Rao, D.P. 
  
  
account (Ikerd, 1990). The role of such factors of production as the availability 
of natural resources and environmental services, but also that of environmental 
impacts as products of economic activity are neglected. In the eco-friendly 
economic development perspective, the ecological equilibrium is taken as norm 
and the focus is mainly on building up a pattern and a rate of resource use which 
the environment can sustain indefinitely (Wilkinson, 1973). Lastly, the social 
perspective lays more emphasis on continued welfare of the society. The role of 
economic - demographic interrelationship is either explicitly or implicitly referred 
to. 
4.0 SUSTAINABILITY INDICATORS 
Quantification of sustainability is essential to objectively assess the impact of 
management systems of actual and potential productivity, and environment. 
However, sustainability is a concept and can not be measured directly. 
Appropriate indicators must, therefore, be selected, tested, and validated to 
determine levels and duration of sustainable land management. Sustainability 
indicators are needed to monitor progress and to assess the effectiveness and 
impact of policies on natural resources development. An ideal indicator should be 
unbiased, sensitive to changes, predictive, referenced to threshold values, data 
transformable, integrative and easy to collect and communicate (Liverman et 
al.j1988). One such indicator is land quality indicator which includes nutrient 
balance, yield trend and yield gaps, land use (agrodiversity) and land cover 
(Dumanski,1997). 
Sustainability can be assessed one or several indices. Although, general 
principles may be the same, these indices must be fine-tuned and adapted under 
local environments. Some of the indices of sustainability are as follows: 
(i) Productivity (p) - Production per unit resource used can be assessed 
by(Lal,1994). 
P=p/R 
Where P is productivity, p is total production, and R is resource used. 
(ii) Total Factor of Productivity (TFP) - It is defined as productivity per unit cost 
of all factors involved (Herdt,1993) and could be expressed as 
x "(Rix Ci) 
  
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.