When nature reclaims abandoned buildings, empty lots, or landscapes after a disaster, ecologists call it ecological succession. It’s the process by which natural communities replace one another over time, transforming bare rock, cracked pavement, or burned forest back into thriving ecosystems. Depending on the context, you might also hear it called rewilding, spontaneous vegetation, or simply nature reclaiming land.
Ecological Succession: The Core Process
Ecological succession is the broad scientific term for what happens when nature takes over. It describes the way the mix of species and habitat in an area changes over time, following a fairly predictable sequence. Small, tough organisms arrive first. Larger, more complex communities follow. Eventually, a stable ecosystem forms.
There are two major types. Primary succession happens when life colonizes a completely new or barren surface, like cooled lava rock or ground exposed by a retreating glacier. There’s no soil to start with. Lichens attach to bare rock, and a few hardy plants that need almost no soil appear. These are called pioneer species. As they die and decompose, they slowly build a thin layer of soil, which lets larger plants move in. Over decades or centuries, enough soil and nutrients accumulate to support a full forest or grassland, known as a climax community.
Secondary succession is faster and more common. It happens when an existing ecosystem is disrupted but the soil remains intact. After a forest fire, for example, grasses sprout first, then shrubs, then various tree species, until the landscape eventually resembles what existed before the fire. Because the soil, seeds, and root systems are still present, this process skips the slowest early stages and can show visible results within just a few years.
Rewilding: The Intentional Version
When people deliberately step back and let nature take over, the term for that is rewilding. It’s defined as restoration that promotes complex, self-sustaining ecosystems by restoring natural processes while reducing human control. Passive rewilding involves little or no human intervention from the start. You simply stop mowing, farming, or managing a piece of land and let ecological succession run its course. Active rewilding, by contrast, involves reintroducing lost animal species to restore food-chain dynamics.
Research on abandoned European farmland has found that passive rewilding produces greater sustainability benefits than planting new forests. Spontaneous regrowth tends to match the local environment better because the species that arrive are already adapted to the soil, climate, and surrounding ecosystems. It’s also cheaper, since there’s nothing to plant or maintain.
How Plants Break Through Concrete and Pavement
One of the most striking images of nature taking over is a tree growing through a sidewalk or weeds splitting asphalt. The plants that do this are called ruderal species, organisms adapted to colonize disturbed, human-altered habitats. They share a set of traits that make them remarkably effective: rapid germination, prolific seed production, and tolerance for pollution, poor soil, extreme heat, and intense light. Annual bluegrass, for instance, can germinate and establish within days, exploiting any temporary opening before other plants can compete.
Soil forms in pavement cracks through a surprisingly simple mechanism. Dust, organic matter, and tiny weathered particles accumulate in crevices and fissures. The depth and composition of this “crevice soil” varies with climate and location, but it’s often enough for pioneer plants to take root. Once those plants establish, their own decomposing leaves add more organic material, deepening the soil layer and inviting larger species.
Tree roots don’t punch directly through concrete, but they don’t need to. As roots grow under or around a structure, they shift the surrounding soil and create uneven pressure. Over time, that pressure causes cracks in walls, floors, and foundations. Roots then find those existing cracks and expand into them, widening them further. This slow, persistent process is how forests eventually dismantle buildings when maintenance stops.
Chernobyl: The Most Famous Example
The Chernobyl exclusion zone is perhaps the world’s best-known case of nature taking over. After the 1986 nuclear accident, 116,000 people were permanently evacuated from a 4,200-square-kilometer area. Nearly four decades later, the zone supports an abundant mammal community. Long-term census data show that populations of elk, roe deer, red deer, and wild boar in the exclusion zone are comparable to those in uncontaminated nature reserves in the same region. Wolf populations are more than seven times higher than in those reserves.
Helicopter surveys tracking the first decade after the accident documented rising trends in elk, roe deer, and wild boar populations. Despite chronic radiation exposure, the removal of human activity (farming, hunting, development) was the more powerful factor. The zone has effectively become one of Europe’s largest wildlife sanctuaries, not by design, but by absence.
Spontaneous Nature in Cities
You don’t need a nuclear disaster or centuries of abandonment to see ecological succession at work. Spontaneous vegetation, plants that establish themselves without being planted or maintained, is a growing area of interest in urban ecology. These self-propagating plants regulate local temperature, provide habitat for pollinators and birds, and improve air quality. Because they’re already adapted to local conditions, they require minimal maintenance compared to landscaped green spaces.
Urban ecologists are increasingly looking at ruderal species not as weeds to remove but as tools for sustainable city planning. Their resistance to disturbance, heat, and pollution makes them candidates for green roofs, vacant lot restoration, and low-maintenance urban landscapes. The same traits that let a dandelion crack a sidewalk also make it a resilient, self-sustaining piece of urban green infrastructure.
How Long the Process Takes
The timeline depends entirely on starting conditions. Primary succession on bare rock can take hundreds to thousands of years to reach a stable forest. Secondary succession after a fire or on abandoned farmland typically shows significant recovery within 20 to 50 years, with a recognizable forest canopy forming within a human lifetime. Urban pavement cracking and ruderal colonization begins within months of a surface being left unmaintained.
The key variable is soil. Where soil already exists, succession accelerates dramatically. Where it has to be built from scratch by pioneer organisms breaking down rock and accumulating organic debris, the process is orders of magnitude slower. Climate matters too. Warm, wet environments support faster plant growth and decomposition, speeding every stage of the sequence. Arid or cold environments slow it down considerably.