True liberty is responsibility. The only people who come and go as they please are those without social or economic commitments and those people likely can't go where they please.
Libertarianism doesn't preclude voluntary collectivism. A libertarian would argue that the environmental degradation you describe would not be possible in a private property regime. Libertarianism means self interest and libertarians have an interest in clean water and air as much as anyone. Only through public ownership can land, air and water be despoiled in a corporate fascist regime like what we live under now.
Libertarians do not interpret the status quo as nature's hand knowing that we live under a corporate cronyism regime where incumbent firms restrict competition through political influence. Unfortunately libertarian ideals and rhetoric have been hijacked by the one percent who want unfettered freedom for the rich and militaristic social control for everyone else.
I sincerely enjoyed your article.