On the practical limits to substitution

This paper considers the arguments for “weak” vs. “strong” sustainability. The weak sustainability position, held by many mainstream neoclassical economists (such as Solow and Weitzman), is that almost all kinds of natural capital can be substituted by man-made capital. The contrary position, known as strong sustainability, holds that many of the most fundamental services provided by nature cannot be replaced by services produced by humans or man-made systems. The paper discusses the limits of substitution from a physical point of view. It concludes that, while there is considerable scope for substitution in some domains, the limits to substitutability in the medium term at least are real and important. In effect, the paper supports the strong sustainability position.