If humanity suddenly disappears, the world will go through a series of profound processes of change and adaptation. Here's what can happen:
1. Adaptation of ecosystems: The artificial environment in the city will gradually disintegrate, and the natural environment will reoccupy the territory. Wildlife may expand habitat ranges and restore erosion from human activities. The balance of plant and animal populations may be readjusted, and the ecological chain will gradually recover.
2. Gradual decay of buildings and infrastructure: Without human maintenance and management, infrastructure such as buildings, bridges, and roads will begin to deteriorate and collapse. For example, untrimmed vegetation may begin to erode buildings, water treatment equipment may fail, and the power system will gradually cease to function.
3. Risks of nuclear power plants and hazardous substances: Nuclear power plants, chemical plants, and other facilities containing hazardous substances may fail, causing environmental pollution and hazards. This can lead to the release of radioactive materials, toxic gases or chemicals, posing a significant threat to ecosystems and wildlife.
4. Restoration of animal habitats: Wildlife may begin to readjust to urban environments, such as animals may occupy abandoned buildings, streets, and parks. This could lead to an increase in the population of some species, while others that are more dependent on humans may face survival challenges.
5. Changes in climate impacts: Human activities have a significant impact on climate change. If humanity disappears suddenly, the reduction in emissions and the cessation of energy use will slow climate change to some extent. However, climate change that has already been caused before is likely to continue to affect the world, going back decades or more.
In conclusion, if humans suddenly disappear, the planet will go through a period of adaptation, ecosystems will try to rebalance, buildings and infrastructure will gradually decay, and flora and fauna may reoccupy territory. However, this is only speculation, and the actual situation may vary depending on factors such as geographical location, climatic factors, wildlife species, etc.