Sydney, Australia is a fantastic city. There are water views everywhere thanks to a harbor that works its way more than 40 km inland from its entrance to the ocean. The 62 beaches are fabulous and the water is warm most of the year. And if you get tired of the beach, there is a wild forest declared a World Heritage Site an hour away in the Blue Mountains.

It’s no wonder there are roughly 4 million Sydney residents. Most live in suburbs spread over a 12,145 km2 metropolitan area, leaving plenty of space between and within homes, and open areas to enjoy. Almost everyone is within walking distance of a park. Throw in some sunshine, those infamous beaches, and you’ve got the ideal city.

Tourists like Sydney too. Every year, the city welcomes about 10 million tourists, 3 million of them from abroad.

The place is so popular that in the last decade around half a million people have decided to become Sydney dwellers, the local name for residents. This is roughly 1,000 new inhabitants per week, a growth rate of 15%, slightly higher than the rate of increase for Australia’s general population during the same period.

In addition to arrivals, social trends have seen families get smaller, dividing faster than they merge. And as young people stay home longer, they eventually want to move.

Over the next several decades, Sydney will need to supply 640,000 new homes just to keep up with projected demand.

While developers may be smiling, this issue has had state and local government planners waving their hands in the air. Even in a place with so much space, such a sustained influx puts enormous pressure on infrastructure, especially transportation.

It also creates environmental challenges.

The supply of water, sewage and energy must increase as the city grows. And there comes a point where utility delivery systems have passed their buy-sell date. They can no longer be upgraded or expanded and a completely new system is required.

Or, as with Sydney and its wastewater discharge to the open sea, the system is no longer acceptable.

640,000 homes and the roads, railways, businesses and public spaces that support them need space. Some will squeeze into the existing suburbs; others will be green field developments. Preserving the natural habitat is a challenge when the concrete area is expanded.

In Sydney, the built-up area is encroaching on fertile farmland that has traditionally supplied a large proportion of the horticultural products consumed by the city’s residents and those 10 million visitors. Planners must make the difficult choice between food production and living space. Good elections need local input and a clear regional strategy.

Sydney also has some wacky problems, such as what to do with a resident population of gray-headed flying foxes, an endangered but pesky fruit bat species the size of a small cat, perched in the botanical gardens that sit outside. the shadow of the CBD Skyscraper.

Then there is the real environmental issue of the city’s footprint. Water, energy, food and waste cannot all be generated within the Sydney Basin. A much larger area is needed to supply the resources and places are needed to dispose of the waste.

There is also the problem of greenhouse gas emissions from lifestyles that use electricity and fossil fuel-based transportation.

It’s a long list of challenges that put pressure on the integrity of the environment.

Sydney is a moderate-sized city by modern standards, similar to Phoenix, Arizona. It is half the size of Chennai, a third the size of London, a quarter the size of Shanghai and a bump in comparison to Tokyo, the world’s largest agglomeration with 34 million inhabitants.

The significant statistic is that there are at least 70 cities in the world that have larger populations than Sydney. Urbanization is a big problem.

The real environmental problem is that we have to have this development. The world’s population of 7 billion will peak at between 9 and 12 billion and, to help retain an environment that can sustain them; we probably want most of these additional people to live in cities.

Attention to how we make these cities livable and how we can manage their environmental footprint should be a priority for all of us.