How Do We Measure the Impact of Biodiversity Offsets? It’s Complicated
The actions of humans in the name of “development” are leading to vast reductions in biodiversity — the significant loss of the variety of plant and animal life on earth. In an effort to balance these losses, policy makers are increasingly mandating the implementation of biodiversity offsets. These program-specific conservation initiatives—such as planting new fields of native grass to replace ones that have been destroyed—seek to ultimately achieve no net loss (NNL) in the biodiversity of a particular area.
In this article, published in Conservation Biology, researchers sought to measure how effective offsets are in achieving NNL. They did so using two frames of reference: one that measured the achieved biodiversity level against the baseline level present at the start of a project; and a second that accounted for the dynamic nature of ecosystems by comparing the achieved level to a predicted level that would have likely been in place without human intervention. With both models, the authors created scenarios in which background biodiversity trends (trends already in place before development) were increasing, decreasing, or stable.
The researchers found that achieving NNL depends upon the interaction between the reference frame and background biodiversity trends. For example, stakeholders using a baseline model in an area with increasing biodiversity will conclude that the offsets have not only achieved NNL, but actually resulted in more biodiversity. Yet, if they use a model comparing the achieved level to the predicted level without development, they will find that offsets failed to achieve NNL.
As the authors note, policy makers must be cognizant of these different methods when they are evaluating the success of offsets and determining the feasibly of new initiatives. Environmental advocates who are already skeptical of the effectiveness of biodiversity offsets will be interested to see that the study identifies several scenarios in which preventing development, even with offsets, is better for biodiversity.