Hi! How long do you think it would take for plants to overgrow an abandoned and destroyed city with no human life in it? For reference this city was bombed and burned (not radioactively).
It would depend on how thickly forested you would want the area.
- 5 years: You will see some small trees and concrete being busted up by new growth. Priorly planted areas will be over grown and unmanageable. Small animals, insects, and large herbivores will be attracted to the area and establish populations.
- 10 Years: Concrete will be almost overgrown and trees will be further busting up the side walks and buildings may start to collapse due to the plants or disrepair from severe weather. Herbivore populations will have attracted small predators and the occasional lone large one.
- 25 Years: Large buildings will have mostly collapsed due to damage done to their structure by tree roots. Asphalt and sidewalks will be mostly gone or reduced to patches of rubble. Roads will be unusable due to their disrepair or gone completely. Ecosystems will be mostly developed and water sources may begin to appear in areas where they may not have before.
- 50 Years: Most traces of buildings and other human civilization except for heaps of rubble will likely be gone or covered in plant growth. Roads and side walks will have disappeared and full blown ecosystems will have re-established themselves in the area.
- 100 Years: Ecosystems will thrive without human civilization and most if not all traces of humans will be gone or buried under new dirt and substrate, allowing plants to grow over it and life to go on without it. Areas will be thickly grown in with trees and shrubbery that would resemble a national park or state sanctuary.
It really depends and most of those times are a guestimate. For cities like NYC or Chicago, would guess it would take about 50% longer because of how heavily industrialized and concreted the area is while small towns or rural areas could disappear about 25% faster due to the spread out nature of most small towns. Severe weather such as hurricanes, wildfires, heavy flooding, tornadoes, tsunamis/tidal waves, sinkholes, and earthquakes would speed things up drastically by the thorough devastation of a civilized area.
I hope this helps and is what you were looking for! So sorry this sat in the ask box for so long!
(Most of these time estimates are just that, estimates, and are based off of what I know about plant growth and the behavior of ecosystems interacting with human civilization.)