Following the recent ‘south coast low’, former Prime Minister Malcolm Turnbull was reported saying ” . . . climate change is bringing about larger and more frequent storms.” However, he added that the ” . . . flooding across eastern Australia can’t be directly attributed to global warming.”
While I have some difficulty trying to separate any weather from climate change, if one were looking for evidence that the storm was larger than usual, the partial destruction of the Eden woodchip mill’s loading wharf is a good regional example. On this issue, the Eden Magnet reported a South East Region Conservation Alliance ‘twitter’ saying “ . . . Act of God wrecks the Eden chip mill jetty and loader. Nature is fighting back.”
Like Malcolm Turnbull, SERCA’s ‘act of God’ would also seem to exclude a direct connection with climate change. Locally there were two moderate flood peaks in the Murrah river, some 15 hours apart. The photo below shows water receding from the front yard after the second peak. Even though most of the Murrah catchment is forested, the flood water is very dirty.
Indeed Bega Valley Shire Council has a ‘boil water before drinking’ alert for customers on the Brogo-Bermagui water supply. The dirty water in the Brogo dam comes almost exclusively from Wadbilliga National Park.
Historically, accepted sources of colloidal materials and suspended sediment have included stream bank erosion, gully incision, roads and logging, particularly when the latter is combined with fire.
What is yet to be considered or accounted for is die-back, in its various forms. Perhaps moving in that direction is a research report titled ‘Bell miner associated dieback: nutrient cycling and herbivore crown damage in Eucalyptus propinqua‘, published early this year.
In essence the research and apart from iron concentrations, couldn’t find a strong correlation between tree crown health and either, leaf nutrients, soils or under-storey, where lantana dominated. Interestingly, very few psyllids were found during the research, undertaken during a dry spell. Rather ” . . . caterpillars of the concealer moth appeared responsible for most defoliation observed during our study the question arises if there is an association between other defoliators and BMAD.”
As usual I have some uncertainties about the soil sampling and analysis. For example, the question of whether the soils are dispersible isn’t answered, although it would have provided a link to current forest management.
However, further research is proposed including ” . . . BMAD-affected trees growing in a soil with significantly different water-holding capacity would be valuable for future analyses because of the possible association of topographic moisture with BMAD.”
This particular suggestion would seem to fit in with DPI research, using lidar and multi-spectral satellite imagery ‘to apply a modelling system that accurately maps the current, and potential, distribution of BMAD.’
For the south coast including the distribution of forests subject to extensive canopy die-back, associated with dry weather and drought, would be appropriate. Based on the possible association between topographic moisture, dead trees and dirty water.