The effects of strong winds on trees is a much-researched
topic. International conferences have been conducted on the issue.
Trees bend and sway in strong winds to dissipate energy and
help them withstand the onslaught without failing. Young trees that are exposed
to persistent one-direction winds develop stronger root systems to resist wind
loads.
The Bureau of Meteorology states, “The
predominant wind stream over Victoria is of general westerly origin, although
it may arrive over the State from the northwest or from the southwest. There
are wide variations from this general description, however, and many
northerlies or southerlies are experienced. Furthermore, the hot northerlies
which bring heatwave conditions from the interior are well known, whilst in
winter and spring exceptionally cold weather may accompany a southerly wind
stream.”
The recent strong easterly wind Gippsland experienced was
caused by the combination of a low-pressure system off the southern NSW coast
and a slow-moving high-pressure system south of Tasmania. Winds travel
clockwise around lows and anticlockwise around highs.
As a result of the developing pressure system, the BoM
published forecasts of strong easterly winds for much of Victoria for several
days in a row.
Some easterly gusts were quite strong and placed trees in
this district under conditions they are not acclimatised to.
Street trees or stand-alone trees, without the protection of
other nearby trees, are more exposed to wind loads. Urban trees will often have
root zones that are restricted by building foundations, roads and footpaths,
etc. Urban trees will often be exposed to environmental stresses that cause
them to exhibit ‘old age’ characteristics years before their wild-growing
relatives. Urban and stand-alone trees may not have the support of a root
system entwined with other nearby trees.
Urban and stand-alone trees are often more susceptible to
failure by windthrow. Trees compromised by decay or previous
damage are at higher risk of wind damage.
Climate change is intensifying the strength and frequency of
strong wind events by increasing atmospheric heat and moisture, leading to more
violent thunderstorms, faster-intensifying cyclones, and stronger gusts.