MTSRF
Project 1.4.3
Effects of fragmentation and associated threats to native wildlife in a spatial and temporal context
Project Leader: Dr Dan Metcalfe, CSIRO
This MTSRF-funded project has been primarily focused on how fragmentation of lowland communities impacts on native species and ecosystem processes, and what an understanding of these processes can tell us about longer-term declines in more extensive areas of native vegetation. An analysis of the distribution of rain forest Regional Ecosystems (REs; Queensland Government Environmental Protection Agency, 2005) in the target area (i.e. Tully, Murray and Johnstone Rivers occurring below 100 m asl) identified 46 separate types, of which 22 appeared to be lacking any full vascular plant surveys from the Bioregion. Survey methodologies were agreed with Queensland Herbarium, with whom survey and collection data were shared. The first year of work filled many of these data gaps, and so provided a baseline dataset for the coastal lowlands from which an appropriate fragmented community could be selected. The selected study RE was scheduled as an endangered habitat (mesophyll vine forest on moderately to poorly-drained alluvial plains, of moderate fertility; Regional Ecosystem 7.3.10a) and fragments of the RE were common in the target area. Twenty such fragments were surveyed, and contextualized in terms of size, age and distance from continuous native vegetation. For the community and context surveyed, time since isolation and size had no effect, but that isolation distance impacted signifi cantly on species composition of the fragments. This suggests that seed dispersers are less willing to cross larger distances to more isolated fragments. In terms of regeneration trajectory, more isolated fragments were more similar in species composition than fragments closer to extensive forest, when sapling recruits were considered. Again, disperser preferences and handling abilities may be restricting the species composition of recruits able to reach the more isolated fragments. From a functional perspective, we also considered the services provided by species in fragments, and analyses suggested that in fragments close to extensive tracts of forest there is a gradual homogenization of community traits, as early successional species are recruited out of the extensive forest and come to dominate the fragment communities. However, weeds were not driving this trend, as weeds make little contribution to functional diversity, as they tend to convey the same traits as native species. Together, these data suggest that all fragments are at risk of declining value in terms of biodiversity and ecosystem services, with remote fragments losing rare species and becoming dominated by a small group of well-dispersed species, and less remote fragments being swamped with early successional species at the risk of rarer species. These results have been reported to managers via the Wet Tropics Building Restoration Knowledge workshop and are the subject of a manuscript in preparation.
Publications
A long-standing 4WD track along the back of the foredunes and sand spit between Cowley Beach and the mouth of Liverpool Creek (south of Innisfail, North Queensland) was extensively damaged by Tropical Cyclone Larry in March 2006. Storm surges removed several metres of beach sand and many established trees, while high winds felled many trees across the track. Quad bike riders and 4WD drivers have subsequently made their own tracks, following the original track at the southern end, but running along the ridge crest for much of its length, damaging sand-stabilising vegetation and potentially disturbing turtle nest sites. The Cassowary Coast Regional Council is assessing the feasibility of re-routing the track to the landward side of the foredune where the sand is better stabilised and potential ecological damage is minimised. This report provides details of a site assessment carried out by CSIRO ecologists to assess community structure and condition in relation to the mapped vegetation communities under the Queensland Department of Environment and Resource Management's Regional Ecosystem Framework (RE), search for significant plant species listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) and Nature Conservation Act 1992 (Qld) (NCA), and for bioregionally important occurrences of other plant species, assess weed abundance and distribution, and assess the ecological values of the site and the damage being caused by on-going motor vehicle access.