what is environmental deterioration?

Answer 1

environmental deterioration. It is what it says.

What causes it is a different question. It depends on the environment? Irresponsible use of fossil fuels is one cause greatly contributing to both global warming and an unnecessary conflict (ahem, WW3 anyone?). Overpopulation is another contributor to Mother Nature's euthanasia. Illegal sewage disposal and other random forms of pollution, overhunting, forestry and natural resource abuse.... etc, etc, etc. It's ruining our ecosystem and destroying our environmental quality.
Eventually, the strain it's putting on the global environment is going to take its toll, but it'll be too late by then and the damage will be incorrigible.