Due to climate change, the regional agro-climatic conditions in Southwest China have undergone changes. The heat sources for the growth of crops have been improved. The number of days with temperatures steadily above 0°C and 10°C (two criteria) have increased during 1960–2010. The area suitable for multiple cropping has increased; the growth period has shortened; the climatic potential productivity has declined; the pest damage has worsened. During 1961–2010, the desired cooling degree days in Southwest China has increased 38.9°C d per decade. Forest fires and pests have increased. The area of meadow and wetlands has decreased. Heterogeneous invasion has intensified; endangered animal and plant species have increased. The tourism landscape has been damaged. The risk of human health has increased.
In the 21st century, with the increase of temperature and precipitation, the number of days with temperature steadily above 10°C and the accumulated temperature will continue to increase, most notably in the Qinghai-Tibetan Plateau. The area of intercropping will expand; multiple cropping will move to higher altitudes. The impacts of agrometeorological disasters, pests and diseases will intensify. The summer cooling energy consumption continues to increase; energy supply will show larger variability; the gap between energy supply and demand will be widened. The phenology will keep on changing, and the habitat will be worsening. Biological population will move northward and to higher altitudes. Some species are at risk of extinction. Negative effects on health will increase.
climate change ; impact assessment ; agriculture ; energy ; human health
The global climate has undergone a significant change characterized by warming in the last 100 years or so [ IPCC , 2007 ]. In China, the climate has changed basically in tune with the globe. Projections indicate that in the next 50–100 years, the global and China’s climate will continue warming. During 1961–2010, annual mean temperature in Southwest China had increased 0.12°C per decade, and annual precipitation had slightly decreased [ Ma et al. , 2013 ]. Global warming has significant impacts on the ecosystem and socioeconomic system [ Li et al. , 2010b ]. This article shall analyze the observed and potential impacts of climate change on the vulnerable aspects of Southwest China, such as agriculture, biodiversity, etc., and explore the countermeasures of adaptation to climate change.
Climate changes in Southwest China have great impacts on agriculture. The first day with temperature steadily above 0°C and 10°C has become earlier, usually at a rate of 2 d per decade, for some area at 4–5 d per decade. The last day with temperature steadily above 0°C and 10°C has postponed at an insignificant rate of 1 d per decade. The number of days with temperature steadily above 0°C and 10°C and the cumulative temperature showed increasing trends.
The planting areas of one crop and two crops per year have decreased, but the area of three crops per year has increased. The sequential cropping index continued to increase. For example in dry land cultivation of Sichuan province, the area of one crop per year has decreased from 489×103 hm2 to 198×103 hm2 , and the sowing ratio of the planting area of two crops per year to the total has dropped from 43.0% to 25.9% during 1986–2008. Although the area of three crops per year reduced 2.63 hm2 , the area ratio increased from 35.5% to 42.3%. The proportion of multiple cropping of paddy increased, too. Due to the increasing temperature, the developmental stage starts earlier, the growth period has shortened, and the climatic potential productivity has declined. In Sichuan, each developmental stage for corns starts earlier. Sowing has advanced at a rate of 4–5 d per decade during 1980–2008; tasseling and maturation have advanced at a rate of 2–3 d per decade. The durations from sowing to jointing for winter wheat and spring wheat in Tibet have shortened. In Nyingchi during 1990–2009, the durations from sowing to tillering and from sowing to stop-growing have prolonged at the rate of 16.2 d per decade and 7.4 d per decade, respectively. However, the durations from sowing to reviving, to jointing, and to flowing have shortened at the rate of 3.6, 1.3 and 4.9 d per decade, respectively. The whole growth period show a shortening trend of 4.1 d per decade in Nyingchi [ Danzeng , 2007 ]. In particular, since the 1990s the climatic potential productivity in Sichuan and Yunnan has decreased persistently [ Wang et al ., 2009 ; Li et al ., 2010a ]. The area of rust and other pest disaster has increased.
