Let’s start this off by imaging a hypothetical. Imagine in the future all of humanity has emigrated somewhere else, maybe another planet or solar system. What would happen to all of the civilizations and cities if humans just packed up and left? How long would it take nature to reclaim our built environment?
Because of our past record, we’ll also assume that everyone climbed aboard the evacuation ship and made no effort to clean up or take down the cities. In this scenario, the process of degradation would begin immediately. Obviously, the speed at which mother nature reclaims the land is going to vary depending on the climate condition of Earth and any major catastrophe that could have caused us to leave but for this example, we will focus on a seasonal temperate climate, like many of the major cities around the globe.
As soon as people stop maintaining the streets, debris, trash, and waste would accumulate, and over time block drains causing water to pool up. Plant seeds being carried by birds and wind drifts would settle in new places and sprout into weeds. The natural process of constant freezing and thawing would cause roads to fracture and break apart. These cracks would allow for fast-growing plants to spread through the cracks eventually leaving a carpet of grass on once roaring highways. It wouldn’t be long before metropolises would have tall vegetation and vines climbing the building walls. As the asphalt begins to erode, this would allow the areas to flourish rapidly. Within a few decades, places like Central Park would turn into forests. This process of plants re-colonizing is called re-wilding, and it happens in areas after natural disasters such as a fire or volcano eruption.
As all of this vegetation starts to reclaim the cities, the risk of fire steadily increases. Dry wood, dead leaves, and other detritus would start to accumulate into perfect kindling for a raging fire. Perhaps the fires would be started by lightning, summer heat, or sunlight being magnified through broken glass. Either way, fire would be a major enemy of these abandoned buildings.
Even if cities managed to escape death by fire, they would surely be brought down by the opposite element, water. Rain would start to overflow in blocked drains and gutters and trickle down into unrepaired roofs. This would lead to rapid decay of timber floorboards and beams, and would slowly but surely erode concrete and metal. For the soaring skyscrapers, the lack of constant maintenance would result in the external windows and facades to break and fall out exposing the inner core to elements. The naturally acidic rainwater would begin to filter through the concrete, rusting the steel rebars, cause cracking. These cracks would grow and over time the weight of the buildings would cause collapses. The majority of suburban houses, inner-city apartments, towns, and cities wouldn’t be recognizable or standing in just a century after humans leave. Nature will regain its territory and turn our megacities into jungles and forests, free from the interference of humans.
If you don’t believe me, just look at the city of Pripyat, Ukraine. Thirty years ago the Chernobyl nuclear power plant suffered a meltdown. Pripyat is only two miles away and since the meltdown, it has become a ghost town for humans. But the site has developed new life, becoming a haven for plants and animals to live freely, grow, and evolve.
The moral of the story is that human life isn’t the most important form of life on earth. What we often forget (or do not even know) is that there were once at least six other species of humans walking the earth. Just as how there are lions, tigers, jaguars, and cute house cats all under the same genus, Panthera, there once was Neanderthals, Erectus, Floresiensis and other species all under the same genus, Homo. Today we do not have these other species so we feel as if we are special and that the world revolves around us living in it. We like to imagine that we were put on Earth for a special purpose (and maybe we were, who knows) but as of now, scientific evidence says we’re just another animal living on a rock. As we saw with the dinosaurs, the most dominant creatures of the time, just because you’re at the top of the food chain, doesn’t mean you can’t be wiped out and turn into a cool piece of history while the next species evolves its way to the top.
The hypothetical shows how fast the earth and other animals can replace us. We need to get the idea of humans being the most important creature on this planet out of our heads and start respecting the other animals and planet that we have because they can keep on living without us, but we cannot keep living without them.