With a population expected to almost double in 50 years and a growing pull toward cities, further densification of the urban environment in Australia is almost certainly inevitable and most likely desirable.

Indeed, densification is now increasingly a reality: more than four in 10 new dwellings approved for construction are now multi-residential in nature (townhouses, units, apartments etc.) – up from three in 10 just 30 years ago.

And to be sure, densification has many benefits if done well. Closer proximity to shops, community facilities and transport links encourages more walking and less driving. Creating a greater supply of more affordable housing closer to critical employment centres (usually CBDs) leads to reduced commuting time (and more time with family), greater equity in employment opportunity and a larger supply of skilled labour in critical growth industries. Less urban sprawl means reduced need to build expensive road networks. Reduced focus on private space (in backyards, for instance) may encourage more focus on community space and greater community engagement.

Density brings major sporting and cultural attractions as well as a greater diversity of restaurants, cafes and leisure facilities closer together, helping to promote social and cultural exchange. By bringing people closer to transport connections, shops and community facilities, density promotes greater liveability for the elderly or disabled.

Nor need density be necessarily associated with crowds, congestion and concrete jungles – as Green Building Council of Australia chief operating officer Robin Mellon points out, Paris has a density more than 10 times that of Sydney, yet it is considered one of the most beautiful cities in the world.

Still, before rushing headlong into creating more and more apartments and subdivisions, costs associated with urban density need to be taken seriously.

First, there is congestion. Notwithstanding that denser environments encourage use of alternative forms of transport, there are genuine fears that bringing more people closer together will lead to localised clogging of streets, shortage of car parking spaces and greater potential for accidents and collisions.

A study by the Goldwater Institute in America in 2000, for example, noted that Europe had a population density more than three times the United States and had a traffic volume intensity which was higher than the US by more than a quarter despite higher usage of public transport. In densely populated cities in South Korea, an absence of almost any form of parking space sees drivers plonk vehicles anywhere they can on the footpath, pedestrians be damned.

That said, evidence in this regard is not uniform. In the New Zealand cities of Auckland and Wellington, for example, senior economist Peter Nunn notes that while the population densities rose by almost one third and around one sixth respectively between 2001 and 2013, Ministry of Transport measures suggest traffic congestion actually eased in the former city over the decade to 2013 while that in the latter has remained roughly the same.

Densification also brings fears about pollution, as busier concrete jungles leave little room for toxic fumes and particles to escape. A NASA study in 2013, for example, found that compared with cities of one million, cities with populations of 10 million had a nitrogen dioxide (a gas commonly linked to respiratory problems) level of 2.6 and 2.9 times higher in the US and Europe respectively.

In extremely dense Hong Kong, over just one 15-hour period from midnight until 3 pm on May 6, air pollution by itself was sufficient to be expected to lead to 1.7 deaths, 94.7 hospital-bed days and 2,653 doctor visits, according to an index developed by The University of Hong Kong which tracks the cities readings in terms of fine particles, respirable particles, nitrogen dioxide and sulphur dioxide.

Then, there are the urban heat island effects, in which surfaces such as roads, footpaths and building facades absorb and release energy from the sun. In Sydney, areas close to the CBD could see temperatures rise by anything from 1.1 degrees to 2.5 degrees between now and 2050, according to a University of New South Wales study – not only arguably contributing to global warming but creating greater stress for physically frail residents on days of extreme heat.

While forcing a focus upon community space, meanwhile, density may also limit room for open space and parklands. In a position paper last year, lobby group Parks & Leisure Australia suggested that to date, growing levels of density in Australia had not been accompanied by any significant corresponding allowance for the provision of open spaces, some of which are thought of as ‘unused’ space.

Another issue is mental health and well-being, and fears that greater congestion, noise and reduced privacy and personal space could lead to more stress and anxiety. A 2005 review of a number of studies by researchers in the UK and France, for example, found that compared with their low density counterparts, those living in high rise apartments were likely to feel alienated, have fewer forms of social support, be less socially involved, encounter more people and have a lower sense of control. Though those studies have been criticised for failing to control for confounding variables such as the quality of the housing studied and the prevalence of that housing in low income neighbourhoods, the results are nonetheless alarming.

There are other impacts as well. A lack of privacy and backyards represents a challenge to the lifestyle many Australians dream of, and could have negative impacts through less time being spent outdoors and on family activities such as backyard sports. In places like South Korea, where backyards are rare, problems associated with teenagers spending excessive amounts of time using electronic devices are significant. Huge apartment complexes also block natural sunlight. Denser populations challenge traditional notions of ‘neighbourhoods.’

Does this mean density should be avoided? Probably not – the benefits of density are significant, and the folly of responding to population growth by putting up more new outer suburbs miles from decent employment opportunities and cultural facilities is obvious.

What it does mean, however, is that things need to be properly planned. Greenery, communal and community spaces need to be allowed for and encouraged. Planning needs to be context specific and done through processes which actively involve residents. Proximity to shops, facilities and transport links is a must.

Done well, density can have enormous benefits. But the downsides cannot be ignored.