It is very easy to find examples of the benefits of grass. On a still, hot day walk from a concrete or, even worse, asphalt-covered surface onto a grassed surface and you will experience a very noticeable drop in air temperature.

Both concrete and asphalt absorb and re-radiate a lot of heat, whereas a grassed surface radiates very little.

I once played tennis in a temperature of 47 degrees. It was quite bearable on the lawn courts, but much more uncomfortable away from them.

Most, if not all people will have noticed how the shade of a tree somehow feels cooler than the shade of a building.

This effect becomes greater with the number of trees in the immediate vicinity. Tree canopies are very good at absorbing — and using — infra-red solar radiation.

I have spent a lot of time in the rainforests of Papua New Guinea.

It was always a great relief to enter the rainforest from a cleared (inhabited) or naturally grassy area, as the temperature seemed to drop by about 10-15 degrees.

It was not only the drop in temperature that felt good: I always felt more refreshed and mentally alert when in the rainforest, possibly due to the extra oxygen that the trees produce. In contrast, it was always an unpleasant, mind-dulling shock to walk out of the rainforest into one of these non-forested areas.

Yes, greenery is certainly good for us. All cities should have many trees and as much grassy space as possible.

Douglas Mackenzie, Deakin

In March this year the US Congressional Budget Office published an "International Comparison of Corporate Tax Rates" of G20 members.

This analysis found that Australia had a "Statutory" rate of 30 per cent (10th lowest of 20 countries); an "Average" rate of 17.0 per cent (15th lowest of 20) and, an "Effective" rate of 10.4 per cent (11th lowest of 20).

Given recent allegations that a number of our larger corporate citizens pay no tax at all I wonder if Mr Morrison and Mr Turnbull could explain, for the benefit of personal income tax "leaners", how he can justify his claims that Australia will no longer attract investment unless we reduce our corporate tax levels.

Just like this week's other fantasies ("end petrol gouging' and "call out mockery against Christianity") Morrison is flailing around using anything he can hang on to in order to divert our attention away from the doubling (to more than $600 billion) of debt that he and his predecessor have overseen since coming to power.

And by the way, Mr Morrison, the electorate has had enough of your continued, asinine and boring attempts to blame the Opposition – you have had more than enough time to get on with the job of fixing the "budget emergency" and reducing the "debt and deficit".

Roger Terry, Kingston

In the history of sport there have rarely been two more excellent achieving nations per head of population than Australia and New Zealand.

Think of them as brothers in arms, countries which through the sweat and sacrifice of their forefathers have become the two finest countries on earth in which to live.

The athletes seem to be bought up on raw meat and raw ingredients. They are tougher, smarter, more resilient and more primed to compete than most athletes anywhere.

So when you see an Australasian name appear in the EPL, the NBA, the AFL, NRL, NBL, the World Rugbys' Leagues, Soccer World Cups, Hockey World Cups, Major League Baseball, NFL, NHL, La Liga, athletics, Olympics, skiing, water-skiing, cricket, golf, tennis, basketball, horse racing anywhere ... then understand this is not an accident.

If you want your girl or boy to grow up healthy, well balanced and with thousands of opportunities for a career in sport, bring them to the land of the Long White Cloud or the Land Down Under. People will welcome you.

And if you want them to be in sporting technology, marketing, media, IT, entrepreneurialism ... do exactly the same.

Arthur Pagonis, Morley, WA

I refer to Richard Denniss' article ("Ditch the coal, politicians", December 23, page 10).

Denniss incorrectly claims that the 2016 South Australian state-wide blackout was caused by "... an unprecedented cyclone in South Australia knocked down a dozen electricity transmission towers ...".

The fact is that the downing of the towers did not cause the blackout.

The final AEMO report states that "Nine wind farms out of 13 operating at the time then shut down (due to excessive high wind), pulling 456MW out of the system in seven seconds and resulting in a surge in draw over the Victorian interconnector. The interconnector then failed due to huge extra demand leaving SA to fend for itself. At that point frequency in the South Australian power island collapsed and sent the state black."

