The impact of Sydney's driest start to a year in half a century is starting to spread from lawns and playing fields to the trees hanging over them, with exotic conifers among the first to wilt.
Pines, cedars and junipers and other northern hemisphere conifer species are showing up as early arboreal victims of the drought, according to Brendan Choat, an expert in tree responses to drought from Western Sydney University.
The conifers "get hit sooner and harder than the natural species", Associate Professor Choat said.
While there are only sporadic signs of dying trees so far, owners should expect instances of "the Christmas tree effect". That's when conifers "all of a sudden go crispy and brown", once water supply is cut off, he said.
Even though many types of pines have been picked for their hardiness, their disadvantage during drought is the shallowness of their root systems. Eucalyptus species, by contrast, typically sink deeper roots, allowing them to tap aquifers that are yet to dry out.
So far this year, Sydney and the rest of NSW has barely had half the usual rainfall, leading to a steep drop in reservoir levels and setting up the state – and much of eastern Australia – for a dangerous fire season.
So far, most local species of conifers are faring better but some native varieties are struggling, Professor Choat said.
He cited the banksis serrata – also known as old man banksia or saw banksia – which are starting to die in regions of the Blue Mountains. Narrow leaf peppermint gum are also affected.
Any species that does not have access to groundwater – including less mature eucalyptus trees – will start to struggle, he said.
Conifers may also be vulnerable because they are often planted as windbreaks, leaving them more exposed to wind, which tends to increase evapotranspiration. As temperatures climb, they may also have less shade from canopies of surrounding trees.
Professor Choat was lead author of a recent paper published in the journal Nature, that looked at how trees perform in droughts and the potential to predict mortality.
The paper noted that future droughts "will almost certainly be worsened by increases in air temperatures associated with global warming; when natural droughts occur they will set in more quickly and be of greater intensity".
Extreme droughts, for instance, are estimated to have killed 102 million trees in California and 300 million trees in Texas, the paper said.
"It's pretty staggering when you see the big diebacks," Professor Choat said. People were asking "what do we do with all this dead wood?"
One consequence has been the massive wildfires that have scorched much of western US this past northern summer.
NSW's dry winter is likely to be followed by a drier and hotter spring than usual, if Bureau of Meteorology forecasts this weeek are any guide.
"We have a sense of dread," Professor Choat said.