During 1961–2009, the heating degree day in Southwest China first increased and then decreased. The heating degree day decreased at the rate of 99.6°C d per decade from 1980 to 2009, and most notably in the Qinghai-Tibetan Plateau. On the contrary, cooling degree day decreased at first and then increased, with the increasing rate of 36.1°C d per decade in 1961–1980 and the decreasing rate of 38.9°C d per decade in 1986–2010. The cooling energy consumption in summer increased, especially in southern Yunnan, northern and western Sichuan Basin. The period with not only the lowest heating degree day but also the highest cooling degree day was 2001–2009.
The run-off in the Yangtze River and its tributaries (including the Minjiang River, the Tuojiang River, the Jialingjiang River, the Brahmaputra River, and the West River) was decreasing during 1960–2010. Drought had significant impacts on hydroelectric power generation. During the drought in the summer of 2006, once-in-100-year low water level was observed in the Fujiang River, the Jialingjiang River and the Yangtze River. As a result, the hydropower had a 1.2×106 kW reduction.
The annual mean wind speed had decreased at the rate of 0.08 m s–1 per decade during 1960–2010 [ Ma et al. , 2013 ]. When the mean wind speed decreases, the amount of wind power generation would decrease. Increase in mean temperatures would lead to decrease in electricity generated by wind turbines under the same wind speed. During 1961–2010, the annual mean sunshine duration in Southwest China showed a statistically significant decreasing trend of 33.3 h per decade, and most noticeably since the mid-1980s [ Ma et al. , 2013 ]. And regional differences were significant in the trend of sunshine duration in Southwest China. Decreasing in sunshine duration in Panxi of Sichuan and Yunnan was not conducive to the exploration of solar energy. Although climate change mainly has negative impacts on renewable clean energy, high temperature favors biomass accumulation [ Shi et al. , 2008 ]. The overall effects of climate change on southwestern biomass were positive.
Southwest China is one of the most typical and concentrated areas of diversified species. During 1960–2010, forest fires and forest pests increased due to the climate warming and the droughts. The annual area of forest fires was as high as 0.25×106 hm2 . From the 1950s to the 1980s, the area of pest in Southwest China doubled every 10 years, with the annual area of 0.86×106 hm2 (1950s), 1.44×106 hm2 (1960s), 3.65×106 hm2 (1970s), and 8.47×106 hm2 (1980s). Natural zones of the plateaus moved to higher altitudes. The forest-line moved upward at a rate of 8.5 m per decade in the arid valley region of Yunnan [ Moseley , 2006 ].
The grassland ecosystem showed different degrees of degradation. In the late 1980s, the area of grassland degradation in Sichuan was 8.5×106 hm2 , and 12.8×106 hm2 in Yunnan, with 15.3% severely degraded. In arid and semi-arid pastoral region of the plateau, climate warming intensified the loss of grassland moisture, and hindered the pasture growth. The proportion of good grade pasture was falling, while that for the lower quality grass rose [ Zhang et al. , 2007 ]. The area of grassland degradation in Tibet was 11.4×106 hm2 in the 1990s, or 17.2% of the available grassland [ Qin et al. , 2010 ]. The area of wetlands declined seriously. During 1960–2010, 70% of the Ruo’ergai marsh wetland has disappeared. A sharp drop of wetland area was observed in Caohai and Napahai [ Tian et al. , 2004 ]. Lalu wetland has been degraded into reed marsh and swamp meadow [ Zhang et al. , 2005 ]. The water level of the Yangzhuoyongcuo Lake decreased significantly. The eutrophication of the Dianchi Lake was serious.
In addition, climate change has led to the increase in the number of endangered plant and animal species. Heterogeneous intrusion has intensified. Twenty-six species of birds disappeared in the plateau lakes [ Ma , 2012 ]. About 62.7% of Yunnan has been affected by eupatorium, which expanded northward at a rate of 10 km per year [ Xiao et al. , 2009 ].
