While the theoretical and practical challenges in achieving No Net Loss of biodiversity are becoming increasingly well described and reported (see papers from Joe Bull, Martine Maron, and David Lindenmayer), the underlying concept of the mitigation hierarchy is both powerful and much more widely applicable than has so far been appreciated.
Currently there is a widespread and piecemeal project-level approach to achieving No Net Loss of biodiversity taking place. This means that, if biodiversity gains and losses were to be aggregated, biodiversity could be lost even if individual projects appear to be reaching their targets.