# Biomass distribution of sympatric mammals in a European temperate forest

## TL;DR

This paper examines how biomass is distributed among mammals in a European forest, revealing a significant imbalance caused by human impact.

## Contribution

The study provides empirical evidence of trophic downgrading in a temperate forest due to human activities.

## Key findings

- The biomass distribution among mammals is bottom-heavy with low biomass of large predators.
- The plant-to-primary-consumer biomass ratio exceeds 6000:1, indicating ecosystem imbalance.
- Human activities are suggested to cause radical changes in terrestrial ecosystem structures.

## Abstract

The distribution of biomass among trophic levels and different types of organisms is a key characteristic of ecosystems. However, such biomass distributions might exhibit large perturbations owing to human activities. We used long-term camera trap data from a temperate forest ecosystem within the Cantabrian range, northern Spain, to quantify the biomass distribution of 10 mammal species ranging in body mass from 300 g to almost 100 kg. The species are representative of three distinct orders and include trophic levels from primary to secondary consumers. The observed biomass distribution was bottom-heavy with a disproportionally low biomass of secondary consumers, in particular large-bodied predators. In addition, the ratio of plant biomass to the biomass of mammalian primary consumers was over 6000 : 1 for total above-ground-plant biomass and over 700 : 1 for plant biomass available for mammal consumption. We suggest that the observed biomass distribution both among mammals and between mammals and plants provide an example of trophic downgrading, and highlight the radical effects human activities might have on the structure of terrestrial ecosystems.