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Research Study: “The Impacts of Climate Change on Water Resources and Agriculture in China,” Piao, Nature Magazine , 2010

Piao et al.’s 2010 paper, ‘Impacts of Climate Change on Water Resources and Agriculture in China’, published in Nature Magazine, qualifies as the most important research conducted in the past five years in China due to its unprecedented headway in investigating the influence of climate change within the country. Prior to its publishing, climate research in China was scarce, apart from the markedly clear observations of nation-wide warming. This study was the first to collect and analyze multidisciplinary data on climatic factors, hydrology, and agriculture. It attempted to synthesize observed data over a period of 50 years, with the objective of producing a cohesive understanding, through trends and models, of the spatial and temporal impacts in regional water cycles and vegetation response, including agriculture production. This research highlighted geographic areas most vulnerable to change, while identifying sources of uncertainty that required further in-depth study.

Consequently, Piao et al.’s paper has been followed by a series of detailed, regional research studies into climate change impacts. These studies all contribute to the ability of China to develop climate change mitigation strategies. China’s mitigation strategies seek to advance effective water use and storage, as well as innovative means of food production. Indeed, both agriculture and water resources are considered highly susceptible to climatic conditions. They reflect China’s vulnerable future in facing complex challenges that ensure continued food security and welfare for its growing population.

The four main findings of this study are:

More than 80% of glaciers in western China are currently in a state of retreat, with warming temperatures causing significant changes in annual glacier mass balance, and critically affecting river runoff and agricultural production in China and south Asian countries (60% of glacier runoff flows out of China). Hydrological models suggest that river runoff in the Yellow river is expected to increase by 11% in the short term, and later decrease due to rising temperatures causing increasing evapotranspiration. Coupled with increasing human water extraction, and high uncertainties from IPCC climate models, water supply remains a high risk for China, particularly in addressing differences between the arid northern and wet southern regions.
The three main crops in China are rice, wheat and maize, together accounting for 54% of the total sown area and 89% of the grain yield in 2007. Warming is believed to be harmful to rain-fed crops but beneficial to irrigated agriculture, as shown in rice and wheat yields; rice yields in the northeast have increased by 4.5 – 14.6% per °C in response to night-time warming during the period 1951 to 2002; whereas, warmer day-time temperatures have negatively affected wheat yields by about 6 – 20% per °C. Nonetheless, crop models in China suggest a 20% decrease in overall yields due to climate change susceptibility.
Regional climate warming has allowed an increase in the geographic expanse of pests and disease, causing an estimated increase of 245Mha in cropland exposure to disease and pest infestations since 1970. The annual harvest loss due to pests and diseases has increased from ~6Mt in the early 1970s to ~13Mt in the mid-2000s.
A non-significant increasing trend in drought affected cropland areas has been observed since 1971. However the area affected by flooding events have increased by over 88% since the 1970s. Nonetheless, both drought and flooding changes remain within the bounds of year-to-year harvest variability.

Legacy and uncertainties:

China’s long emphasis on enlarging regional water storage and strengthening water resource management infrastructure has now become more detailed and comprehensive.
Regional climate simulations were found to have a high uncertainty in this study, particularly for precipitation models, and improvements continue to be met through scientific research.
The magnitude of CO2 fertilization effect on crop yields is still being debated and remains a variable of high uncertainty. Certain crop models suggest that cereal yields will benefit from global climate change, with elevated levels of CO2 acting as fertilizer, however, others suggest that the benefits will be outweighed by other negative factors such as the spread of pests.
Increasing surface ozone concentration, causing crop plant damage in cases of high exposure, could also negate the benefits of CO2 fertilization, and levels must be monitored.

The study was conducted by a series of scientists from different research labs at Chinese universities based in Beijing and was intended to inform both the scientific community, as well as China’s climate policy. This paper has no direct implications for policies related to the Paris Agreement; however, it was an important precursor for climate research in China and its legacy performs an important role in guiding China’s Five Year Plans, as well as policies for national emission reduction. In particular, China’s ‘green wall policy’ and the ‘grain for green program’ are both reforestation projects that have been stressed in China’s national climate change program to protect existing forest carbon stock and enhance carbon sequestration.

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