Aquatic assessments

Aquatic systems such as streams, rivers and dams are governed by a number of acts. In future aquatic assessments are likely to become more integrated with wetland assessments. Ecological information is vital to manage aquatic systems, not only for the local area where a stream, river or dam is located, but also in the region where these aquatic systems are connected in water catchment systems.

Objectives:

The objectives of the wetland habitat assessment are to provide:

  • - An identification of major aspects of river health;
  • - An estimate of compositional aspects of aquatic invertebrates in terms of the appropriate version of the South African Scoring System (SASS);
  • - An estimate of fish assemblages at the site;
  • - An assessment of riparian vegetation (riparian vegetation index);
  • - An indication of the importance of a catchment area;
  • - An indication of the habitat functions of the aquatic system for the aquatic organisms present;
  • - An indication of the land uses and conservational aspects at the aquatic system and the surrounding areas
  • - An environmental management plan should to indicate impacts of the proposed developments on an aquatic system and relevant rehabilitation actions, biomonitoring actions and fish way design.

Estimating ecological conditions for conserving biodiversity or highly localised species

For the conservation of localised or threatened species such as rare or localised plant species, rare small mammals and many localised invertebrate species, rangeland condition models are limited. A good veld condition or rangeland condition for megaherbivores such as cattle, is not necessarily ideal for the conservation of smaller fauna and flora, especially at ridges where soils are naturally poor in nutrients. For the purposes of this ecological conditions for environmental impact assessments, the application of these rangeland condition methods may be limited for three main reasons.

Firstly, natural grassland on rocky ridges may contain a low frequency or abundance of grass species that are of high ecological status in terms of grazing by megaherbivores, even though a patch may be ideal for rare flora and smaller fauna. For example a Melinis nerviglumis – Aristida transvaalensis community, which is inhabited by a number of grass species of lower ecological status, was found to include the ideal habitats of the rare and threatened Golden Copper butterfly, Chrysoritis aureus (Terblanche, Morgenthal & Cilliers, 2003). Threatened insect species often require habitats that are to some extent disturbed, for example the Brenton Blue Butterfly, Orachrysops niobe (Edge, Cilliers & Terblanche, 2008). Secondly, the diversity of indigenous forb species, and not necessarily grass species, is often of paramount importance for smaller fauna and flora. Thirdly, especially within and on the fringes of urban areas, pioneer forbs, shrubs and trees may be more important to indicate degradation of ecosystems than low ecological status grass species. Patches opened up by excavations do not necessarily follow the same succession pattern as patches that are opened up by overgrazing or fire (Terblanche In prep b).