What would happen if every human suddenly disappeared? - Dan Kwartler

Summary

The script explores a hypothetical world where humans suddenly disappear, detailing the immediate and long-term consequences. Without human intervention, oil refineries ignite, underground systems flood, and cities slowly decay. Over decades, nature reclaims urban spaces, with invasive plants and animals thriving, while domesticated species struggle. As Earth's climate heals, human-made pollutants vanish over millennia. Even after millions of years, remnants of human civilization, like Mt. Rushmore and technofossils, endure, showing that while humanity may vanish, its impact will remain long after we're gone.

Takeaways

• 😀 Human beings have a profound impact on Earth, which is so significant that many scientists believe humanity has left a permanent mark on the planet's geological record.
• 😀 If humans suddenly disappear, immediate effects would include the malfunctioning of oil refineries and the flooding of underground rail systems due to abandoned infrastructure.
• 😀 Within a few days, emergency generators would stop working, leading to widespread power outages and darkness across the Earth.
• 😀 After the first month, the changes would become more gradual, with weeds and tree roots cracking sidewalks, and urban environments eroding into rivers due to flooding and deterioration.
• 😀 Over the course of 20 years, nature would reclaim cities, breaking down human-made structures like concrete buildings and roads through flooding, freezing, and thawing cycles.
• 😀 Within 200 years, most skyscrapers would collapse, and cities built on river deltas, like Houston, would see buildings washed away into nearby tributaries.
• 😀 In rural and suburban areas, decay would happen more slowly, but issues like leaks, mold, and pest infestations would go uncontested as homes deteriorate.
• 😀 The disappearance of humans would lead to a wild spread of non-native plants, such as water hyacinth, giant hogweed, and Chinese Ailanthus trees, which would dominate former cities.
• 😀 Animal populations would shift as infrastructure—like bridges—provides new pathways for creatures to expand their habitats, while some species thrive and others die out.
• 😀 While some domesticated animals might struggle to survive, others, like pigs, dogs, and housecats, could adapt and thrive in the post-human world.
• 😀 The absence of light pollution would allow bird populations to recover, saving over a billion birds each year from disrupted migration patterns caused by artificial lights.
• 😀 Over time, Earth's climate would slowly recover from human impact, with plant life eventually eliminating pollutants like lead from the soil, and CO2 levels returning to pre-human levels after tens of thousands of years.
• 😀 Even after millions of years, humanity’s legacy would persist in the form of landmarks like Mt. Rushmore, as well as remnants of cities and sculptures that could be preserved as technofossils.
• 😀 Ultimately, the Earth will erase all traces of humanity, but the study of a world without humans can teach us valuable lessons about our current world and our impact on it.

Q & A

What happens immediately after humans disappear from Earth?

Immediately after humans disappear, some of our creations backfire. Oil refineries malfunction, leading to month-long fires at plants in places like western India, the southern U.S., and South Korea. In underground rail systems, drainage pumps stop working, flooding tunnels within three days.

How long does it take for Earth's infrastructure to degrade significantly without human maintenance?

Within the first month after humans disappear, many emergency generators shut down, and Earth goes dark for the first time in centuries. In the following 20 years, sidewalks are torn apart by weeds and tree roots, and underground tunnels erode streets above them.

What impact does the absence of humans have on urban environments?

Urban environments degrade over time as buildings and infrastructure fall apart. Concrete foundations crack, and within 200 years, most skyscrapers collapse. In cities built on river deltas, such as Houston, these buildings are eventually washed away.

How do rural and suburban areas decay after humanity's disappearance?

Rural and suburban areas decay more slowly, but common issues like leaks, mold, and pest infestations go uncontested. Over 75 years, houses collapse due to rotting beams and structural failure, becoming homes for rodents and lizards.

What happens to plant life in cities without human intervention?

Without humans, imported plants that had previously been controlled run wild. For example, water hyacinth covers the waterways in Shanghai, giant hogweeds overgrow the Thames in London, and Chinese Ailanthus trees burst through streets in New York City.

How does Earth's biodiversity change in the absence of humans?

Biodiversity flourishes as both native and non-native plants spread unchecked. Animals follow these plants, using bridges and other human structures to venture into new habitats. Some species thrive, while others, like cockroaches, continue to adapt to their native tropical environments.

Which animals are most likely to survive without human care?

A few domesticated animals, like pigs, dogs, and feral housecats, may survive without humans. However, most other domesticated animals struggle to adapt to the post-human world and likely die out.

How does the disappearance of humans impact bird populations?

The absence of human-made light pollution allows over a billion birds to survive each year, as their migrations are no longer disrupted by blinking communication tower lights and high-tension wires.

What environmental changes occur over a much longer time frame after humanity's disappearance?

Over thousands of years, Earth’s climate slowly recovers. Within 35,000 years, plants remove the last traces of lead from the soil, and it may take up to 65,000 years for CO2 levels to return to pre-human levels.

How long will humanity's legacy last on Earth after we disappear?

Humanity’s legacy will persist for millions of years. For example, Mt. Rushmore survives for 7.2 million years, and bronze sculptures last for over 10 million years. Additionally, remnants of cities, buried deep underground, are preserved as technofossils.