Descontar ou não descontar? Como ponderar custos e benefícios ambientais futuros

Resumo Ingles

The economic evaluation of projects involving long-term environmental impacts presents significant challenges regarding the appropriate weighting of future costs and benefits, particularly within the framework of cost–benefit analysis applied to public policies and infrastructure projects. In this context, the social discount rate constitutes a central parameter in the decision-making process, as it determines the weight assigned to intertemporal impacts and directly influences the perceived economic viability of investments. This dissertation aims to examine the conceptual and methodological adequacy of the criteria used in weighting environmental costs and benefits in economic project appraisal, with emphasis on the discussion of how discounting should be applied to natural resources and environmental assets. The research is characterized as an applied study, with a qualitative approach and an exploratory and analytical nature, grounded in a bibliographic and documentary review of national and international literature, including scientific articles, books, technical manuals, and institutional guidelines related to project appraisal and sustainability. The analysis developed is based on the critical interpretation of the theoretical foundations of welfare economics, environmental economics, and ecological economics, seeking to identify convergences and limitations associated with the treatment of environmental goods in economic feasibility assessments. The results indicate that the use of uniform discount rates may lead to the undervaluation of environmental goods and services, particularly when externalities affect irreplaceable environmental assets — or assets with extremely limited substitutability — and manifest themselves over very long analytical time horizons. Under such circumstances, applying discount rates identical to those used for conventional economic capital tends to distort the intertemporal evaluation of environmental impacts, potentially resulting in decisions that are inconsistent with the principles of sustainability and intergenerational equity. It is therefore concluded that externalities associated with critical and long-lasting environmental goods and assets should be evaluated using differentiated discounting criteria — dual discount rates — distinct from those applicable to reproducible economic capital, in order to adequately reflect their ecological relevance, their potential irreversibility, and their role in maintaining the well-being of present and future generations. Such an approach represents a methodological improvement in economic feasibility analysis and contributes to a more consistent incorporation of sustainability into the public decision-making process.