The Impact of Climate Change on Rice Spatial Distribution in the Northeast China Plain

Pengqin Tang, Peng Yang, Zhongxin Chen, Zhenhuan Liu

The Institute of Agricultural Resource and Regional Planning

Chinese Academy of Agricultural Sciences Beijing, China

The Key Laboratory of Agro-Informatics Ministry of Agriculture

Beijing, China tpqin@hotmail.com

Abstract—Rice is one of the staple grains in China and has a strong relationship with annual accumulation temperature which has a potential effect on rice planting area. This study utilizes a model called SPAM (Spatial Allocation Model) to detect the rice spatial distribution change during the 1981-2010 under the climate change in the Northeast China Plain. The result shows that climate change plays an important role in the rice spatial distribution. The tendency of rice spatial distribution has an obvious feature which has extended to north dramatically in the Northeast China Plain. Annual accumulation temperature is the main factor to rice planting in the higher latitude region.

Keywords-Climate change, Rice, Spatial distribution, the Northeast China Plain

I. INTRODUCTION Climate change has gained significant international

attention over the past decade due to concerns of deleterious long-term impacts on agriculture, water supply, human welfare, and regional political stability. During the nearest 100 years, global mean temperatures have risen approximately 0.74℃ (IPCC, 2007) and the higher latitude warming is heavier than lower latitude. The warming trend is projected to accelerate in the future. Meanwhile, there are some evidences have proved that climate change has impacted on natural system and agriculture is very sensitive to climate change. The potential impacts of climate change will make agriculture more instability. Under the circumstance of the world’s population growth continuously, food security is needed to ensure for about 9 billion people in the middle of this century. The world’s agriculture is meeting the great challenge.

There have many studies which focus on the impact of climate change for agriculture, including crop phonology, yield and the cropping system and so on. In some agriculture areas, climate change may have a positive influence, but in other areas, the result may be adverse. The impact on climate change is debated pros and cons for the agriculture. For example, gradual temperature changes from 1982 to 1998 have caused a measurable impact on the yields of corn and soybeans in the United States. Also, in the Philippines, rice grain yield was found to decline by 10% for each 1℃increase in growing-season minimum temperature in the dry season (January–April) from 1992 to 2003.

Rice is the most important food for Asians, Africans and Latin Americans and it serves as a basic staple for more than

half of the world’s population and feeds more people than any other crop. China has the second largest area of rice planting and the highest rice production, contributing ∼19% and ∼29% of the world rice planting area and rice production (FAO, 2010), respectively, as well as more than 40% of the national cereals yields of China (National Bureau of Statistics of China, 2009). In the recent years, rice planting in the Northeast China Plain has increased gradually, while the region lies in higher temperature and has a lower temperature than southern china where there is the main producing area of rice. Climate change is recognized the main factor to affect rice production. So this study mainly focuses on the relationship between the climate change and rice expansion in the Northeast China Plain and uses a model to simulate the change of rice spatial distribution during the recent 30 years. It is beneficial to better understanding the impact of climate change on rice planting and take some adaption strategies to ensure food security.

II. MATERIALS AND METHOD

A. Study area This study area is located in Northeast China, including

Heilongjiang, Jilin and Liaoning provinces, which covers 3.5 ×105 km2 and contains a total area of 1.82×105 km2 of farmland. Most of this region is located in 40°north with a humid and semi-humid climate pattern and has abundant agricultural resources. The annual precipitation reaches 400–1000mm, 80% falls in the period of May – September. Meanwhile, there has the richer black soil comparing with other soils which will produce more crops.

The study area is one of the main producing regions of grain in china and mainly contains three crops: rice, soybean and maize. During the period of 1981-2010, the area of rice increased dramatically from 6×106 ha to 2.85×107 ha, along with the production of rice in 2010 has seven times as much as the production of 1981.

