Tuesday, April 17, 2018

Blowing In the Wind

A few recent wind ‘events’ sets the mind to ponder. Trees and strong winds are not a good mix but we do need to put things into perspective a little.

Up to date Australian figures for the risk of being killed by a falling tree are difficult to locate. Obviously if you shelter under a tree in a windstorm you will raise the chances. In 2017, Hellis Tree Consultants in the UK stated that the chance of being killed by a falling tree in that country was estimated at 1 in 10 million, an insignificant risk in most terms.

In 2012, hurricane Sandy toppled 8,500 trees in New York City alone, killed 233 people in eight countries and cost the USA government $69 billion. Sandy’s maximum wind speed was 185km/h.

The strongest wind speed, (gust), in Melbourne this year to date, 18th March, (remember?), was a mere 92 km/h. Melbourne’s windiest month is September and the average wind speed for September over the years from 1955 to 2010 is just over 15km/h.

Eucalypts, and in fact many other species of large trees do not have a deep root system. 90% of the roots of most eucalypts are less than 35cm below the surface.

Drouin South, July 2017 - large tree/shallow roots
Alex Goudie Reserve, August 2017 - a relatively large Mountain Grey Gum
Same tree as above - shallow roots, no tap root, wet ground.
 (To protect the shallow roots of many trees during construction and other work, local authourities require a Tree Protection Zone (TPZ) to be observed. The radius of the TPZ is calculated as 12 times the diameter of the trunk of the tree at breast height (DBH). Thus, a fairly large tree with a DBH of 1m requires a TPZ radius of 12m. Many of Drouin’s large eucs have trunk diameters greater than 1m!)

So, tall trees with shallow root systems along with strong winds will mean the likelihood of ‘windthrow’ occurring. Windthrow is the phenomenon of the trunk of a tree acting as a lever during a windstorm and uprooting the tree. The windthrow effect is greatest for tall trees.

Other factors that may influence uprooting during high winds is the moisture content of the soil – trees growing near creeks, etc are more vulnerable, and the type of root system – trees with tap roots are less vulnerable to windthrow.

The intertwining of the roots of a group of trees helps to support individuals within the group. Windthrow, uprooting of a tree, is far more likely to affect an isolated tree rather than a group of trees. If one tree in a group fails, it can affect other neighbouring trees. (Link to a video of windthrow occurring on the Black Spur Victoria in December 2014 - worth a look!).

Clusters of trees help support one another in strong winds
We need our trees for all the benefits they provide and it seems, at times, the trees just like us need one another!

Wednesday, March 28, 2018

Do Birds Matter?

I don’t know why, but ever since pre-teenagerhood, birds have occupied my conscience. Yes, through much of my earlier years as a teenager and young adult other matters were at the forefront of my mind – school, sport, work, family, etc. I think I was normal, but I suspect for much of that time, a fondness for our avi-fauna was ever-present in the further reaches of my subconscious.

It was a bit later in life that I really became aware of how my spirits were lifted at the sight of the magnificent aerial displays of a Woodswallow or of hearing the call of the first Oriole to arrive each Spring in my little patch of Gippsland.

And, not until retirement was I able to focus a little deeper on why birds matter.

Many birds of course are beautiful. Many have glorious song, (although Rossini’s ‘Thieving Magpie’ does not come close to the real thing), but birds are important for much more than this.
Golden Whistler - a beautiful songster often seen on the edges of Drouin

Birds occupy pretty much any habitat on our planet. The only other animal species to do this are generally microscopic. Birds live in the arctic and antarctic, the driest deserts and wettest forests, oceans, mountains and plains. They live with us in our cities and towns.

Some birds are inquisitive of humans. Our own Grey Fantails and Eastern Yellow Robins will sometimes fly around anyone that strays into their territory. Others can be downright aggressive toward us – Magpies at nesting time.
Eastern Yellow Robin on a friend's walking stick.

Many birds are sedentary, seldom leaving their small patch of habitat. Others fly thousands of kilometres each year on their amazing migratory flight paths. In 2007, a Bar-tailed Godwit was recorded flying from Alaska to New Zealand, non-stop, in 9 days, an astonishing 11,500km!

And, don’t believe that birds are unintelligent or don’t enjoy some fun from time to time – check out this YouTube video of a wild Crow in Russia snowboarding on a plastic lid!

