Ecosystem Viable Yields

TL;DR

This paper introduces the concept of ecosystem viable yields (EVY) as a sustainable harvesting approach that considers ecosystem dynamics and safety levels, addressing limitations of traditional MSY.

Contribution

It defines EVY based on viability theory for multispecies models, providing explicit formulas and demonstrating application to the Peruvian anchovy-hake ecosystem.

Findings

EVY ensures biological safety over time.

Explicit formulas for EVY in multispecies models.

Application to Peruvian ecosystem shows practical relevance.

Abstract

The World Summit on Sustainable Development (Johannesburg, 2002) encouraged the application of the ecosystem approach by 2010. However, at the same Summit, the signatory States undertook to restore and exploit their stocks at maximum sustainable yield (MSY), a concept and practice without ecosystemic dimension, since MSY is computed species by species, on the basis of a monospecific model. Acknowledging this gap, we propose a definition of "ecosystem viable yields" (EVY) as yields compatible i) with guaranteed biological safety levels for all time and ii) with an ecosystem dynamics. To the difference of MSY, this notion is not based on equilibrium, but on viability theory, which offers advantages for robustness. For a generic class of multispecies models with harvesting, we provide explicit expressions for the EVY. We apply our approach to the anchovy--hake couple in the Peruvian upwelling ecosystem.