But shifting the focus of sustainable development from conservation to development has had the imperceptible effect of stretching the original forest management term of sustainable yield from the use of renewable resources only (like forestry), to now also accounting for the use of non-renewable resources (like minerals). This stretching of the term has been questioned. Thus, environmental economist Kerry Turner has argued that literally, there can be no such thing as overall "sustainable development" in an industrialised world economy that remains heavily dependent on the extraction of earth's finite stock of exhaustible mineral resources: "It makes no sense to talk about the sustainable use of a non-renewable resource (even with substantial recycling effort and reduction in use rates). Any positive rate of exploitation will eventually lead to exhaustion of the finite stock."