Irreplaceable Biotopes

Irreplaceable biotopes are difficult to successfully restore or create because methods of restoration are difficult or unknown, they are very slow to recover, they may be rare based on their extent, range or distribution. They might also exist in rare, unusual or distinct environmental contexts.

The identification and classification of irreplaceable marine biotopes can guide decisions about the sensitivity, risk and consequences of potential activities, disturbances and pressures in these locations.

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Why identify irreplaceable biotopes?

The identification and classification of irreplaceable marine biotopes serve to guide decisions regarding the sensitivity, risk, and consequences associated with disturbances by anthropogenic activities and pressures. By pinpointing these irreplaceable biotopes, planners and developers can avoid actions that would result in irreversible damage given challenges in recreating them elsewhere.

Additionally, this classification aims to inspire scientists to develop technically feasible restoration methods for certain biotopes currently considered irreplaceable. Developing effective and scalable restoration techniques in the marine environment is recognised as difficult (Tillin et al. 2022). Many methods that work on a small scale may not be feasible or effective on a larger scale. Irreplaceable biotopes that have evolved in a distinctive environmental setting that is not replicated elsewhere would be challenging to restore as it is cost prohibitive and unfeasible to recreate that environmental setting in another location.

What about Key Ecological Features (KEFS)?

Marine biotopes can also be designated as KEFs if they are recognised as important for biodiversity or provide an important ecosystem function. For example, a marine biotope may be the critical habitat for the persistence of a threatened species, or it may serve as nursery habitat for a commercial fish species. KEFs may relate to a species (e.g. a predator that impacts a large biomass or number of species), an important habitat type (e.g. supports high productivity or aggregations of breeding animals), or a unique seafloor or oceanographic feature that positively influences the surrounding ecosystem (e.g. a deep canyon that stimulates upwellings of nutrient rich water).

Victoria’s marine KEFs will be described in a separate project using scientific criteria for identifying Ecologically or Biologically Significant Marine Areas (Ninth meeting of the Conference of the Parties to the Convention on Biological Diversity, Annex I, Decision IX/20).

Irreplaceability Criteria

Marine biotopes can be attributed based on their life history context with irreplaceability criteria. Each criterion is scored with a set of standardised criteria with ordinal rank definitions for natural recovery potential (years to recover); restoration potential and feasibility; rarity (based on number of records, regional and global distribution); and the uniqueness of the environmental context (physical and hydrodynamic).

Each biotope was assessed against the criteria and assigned as ‘Irreplaceable’ if scored highly in either ‘Recovery’ (4 and above) and ‘Restoration potential and feasibility’ (3 and above); and assigned as ‘Restricted or Rare’ if scored highly in any of the ‘Rarity’ (4 and above) and ‘Uniqueness of the Environment’ (3) criteria.

Statutory Protection

Statutory protection status was incorporated into the final score. Although not used as a criterion for determining irreplaceability, it is an important consideration for managers, planners and developers. Statutory protection status pertains to a biotope, or a species that is characteristic of a biotope, that is listed under the Flora and Fauna Guarantee Act 1988 (FFG Act), or the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), or known to occur in a protected area under the National Parks Act 1975.

The status of statutory protection of biotopes is based on best available information. It should be used cautiously and is intended as a guideline. A biotope is considered protected if it is located within a marine protected area (MPA) or is part of a listed threatened community, based on available historical surveys. However, this does not guarantee protection in all locations where the biotope occurs. Conversely, a biotope may not be recognized as protected even if it is within an MPA, if this information was not available during the assessment. Statutory listing information can change, so always use the most current data for the FFG and EPBC Acts, and within MPA boundaries. MPAs include Marine National Parks and Marine Sanctuaries, which are highly protected "no-take" areas, while Marine and Coastal Parks, Marine Parks, and Marine Reserves are managed for multiple uses.

Which biotopes are irreplaceable?

In general, biotopes that are found in the CBICS Level 3 Habitat Complex, defined by substratum, depth, and energy, that typically exhibit many irreplaceable at CBICS Level 4 to 6 biotopes include:

• Moderate and low energy supralittoral rock biotopes (e.g. characterised with rare lichen communities)
• High and moderate energy infralittoral rock biotopes (e.g. characterised with species of Macrocystis and Amphibolis)
• Tide swept channels of circalittoral rock biotopes (e.g. biotopes associated with Port Phillip Bay Entrance Canyon, Crawfish Rock and Corinella Circalittoral Reef)
• Sublittoral rhodolith bed biotopes. Rhodoliths are agglomerations of coralline algae forming nodules of various morphological types (Harvey et al. 2008, Harvey et al. 2016). Rhodolith beds create biogenic habitat that enhances biodiversity compared to surrounding sediment beds and are major producers and sinks of calcium carbonate. Rhodolith beds can occupy vast areas around the world and in Australia (Harvey et al. 2016). They are likely to play an important role in carbon cycles, carbon sinks into sediments and are susceptible to ocean acidification.
• Sublittoral sediment seagrass biotopes. Presently, there is no evidence that Heterozostera/ Zostera spp. seagrass beds in Victoria can be restored at scale, although research efforts to redress this are in progress. Posidonia australis recovers very slowly from disturbance. It is long-lived, slow growing species only found in the marine waters of Corner Inlet and Nooramunga in Gippsland. Historic projects that have attempted to restore this seagrass species have been unsuccessful.

Which are not considered irreplaceable?

Biotopes that are not considered irreplaceable include many intertidal sedimentary habitats that recover quickly from disturbances, are widespread, and are characterized by common species. Subtidal sedimentary biotopes are similar but are not as easy to restore and/or may take a longer period to recover. Whilst saltmarsh and mangrove biotopes have slow recovery rates, they are the most feasible marine biotopes to restore with high success rates reported globally.

Irreplaceability categories

One of four irreplaceability categories, with a corresponding sub-category, were assigned to each biotope complex, biotope or sub-biotope in the CBICS catalogue by combining the irreplaceability criteria scoring and relevant statutory protection association.