Aquatic ecosystems are notoriously difficult to classify, largely because of the highly variable nature of water and vegetation in terms of extents, conditions and dynamics. This has resulted in a number of taxonomies being developed to encompass different principles deemed important or relevant to particular regions or countries. This is particularly the case in Australia, where the highly variable climate regimes lead to equally dynamic wetlands systems. This has lead to differing taxonomies being used amongst the states and territories, many of which have been determined based on relevance to the principles and attributes of that taxonomy. Examples include vegetation (Keith, 2004), geomorphology (Semeniuk & Semeniuk 1995) and water (Corrick & Norman, 1980). However, agreed taxonomies and accurate, robust and consistent classifications of wetlands are essential for accurate and consistent mapping and monitoring, particularly from EO data.
Ramsar Wetlands Classification
At a global level, the most widely applicable is the Ramsar Classification, which was adopted in 1990 as a broad framework to assist development of international inventories and to support documentation associated with the List of Wetlands of International Importance (Ramsar Convention Secretariat, 2010). The taxonomy used in the classification is based on the hierarchical scheme used in the United States and developed by Cowardin et al. (1979) and contains 5 systems and 11 subsystems. In total, 42 different types of wetlands are described, with these grouped under the headings of marine, coastal, inland and human-made.
Australia and New Zealand ECC (ANZECC) Wetlands Network
In Australia, the Ramsar classification is used at a national level to document wetland types present within sites listed under the Ramsar Convention. In 1994, the ANZECC Wetlands Network agreed upon and implemented a slight modification of the Ramsar classification to suit the Australian context for constructing the Important Wetlands in Australia (DIWA) inventory. Two additional types were defined, two were removed and four were merged into two. The majority of these wetlands categories overlap but the documented codes vary between those used by Ramsar (letter or numbers; e.g., B) or ANZECC (letters and numbers, e.g., A2).
Interim Australian National Aquatic Ecosystems (ANAE)
In 2005, the Queensland State Government began the process of mapping and classifying their wetlands and based their taxonomy on that of Cowardin et al. (1979) but included relevant modifiers. In 2012 the Aquatic Ecosystems Task Group (AETG), within input from the Queensland State Government, developed and agreed on the Interim Australian National Aquatic Ecosystem (ANAE) Classification Framework (AETG, 2012). This consisted of three levels relating to regional (Level 1) and landscape scales (Level 2), with these then collectively divided according to the nature of surface water or subterranean systems (Level 3). Again, this system was based on Cowardin et al. (1979) but floodplains were introduced into the surface water class. Subterranean classes were also described.
State and Territory classifications
In light of the ANAE framework, New South Wales (NSW) and Victoria re-evaluated their classification system for inventory creation but several attributes differed from those used in Queensland. The Australian Capital Territory remained with the original ANAE classification. Queensland continues to use the ANAE system based on Cowardin et al. (1979). The Northern Territory (NT), Tasmania and Western Australia have adopted the original Ramsar classification.
Translations between wetlands taxonomies
The majority of taxonomies relating to aquatic environments are based around a hierarchical structure with the level of detail and complexity increasing with scale as more detailed descriptions are required at the local scale. Due to this structure, a nesting of descriptors can be visualised (Figure 2). The majority of taxonomies (in Australia, but also internationally) distinguish between marine, estuarine, riverine, lacustrine or palustrine systems (Cowardin et al., 1979) and these categories also provide a framework within which to provide more detailed classifications and allow comparisons between these. With reference to Figure 2, the Ramsar classification is represented in the outer circle, with the code descriptions provided in Table 1.
The Ramsar taxonomy is widely used (e.g., by the Australian Department of Environment) because of its requirement on Ramsar Information Sheets for wetlands nomination. It consists of 3 main categories (marine/coastal, inland and human made) and 40 sub-categories, with the latter providing an entry point for comparison with other taxonomies. For example, the Level 1 of nesting is the Ramsar broad categories (marine/coastal, inland or human-made) whilst Level 2 arises from Cowardin et al., (1979; i.e., marine, estuarine, riverine, lacustrine and palustrine), which fall into the Ramsar Level 1 classes of marine/coastal or inland. The floodplain and subterranean classes from ANAE are also included, with these overlapping with one of the other 5 categories in Level 2 (through the Ramsar categories) that can also be classified, for example, as riverine (see AM2 in Table 1 and Figure 2). Descriptors of human-made wetlands are also included in Level 2. Level 3 classes are based on attributes (variables) of wetlands relating to water regime, salinity and vegetation. These three attribute categories were chosen because of their broad use in describing wetland characteristics. Many of the Ramsar categories have overlapping descriptors at Level 3 due to the possibility (as an example) of both permanent and intermittent inundation occurring in that wetland.
AETG, 2012. Aquatic Ecosystems Toolkit. Module 2. Interim Australian National Aquatic Ecosystem Classification Framework. Australian Government Department of Sustainability, Environment, Water, Population and Communities, Canberra. Retrieved from: https://www.environment.gov.au/system/files/resources/08bfcf1a-0030-45e0-8553-a0d58b36ee03/files/ae-toolkit-module-2-anae-classification.pdf
Corrick, A.H., Norman, F.I., 1980. Wetlands and waterbirds of the Snowy River and Gippsland Lakes catchment. Proc. R. Soc. Vic. 91, 1-15.
Cowardin, L.M., Carter, V., Golet, F.C., LaRoe, E.T., 1979. Classification of Wetlands and Deepwater Habitats of the United States. U.S. Fish and Wildlife Service, FWS/OBS-79/31, Washington, D.C.
Keith, D., 2004. Ocean shores to desert dunes: the native vegetation of New South Wales and the ACT. Dept. Environ. Conserv. Hurstville.
Ramsar Convention Secretariat, 2010. Handbook 17: Designating Ramsar Sites: Strategic Framework and guidelines for the future development of the List of Wetlands of International Importance, in: Ramsar handbooks for the wise use of wetlands, fourth edn. Ramsar Convention Secretariat, Gland. Retrieved from: https://www.ramsar.org/sites/default/files/documents/pdf/lib/hbk4-17.pdf
Semeniuk, C.A., Semeniuk, V., 1995. A geomorphic approach to global classification for inland wetlands, Vegetatio, 118, 103–124. https://doi.org/10.1007/BF00045193.