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. 2018 Nov 20;8(23):11887-11899.
doi: 10.1002/ece3.4645. eCollection 2018 Dec.

Decreasing brown bear (Ursus arctos) habitat due to climate change in Central Asia and the Asian Highlands

Junhu Su  1   2 , Achyut Aryal  2   3 , Ibrahim M Hegab  1   2   4 , Uttam Babu Shrestha  5 , Sean C P Coogan  6   7 , Sambandam Sathyakumar  8 , Munkhnast Dalannast  9 , Zhigang Dou  10 , Yila Suo  10 , Xilite Dabu  10 , Hongyan Fu  10 , Liji Wu  10 , Weihong Ji  1   2   3
Affiliations

Decreasing brown bear (Ursus arctos) habitat due to climate change in Central Asia and the Asian Highlands

Junhu Su et al. Ecol Evol. .

Abstract

Around the world, climate change has impacted many species. In this study, we used bioclimatic variables and biophysical layers of Central Asia and the Asian Highlands combined with presence data of brown bear (Ursus arctos) to understand their current distribution and predict their future distribution under the current rate of climate change. Our bioclimatic model showed that the current suitable habitat of brown bear encompasses 3,430,493 km2 in the study area, the majority of which (>65%) located in China. Our analyses demonstrated that suitable habitat will be reduced by 11% (378,861.30 km2) across Central Asia and the Asian Highlands by 2,050 due to climate change, predominantly (>90%) due to the changes in temperature and precipitation. The spatially averaged mean annual temperature of brown bear habitat is currently -1.2°C and predicted to increase to 1.6°C by 2,050. Mean annual precipitation in brown bear habitats is predicted to increase by 13% (from 406 to 459 mm) by 2,050. Such changes in two critical climatic variables may significantly affect the brown bear distribution, ethological repertoires, and physiological processes, which may increase their risk of extirpation in some areas. Approximately 32% (1,124,330 km2) of the total suitable habitat falls within protected areas, which was predicted to reduce to 1,103,912 km2 (1.8% loss) by 2,050. Future loss of suitable habitats inside the protected areas may force brown bears to move outside the protected areas thereby increasing their risk of mortality. Therefore, more protected areas should be established in the suitable brown bear habitats in future to sustain populations in this region. Furthermore, development of corridors is needed to connect habitats between protected areas of different countries in Central Asia. Such practices will facilitate climate migration and connectivity among populations and movement between and within countries.

Keywords: Asian highlands; Central Asia; brown bear; climate change; habitat shift; species distribution model.

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Figures

Figure 1
Figure 1
Brown bear (Ursus arctos)
Figure 2
Figure 2
Results of the jackknife test of variable importance. The environmental variable with highest gain when used in isolation is Mean Temperature of Warmest Quarter (Bio10), which therefore appears to provide the most useful information by itself. The environmental variable that decreases the gain the most when omitted is land cover, which appears to have the most information that isn't present in the other variables
Figure 3
Figure 3
The omission rate and predicted area as a function of the cumulative threshold. The omission rate is calculated both on the training presence records, and (if test data are used) on the test records. The omission rate should be close to the predicted omission, because of the definition of the cumulative threshold
Figure 4
Figure 4
The receiver operating characteristic (ROC) curve for the same data. Note that the specificity is defined using predicted area, rather than true commission. This implies that the maximum achievable AUC is less than 1. If test data are drawn from the MaxEnt distribution itself, then the maximum possible test AUC would be 0.868 rather than 1; in practice, the test AUC may exceed this bound
Figure 5
Figure 5
Response curves. These curves show how each environmental variable affects the MaxEnt prediction. The curves show how the logistic prediction changes as each environmental variable is varied, keeping all other environmental variables at their average sample value
Figure 6
Figure 6
Current and future suitable habitat of brown bear in Asia
See this image and copyright information in PMC

References

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