Part 3 – Management Strategies to Protect Park Values
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PART 3 – MANAGEMENT STRATEGIES TO PROTECT PARK VALUES Draft Wellington Park Management Plan 2012 103 Draft Wellington Park Management Plan 2012 104 CHAPTER 5 THREATS AND PRESSURES ON PARK VALUES 5.1 Introduction The primary objectives for the management of the Park, as described in chapter 2, include references to conserving and protecting natural, cultural and use values. To protect these values it is useful to have an understanding of the threats or pressures they may be under. This allows for management prescriptions to be developed which can focus on minimising the threats and managing the pressures. The threats and pressures on the Park’s values can be grouped as follows: - climate change impacts; - disturbance from fire; - disturbance from natural hazards; - the introduction and spread of exotic species (flora and fauna); - inappropriate activities, use and development in the Park; - overuse of the Park; and - vandalism. 5.2 Climate Change Impacts Over the 21st century, Tasmanian temperature is projected to rise by about 2.9 °C under the high emissions scenario, and about 1.6 °C under the low emissions scenario. In both emissions scenarios, this is less than the projected global average temperature rise, due to the moderating influence of the Southern Ocean. Increasing temperatures are also likely to lead to increases in evaporation, decreased average cloud cover, increases in relative humidity and increased winds in spring (Antarctic Climate and Ecosystems Cooperative Research Centre, 2010). While there are regional predictions of the possible effects of climate change, there is little specific information available as to how it may impact Wellington Park itself. Tasmania’s natural values are impacted by a range of threats and disturbance regimes such as fire, weeds and disease. The greatest uncertainties in projecting the effects of Draft Wellington Park Management Plan 2012 105 CHAPTER 5 – THREATS AND PRESSURES ON PARK VALUES climate change are associated with the interaction of these effects with the other stress factors. It is likely that climate change impacts will exacerbate current stress factors through complex and cumulative interactions with multiple system components. Climate change may initiate or magnify the impacts of threats such as fire, invasive species, and natural hazards eg storms, floods and landslides. The influence of changing climate therefore cannot merely be considered as ‘one more stressor’, but must be considered in every natural resource management activity planned and executed (DPIPWE, 2010). Fire is a particularly good example of this complex interaction. In the recent past, almost all wildfires affecting the Park have been: caused by humans; close to adjoining urban areas; and along roads and fire trails where they are relatively easy to access. Fires started by lightning would be a major threat to the Park if they occur in inaccessible areas. There are no records of any recent fires caused by lightning in the Park, however this could change in the future, as evidenced in the Tasmanian Wilderness World Heritage Area: In the decade of fire seasons 1991- 2000, unpublished Tasmanian Parks & Wildlife Service records show 14 lightning fires were recorded on reserved land with a total area burnt of 11,245 ha. In the seven fire seasons from 2000-2001 onwards there were 55 lightning fires and 160,698 ha of reserved land burnt. Lightning is now the major cause of wildfire in the TWWHA, whereas in 1986 it was considered that ‘[i]n Tasmania there is no strong relationship between thunderstorms and fire’ (Bowman and Brown 1986). (DPIPWE, 2010, pg 12) Snow cover is expected to diminish in all of Tasmania’s alpine areas and is patchy and variable in Wellington Park. While the extent of snow cover itself has not been measured in a consistent way, data relating to the closure of Pinnacle Road gathered since 1996 shows significant variability from year to year in terms of the number of days the road is closed due to snow or ice. The data appears to show a reducing trend in the number of hours that the road is closed however this may be the result of improvements in snow clearing procedures, and is not a reliable indicator of snow falls. Both the reduction in snow and ice cover, and any increase in fire frequency, have immediate implications for access management, however the implications for the Park’s vegetation are not so obvious. Alpine vegetation, adapted to being covered by snow for weeks at a time, or extended fire frequencies, is likely to become more stressed: Australian alpine environments have been identified as one of the most sensitive Australian environments to the potential impacts of climate change, with a high risk of biodiversity loss predicted by 2020 (Green and Pickering 2002; Hennessey et al. 2007). Endemic alpine species have been identified as having a disproportionately high vulnerability to climate change (Pauli et al. 