It is not uncommon to hear people referring to tipping points, positive feedback, path dependence, irreversibility, and even catastrophic risks when talking or writing about climate change and biodiversity loss. As the expressions point to features of the processes governing the biosphere, it is important to understand what they amount to. Otherwise the terms will remain in wide use even when their significance for economic policy remains unclear.

The source of those features is the non-linearity of the processes that govern the biosphere. Non-linearity is a ubiquitous feature of Earth System processes, so ubiquitous that it would not be an exaggeration to say that the economics of biodiversity is the study of non-linear processes.91 The meaning of non-linearity is simple enough: if, to take an example, you were to replicate an ecosystem M times, the functions of the enlarged ecosystem would not be an M-fold replica of the original ecosystem.