From Aristotle to Rousseau via Wilderness
There are various problems with this school of argument. The most commonly noted is its use of a human-nature dualism, in which nature is a holistic system and (non-Noble-Savage) humans are inevitably exogenous interferers who can only damage (never sustain, improve, or productively provoke) the course of nature. Less often noted is the flawed analysis of artefacts that the argument depends on. On the one hand, artifact-making is a process of alteration, not creatio ex nihilo, so any artefact is a product both of its human* creator but also of the cooperation and resistance of the chunk of nature that the creator took as his or her material -- after all, there's a reason we bred dogs from wolves, not from fish. Further, there is no reason to think that the creator's purposes bind anyone else's evaluation or the object. I think that existentialism is correct in holding that objective essences can only be self-defined (note that this would not rule out "autopoietic" defenses of nature preservation, in which natural entities, like human individuals, are self-defining systems -- though I disagree with autopoietic arguments on other grounds).
Also problematic is the anti-artifact perservationist view of human-to-human relationships. Preservationists of this stripe, who clearly count humans as non-artefacts, seem to be committed to taking one or the other sociologically indefensible extreme on the spectrum of liberal to communitarian views of humanity. At the communitarian pole, "humanity" can be concieved of as a single entity with shared will and purposes. At the liberal pole, each individual is a presocial atom that can be in conflict with others over the use of nature but whose essence is independent of interactions with others. Either of these positions would deny the ability of humans to be artifacts -- for communitarians because the only possible purposeful shaping of humanity would be self-shaping (since humanity is the only shaper), and for liberals because individuals cannot be shaped by anything.
But of course neither of those extreme poles is realistic. Humans are shaped by other humans, both physically and mentally. This shaping is an inevitable consequence of growing up and living socially, not just a process that occurs in cases of oppression. Human beings are, on the preservationist argument at issue, just as artifactual as humanized landscapes. Thus holding to the Aristotelian analysis of artefacts seems to imply a need to return to a Rousseauian state of nature. In Rousseau's original state of nature (unlike Hobbes' more famous vision), humans are spread thinly enough over the land that they never interfere with one another (much less with nature), living lives that are solitary and hence free of shaping by others. Or we might be led the other way to Rousseau's ultra-communitarian ideal for a society too large to remain in a state of nature: a republic guided by the "will of all" that harmonizes people and hence makes all shaping of humans into collective self-shaping.
*Or in a few cases, animal.