During 1961–2010, the region-averaged annual apparent temperature rose significantly (at the rate of 0.19°C per decade) in Southwest China, especially in 1991–2010 the rate of increase was 0.40°C per decade. Geographically, the increase was greater in west and less in east. The apparent temperature and human comfort index rose at a different pace in each province, and most notably in the Qinghai-Tibetan Plateau. As a result of the increasing apparent temperature, it was more suitable for human to live in western Sichuan and Tibet, but was uncomfortable to live in parts of Chongqing and Guizhou. Extreme weather events increased the morbidity, mortality and risk of epidemics. The climate, ecology and the environment of the Three Gorges Reservoir are becoming more suitable for snails, which increases the risk of schistosomiasis [ Zheng et al. , 2003 ]. In eastern Sichuan and eastern Yunnan, foggy days increased significantly, resulting in increasing number of patients with respiratory diseases [ Wang et al. , 2006 ]. Eutrophication of freshwater in the lakes in most of the Yunnan-Guizhou Plateau increased year by year, which directly affected the safety of drinking water for human beings in these areas [ Wu et al. , 2010 ].
Climate in Southwest China would keep warming and wet in the 21st century. The annual mean temperature will increase at the rate of 0.23–0.60°C per decade; the annual precipitation will increase at the rate of 0.68%–1.31% per decade. In terms of seasonal variation, the greatest increase will occur in winter temperatures and summer precipitation. For the spatial distribution, temperature increase will be different between the east and west, while precipitation increase will show meridional differences. Extreme temperature and rainfall events will increase at different degrees, especially in the late of the 21st century [ Zhou et al. , 2008 ].
Compared with 1971–2000, the first day with temperature steadily above 10°C will advance 6 d in 2001–2030 under SRES A1B, B1 and A2 scenarios, in a few regions it can be 8 days earlier. In 2031–2050, the first day with temperature steadily above 10°C will be 16 d, and 18–20 d in advance for some part, which will provide favorable conditions for early sowing in the plateau and mountainous region. The last day with temperature steadily above 10°C will postpone about 4 d in 2001–2030, and 9–11 d in 2031–2050. The number of days with temperature steadily above 10°C will increase 16–20 d, and the accumulated temperature will increase 300–360°C d in 2001–2030. In 2031–2050, the number of days and the accumulated temperature will increase 31–62 d and 630–920°C d respectively, most notably in the Qinghai-Tibetan Plateau.
The area of sequential cropping and sequential cropping indices will increase; multiple cropping will advance to higher altitudes. IPCC showed that if the annual mean temperature increases 1°C, crop in midlatitudes of the Northern Hemisphere will move northward 150–200 km, and upward 150–200 m. Increase in evaporation will be more than that in precipitation, so agriculture drought in the plateau will be exacerbated [ Wang and Ma , 2009 ]. Drought frequency in central Southwest China will decrease slightly, while drought intensity and frequency in western Southwest China will increase [ Liu et al. , 2003a ]. The impact of agro-meteorological disasters, pests and diseases will intensify. The yield of wheat, rice and corn will decrease [ Xiong et al. , 2005 ]. Under PRECIS prediction in the 2070s, winter wheat in Southwest China would reduce significantly, up to 30%–60% [ Jü et al. , 2005 ]. However, due to the improvement of heat source in high altitude areas, wheat yield will increase.
With increasing in extreme weather events, such as heavy precipitation, snow and ice [ ESCNCC , 2011 ], there will be negative impacts on energy facilities. Energy supply will show large variability; contradiction between supply and demand will be exacerbated. Under A1B scenario in 2011–2040, temperature in Southwest China will increase 1.3°C and 1.0°C in winter and summer respectively. With the increase of hot days, the frequency and intensity of heat waves will increase, as a result, the energy consumption of refrigeration will increase in summer. Meanwhile, requirement of heating energy will vary periodically because the extreme cold events may become more frequent. Increasing in runoff is beneficial to increase in the overall hydropower capacity. However, increasing of droughts will lead to hydroelectric power decrease recurrently.
