If you think cities are big and numerous now, just wait another 15 years.
By 2030, some 5 billion people will be living in cities -- many of them mega-cities that each sustain over 10 million residents. And the total area affected globally by urban sprawl will triple, compared to that in the year 2000.
Those are just a few of the alarming predictions of a recent study by Karen Seto and colleagues, published in the leading journal Proceedings of the National Academy of Sciences USA.
Seto and her team also estimate that, by 2030, an additional 120 million hectares of land will be engulfed by cities -- an area the size of South Africa.
Notably, some of the most dramatic urban expansion will occur in certain biodiversity hotspots -- regions with high biodiversity and large concentrations of locally endemic species that have already suffered severe habitat loss.
In fact, the most explosive urban expansion will occur in hotspots that have been relatively undisturbed so far by urban development. These include the Eastern Afromontane hotspot, the Guinean Forests of West Africa hotspot, and the Western Ghats and Sri Lanka hotspot.
In each of these biodiversity hotspots, the expansion in urban lands from 2000 to 2030 is expected to range from 900 to 1900 percent, according to the study.
Such changes reflect the dramatic growth in human populations still occurring in Sub-Saharan Africa and South Asia, as well as increasing urbanization trends globally.
Other places slated for sharp increases in urban area include eastern China, Turkey, the Himalayas, and parts of Mexico.
The world that Seto and colleagues project is not a distant, dystopian future. This is our near-term tomorrow.
This will be our reality if we fail to address unbridled population growth in those regions of the Earth most at risk.
As Seto and colleagues show, our new reality will be a planet increasingly dominated by sprawling cities. Whether those will be polluted, stressful cities or innovative, well-designed cities remains to be seen.