B. Method The spatial allocation model (SPAM) takes crop statistics

data, land cover, crop distribution, irrigation data and crop suitability and so on as input data, and utilizes a cross-entropy approach to analyze these data and obtains the final estimation of crop distribution. The model can achieve crop distribution

The study sponsored by the Major Project of Chinese National Programs for Fundamental Research and Development (Grant No. 2010CB951502) and the Open Project of the Key Laboratory of Agricultural Information Technology, Ministry of Agriculture (Grant No. 201210)

from census to grid and has applied in Africa, Asia, and America and so on and made a better result. Comparing with previous studies, SPAM has some advantages for the large area crop spatial distribution simulation. Firstly, we obtain the agricultural production statistics data which may typically be national or sub-national administrative regions such as states, districts, or counties. Secondly, we reinterpret the already classified land cover imagery which will provide valuable information on where and how much agricultural land is at the pixel level and crop-specific suitability will be judged from local climate and soil conditions. Lastly, the SPAM utilizes all these input data, and applies a cross-entropy approach to obtain the final estimation of crop distribution.

III. RESULT

A. Climate change has occurred significantly in the Northeast China Plain Meteorological site record data has been collected to

analyze the climate change of the Northeast China Plain during 1981-2010. We get rid of the irrational data and utilized the spatial analysis tool to interpolate these data in the whole area. According to the interpolation result, the whole area accumulation temperature above 10℃ was been calculated. Meanwhile, four typical years was been choose to identify climate change of the different age, including 1981, 1990, 2000, 2010. Fig.1 shows the accumulation temperature above 10℃ of the four typical years in the Northeast China Plain. The result reveals the annual accumulated temperature above 10℃ is increased significantly. In 1980s, the lowest and the highest of the annual accumulated temperature above 10℃ are 1673℃ and 3964 ℃ separately. The corresponding values in 2000s went up 1730 ℃ and 4159℃. The climate warming is very significant.

We make a difference of the average of five years annual accumulation temperature above 10℃ between 1980-1984 and 2006-2010 to eliminate the error of specific year value. Fig.2 is the result manifests the trend that the average accumulation temperature above 10℃ of the north of the Northeast China Plain become warmer and the south of that has an adverse trend which is colder than earlier. The area of warming is distinctly bigger than the colder.

B. The correlation analysis of rice area and climate change Rice is the staple grain for china and very sensitive to

annual accumulation temperature. The Northeast China Plain lies in higher latitude region and has the lower temperature which is not benefit to rice planting. In the earlier, rice area accounted for a small proportion of the whole grain area. But, with the climate change, rice planting is more popular in the recent years in the Northeast China Plain. Climate warming is an important factor and has a positive effect on rice spatial distribution expansion. We gathered rice area of the study area during the 30 years and analyze the correlation between the rice area and the annual accumulation temperature above 10℃. Fig.3 shows the result between the rice area and annual

Fig.1 the annual accumulation temperature above 10℃

of four typical years

Fig.2 the difference of average annual accumulation temperature between

1980-1984 and 2006-2010 temperature above 10℃. From the agriculture statistical data, the rice area reaches a peak in 1994 about 5.2 × 106ha corresponding to a higher accumulation temperature. Although the graph shows an obvious trend that accumulation temperature and rice area increased simultaneously, the slope of the rice area is higher than accumulation temperature. This also indicates there has a correlation between rice planting area and climate change, and it has also been affected by other factors.

Fig.3 the correlation of rice area and the average accumulation

temperature above 10℃

C. Rice spatial distribution change during the recent 30 years Using the county agricultural statistics data which contains

rice yield, area and production and associating with the other auxiliary data, the SPAM calculates the rice spatial distribution of the four typical years in the recent 30 years. Fig.4 shows the rice spatial distribution change in the 1981, 1990, 2000 and 2010. The rice spatial distribution of the four years has an apparent trend that rice area rose sharply and the rice spatial distribution moved to north which is very similar with the truth. This proves that the crop spatial distribution simulation result of SPAM is reliable. Fig.5 is the rice spatial distribution comparison between 2010 and 1981; the red stands for rice area increased and the green is reduced. It is easy to find that rice planting area increased sharply in the whole area, especially for the north of the Northeast China Plain. According to fig.2, the region of climate change occurred significantly lies in the north of the Northeast China Plain which is better fit with the rice spatial distribution change. It is a strong proof that climate change will influence the rice spatial distribution.

