Climate and anthropogenic activities threaten two langur species irrespective of their range size

Aim

If species fail to track the pace of climate change, areas of suitable habitat and population size are likely to decline, threatening species survivorship. Here, we incorporated multiple measures of environmental change and species-specific habitat requirements to assess the responses of two closely related primate species to future changes in climate and habitat conversion. Specifically, we tested whether the comparatively wider-ranging and Endangered François' langur (Trachypithecus francoisi) is better suited to withstand future anthropogenic habitat conversion and climate change than is the more narrowly ranging and critically endangered white-headed langurs (T. leucocephalus).

Location

China.

Methods

We used species distribution models (SDMs) models and population viability analyses, and calculated dispersal velocity and biotic velocity, to predict the impact of climate and anthropogenic activity on the distribution and survivorship of two closely related primate species.

Results

We found that: (1) by the year 2050, the area of suitable habitat for both primate species is expected to decline by 45% to 47%; (2) the population size of François' langurs is expected to increase to 4000 individuals (129%) and the population size of white-headed langurs is expected to increase to 1400 individuals (133%); (3) biotic velocity, defined as the minimum migration rate required by a species to track its preferred climatic conditions, was 2.84 and 1.48 km/year for François' langurs and white-headed langurs, respectively; and (4) dispersal velocity, defined as the distance a species has spread over a given period, was 0.82 km/year for both langur species.

Main Conclusions

We demonstrate that despite expected population growth, by the year 2050, habitat contraction and insufficient opportunities for dispersal will likely prevent both primate species from tracking and adjusting to changing climate conditions. Moreover, the more widely ranging species, T. francoisi, was not found to have a survival advantage over the more narrowly ranging species (T. leucocephalus) under future conditions of climate change and continued anthropogenic habitat conversion, resulting in a high risk of extinction for both langur species. The modelling approach used here is robust and can be successfully applied to other threatened animal taxa.