首页 > 热闻趣事 > 地球变绿,中国做了多大贡献?卫星遥感有图有真相


2019-07-04 08:40:26



The earth has become greener, with China leading the way.


This conclusion has been reached from data compiled by NASA's Aqua and Terra earth observation satellites.


From 2000 to 2017, the global areas covered by greenery increased by 5%, of which, 25% of such territory lies in China. In fact, China only accounts for 6.6% of global vegetation coverage. So, how did these changes happen?


To this end, we have invited experts from the Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences who have been engaged in monitoring vegetation change for a long period of time, to explain the process with the sufficient statistical data and satellite remote sensory images.


Earlier this year, a multinational cooperative research paper led by Boston University and mainly funded by NASA was published in Nature Sustainability. The paper was entitled 'China and India Lead in Greening of the World Through The Land-Use Management', and found that during the period from 2000 to 2017, China and India dominated global land greening (increases in leaf-covered areas). More importantly, in the process of turning China greener, forests contributed 42%, greater than the 32% contribution of agricultural land and much more than India's forest contribution of 4.4%.


▲ Source: https://zhuanlan.zhihu.com/p/56452684, https://www.nature.com/articles/s41893-019-0220-7


Over the Years, What Has China Done to Protect the Earth?


China's afforestation and forest protection are crucial parts of the results achieved.


Since the 1970s, China has successively launched many large ecological projects, including six projects which are directly related to land greening: the "Three-North" Shelter Forest Program, the Natural Forest Resource Protection Project, the Project of Returning Farmland to Forest (Grass), the Shelterbelt Forestry Project of the Yangtze/Pearl River Basin, the Beijing-Tianjin Sandstorm Source Control Project and the Project of Returning Grazing Lands to Grasslands. These projects cover most of the regions of China.


Beginning in 1979, the "Three-North" Shelter Forest Program involving 13 provinces, autonomous regions and municipalities directly under the Central Government, has achieved a total construction area of 4.069 million square kilometers, accounting for 42.4% of China's total land area, with total investment adding up to more than 50 billion yuan so far.


Beginning in 1998, the Natural Forest Resource Protection Project involving 724 counties, 160 key enterprises and 14 nature reserves in 17 provinces and autonomous regions, reached cumulative investment of 48.83 billion yuan by 2004.


Having been started in 1999, the Project of Returning Farmland to Forest (Grass) involves 1,897 counties in 25 provinces and autonomous regions. It is one of the largest ever ecological project to be carried out worldwide. The central government alone has invested more than 430 billion yuan in the project.


Phase I of the Shelterbelt Forestry Project of the Yangtze/Pearl River Basin was carried out between 1989 and 2010. According to forest inventory data and the forestry statistical yearbook, a total of 63,000 square kilometers of forest were planted and 55,000 square kilometers were afforested. The Phase II covers a wider range, of which the Shelterbelt Forestry Project of the Yangtze River Basin Phase II includes 1,033 counties (cities and urban districts) in 17 provinces (municipalities directly under the Central Government) with a planned afforestation task of 69,000 square kilometers.


Having begun in 2002, the Beijing-Tianjin Sandstorm Source Control Project involves 75 counties across five provinces (autonomous region and municipalities directly under the Central Government) including Beijing, Tianjin, Hebei, Shanxi and Inner Mongolia, with a total area of 458,000 square kilometers. The initial estimated investment for Phase I is 55.8 billion yuan.


Since 2003, the Project of Returning Grazing Lands to Grasslands has covered 640,000 square kilometers in seven northern provinces and autonomous regions. The Central Government has invested 29.57 billion yuan in the project.


Data Illustrate the Reasons Behind this Green Miracle


The most effective way to understand the results of these afforestation projects in China is to observe changes in collected data. In the field of ecological environment change monitoring, the most widely used technology is that of acquiring images of the earth for continuous monitoring through remote satellite sensing.


Here are a few sets of data and images which illustrate the reasons behind this green miracle.


In the field of remote sensing applications, the "vegetation index" is widely used for evaluating vegetation coverage and vegetation growth and the "normalized difference vegetation index" (NDVI) is most widely used. In general, the higher the NDVI, the higher the vegetation coverage.


The NDVI(at the national level) in China, India and most European countries show significant increases in 2015 compared with 1982, indicating that the land of these countries has turned significantly green. However, the NDVI in the countries in North America, Australia, Africa and South America showed a decreasing trend in 2015 compared with 1982.



Another measurement indicator is net primary productivity (NPP).


NPP is the amount of photosynthetic products or organic carbon formed by plants after converting the carbon dioxide in the atmosphere through photosynthesis, and is the material basis for the survival and reproduction of other organisms in the ecosystem.


We quantifies moderate-resolution imaging spectroradiometer (MODIS) NPP from 2000 to 2014 at the country level, and the results show that the combined NPP for 53 countries represents >90% of global NPP. The top three and top 12 countries accounted for 30% and 60% of total global NPP, respectively. China accounts for about 5% of the world's total NPP, ranking 4th globally. However, it cannot be ignored that western China is mostly covered by desert or sparse vegetation, and the average NPP per unit area in China is about 300gC/㎡/y — not high in the global ranking, at a similar level compared to Canada, Australia, India and other countries.



