The development of a classification system for inland aquatic ecosystems in South Africa

Abstract

A classification system is described that was developed for inland aquatic ecosystems in South Africa, including wetlands. The six-tiered classification system is based on a top-down, hierarchical classification of aquatic ecosystems, following the functionally-oriented hydrogeomorphic (HGM) approach to classification but incorporating structural attributes at the lower levels of the hierarchy. At Level 1, a distinction is made between inland, estuarine and shallow marine systems using the degree of connectivity to the open ocean as the key discriminator. Inland systems are characterised by the complete absence of marine exchange and/or tidal influence. At Level 2, inland systems are grouped according to the most appropriate spatial framework for the particular application. At Level 3, four primary Landscape Units are distinguished (Valley floor, Slope, Plain, Bench) on the basis of the topographic position within which a particular inland aquatic ecosystem is situated, in recognition of the influence that the landscape setting has over hydrological and hydrodynamic processes acting within an aquatic ecosystem. Level 4 identifies HGM Units, defined primarily according to landform, hydrological characteristics and hydrodynamics. The following primary HGM Units (or HGM Types), which represent the main units of analysis for the classification system, are distinguished at Level 4A: (1) River; (2) Floodplain Wetland; (3) Channelled Valley-Bottom Wetland; (4) Unchannelled Valley-Bottom Wetland; (5) Depression; (6) Seep; (7) Wetland Flat. Secondary discriminators are applied at Level 5 to classify the hydrological regime of an HGM Unit, and Descriptors at Level 6 to categorise a range of biophysical attributes. The HGM Unit at Level 4 and the Hydrological Regime at Level 5 together constitute a Functional Unit, which represents the focal point of the classification system. The utility of the classification system is ultimately dependent on the level to which ecosystem units are classified, which is in turn constrained by the type and extent of information available.

Assessing wetland health using a newly developed land cover citizen science tool for use by local people who are not wetland specialists

“…Wetland health is defined as the difference between the wetland's current structure and function, and the wetland's natural structure and function (Ollis, Ewart-Smith, Day, Job, Macfarlane, Snaddon & Mbona, 2015). Wetlands are a crucial ecosystem, as they are irreplaceable.…”

Managing wetlands for disaster risk reduction: A case study of the eastern Free State, South Africa

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Physical and hydrological properties of peatland substrates from different hydrogenetic wetland types on the Maputaland Coastal Plain, South Africa

“…The corresponding wetland types are either channelled or unchannelled valley-bottom wetlands (Ollis et al 2013). Interdunal depression wetlands often lack surface out-and inflow pathways (Ollis et al 2013). This wetland type is characterised predominantly by grass and sedge vegetation and the absence of trees (Sliva et al 2004).…”

“…These forested peatlands mainly occur along slightly sloped interdunal drainage lines and are characterised by fluctuating water tables and horizontal water through-flow. The corresponding wetland types are either channelled or unchannelled valley-bottom wetlands (Ollis et al 2013). Interdunal depression wetlands often lack surface out-and inflow pathways (Ollis et al 2013).…”

“…Lines and points in (b) to (e) indicate the sampled transects. The satellite image was acquired by LANDSAT in 2008Ollis et al (2013) published a classification system for wetlands and other aquatic ecosystems in South Africa, based on that developed by…”