In evolutionary and ecological literature you will understand the generally accepted and assumed philosophy that any change to the environment and organisms by humans is artificial. By this assumption we have to take that the domesticated animals of today are not natural, the conversion of natural lands into agricultural, industrial and urban land is not natural either, and extinction of species is not natural either. Well, academics who specialize in these subjects will be quite tempered in their commentary, but the lay people and activists usually understand only the extreme scenarios.
In common parlance 'artificial' refers to anything made by humans, lacking the spontaneity, and perhaps sometimes against straight forward logic.
There are two sides to the issue. Man is a conscious animal capable of choosing their immidiate actions and fates. The animal in the previous sentence suggests that any action by man is ecologically and evolutionarily legitimate. The conscious part of that statement suggests that man can sometimes choose against themselves or to compromise their own interests for the sake of their longer term survival (i.e. choose long term fitness gains over short term gains).
With our new understanding of selection on living organisms we have to ask what is wrong with converting natural lands (forests, lakes, grasslands, rivers) to benefit the ecology of humans or should we call that 'economy' of humans? Is damming rivers against the thesis of nature, is consuming exotic meats and their skins against nature, is overpopulating and overexploiting our resources against our nature? is conserving nature and its living and non-living resources against the thesis of nature? Is the spread of domesticated organisms and parasites and commensals by humans against the thesis of nature?