest of Western Australia has been the sub- ject of over 20 individual studies. Projects range from arthropods in soil and leaf litter, to the understorey vege- tation, and the tree canopy. Moreover, projects span a range of trophic groups, including decomposers (e.g., springtails and termites), predators (e.g., ants and spiders), and herbivores (e.g., true bugs and ants preying on seeds). Elucidation of recolonization trajectories uses both space- for-time substitutions and long-term regular sampling. Importantly, many studies are at species level rather than coarser taxonomic ranks. This paper provides an historical account and an integrated review of this research. The role of ants as seed predators and as indicators of eco- system health is described. Successional data for other groups, when measured by species richness (ants, spiders, and hemipterans) and composition (ants and spiders), show their reassembly trajectories tracking toward un- mined reference areas. Hemipteran species composition tracks the vegetation reassembly trajectory but not toward unmined reference areas. Studies also have revealed opti- mal sampling methods for surveying invertebrates and their rich biodiversity in southwestern Australia. In restored mine pits burnt to reduce fuel loads, the response of spiders to this additional disturbance was retrogression/alteration of the post-mining trajectory. Finally, attention is drawn to research areas receiving limited scrutiny to date, such as the contribution of terrestrial invertebrates to ecosys- tem function and taxonomic groups not yet studied. Key words: Araneae, coarse woody debris, Collembola, ecosystem reassembly, Formicidae, habitat structure, Hemiptera, Hymenoptera, insects, Isoptera, rehabilita- tion, restoration, revegetation, seed predators. Introduction With few notable exceptions, Alcoa World Alumina Australia’s bauxite mining operation in southwestern Australia (Western Australia) is the first mining enter- prise to consistently consider invertebrates in its research agenda. The exceptions are Dunger’s (1989) work on coal mine dumps in the former German Democratic Republic, and various studies on individual groups such as thrips (Stannard 1967), mites, and Collembola (Hutson 1980). At Alcoa’s operations, knowledge of invertebrate recolo- nization is considered essential in efforts to meet the cur- rent restoration objective of establishing a self-sustaining forest ecosystem, which aims to enhance or maintain tim- ber, water, recreation, and conservation values (Gardner 2001). Subsequently, the past 30 years has seen a concerted research effort that has made this ecosystem one of the most thoroughly studied for terrestrial invertebrates. The original Jarrah (Eucalyptus marginata) forest eco- system includes a myriad of terrestrial invertebrates. To reestablish a self-sustaining ecosystem, one must reestab- lish the full range of ecosystem functions and processes. Therefore, it is important to reestablish all components of the biota. Although microorganisms, plants, and verte- brates are of unquestionable importance, invertebrates feature prominently as drivers of ecosystem functions and processes. Therefore, the outcome of restoration attempts is profoundly influenced by the presence or absence of some of these animals. Mining companies should there- fore revegetate areas in a manner that maximizes the return of the full range of biodiversity. Particular attention should be paid to conserving rare or threatened species that might exist in the area. High-quality restoration therefore demonstrates compliance with biodiversity poli- cies and, of course, brings good public relations. This review outlines the scope of the terrestrial in- vertebrate projects that have been performed in Alcoa’s Western Australia bauxite mines, illustrating their taxo- nomic coverage, their importance in different strata of the habitat, and their varying roles in ecosystem functioning. The ways in which these studies provide input into key 1 Department of Environmental Biology, Curtin University of Technology, PO Box U1987, Perth, Western Australia 6845, Australia 2 Address correspondence to J. D. Majer, email j.majer@curtin.edu.au 3 Department of Environment and Conservation, PO Box 10173, Kalgoorlie, Western Australia 6430, Australia 4 Forest and Ecosystem Science, University of Melbourne, Water Street, Creswick, Victoria 3363, Australia Conflict of Interest Statement: The authors have declared no conflicts of interest. Ó 2007 Society for Ecological Restoration International S104 Restoration Ecology Vol. 15, No. 4 (Supplement), pp. S104–S115 DECEMBER 2007