China is the world's most populous country and a major emitter of greenhouse gases. Consequently, much research has focused on China's influence on climate change but somewhat less has been written about the impact of climate change on China. China experienced explosive economic growth in recent decades, but with only 7% of the world's arable land available to feed 22% of the world's population, China's economy may be vulnerable to climate change itself. We find, however, that notwithstanding the clear warming that has occurred in China in recent decades, current understanding does not allow a clear assessment of the impact of anthropogenic climate change on China's water resources and agriculture and therefore China's ability to feed its people. To reach a more definitive conclusion, future work must improve regional climate simulations-especially of precipitation-and develop a better understanding of the managed and unmanaged responses of crops to changes in climate, diseases, pests and atmospheric constituents.

http://re.indiaenvironmentportal.org.in/files/The%20impacts%20of%20climate%20change%20on%20water.pdf

The impacts of climate change on water resources and agriculture in China

million km 2 of cropland (12% of the Earth’s ice-free land surface) and 28.0 (90% confidence range of 23.6–30.0) million km 2 of pasture (22%) in the year 2000.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2007GB002952

Farming the planet: 1. Geographic distribution of global agricultural lands in the year 2000

A copy of Guangbo jiemu bao [Broadcast Program Report] was being passed from hand to hand among a group of young people eager to be the first to read the article introducing the program "What Is Revolutionary Love?" It said: "… Young friends, you are certainly very concerned about this problem'. So, we would like you to meet the young women workers Meng Xiaoyu and Meng Yamei and the older cadre Miss Feng. They are the three leading characters in the short story ‘The Place of Love.’ Through the description of the love lives of these three, the story induces us to think deeply about two questions that merit further examination.

This is How the Discussion Started

Urban heat island (UHI) is one major anthropogenic modification to the Earth system that transcends its physical boundary. Using MODIS data from 2003 to 2012, we showed that the UHI effect decayed exponentially toward rural areas for majority of the 32 Chinese cities. We found an obvious urban/rural temperature “cliff”, and estimated that the footprint of UHI effect (FP, including urban area) was 2.3 and 3.9 times of urban size for the day and night, respectively, with large spatiotemporal heterogeneities. We further revealed that ignoring the FP may underestimate the UHI intensity in most cases and even alter the direction of UHI estimates for few cities. Our results provide new insights to the characteristics of UHI effect and emphasize the necessity of considering city- and time-specific FP when assessing the urbanization effects on local climate.

/pdf/the-footprint-of-urban-heat-island-effect-in-china-20czw9nj97.pdf

The footprint of urban heat island effect in China

Coastal populations and wetlands have been intertwined for centuries, whereby humans both influence and depend on the extensive ecosystem services that wetlands provide. Although coastal wetlands have long been considered vulnerable to sea-level rise, recent work has identified fascinating feedbacks between plant growth and geomorphology that allow wetlands to actively resist the deleterious effects of sea-level rise. Humans alter the strength of these feedbacks by changing the climate, nutrient inputs, sediment delivery and subsidence rates. Whether wetlands continue to survive sea-level rise depends largely on how human impacts interact with rapid sea-level rise, and socio-economic factors that influence transgression into adjacent uplands.

Tidal wetland stability in the face of human impacts and sea-level rise

Spatial and temporal patterns of China's cropland during 1990¿2000: An analysis based on Landsat TM data

Considerable efforts have been made to assess the contribution of forest and grassland ecosystems to the global carbon budget, while less attention has been paid to agriculture. Net primary production (NPP) of Chinese croplands and driving factors are seldom taken into account in the regional carbon budget. We studied crop NPP by analyzing the documented crop yields from 1950 to 1999 on a provincial scale. Total NPP, including estimates of the aboveground and belowground components, was calculated from harvested yield data by (1) conversion from economic yield of the crop to aboveground mass using the ratio of aboveground residue production to the economic yield, (2) estimation of belowground mass as a function of aboveground mass, and (3) conversion from total dry mass to carbon mass. This approach was applied to 13 crops, representing 86.8% of the total harvested acreage of crops in China. Our results indicated that NPP in Chinese croplands increased markedly during this period. Averaging for each decade, the amount of NPP was 146 +/- 32, 159 +/- 34, 260 +/- 55, 394 +/- 85, and 513 +/- 111 Tg C/yr (mean +/- SD) in the 1950s, 1960s, 1970s, 1980s, and 1990s, respectively. This increase may be attributed to synthetic fertilizer application. A further investigation indicated that the climate parameters of temperature and precipitation determined the spatial variability in NPP. Spatiotemporal variability in NPP can be well described by the consumption of synthetic fertilizer and by climate parameters. In addition, the total amount of residue C and root C retained by the soils was estimated to be 618 Tg, with a range from 300 to 1040 Tg over the 50 years.