The AEMO report makes it clear that the state-wide blackout would not have occurred if the wind farms had ridden through a number of voltage disturbances across the network.

The downing of the towers was incidental to the blackout.

Colin Toll, Bywong NSW

Now the numbers are in we see that "star candidate" Kristina Keneally failed to drum up a swing greater than average in any other byelection.

On scrutiny it may now be a tad harder for Labor's mates club to parachute her in to the soon to be vacated NSW Senate seat.

So what is Plan C?

Watch out Canberra, the ACT is soon to get a third Federal House of Representatives seat.

I am so glad I moved away from the capital and now live in the bush.

Chris Longhurst, Bourkelands, NSW

It would be useful in the elective surgery waiting times discussion if "elective" could be defined.

Does it mean a patient can decide whether to have, for example, a heart valve replacement, an ingrown toe nail removed, or a facelift?

Does it mean "You don't need it but you can have it if you want"? The figures for waiting times for "non-elective" surgery should also be published for comparison.

One assumes the latter is emergency surgery. That is, people get urgent attention in hospital when they need it.

It is easy for the knockers to beat up waiting times for elective surgery without comparing them to emergency surgery rates.

James Mahoney, McKellar

As someone who worked for Defence procurement for nearly two decades I welcome the investigation mentioned in the Canberra Times ("Allegations of systemic fraud sparked Defence Department internal audit", December 26, p.1).

The issue of bribes paid to public servants, not in unmarked bills in brown envelopes, but in Post Separation Employment (PSE) contracts given out to co-operative individuals after retirement even extended to the internal audit area.

After doing a detailed investigation of undesirable contracting at HMAS Watson I personally notified the Deputy Secretary of this issue but nothing was done.

The problem is those with the power to end this fraud have the least incentive to do so.

John Coochey, Chisholm

With the exception of an MP who dies in office or retired early because they are terminally ill, no MP should burden the taxpayer with the costs associated for the AEC to run a by-election.

The recent dual citizenship senators and MHR's is one example but another example is an MP who retires early because they are sulking after being removed as leader or did not get a ministry is no justification for this AEC cost to the taxpayer.

Adrian Jackson, Middle Park, Vic

I really can't see why Catalonia should not become a member of the European Union in its own right.

The countries of Europe are the size they are largely because they had to be that size to hold their own with other comparable countries.

That is also why the EU is needed, to hold its own with other large countries like the US, Russia and China.

Thus the members of the EU no longer need to be so big, but can be the size at which they are comfortable.

Michael McCarthy, Deakin

President Donald Trump appointed Attorney-General Jeff Sessions and his Deputy, Rod Rosenstein.

On March 2 Rosenstein became responsible for investigations into Russian interference in the 2016 election and possible collusion between the Trump campaign and Russian officials, following Sessions' recusal. On May 9 President Trump sacked James Comey as FBI Director. Subsequently, on May 17, Rosenstein appointed Robert Mueller as special counsel to conduct an investigation into "any links and/or co-ordination between the Russian government and individuals associated with the campaign of President Donald Trump" and any matters arising directly from that investigation.

During a New York Times interview on July 19 President Trump stated that "Sessions should have never recused himself, and if he was going to recuse himself, he should have told me before he took the job and I would have picked somebody else".

During the same interview President Trump also stated that Mueller's investigation would cross a red line if it expanded to look at his family's finances.

Mueller's investigations net is tightening. He has negotiated plea deals with two members of President Trump's campaign team, Mike Flynn and George Papadopoulos, in return for their co-operation and he's obtained thousands of Trump campaign emails.

Judging from President Trump's attacks against the FBI and Messrs Rosenstein and Mueller he seems to be worried that the investigation might impact upon him and his family.

Rumours have begun circulating in Washington that President Trump wants to sack Rosenstein and replace him with someone who is willing to sack Mueller.

