Although various anthropogenic pressures or impacts have been understood to cause biodiversity loss in concerted manners, the role of each type of pressure in the loss has been insufficiently evaluated.

Correlating each pressure to lost biodiversity (difference between the species set of a target site and the regional species pool of a given taxa), hereafter defined as “Lost Biodiversity Approach” (LBA), may be a direct and comprehensive approach for evaluation of such a role. When nestedness exists, differential species richness from the original biota (DROB) is likely to be a good measure of the state of impacted biodiversity.

We applied LBA to agricultural-pond damselfly fauna of the rural area of Iwate Prefecture, Japan in order to demonstrate its feasibility. Direct and indirect effects of alien species (bull frog and common carp) on DROB were examined by Bayesian method, after confirmation of nestedness. As a result, a reliable negative indirect effect of common carp was quantified with credible intervals.

This simplicity of LBA is expected to be effective if applied to the “hotspot” areas, where urgent evaluations of pressures or impacts are needed in spite of general lack of species abundance data.