Spatial distribution of average annual pixel scale NPP from 2000 to 2014

(Editor's Note: Pixels are the basic units that make up remote sensing)


Spatial distribution of annual total NPP at national scale


Spatial distribution of mean national NPP per unit area


Average annual country-level NPP (2000–2014) for the top 53 countries representing >90% of the total global NPP

Source: http://www.science direct.com/science/article/pii/S0048969716319507

就2000—2014年变化趋势来看,中国大面积区域NPP是在上涨的,尤其是西部区域。几个NPP大国中,中国的NPP年净增加约11Tg C,远大于NPP总量排在第一位的巴西(5Tg C/y)、第三位的美国(2Tg C/y)。

According to the trend of change from 2000 to 2014, NPP in large parts of China is rising, especially in western regions. Among several countries with high NPP, China's NPP has increased by about 11Tg C per year, far exceeding that of Brazil (~5Tg C/y) — ranking 1st in terms of total NPP — and the United States (~2Tg C/y) — ranking 3rd.


▲ (a)2000—2014年像元尺度NPP年际变化率空间分布

Pixel scale: Spatial distribution of inter-annual variation rate of NPP from 2000 to 2014


National Scale: Spatial distribution of inter-annual variation rate of NPP from 2000 to 2014

Source: https://www.sciencedirect.com/science/article/pii/S0048969716319507


For the inter-annual variation rate of NPP in China from 2000 to 2014, most areas of the "Three-North" Shelter Forest Program show an increasing trend, especially in Shaanxi Province.


▲ 2000—2014年中国像元尺度NPP年际变化率空间分布(图中墨绿色粗线为“三北”防护林工程五期界线)

Spatial distribution of the inter-annual variation rate of NPP at the pixel scale in China from 2000 to 2014 (The dark green thick line in the figure is the boundary line of Phase V of the "Three-North" Shelter Forest Program)


In addition to the statistical changes, the image is fairly self-explanatory.


The first area reviewed is the city of Yulin in Shaanxi Province.


According to the classification from the American Landsat series satellite images of 1987 and 2014, the forested land area in Yulin in 2014 was about four times higher than that of 1987, and the bare land area in 2014 was only one quarter of that of 1987. In addition, the grassland area increased by 3,000 square kilometers.



The following two satellite images show Yulin clearly. It was a large area of sand or bare land in 1984, but was covered in vegetation by 2016.


▲ 以东经108°43′14.916″,北纬37°41′0.996″为观测中心点拍摄的榆林

Yulin, taken at 108°43′14.916″E-37°41′0.996″N


Another illustration covers the city of Baoji in Shaanxi Province.


Although there was some vegetation in the vicinity of Baoji in 1984, the vegetation coverage rate was only about 40%, while 32 years later in 2016, the vegetation coverage rate exceeded 90%. According to the China Forestry Statistical Yearbook, from 2002 to 2016, Baoji introduced a total afforestation area of 4,064.9 square kilometers, including an artificial afforestation area of 2,117.06 square kilometers, an aerial afforestation area of 779.51 square kilometers and newly closed hillsides for afforestation of 1,168.33 square kilometers.


▲ 以东经107°10′50.01″,北纬34°52′04.29″为观测中心点拍摄的宝鸡附近

Vicinity of Baoji, taken at 107°10′50.01″ E-34°52′04.29″N


The next illustration is the city of Tianshui, Gansu Province.


The satellite images show that duringthe 1980s, most of the land in the area was bare. According to the China Forestry Statistical Yearbook, during the period from 2002 to 2016 alone, Tianshui benefited from afforestation of 3,427.56square kilometers, including artificial afforestation of 2,877.52 square kilometers, afforestation by aerial seeding of 29.45 square kilometers and newly closed hillsides for afforestation covering 520.59 square kilometers. Today, Tianshui is a lush city, enjoying the fame of “rich area south of the Yangtze River” in the northwest.


▲ 以东经106°10′53.97″,北纬34°53′11.03″为观测中心点拍摄的天水

Tianshui, taken at 106°10′53.97″E-34°53′11.03″ N


The most noteworthy is the green miracle — Saihanba, Hebei Province.


The two satellite images below show that the forest coverage rate of Saihanba increased significantly in 2016 compared to 1984.


▲ 以东经117°25′34.824″,北纬42°28′57.36″为观测中心点拍摄的塞罕坝

Saihanba, taken at 117°25′34.824″ E-42°28′57.36″N


This photo shows that the Saihanba area was basically desert before the founding of the People's Republic of China. After more than 50 years of unremitting efforts across three generations, the forest coverage rate of Saihanba increased from 11.4% to 80%. Now, Saihanba is a contiguous artificial forest. In December 2017, the United Nations Environment Programme announced that the builders of the Saihanba Forest Farm in China were to be awarded the "Champions of the Earth" prize in 2017 — the United Nations' highest honor for environmental protection.



Saihanba desert before the founding of the People's Republic of China in 1949.


▲ Source: https://www.diyitui.com/content-1533789034.74527271.html


Now, Saihanba is home to the largest contiguous artificial forest in China.




China is home to the largest artificial afforestation area in the world, and its forest coverage rate has reached 22%.



In tackling climate change and saving the earth, China has been moving forward with earnest.



Green hills and clearwaters are gold & silver mountains. In the future, an even greaternumber of places in China will be home to green miracles, transforming deserts to forests.

作者 / 中国科学院遥感与数字地球研究所副研究员彭代亮、研究生张赫林、研究员张兵

Author / Associate Professor Peng Dailiang, Graduate Student Zhang Helin, Professor Zhang Bing, the Institute of Remote Sensing and Digital Earth of the Chinese Academy of Sciences

编辑 / 宁静、董翎依

图片 / 网络

美编 / 高铭