Climate change
Climate change is without doubt a serious conservation issue that threatens 19% of already threatened or near-threatened species world-wide (Maxwell et al, 2016) and it very clearly threatens the survival of our western ringtail possum.
As the impacts accelerate, those that are geographically or climatically restricted will be the most vulnerable (Cabrelli et al, 2015). Western ringtails fall in both categories.
Extreme events will intensify – heatwaves, droughts, fires (wild or prescribed), habitat damaging cyclones, sea level rise and changes in hydrology – with potentially fatal consequences for the species as its capacity to adapt is very limited.
A high proportion of those species that are already suffering from a high level of other threats could face extinction as ecosystem degradation exacerbates.
Habitat loss is currently regarded as the most potent driver of species extinction. Land-clearing is not only responsible for a third of our greenhouse emissions since 1850 but it also contributes to the reduction in rainfall, increased temperatures and high fire risk. (McAlpine et al, 2007)
Land clearing is a direct climate change driver. The increasing speed of climate change plus its synergistic effects with habitat alterations and introduced predators (Root et al, 2006) is just as dangerous as our stubborn reliance on fossil fuels.
Species have to adapt to changing conditions or move/contract to areas with still adequate conditions. However the western ringtails’ small area of occupancy, the fragmentation of these habitats which restricts movement and therefore limits genetic diversity and the potentially rapid changes in conditions do not allow for either.
Modelling (Molloy et al, 2014) predicted a reduction of up to 60% in the range of the western ringtail and in its habitat as a result of climate change. Predictions for rainfall decreases are especially grave for the South West and jarrah, marri and peppermint were all predicted to experience similar contractions throughout most of the species’ range.
There is also legitimate concern that the spread of dieback, Phytophthora cinnamomi, may become even more vigorous under changed climate conditions.
Hotter, drier conditions influence tree vigour negatively and tree canopy decline is directly related to ringtail decline and is limiting a region’s carrying capacity. (B. Jones, pers. comm.)
Heatwaves have increased in intensity and length. If there is no escape, death by hyperthermia is unavoidable as a study proved the species’ limited ability to cope with high ambient temperatures above 35°C. (Yin, 2006)
As we cannot reverse current manifestations of climate change, reducing existing threats in the way of restoring cleared and degraded habitat, increasing habitat connectivity, protecting refugia and lowering predation levels would be the only options of decelerating the steep decline.
Climate change will increase those already exiting threats. If we can manage to ameliorate them, the capability to adapt to climate change might be improved.(Jackson, 2017)
When levels of atmospheric CO2 increase, photosynthesis and growth rates of plants seem to benefit. Positive changes to forest productivity might actually occur in some plantation regions but for the south-west of WA the predicted declines in precipitation are more likely to decrease productivity as plant growth is also strongly dependent on water availability and soil nutrient levels.(Cabrelli et al, 2015)
Increased photosynthesis in plants that grow on infertile soils such as those in the South West leads to higher production of carbon-based secondary metabolites as defence mechanism against herbivory. If levels of for instance terpenes and phenolics in eucalyptus and peppermint leaves should increase even more, it could make them too toxic for folivores. (Lawler et al, 1997)
Plants grown at higher concentrations of atmospheric CO2 also tend to have lower concentrations of nitrogen in their leaves and increased fibre content. (Coley, 1998, Lawler et al, 1997)
Foliage that is already low in nutrients and relatively high in toxic compounds could with further elevation in CO2 become unsuitable as a food source and carrying capacity of remnant areas with low abundance could be reduced to non-viable levels. (Hume, 1999)
