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Insect decline in Brazil: an appraisal of current evidence
Thomas M Lewinsohn1, Kayna Agostini2, André Victor Lucci Freitas1
1Departamento de Biologia Animal, Instituto de Biologia, University of Campinas, 13083970 Campinas, São Paulo, Brazil.
Biology Letters
|August 24, 2022
Summary
Insect populations in Brazil are declining, particularly terrestrial species like butterflies and bees. Aquatic insect trends show no clear pattern, possibly due to shorter study durations and degraded sites.
Area of Science:
- Ecology
- Zoology
- Conservation Biology
Background:
- Global insect decline is a growing concern, yet data from Brazil remains scarce.
- Existing reviews lack comprehensive information on insect population trends within Brazil.
Purpose of the Study:
- To assess insect population trends in Brazil using available literature and expert surveys.
- To identify patterns of decline or increase in both terrestrial and aquatic insect communities.
Main Methods:
- Conducted literature searches and distributed a survey to researchers across Brazil.
- Analyzed 75 instances of recorded trends from 56 respondents, spanning an average of 11 years for aquatic and 22 years for terrestrial insects.
- Included time-replicated samples and expert opinions based on long-term local collections.
Main Results:
- Terrestrial insects exhibited significantly more declines than increases in both abundance (17:3) and diversity (11:1).
- Aquatic insects showed no discernible trend in abundance (2:2) or diversity (3:4).
- Data primarily focused on butterflies, bees, and scarab beetles for terrestrial insects, and various orders for aquatic insects.
Conclusions:
- Terrestrial insect populations in Brazil are experiencing significant declines.
- Aquatic insect trends were inconclusive, potentially due to shorter study durations and pre-degraded sampling sites.
- Guidelines for future long-term insect assessments, including resampling legacy sites, are proposed.
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