As energy grows scarcer and is devoted to growing food and other life-support services, our infrastructure will crumble.

Bob Holmes. 12 Oct 2006. Imagine Earth without people. NewScientist.com

Lack of maintenance will spell an early demise for buildings, roads, bridges and other structures. Though modern buildings are typically engineered to last 60 years, bridges 120 years and dams 250, these lifespans assume someone will keep them clean, fix minor leaks and correct problems with foundations. Without people to do these seemingly minor chores, things go downhill quickly.

Consider the city of Pripyat near Chernobyl in Ukraine, abandoned after the nuclear disaster 20 years ago and still deserted.

“From a distance, you would still believe that Pripyat is a living city, but the buildings are slowly decaying,” says Ronald Chesser, an environmental biologist at Texas Tech University in Lubbock who has worked extensively in the exclusion zone around Chernobyl. “The most pervasive thing you see are plants whose root systems get into the concrete and behind the bricks and into doorframes and so forth, and are rapidly breaking up the structure. You wouldn’t think, as you walk around your house every day, that we have a big impact on keeping that from happening, but clearly we do. It’s really sobering to see how the plant community invades every nook and cranny of a city.”

With no one to make repairs, every storm, flood and frosty night gnaws away at abandoned buildings, and within a few decades roofs will begin to fall in and buildings collapse.

“For many thousands of years there would still be some signs of the civilizations that we created. It’s going to take a long time for a concrete road to disappear. It might be severely crumbling in many places, but it’ll take a long time to become invisible.”

Roman concrete: has lasted 2,000 years.  Lawrence Berkeley National Lab scientists have recently made some progress in understanding how the Romans made their concrete, which even did well in ocean water and could be made at lower temperatures than concrete now (Yang).

Yang, Sarah. 4 June 2013. To improve today’s concrete, do as the Romans Did. University of California, Berkeley.