02 Contents Frame
Qualitative or quantitative and physical or economic evaluation
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40 2019 ND-CP 413905
| Qualitative or quantitative and physical or economic evaluation
Land evaluation may be conducted in either physical or economic terms. In physical evaluation, the boundaries between suitability classes are defined in terms of land qualities or characteristics (e.g. of soil, climate, water), using quantitative values wherever possible. For example, high nitrogen availability may be defined as total N content greater than 0.2 percent in the soil to 20 cm depth; a high level of remoteness (a land quality appropriate for determining boundaries of nature reserves) may mean more than 20 km from the nearest road. Most evaluations carried out to date have been in physical terms. In the original Framework, physical evaluations are referred to as qualitative evaluations. This is a misnomer, as many of them are carried out in quantitative terms, sometimes rigorously so (e.g. the AEZ evaluation of suitabilities for crop production). It is now proposed that such evaluations should be called physical. In economic evaluation, the boundaries between suitability classes are defined in economic terms, often involving cost-benefit analysis. Economic evaluation has the advantage that it can indicate the likely return on investment, e.g. 10 or 15 percent. The appearance of precision is deceptive, however. Economic analysis involves many assumptions. Examples are the discount rate, which can be changed more or less arbitrarily (Young 1998, p. 161); or the shadow prices placed on intangibles, e.g. a monetary value assigned to preservation of a rare plant or animal species. The distinction between physical and economic suitability can be partly handled by the suitability classes N1 and N2. Land assessed as N2, Permanently Not Suitable, is so unsuited that the specified land use is never likely to be economic; N1, Temporarily Not Suitable, means that the use is physically possible, but at present costs, prices, etc., is not economically viable, although it might become so in the future. It follows that N, Not Suitable, land can only be separated into N1 and N2 on the basis of economic evaluation. Where an evaluation is being conducted to provide guidelines to future development intended to be of lasting value, there is much to be said for physical evaluation. Where it is intended as a guideline for immediate investment decisions, then economic evaluation will be needed. A two-stage procedure, in which physical evaluation is carried out and the results set out, followed by a stage of economic evaluation, is a solution to this dilemma. tải về 0.57 Mb. Chia sẻ với bạn bè của bạn:
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