Flood Plain Lower Ringarooma River Ramsar site Ecological Character Description March 2012 Blank page Citation

Changes in Ecological Character Since Listing

Some information is available through comparison of aerial photographs taken in 1978 and in 1999 (Jerie and Houshold 2001), supplemented by a site inspection and aerial survey in 2007. The key pieces of information gained through these comparisons relate to two of the major threats to the site: sediment encroachment and dairying encroachment. The clearest differences between the 1978 and 1999 aerial photographs are the development of pivot irrigation south of Shantys Lagoon.

This encroachment of pasture irrigation is difficult to assess, as the area now under pivot irrigation was previously grazed ‘unimproved’ pasture. As the aerial photographs do not coincide directly with the 1982 listing (for example there is an aerial photograph for 1978 and one for 1999), they do not distinguish whether the pivot system was installed before or after listing. However, members of the steering committee for this project (Dominique Couzens, Parks and Wildlife; Stewart Blackhall, DPIW) have stated that prior to Ramsar listing the site was not used for pivot irrigation and dairying. The major changes that might be expected from grazing and pasture improvement of the agricultural land are damage to soil structure and impacts on threatened vegetation communities (Figure 23). However, these impacts would already have been occurring on the agricultural land under rough grazing (albeit at a slower rate). Therefore, it is unlikely that this intensification of grazing will have led to a change in ecological character, when the irrigated land was already under agricultural use.

A further complication is that during the same period that the pivot irrigation was installed, a large area in the centre of the site (Fosters Marsh) had grazing removed and has been set aside for regeneration. This has resulted in a large area of land changing from agricultural land to freshwater aquatic sedgeland and rushland (Ts), increasing the overall area of wetland at the site since listing (compare Figure 10 with Figure 29). Therefore the intensification of grazing on the agricultural land is not assessed as causing significant changes to the critical components or listing criteria.

Although the pivot irrigation was established on existing agricultural land, it does have the potential to change the character of the site if not appropriately managed. One issue is the potential impetus for further expansion into the site and another is likely impact on water quality through (a) loss of capacity for filtering surface runoff, and (b) through discharge of dairy effluent to the site. However, these threats cannot be assessed as having caused change to the ecological character of the site, partly due to a lack of baseline data but largely due to the fact that the major change - the loss of unimproved pasture to irrigated pasture - is difficult to measure as a change.

The issue of discharge of dairy effluent is being addressed through the implementation of best practice dairy effluent management in the three dairies on the site (AAS and BIS 2007). Although the implementation of best practice could be expected to reduce impacts, water quality monitoring focused on this issue is recommended (see Section 7).

Similar to the irrigation, the in-stream sedimentation resulting from historical tin mining activities higher in the catchment also appears to have made some advances between the 1978 and 1999 photographs. The advances made into Shantys Lagoon, discussed in Section 3, indicate that part of the wetland has been lost since listing. This process was occurring at the time of listing and is likely to continue for decades (Knighton 1991, Jerie, personal communication), occurring during large hydrological events. While it is not known what size flow event is required to move sediment further into the wetlands, it is known that the 2007 event (an ‘annual’ high flow event) did not move measurable amounts of sediment (Bobbi personal communication and personal observations). As some areas are covered in the fine sands and silt, they may change from one wetland type to another (e.g. from open water to rushland). The changes that have occurred since listing cannot be assessed as significant enough to be classed as changing character. However, the ongoing nature of this process also warrants its inclusion in the monitoring program (Section 7).

In addition to direct evidence, anecdotal evidence can also provide some useful information on changes within the site. Comments from a landholder at Ringarooma have indicated a decline in eastern quoll numbers and a simultaneous rise in feral cat sightings. This phenomenon has been noticed elsewhere in Tasmania and has been associated with the decline in Tasmanian devils over the last five years, whereby the devil population previously kept feral cat numbers low, which reduced cat predation on the quolls (Jay Wilson, personal communication).

Another piece of landholder anecdotal evidence for faunal changes is a noted decline in wombats. A landholder on the site noted that once wombats were common enough to be regarded as pests, whereas now the few that are observed appear to be suffering from severe mange. Mange has been noted in other areas across Tasmania and also the south-east Australian mainland (Skerratt 2001).

In summary, it is difficult to argue that the alterations of use of the site are a change in ecological character of the site. The site features that supported its listing remain intact and in fact there has been a rehabilitation of some grazed areas resulting in an increase of sedgeland/rushland.

Cessation of grazing has allowed the seasonal wetland in the central part of the site to regenerate into a more natural wetland type (Figure 29), although the intensification of dairying has meant that other areas of rough grazing have been permanently altered from natural wetlands (that is, prior to pivot irrigation the areas may have been more readily restored).

The encroachment of irrigated pasture is a serious and potentially continuing cause for concern for the ecological character of the site. If not controlled, this activity may jeopardise the site’s Ramsar status. However, the expansion has now ceased and the owners have developed management plans for the property (Sherriff 2007; AAS and BIS 2007) and an overall Ramsar Site Management Plan has also been developed (GHD 2008). The implementation of these plans should adequately manage and reduce any impacts from the use of the site.

Future mining operations may also pose a threat to the site, although these impacts may be avoided through strict environmental management plans and systems.

The lack of substantial changes to the site’s critical components, and the Limits of Acceptable Change (LAC) set in this ECD currently being met, is indicative of the site retaining its ecological character as at the time of listing.

Figure 29: Ramsar wetland types as present on the site in March 2010.