Net primary production of chinese croplands from 1950 to 1999

[1] Several models have been developed over the past decade to estimate CH4 emission from rice paddies. However, few models have been validated against field measurements with various parameters of soil, climate and agricultural practice. Thus reliability of the model's performance remains questionable particularly when extrapolating the model from site microscale to regional scale. In this paper, modification to the original model focuses on the effect of water regime on CH4 production/emission and the CH4 transport via bubbles. The modified model, named as CH4MOD, was then validated against a total of 94 field observations. These observations covered main rice cultivation regions from northern (Beijing, 40°30′N, 116°25′E) to southern China (Guangzhou, 23°08′N, 113°20′E), and from eastern (Hangzhou, 30°19′N, 120°12′E) to southwestern (Tuzu, 29°40′N, 103°50′E) China. Both single rice and double rice cultivations are distributed in these regions with different irrigation patterns and various types of organic matter incorporation. The observed seasonal amount of CH4 emission ranged from 3.1 to 761.7 kg C ha−1 with an average of 199.4 ± 187.3 kg C ha−1. In consonance with the observations, model simulations resulted in an average value of 224.6 ± 187.0 kg C ha−1, ranging from 13.9 to 824.3 kg C ha−1. Comparison between the computed and the observed seasonal CH4 emission yielded a correlation coefficient r2 of 0.84 with a slope of 0.92 and an intercept of 41.1 (n = 94, p < 0.001). It was concluded that the CH4MOD can reasonably simulate CH4 emissions from irrigated rice fields with a minimal number of inputs and parameters.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2003JD004401

Modeling methane emission from rice paddies with various agricultural practices

A synthesis of change in deep soil organic carbon stores with afforestation of agricultural soils

Cropland soil organic carbon (SOC) is undergoing substantial alterations due to both environmental and anthropogenic changes. Although numerous case studies have been conducted, there remains a lack of quantification of the consequences of such environmental and anthropogenic changes on the SOC sequestration across global agricultural systems. Here, we conducted a global meta-analysis of SOC changes under different fertilizer managements, namely unbalanced application of chemical fertilizers (UCF), balanced application of chemical fertilizers (CF), chemical fertilizers with straw application (CFS), and chemical fertilizers with manure application (CFM). We show that topsoil organic carbon (C) increased by 0.9 (0.7–1.0, 95% confidence interval (CI)) g kg−1 (10.0%, relative change, hereafter the same), 1.7 (1.2–2.3) g kg−1 (15.4%), 2.0 (1.9–2.2) g kg−1 (19.5%) and 3.5 (3.2–3.8) g kg−1 (36.2%) under UCF, CF, CFS and CFM, respectively. The C sequestration durations were estimated as 28–73 years under CFS and 26–117 years under CFM but with high variability across climatic regions. At least 2.0 Mg ha−1 yr−1 C input is needed to maintain the SOC in ~85% cases. We highlight a great C sequestration potential of applying CF, and adopting CFS and CFM is highly important for either improving or maintaining current SOC stocks across all agro–ecosystems.

/pdf/changes-in-soil-organic-carbon-in-croplands-subjected-to-hkvk36zhvy.pdf

Wen Zhang

Papers

Spatial and temporal patterns of China's cropland during 1990¿2000: An analysis based on Landsat TM data

Net primary production of chinese croplands from 1950 to 1999

Modeling methane emission from rice paddies with various agricultural practices

A synthesis of change in deep soil organic carbon stores with afforestation of agricultural soils

Changes in soil organic carbon in croplands subjected to fertilizer management: a global meta-analysis.