Liao Xiawei, Liu Ao, Chai Li
Bay Area International Business School, Beijing Normal University, Zhuhai 519087, China.
College of Economics and Management, China Agricultural University, Beijing 100083, China.
iScience. 2023 Aug 30;26(10):107794. doi: 10.1016/j.isci.2023.107794. eCollection 2023 Oct 20.
Food systems are among the leading causes for transgression of planetary boundaries globally, which define the safe operating space for humanity. We quantify unsustainable environmental impacts of food systems, indicated by the transgression of national-scale planetary boundaries (i.e., the safe operating space for food production in each country), from both production and consumption perspectives of 189 countries/regions around the world. A multi-regional input-output model is used to map the global transfers of the national-scale transgression of planetary boundaries, including freshwater use, land change, and biogeochemical flows (nitrogen and phosphorus). Our results show that China is a major global unsustainable water and nitrogen exporter and an unstable land and phosphorus importer. This means that water and nitrogen uses in China are used to support food demands in other countries, and food consumption in China requires unsustainable land and phosphorus uses elsewhere. In contrast, the US is a major exporter of unsustainable water, land, and nitrogen uses but only an importer of unsustainable phosphorus for food consumption. Globally, compared to a counterfactual scenario where there is no food trade among any countries, food trade saves massive transgressions of planetary boundaries (270 km of water, 18 million tons of nitrogen, 7 million tons of phosphorus, and 5,431 million km of land). Alleviation of national-scale planetary boundary transgression has been achieved primarily in the US, China, Saudi Arabia, etc., while aggravation was incurred in Pakistan, Australia, Argentina, and so forth.
粮食系统是全球范围内突破地球边界的主要原因之一，地球边界界定了人类的安全运行空间。我们从全球189个国家/地区的生产和消费角度，对粮食系统不可持续的环境影响进行了量化，这种影响以国家层面地球边界的突破（即每个国家粮食生产的安全运行空间）来表示。采用多区域投入产出模型来描绘国家层面地球边界突破的全球转移情况，包括淡水使用、土地变化以及生物地球化学流动（氮和磷）。我们的结果表明，中国是全球不可持续的水和氮的主要出口国，以及不稳定的土地和磷的进口国。这意味着中国的水和氮的使用被用于满足其他国家的粮食需求，而中国的粮食消费需要在其他地方不可持续地使用土地和磷。相比之下，美国是不可持续的水、土地和氮使用的主要出口国，但只是不可持续的粮食消费用磷的进口国。在全球范围内，与各国之间不存在粮食贸易的反事实情景相比，粮食贸易减少了大量地球边界的突破（270千米水、1800万吨氮、700万吨磷和54.31亿平方千米土地）。国家层面地球边界突破的缓解主要在美国、中国、沙特阿拉伯等国实现，而在巴基斯坦、澳大利亚、阿根廷等国则出现了加剧。
