A novel approach to transforming desert into farmland has been the subject of heated debate between scientists over the past week.
In January, Yi Zhijian, a professor of mechanics from Chongqing Jiaotong University published an article claiming his team has managed to turn patches of desert into soil at multiple sites across northern China, by applying a plant-based cellulosic material and spraying it with water to bind sand grains.
Yi calls this process “desert soilisation”. He also claims that sowing and planting can start immediately after the process, and that the yields of sorghum and radish were high on several of his demonstration plots in the Ulan Buh desert, Inner Mongolia. This technology, Yi suggests, will help deserts contribute to food security and carbon sequestration.
In early April, the same journal published a rebuttal by Wu Bo, a desert ecologist from the Chinese Academy of Forestry Sciences, and Zheng Yongchun, from the Chinese Academy of Sciences. They argue that cellulose has long been used in agriculture and desertification control to retain water. Although it can make sand grains more cohesive, they say this does not change the characteristics of sand, nor bring nutrients to plants. The sodium-based material used by Yi’s experiments could also result in alkali pollution.
Worse still, Wu and Zheng say, growing crops in deserts massively increases the evaporation of local surface and groundwater, and such practices will ultimately rely on irrigation. They argue that the limited evidence of crop success in Yi’s plots benefitted from the shallow groundwater table in the area, and point out that the project itself is equipped with irrigation ponds.
There was an additional exchange between the two sides this week. The rebutters argue that all evidence from Yi’s team are photos rather than basic data on groundwater impact, nor is there consideration for the cost of the cellulosic material they use, which has implications for the economic viability of such an approach. They point out that the ultimate constraint of vegetation in deserts is not soil, but water, and stress natural deserts are important ecosystems not to be eliminated.
When Yi’s approach was first reported in 2017, it caused controversy immediately. However, in the same year he was recognised by the publicity department of the CCP as one of 10 model scientific researchers. Yi told a journalist at the time that the average cost of his approach in Ulan Buh is 2,000 yuan per mu (about US$300 per 1/15 of a hectare), and that many interested companies withheld their investment after learning about the high cost.
Read our report from 2017 on yaks being employed to fight desertification in the Zoigê grasslands of northwestern China.