Answer:
natural
Step-by-step explanation:
Humans have been exploiting the natural resources since the start of human evolution.
Human have started clearing the forest in order to accommodate themselves by building residential buildings and townships. In order to do business and earn wealth , he started developing more and more infrastructure and commercial areas.
Humans have overused naturally occurring fossils such as petroleum, coal, natural gas etc. They have exploited flora and fauna to an extent of devastation. They polluted the essential resources like water, air and land.
Hence, A major problem caused by humans is the contamination and depletion of natural resources.