# Effects of oil palm monoculture and agricultural land use on shredder insects in Eastern Amazonian streams

## TL;DR

This study examines how different land uses, including oil palm monoculture, affect shredder insects in Amazonian streams, highlighting their role in maintaining aquatic ecosystems.

## Contribution

The study provides new insights into how land-use changes impact shredder insect communities and their ecological functions in the Amazon.

## Key findings

- Forest streams had higher shredder species richness compared to pasture streams.
- Oil palm and forest streams showed greater shredder abundances than pasture streams.
- Shredder biomass variability increased in pastures but decreased in oil palm areas.

## Abstract

Aquatic insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are vulnerable to changes in allochthonous inputs, mainly shredders, important to leaf litter decomposition and energy flow. This study evaluated the effects of land-use patterns (forest, pasture, oil palm, and mosaic) on the abundance, richness, biomass, and proportion of shredder EPT, as well as predictors of genus distribution. The study was conducted in northeast Pará, Brazil (2011–2017). One-way ANOVA and Redundancy Analysis (RDA) were used to test land-use effects and environmental influences on genus composition. Oil palm and forest streams presented greater abundances compared with the pasture streams. The forest treatment showed more shredder species than the pasture treatment. Biomass variability increased in pastures but decreased in oil palm areas, whereas forest streams did not differ from oil palm. The relative composition of shredders across land-use types followed similar patterns: the highest proportion was observed in forest streams, intermediate values in oil palm and mosaic, and the lowest in pasture. RDA explained 34% of the variation in genus composition, which was associated mainly with fine root cover and fast flow. Phylloicus, Anacroneuria, and Triplectides were negatively associated with fast flow. Triplectides responded positively to fine root cover, whereas Nectopsyche and Fittkaulus responded positively to fast flow. Anthropogenic alterations reduce shredder biomass and diversity, destabilizing aquatic communities. Forest conversion compromises the structure and function of Amazonian streams, reinforcing shredders as key indicators for long-term monitoring and conservation.