# Distribution Changes in Lichen: A Staple Fallback Food for Yunnan Snub-Nosed Monkey and Their Implications for the Species

## TL;DR

Lichen distribution changes due to climate change may threaten the habitat of Yunnan snub-nosed monkeys, which rely on lichens as a key food source.

## Contribution

This study links lichen distribution modeling with primate habitat preferences to predict future conservation challenges for Yunnan snub-nosed monkeys.

## Key findings

- Lichen and Yunnan snub-nosed monkey habitats show 72.24% overlap, with monkeys preferring large lichen patches.
- Lichen suitable habitat is projected to expand in the southern Hengduan Mountains by 2050 under RCP 6.0.
- Lichen habitat and patch size within monkey ranges may decline, risking monkey populations.

## Abstract

Lichens, as a staple fallback food, play a crucial role in the survival of Yunnan snub-nosed monkey (Rhinopithecus bieti). We used the species distribution models (SDMs) to simulate and predict the current and projected (2050) suitable distribution areas of lichens and explored how lichens affect the distribution of Yunnan snub-nosed monkey through spatial pattern analysis. The results showed a high degree of spatial consistency between the suitable distribution areas of Yunnan snub-nosed monkey and lichens, indicating that Yunnan snub-nosed monkey preferred to select the lichens with a large continuous area as their habitat. While the suitable distribution area of lichens in the southern part of the Hengduan Mountain Range is projected to expand by 2050, lichens within the suitable habitat of the Yunnan snub-nosed monkey are at risk of decline in the future. This study provides important insights into the habitat selection of Yunnan snub-nosed monkey and offers a scientific basis and theoretical support for their conservation.

Under the background of global climate change, lichens as a staple fallback food source for the endangered Yunnan snub-nosed monkey (Rhinopithecus bieti) exert a critical influence on the survival of Yunnan snub-nosed monkey populations through their distribution dynamics. This study focused on the contiguous habitats of the Yunnan snub-nosed monkey in the southern Hengduan Mountains. By species distribution models (SDMs) and landscape pattern analysis, we investigated the changes in suitable habitats of lichens under four Representative Concentration Pathway (RCP) scenarios and their implications for the habitat utilization of the Yunnan snub-nosed monkey until 2050. The results indicate that the current suitable habitat for lichen spans approximately 16,821.96 km2, with highly suitable habitats predominantly located in Deqin County and Weixi County. Altitude and vegetation type emerged as primary factors influencing lichen distribution. The overlap rate of suitable habitats between lichens and the Yunnan snub-nosed monkey is 72.24%. Furthermore, the Yunnan snub-nosed monkey exhibits a preference for selecting habitats characterized by the largest patch index (LPI) of lichen distribution. By 2050, the suitable habitat for lichen is projected to marginally increase in the southern Hengduan Mountains, particularly under the RCP 6.0 scenario, by 22.20% compared to the current expansion. However, both the suitable habitat and the LPI of lichen face potential decline within the habitat of the Yunnan snub-nosed monkey. Therefore, we recommend conducting a quantitative investigation into the correlation between the actual productivity of lichen radiata and the population dynamics of Yunnan snub-nosed monkey as a priority. This research will offer a more precise scientific foundation for conservation decision-making for Yunnan snub-nosed monkey.