Bruce Taggart, Aranda

I watched the ABC's broadcast of PM Malcolm Turnbull's Christmas message in which he exhorted the nation to think of those who are less fortunate.

I felt sick as my thoughts turned immediately to the poor unfortunate wretches on Manus Island and Nauru, abandoned by the Australian government and condemned indefinitely to live out an uncertain, fraught and dangerous half life.

Has there ever been a more disingenuous and disturbing message by a sitting Prime Minister to the nation?

Judith Davis-Lee, Crace

Your article ('Morrison vows to guard Christianity' (December 22, p.4) caught my attention.

Mr Morrison clearly does not know that the best way to 'guard', protect, or defend, one's faith, beliefs and values, is to exemplify them in your actions, words, and the way you live your life.

I wait in vain for the slightest indication that there are any Christians at all in our government, including MrMorrison.

It is not as if there are not people willing and able to help them understand what this means.

Try Mr Tim Costello, for one.In him you will find a Christian who through his words, actions and deeds sets an example for all.

Ponder the findings of a recent royal commission. Five years, 17volumes and $500 million, to understand why people in this country might have a reason to mock Christianity.

As the various churches and related organisations now must know, their institutions, thence their religion, needed to be protected from their leaders and themselves.

H. Tan, Deakin

I'm amazed Greg Baum ("New day but the same story for battling England," December 19, p. 55) could describe Starc's wonder ball as an "off-break."

It was clearly a leg-break or leg-cutter, deviating from leg to off.

David Stephens, Bruce

Douglas Mckenzie's letter of December 23 said the ivory trade "involves the slaughter of tens of thousands of elephants." Suspecting that this was a gross exaggeration, I looked it up. It isn't.

Gary J. Wilson, Macgregor

TOILETS PUBLICLY FUNDED

Re the claim denial of access to the Lobby toilets is NCA payback for the "occupation" of the restaurant, I suggest tent embassy residents are upset the public might be using the publicly funded portable toilets near the embassy. A reasonable person might suggest they focus on their core goal; not quibble over who has access to publicly funded facilities.

Craig Thomas, Watson

LIKE A DUCK ON DRY LAND

Clips of Malcolm Turnbull attempting the common touch – be he among workers, at sport or helping out with charity meals – indicate he takes to such situations like a duck to dry land.

M.F.Horton, Adelaide

BUSES A BETTER OPTION

Light rail will not service neither Mitchell nor the Canberra Hospital. It will require longer walks to fewer stops, for less-frequent services that will require more transfers to and from buses. How long before we realise that bus rapid transit is a better option?

Leon Arundell, Downer

MEDICARE CHANGES

Events in Melbourne, both involving cars and the mentally ill, show much more needs to be spent on mental illness in Australia. Changes to Medicare payments would help a lot.

Ken Morehouse, Wangaratta

CLEAN UP OUR LAKES

It's time to clean up Canberra's lakes so we all can swim in them again. The Friday Flashback photos of December 22 reminded me of the thousands of people who enjoyed them before they got too risky for eye and ear infections. Maybe all that is required is periodic netting of carp and aerating fountains.

John Skurr, Deakin

DRIVERLESS CARS

While not a supporter of the tram arguments, I am nonplussed by M. Flint's enthusiasm for presumably privately owned and operated driverless cars. Does he think that this form of operation will solve freeway car parks and gridlocks?

Peter Curtis, Waramanga

WHO'S BEING CHURLISH?

I'm afraid I laughed at Father Peter Day's (Letters, December 24) talk of "churlish" greetings from two Greens senators, who, after all, were offering an all-encompassing seasonal greeting. The only person with a mocking, powerful, noisy, intolerant point of view here is the letter writer himself. Season's greeting to all.

Lilian Andrew, Mosman, NSW

FAILING TO VOTE

For the second time in a month, Australia has shamefully abstained from voting on a resolution at the United Nations General Assembly, regarding Israel's right to call Jerusalem its capital city. Is this the price we paid for admission to the UN Human Rights Council?

Kate Ashmor, Caulfield