# Intermediate Habitat Fragmentation Buffers Droughts: How Individual Energy Dynamics Mediate Mammal Community Response to Stressors

## TL;DR

Intermediate habitat fragmentation helps small mammals survive droughts by balancing energy needs and reducing stress from resource shortages.

## Contribution

A novel individual-based metabolic model reveals how energy dynamics mediate mammal community responses to droughts and fragmentation.

## Key findings

- Moderate habitat fragmentation best buffers drought effects on species richness.
- High fragmentation leads to low energy balance and high mortality during droughts.
- Energy allocation and storage mechanisms help species coexist under stress.

## Abstract

Biodiversity is threatened by land‐use and climate change. Although these processes are known to influence species survival and diversity, predicting their combined effects on communities remains challenging. We here aim to disentangle the combined effects of drought‐induced resource shortage and habitat fragmentation on species coexistence. To understand how both fragmentation and droughts affect individual movement and physiology, and ultimately influence population and community dynamics, we use an individual‐based metabolic modelling approach to simulate a community of small mammals. Individuals forage in the landscape to ingest energy, which they then allocate to basal maintenance, digestion, locomotion, growth, reproduction, and storage. If individuals of several species are able to balance their energy intake and needs, and additionally store energy as fat reserves, they may overcome stress periods and coexist. We find that species recover best after a drought when they live in moderately fragmented landscapes compared to those with low or high fragmentation. In low fragmented landscapes, high local competition during resource shortages is problematic, while in highly fragmented landscapes, low energy balance and storage often lead to high mortality during drought. Intermediately fragmented landscapes balance these effects and show the least impact of droughts on species richness, a pattern that holds also when integrating observed drought time series from monitoring data in the model simulations. Due to the interacting negative impacts, we suggest that with ongoing global change, it is increasingly important to understand stressors simultaneously to identify measures that support species coexistence and biodiversity. Including individual energy dynamics allowed us to conflate the different global change effects through energy storage and energy allocation to different processes. Our presented community model, which integrates metabolic and behavioural reactions of individuals to different stressors and scales them to the community level, offers valuable insights with great potential to support nature conservation.

Simulations of our novel individual‐based metabolic community model for a terrestrial mammal community revealed a positive effect of intermediate habitat fragmentation on coexistence when simulating habitat fragmentation and droughts as multiple stressors. Landscapes with intermediate habitat fragmentation buffered drought effects best compared to low or high fragmentation, both when simulating experimental droughts of varying length and magnitude, and when integrating observed drought timeseries from monitoring data. The energetic model allowed to conflate these different global change effects and provided insights into coexistence mechanisms with similarity in energy balance among species promoting coexistence and thus diversity.