Fig.7 Results of jackknife train of relative importance of
predictor variables forB.
gargarizans
4.2 Future distribution change and barycenter migration ofB. gargarizans
Many studies suggest that global temperatures are rising and will
continue to do so for some time to come, with an expected increase of
0.6℃ in the 20th century and 1.4℃ ~ 5.8℃ by the 21th
century (Budikova, 2009; Mccarthy, Canziani, Leary, Dokken, & White,
2007). The rising global temperature will inevitably affect the change
of species distribution, which will eventually lead to two results: one
is the reduction of species distribution, which will eventually lead to
extinction of species; the other is the migration of species to
previously undistributed areas, which will expand the distribution
(Bellard, Bertelsmeier, Leadley, Thuiller, & Courchamp, 2012;
Morueta-Holme, Camilla, & Svenning, 2010; Thomas et al., 2004).
In this study, under the background of climate change, the suitable
distribution area of B. gargarizans will continue to decrease in
the next 30~50 years. In comparison to three other
global Change Scenarios, we can see the smallest reduction in suitable
habitat for B. gargarizans under RCP2.6 Scenarios (The most
optimistic scenario is that greenhouse gas emissions peak between 2010
and 2020, then continue to decline, with a negative value by the end of
the century). And the suitable habitat ofB.
gargarizans will be further reduced Under the scenarios of RCP4.5 and
RCP6.0(That represents a decline after greenhouse gas emissions peaked
in 2040 and 2080, respectively). the suitable habitat of B.
gargarizans of China decreased to the maximum extent under the
condition of RCP8.5(Greenhouse gas emissions continue to rise in this
century). The results show that with the increase of greenhouse gas
emission concentration, the area of suitable habitat of B.
gargarizans decreases more, on the other hand, it suggests the
importance of energy conservation and emission reduction to the
maintenance of ecological balance.
As show in Fig. 4 and Fig. S5, the suitable habitat ofB. gargarizans will decrease
in the south, southeast coast and central part of China, and
correspondingly increase in the central and western part of China from
now to 2050. And the trend will become more pronounced by 2070. In the
next 30 to 50 years, the distribution centers of B. gargarizanswill gradually move from Yunyang County in northeast Chongqing City to
Wanyuan County, Tongjiang County and Xuanhan County in northeast Sichuan
Province and Langao County, Ziyang County, Zhenba County, Nanzheng
County and Chenggu County in southwest Shaanxi Province. Compared with
the present, the distribution focus has gradually shifted to the
northwest, and this trend has not weakened with time. In addition, it
can be seen from Figure 1 that Bio9 and Bio14, two climatic factors that
have a great influence on the distribution of B. gargarizans . are
increasing from 2050 to 2070 compared with the present, and the growth
trend is more obvious in eastern and southern China. And these are the
areas where B. gargarizans , will be less concentrated in the
future. And the reason for this phenomenon is that the average
temperature and precipitation in these regions are higher at present,
and the further increase of temperature and precipitation in the future
will make the values of these factors beyond the range suitable for the
distribution of B. gargarizans (Table S6) .
Four GCMs under four RCPs were used in this study, and the results show
that under the global climate change, like other species that have been
reported, the distribution area of B. gargarizans will migrate to
the high latitude and high altitude area (China’s terrain is low in the
east)(Kelly & Goulden, 2008; Parmesan & Yohe, 2003). On the other
hand, this paper is more inclined to think that the current distribution
pattern of B. gargarizans , is caused by the dispersion, because
from the perspective of the current distribution, there is no obvious
geographical isolation between the distribution areas of different
regions of B. gargarizans ,, and the future distribution ofB. gargarizans , showed that the future distribution of B.
gargarizans , would gradually break up, and the geographical separation
would gradually form between different regions (Fig.2, Fig. S1). The
results of this study indicated that the distribution area of B.
gargarizans would be reduced in the future, and the habitat
connectivity, resilience and gene exchange between the populations would
be reduced with the serious habitat fragmentation year by year, finally
leading to the gradual decline of B. gargarizans population(Duan
et al., 2016). And it suggests that some amphibians, which are more
sensitive to environmental changes and narrower than B.
gargarizans , the changes to their niches from climate change will be
even more dramatic and even devastating. Due to the influence of the
resolution of the environmental layer, the prediction results cannot be
very accurate. However, we still believe that this study will provide
theoretical support for the direction of conservation and ecological
management of B. gargarizans , and it is believed that it can
provide a research direction for other amphibians to cope with climate
change.