2003), with limited capacity to adapt (Fischlin et al. 2007). In particular the predicted incidence of extreme events such as wildfire and drought could have a very significant impact. (DPIPWE, 2010, pg 32) Draft Wellington Park Management Plan 2012 106 CHAPTER 5 – THREATS AND PRESSURES ON PARK VALUES Expert advice anticipates that the most serious future threat to the Park’s vegetation, especially its alpine vegetation, would be an increase in the frequency and intensity of wildfires in the alpine and sub-alpine areas of the Park. Wellington Park is particularly at risk from wildfires due to it ‘having extensive areas of dry (<600mm p.a.) country to its north and north west, the directions from which most fires emanate in Tasmania’ (Dombrovskis, 1996). Over the longer term, any increases in extreme wind events and hotter drier days will increase the threat to the Park, beyond what already occurs due to current variable climatic conditions. While fire can benefit the dry forest plant communities on the lower slopes of the Park, past wildfires have caused considerable damage to more sensitive plant communities, particularly in the alpine and subalpine areas of the Park. In the shorter term (10 - 20 years), little real change is expected to be observed in vegetation cover, however a significant event (such as a wildfire) could trigger an upward altitudinal shift of the tree line. It has been noted that little evidence so far exists of such a shift, although there is an expectation is that, in the longer term (and certainly by 2090), higher altitude vegetation will be significantly impacted. Currently the relatively treeless vegetation, composed of alpine species, interspersed with stands of Eucalyptus coccifera open forest is found down to the 950m contour (Dombrovskis, 1996). 5.3 Disturbance from Fire Natural disturbance regimes including floods, wildfires, and storm events are predicted to change and intensify under climate change scenarios. Proactive management may help reduce the impacts. For example, controlled burning and other techniques could be used to reduce the potential impacts of catastrophic wildfires, particularly on fire sensitive native vegetation such as Tasmania’s unique conifer and alpine communities. However, there is likely to be a reduced safe window of opportunity for fuel reduction. (DPIPWE, 2010, pg 58) Fire in the Park has always been recognised by land managers as both a natural disturbance necessary for many of the fire adapted plant communities in the Park, and a threat to the Park’s natural and cultural assets, and to surrounding areas. As noted above, the potential for more extreme fire weather events and the possibility of ognitions by lightning may require a change in fire management strategies and the resources required for effective fire control. Possible impacts on wildfire frequency, intensity and distribution are not covered in the current Fire Management Strategy for the Park. The strategy however allows for an Adaptive Management approach to be followed, which can accommodate climate change as well as other variables. Long term rainfall modeling for Tasmania indicates no significant change to total annual rainfall across the state, however identifies emerging pattern of changes to spatial patterns of rainfall, with increases in coastal areas and decreases in inland areas. Further, the modeling suggests changes in seasonality of rainfall, and a reduction in the number Draft Wellington Park Management Plan 2012 107 CHAPTER 5 – THREATS AND PRESSURES ON PARK VALUES of exceptionally wet years (Antarctic Climate and Ecosystems Cooperative Research Centre, 2010). However, in the short term, there is likely to be little change to the rainfall amount or seasonality affecting the Park, beyond normal weather variability, and thus little real impact from this variable on fire threat. However wildfire remains the largest threat to the Park both in the short term and into the future, and thus requires a significant management focus. There are relatively few built assets in the Park that are vulnerable to wildfires and much of the Park’s fire-susceptible historic infrastructure has been burnt in fires up to and including the 1967 bushfires. The major impact of a large wildfire in the Park is likely to be on the quality and yield of the runoff in the various drinking water catchments in the Park. However the close proximity of many residential properties and rural residential developments to the Park means there is also a significant threat to life and property from wildfires moving out of the Park. Arson is currently the greatest single cause of wildfires within the Park, and there is little to prevent wildfires that start on adjoining private property from entering the Park. Urban and residential areas on the eastern side of the Park, although downslope of the Park, are at considerable risk from wildfires originating in, or moving through the Park. The Park has experienced several large fires, the largest being in 1967 when much of the Park was burnt.