Active Sampling and Understory Traps Can Cost-Effectively Detect Changes in Butterfly Communities after Hydroelectric Dam Construction

Abstract

(1) Background: Monitoring programs are essential to conservation but are often restricted by limited financial resources. Optimal monitoring can lead to higher cost-effectiveness. (2) Methods: In this study, we used butterflies as bioindicators to assess the effects of filling a dam in the Brazilian Amazon. We studied the effects of flooding on butterfly assemblages through samples collected before and after the flooding. We contrasted three sampling techniques: baited traps in the (a) canopy and (b) understory and (c) active collections using entomological nets. (3) Results: Community composition showed low resistance, with pronounced changes after disturbance, and low resilience, with the failure to recover taxonomic diversity even after two years. We found that using the three techniques together was redundant and baited understory traps alone were sufficient to detect community changes. (4) Conclusions: Our study adds to the currently limited knowledge about the effects of hydroelectric plants on terrestrial insect fauna. In addition, identifying cost-effective monitoring, which is often lacking in conservation studies, allows projects to use time and financial resources more efficiently, particularly given the financial limitations available for conservation studies in tropical countries.