Fig.4 the rice spatial distribution simulation result of four typical years in

the Northeast China Plain

Fig.5 the rice spatial distribution comparison between 2010 and 1981

IV. DISCUSSION

A. Rice spatial distribution in the Northeast China Plain has been influenced by the climate change, but it isn’t the only factor. As one of the staple grains, rice is vital not only for china,

but for the world to ensure the food security. Climate change has an important influence on rice spatial distribution in the higher latitude which has a lower temperature is not benefit to rice planting. With the climate warming, rice planting is more popular in the higher latitude region, such as the Northeast China Plain. In this study, we discussed the impact of climate change on rice spatial distribution and make a conclusion that rice planting boundary has expanded to north significantly in the Northeast China Plain during the recent 30 years under the climate warming. To validate the simulation result of the SPAM, we made use of the rice statistical map of 2000 in the Northeast China Plain which was made of high resolution remote sensing images and can reflect the truth of rice spatial distribution. Fig.6 is the comparison of the SPAM result and the rice statistical map. The two images have a better consistency.

Furthermore, this study has noticed that rice spatial distribution change is not only affected by the climate change, but other factors will also accelerate this change such as food policy, rice price and breeding technology and so on. But in this study, we don’t considerate the other factors except the climate change because the temperature is the main factor for rice planting. Some published papers have proved this point. Compared with the climate change, socio-economic factors can’t generally determine the rice spatial distribution in the large area. In particularly, there has some small places where it has sufficient agricultural natural gift, food price or food policy may be dominated the rice spatial distribution. This study is focus on the Northeast China Plain which is about 1.82×105

km2 cropland and climate change will be the main factor for rice planting. In the further study, we will pick up some factors for rice planting and use statistics method to determine the main factor and minor factor to improve the study accuracy.

Fig.6 the comparison of the SPAM result and the rice statistical map in 2000

B. Data biases and errores may lead to inaccuracy This study utilized some kinds of data which includes land

use data, irrigation data, crop distribution and agricultural statistical data. These data are come from different studies, institutes or organizations. For example, the agricultural statistical data of the Northeast China Plain come from National Bureau of Statistics of China and the irrigation data origin from University of Kassel, Germany. The different of data resource may lead to discrepancy and biases and affect the model simulation precision. Although the SPAM model has coped with these questions partly and integrated these data resources into the model, these data still exist some errors inevitably which may be the important reasons to improve model simulation accuracy. More important, the spatial resolution of these data is 10 ㎞×10 ㎞, which is the potential reason lead to the result is coarse and can’t provide more information. Additionally, agricultural statistical data as an important input data may take some uncertainty because of the accuracy of the earlier data and deficiency of statistical data of some counties. For the county unit, agricultural statistical data has sometimes a lower confidence. This is why the model recommends higher hierarchy statistical data such as national or provincial. This study area contains only three province, Heilongjiang, Jilin and Liaoning provinces and each province has large area cropland. We choose the county agricultural statistical data as the statistical unit and may take some data errors into the model which cause the result inaccuracy

V. CONCLUSION This study analyzes the climate change occurred in the

Northeast China Plain, uses a spatial allocation model to simulate rice spatial distribution during the 1981-2010 and obtains a better simulation result. The correlation of climate change and rice planting is also discussed. The result shows there has an obvious warming trend in the Northeast China Plain. Rice planting boundary has moved to north and rice area increased apparently in the Northeast China Plain. Climate change plays an important role in rice planting and spatial distribution expansion.

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