Climate change will weaken the difference of phenology with latitudes. The phenology in spring will generally advance, and defoliation will delay in autumn [ Xu et al. , 2004 ]. The habitat of panda will move northwestward before 2050. The distribution range of Yunnan golden monkey will be much narrower, but the new appropriate region and total appropriate region will expand [ Wu and Lü , 2009 ]. In the Lancangjiang River, some of the fish more sensitive to climate change will be extinct [ Kang and He , 2007 ]. Under same rainfall, if temperature increases 0.44°C in 10 years with no change in precipitation, biomass in alpine meadows and alpine grassland will reduce 2.7% and 2.4%, respectively. If precipitation increases 8 mm at the same time, the biomass will decrease slightly. If temperature increases 2.2°C with no change in rainfall, biomass in alpine meadows and alpine grassland will decrease by 6.5% and 4.6%, respectively. If precipitation increases 12 mm at the same time, biomass in alpine meadows will increase slightly, and biomass in alpine grassland will increase by 5.2% [ Wang et al. , 2007 ].
Climate change will also lead to some changes (even the disappearance of) in tourism landscape. In 2050, melting water in Hailuogou scenic area will turn into decreasing from increasing. The snow line of Yulong Snow Mountain will rise 166 m. Forest fires will do serious damages to the forest landscape, and even lead to its disappearance [ Meng and Wang , 2007 ].
Without considering humidity, the apparent temperature under different SRES scenarios shows a continuing upward trend when wind speed is constant. The apparent temperature under A2, A1B and B1 scenarios will increase 2.2°C, 2.4°C and 1.8°C respectively during 2041–2070, and will increase 4.0°C, 3.6°C and 2.4°C after 2070 respectively [ Shi et al. , 2012 ]. The apparent temperature will increase gradually from northwest to southeast in Southwest China in the 21st century. Abnormal low temperature will increase the suffering possibility of frostbite, snow blindness, and myocardial infarction [ Jia et al. , 2008 ]. Climate warming will also lead to the spread and recurrence of infectious diseases, and affect the distribution and incidence of diseases. If temperature of Yunnan and Guizhou rises 1.7–2.0°C in 2050, the malaria epidemic will extend northward and to high altitude [ Zhai et al. , 2009 ]. Fresh water deterioration and floods will cause spread of water-borne diseases [ Zheng et al. , 2003 ]. In addition, if the ultraviolet radiation in Yunnan and Tibet enhances, non-melanoma skin cancer will take place more often [ Zhu and Yu, 2005 ; Liu et al ., 2003b ; Zeng and Wu, 2003 ]. With significant increasing of foggy days in eastern Sichuan and eastern Yunnan, patients with respiratory disease will increase significantly [ Wang et al. , 2006 ].
Establishment of reasonable measures plays a very important role in mitigating the negative effects of climate change and promoting sustainable development in Southwest China. The IPCC Fourth Assessment Report shows that if the existing mitigation potential can be realized before 2030, the growth of global greenhouse gas emissions can be partially offset or even kept under the current levels [ Pan et al. , 2007 ]. The adaptation measures for various fields in Southwest China are suggested as follows.
Adjust the layout and collocation of varieties; optimize cropping system and planting mode . Based on the characteristics of the local environment, specialty agriculture should be developed. Because the plant boundary would move to higher altitude areas, proportion of medium and late varieties should be expanded in high altitudes.
Strengthen reduction of meteorological disasters and pests; improve the capability of resisting agricultural disasters . Studies on monitoring and early warning systems for agro-meteorological disasters and agricultural pests should be carried out as a priority.
Develop renewable clean energy vigorously . Observation network for wind energy and solar energy resources should be set up. Climatic zoning on wind energy and solar energy resources should be established. And the development of complementary energy should be carried out to reduce the dependence on fossil energy.