Yes, all very well I hear you say, but do they matter?

Birds may be the last connection we have to the disappearing natural world. Many birds are pollinators and seed dispersers, some eat annoying pests like insects and rodents, a few are a food source themselves for other animals and humans. In many situations, birds are fantastic bio-indicators – they can tell us the health of an ecosystem.

Of course birds matter. They remind us of our own decency. What right do we have to be the cause of their loss to the world? Birds may not contribute to our economy but is that the highest standard we can ascribe them? If we are so intelligent, shouldn’t we be helping to ensure their survival rather than be the cause of their demise?

Sorry for the rant, I digress.

April is bird monitoring month for
 the Friends of Drouin’s Trees

Our members are conducting some surveys in various locations of our beautiful town and the public is invited to join in.
Crystal Waters Drouin will be 'surveyed'.

Surveys of between 1 and 2 hours duration will be conducted …
Monday 02/04/18, 8am and 3pm.
Wednesday 04/04/18, 8am and 3pm.
Monday 09/04/18, 8am.
Thursday 12/04/18, 8am and 3pm.
Monday 16/04/18, 8am and 3pm.
'Golden Whistler Reserve' in Drouin

We will be meeting for car-pooling and instructions at the Drouin Bowls Club car park at the above times. If you would like further details, please email me – drouinwaresATgmailDOTcom – otherwise, just turn up, preferably with your binoculars.

Want some more?
Europe faces biodiversity oblivion after collapse in French birds, experts warn – The Guardian
Birds as environmental indicators – Environmental Science.org.
What do birds do for us – Audubon.
Threats to birds – Bird Life Australia.

Sunday, March 25, 2018

Roadside Vegetation vs Wire Ropes

Much worldwide research suggests the aesthetic effect of roadside vegetation provides safety benefits to drivers.

In Europe and the USA, transportation psychologists are suggesting that safer driver behavior is generated by improving landscape and streetscape vegetation.

Studies in Canada and other countries show that streetscape improvements, including the planting of trees, reduced the frequency and severity of vehicle crashes.

“The presence of trees significantly dropped the cruising speed of drivers”.

“The addition of curbside trees significantly increased driver perception of spatial edge”.

Roadside vegetation can delineate the alignment of a road.
Could correctly selected and placement of roadside vegetation do a similar job to the wire rope barriers currently being installed along our freeways and major link roads – at considerable cost to Victorian ratepayers, ($120/m? VicRoads)?

Wire rope barriers are designed to stretch and absorb the force of impact and minimize the chance of rebound back onto the carriageway. There is some debate that roadside vegetation could achieve the same effect.

Costly? Effective (in reducing death & serious injury)
Studies by Monash University Accident Research Centre conclude that wire rope barriers significantly reduce deaths and serious injuries in crashes although there is some debate continuing in regard to their effect on motorcyclists.
Is the answer a combination of wire barrier and vegetation?
 Wire rope barriers do not reduce the frequency of accidents. World-wide research suggests that roadside vegetation does.

Further reading:
·         VicRoads Towards Zero – Flexible Wire-rope Safety Barriers Facts.
·         VicRoads Towards Zero – Roadside Management Strategy.
·         Landscape and Urban Planning – Landscape Improvement Impacts on Roadside Safety in Texas, (Abstract – “Environmental psychologists suggest that appropriately landscaped roadside scenes may have a reducing influence on travel-related stress or may improve attention…”).
·         Canadian Journal of Transportation – Roadside Aesthetic Appeal, Driver Behavior and Safety, (Abstract – In contrast with the assumption that roadside trees distract travellers from the driving task and thus add to collision risk, several studies actually support the notion that the presence of trees along the roadside has a calming and restorative effect on the state of mind of passing drivers and leads them to lower moving speeds.”).
·         US national Library of Medicine - The Effects of Clear Zone Size and Roadside Vegetation on Driver Behavior, (Abstract – “… studies have shown that natural landscapes can effectively lower crash rates and cause less frustration and stress to the driver.”).
·         The Arboricultural Journal – A Review of the Impact of Roadway Vegetation on Drivers’ Health and Well-being and the Risks Associated with Single-vehicle Crashes, (Abstract – “Roadside trees can help calm traffic, define roadways and reduce drivers’ stress.”).