One of the main environmental factors that are a cause of global warming is deforestation.
Why do people deforest? People deforest for money.
With the need for trees rising up, people who do not understand how much trees affect the environment tear down so many trees and tend to not replant.
Trees take in the carbon dioxide in the air and replace it with oxygen.
Without as many trees, there is more carbon dioxide in the air and less oxygen in the air.
Humans need oxygen to breathe and carbon dioxide causes pollution. This is why there are increased levels of pollution in the air, especially in major cities like Hong Kong and New Delhi.
The Current Environmental Crisis 