If the ozone layer is damaged, how will Earth be affected?
Actually the thinning of ozone layer can be harmful to human in a way that ozone layer has a function of protecting the human from being effected by the beta rays coming from sunlight and when ozone layer will be too much thin then we will suffer from disease such as skin cancer which can be too much dangerous for us off course it will contribute in global warming too.
Mostly life on land is impacted by a damaged ozone layer.
It took billions of years for enough oxygen to accumulate in the atmosphere, and in particular, the O3 type (ozone) which then provided enough of a UV radiation shield for life to gradually crawl onto land about 400 million years ago. The ozone layer absorbs incoming UV radiation that otherwise would "ionize" organic molecules. This means, the bond between key chemicals. like DNA, would be ripped apart if the ozone shield were weakened. In humans, this usually manifests itself as skin cancer, or melanoma. But other animals and plants are impacted by high UV radiation and if its high enough, can kill life on Earth.
There is some evidence that past extinction events on Earth may have been caused, in part at least, by a damaged ozone layer.
Since the early 20th century, humans have been pumping ozone depleting chemicals, like CFCs into the atmosphere and this has damaged our natural UV shield. However, an international treaty, called the Montreal Protocol was signed in the late 1980s and the hole in the ozone layer is "healing". However, this repair work may well take another 50 years.