Biodiversity trajectories and the time needed to achieve no net loss through averted-loss biodiversity offsets

Biodiversity offsetting is a conservation tool that compensates for the residual loss of biodiversity at one geographic locality with an equivalent gain elsewhere. The goal is generally to ensure no net loss of biodiversity after development. One path to no net loss is preventing the imminent loss of biodiversity at the offset location through increased conservation; a strategy known as averted-loss. No net loss is most feasible in these instances when (a) the initial loss of biodiversity is small, (b) the background decline in biodiversity is rapid and (c) conservation interventions are effective. This study, however, demonstrates that the functional form of the biodiversity trajectory also plays a considerable role in determining the feasibility of achieving no net loss. Using a simple framework of equations with fraction exponents, I demonstrate that the time required to reach no net loss is generally longer when background biodiversity trajectories are concave, compared to when they are convex. Moreover, the net effect of conservation must be greater for concave biodiversity trajectories if no net loss is to be reached within time-frames similar to convex trajectories. Incorporating different forms of biodiversity trajectories into existing frameworks may have major implications for the feasibility of averted-loss biodiversity offsets.