Establish energy security meteorological service system to cope with extreme weather events . Revise and complete standards for energy facilities to enhance their resistance to extreme climate events and disasters. Establish monitoring and forecasting platform of meteorological disasters that could have significant impacts on energy production, storage facilities, and energy supply.
Reinforce the protection of endangered animals and plants; increase the number of endangered species . Establish information database and gene bank of biological resources in Southwest China. Control alien heterogeneous species.
Restore the degraded ecosystems; improve the flora and fauna habitats conditions . Expand forest area and improve degraded pastures. Enhance researches on mechanism of ecosystem degradation and prevention measures on forest, grass land and wetland.
Protect tourism resources; develop new tourist attractions . Develop climate demonstration and environmental impact assessment of new tourist attractions.
Strengthen researches on the impact of climate change on human health . Carry out researches of the climate change impacts on snail and schistosomiasis in the Three Gorges Reservoir area. Study the mechanism and effect of ultraviolet radiation on sunburn, cataracts and skin cancer in plateau region. Carry out researches on the possible effect of extreme weather on cardiovascular, respiratory and digestive diseases.
Establish meteorological monitoring and prediction system for human health . Cooperation between health departments and meteorological departments should be strengthened in establishment of meteorological monitoring and forecasting systems to serve the needs of public health.
Improve meteorological responsiveness to health emergencies . Develop risk assessment of climate change on human health. Determine the public health needs for prevention of seasonal and regional outbreaks of diseases.
(1) Climate changes have had great impacts on agriculture in Southwest China. The first day with temperature steadily above 0°C and 10°C has a rate of 2 d per decade in advance. The last day with temperature steadily above 0°C and 10°C has postponed at a rate of 1 d per decade. The number of days with temperature steadily above 0°C and 10°C and the accumulated temperatures showed increasing trends. The area of multiple cropping has increased; growth period has shortened; the climatic potential productivity has declined. Pest damage has becoming worse. In the 21st century, with the temperature increasing, the area of sequential cropping and sequential cropping indices will increase; multiple cropping will move to higher altitudes. The impacts of agro-meteorological disasters, pests and diseases will intensify.
(2) During 1961–2009, heating energy consumption in Southwest China first showed increasing trend and then decreased. However, cooling energy consumption during the same period decreased at first and then increased, with a decreasing rate of 38.9°C per decade in 1986–2010. The uncertainty of renewable energy has increased. In the future, with increasing in extreme weather events, variability in energy supply will increase, and the imbalance between energy supply and demand will be exacerbated.
(3) In addition, climate change increased the loss of forest. The area of meadow and wetlands has degraded; heterogeneous invasion has intensified; endangered animal and plant species has increased; tourism landscape has been damaged. During 1961–2010, annual apparent temperature has risen significantly at a rate of 0.19°C per decade in Southwest China. The risk of human health has increased. In the future, phenology will keep on changing; the habitat will go on worsening. Biological population will move northward and to higher altitudes. Some species will be at risk of extinction. The negative effects on human health will increase.
In conclusion, the difference of climate change in different local areas in Southwest China will be significant. Strengthening researches on local impacts and adaptation to climate change, expanding assessment field sand developing reasonable adaptation strategies will play an important role inreducing the negative effects of climate change, and in improving ability of disaster prevention and mitigation.
This study was supported by the fund for Special Climate Change in 2010 from China Meteorological Administration (No. CCFS-2010), and by a grant from the National Natural Science Foundation of China (No. 41275097). The authors thank National Climate Center, China Meteorological Administration and Southwestern Regional Center for Climate Change for providing the meteorological data for this study. The authors also thank each provincial climate center, Chengdu Institute of Plateau Meteorology, and the editors of Southwestern Regional Climate Change Assessment Report . We are very grateful to the reviewers for their constructive comments and thoughtful suggestions.
Received: 8 July 2013