Sand mining speed exceeds regeneration.
The commentary quoted a research result published in 20 17, and pointed out that the current mining speed of sand and gravel has exceeded its natural regeneration speed.
It is worth mentioning that the sand discussed in this paper refers to angular sand that can be put into industrial use, most of which comes from rivers (less than 1% of the earth's area). The sand in the desert is too smooth to use.
According to an article published in the journal Science on 20 17, at present, sand and gravel are the most exploited raw materials, even surpassing fossil fuels. The cited United Nations data report "Global Material Flow and Resource Productivity" shows that sand and gravel are the most important nonmetallic materials in mining. In 20 10 year, the proportion of sand and gravel in all non-metallic materials reached 3 1. 1% and 40.8% respectively.
The decrease of sediment discharge of major rivers in China may lead to the shortage of sand supply.
In recent years, the sediment discharge of the Yangtze River has been greatly reduced. 20 16 According to the People's Changjiang Daily, with the sharp drop in the amount of sand coming from the Yangtze River, the contradiction between supply and demand of sand and gravel has become increasingly apparent. According to the characteristics of river evolution and the decrease of sediment transport, the government has adjusted the sand and gravel mining in the middle and lower reaches of the Yangtze River.
This is not an individual phenomenon of the Yangtze River.
China River Sediment Bulletin, published annually by the Ministry of Water Resources, provides the annual sediment discharge data of China 12 major rivers. This paper (www.thepaper.cn) collates the annual sediment discharge of major rivers from 2005 to 20 17, and draws the trend line accordingly. The data show that the sediment discharge of the Yellow River, Yangtze River, Pearl River, Tarim River, Songhua River, Minjiang River and Huaihe River shows a downward trend.
The data is missing, and no one knows how much sand there is.
"No one knows how much sand there is now and how much sand is being mined," wrote a commentary in Nature magazine.
Academic circles have been lacking high-quality data related to sand, which makes it difficult for people to consume and dig sand at a reasonable speed with the help of research and policies. Through the sand trade data provided by the United Nations Comtrade database, we can get a glimpse of the embarrassment of missing data.
First of all, the database only provides one category and two subcategories of sand import and export information. There is no distinction between sand sources and active sources with natural supplements, such as rivers and deltas; Or passive sources that are not supplemented, such as geological sediments. Second, some international sand trade has not been recorded. Some studies have compared the import and export data of sand in some countries in the database. A United Nations report compared the amount of sand imported from Indonesia with the amount of sand exported from Indonesia to Singapore, and found that there was little overlap between them. The report believes that the illegal trade in sand is an important reason for the data difference.