Why Have Governments Introduced the Concept of "A Degree of Acceptable

Why have governments introduced the concept of "a degree of acceptable environmental damage" by way of sophisticated and complex environmental legislation?

A) to displace the importance of common law protections set in nuisance
B) to make environmental trespass actionable without proof of harm or damage
C) to ensure that any guest refusing to leave a campsite when asked is a trespasser
D) to provide the certainty needed for resolving boundary/title disputes