What does the term sustainability mean when applied to cities and urban growth?

What does the term sustain" rel="nofollow">inability mean when applied to cities and urban growth? The NSW government forecasts that Sydney’s population will grow by 1.6 million people by the 2035 (httpszllwww.rdasydney.org.au/A-Plan-For-Growin" rel="nofollow">ing-Sydney- WEB.pdf). Can such gr