Australia is a world leader in spatial conservation planning. The IBRA (terrestrial) and IMCRA (marine) bioregionalisation programs were significant conservation management achievements. However, such initiatives require periodic review and updating in order to incorporate new data and tools. While IBRA is in its seventh version, the IMCRA marine bioregionalisation is in its second substantial version. It was last updated in 2006 (IMCRA v4.0) with the recommendation that it not be updated before 2010.  Triggers identified for updating IMCRA v4.0 were: 1) substantial new biodiversity or process data; 2) jurisdictional need, and 3) international obligations. Areas that could be addressed to improve the utility of IMCRA were: conceptual classification models; improved data coverage, and improved ecosystem understanding, including the role of surrogates. New biodiversity data collated since 2006 have identified numerous inconsistencies in the formation of existing marine bioregions, particularly for inshore areas and island territories. There has been a considerable accumulation of national biological and environmental datasets and the development of new analytical tools. Our understanding of processes that structure biodiversity at large scales has also changed, with an increased emphasis on the importance of depth, carbon flux and connectivity. Some of this new knowledge, including identification of Key Ecological Features, was used in designing the Commonwealth Marine Reserve (CMR) network, but the data were never added to IMCRA. New observations have refined our understanding of when surrogates are useful.  New genetic datasets have provided a novel conceptual model that distinguishes long term evolutionary change and shorter term ecological processes. These scientific advances justify revising IMCRA. It would be useful to have a revised IMCRA available to inform reviews of marine reserves and reserve networks and marine bioregional plans, for example the South-east CMR Network Management Plan is expected to be reviewed in 2023 when it expires. Up to date and improved versions of IMCRA also have the potential to inform ongoing environmental impact assessments of new or planned activities. 
In working towards a best-practice bioregionalisation, a number of challenges remain. This includes filling large remaining biological data gaps, finalising national datasets of important environmental variables, and extending analytical techniques so that they can rigorously incorporate biological data from mixed sampling regimes (e.g. most museum data), historical (genetic) information and connectivity (dispersal) data.


Document Type: