ABSTRACT
That is, the portfolio as a whole is continuing to degrade the environment. Over the long run, the cumulative degradation (e.g. soil erosion, deforestation and waste accumulation) may severely degrade or deplete the resource base.' Consequently, to ensure that a portfolio of projects does not undermine the sustainability of the resource requires the adoption of an explicit constraint on the above appraisal process (rule A3.2). There are two possibilities: a weak and a strong sustainability criterion.
