The functioning of human society requires the services provided by natural ecosystems. One of the most important ecosystem services is the supply of fresh water. The spatial flows of fresh water establish the linkage between freshwater sources and human demands, and affect interregional water security. This is termed as "freshwater services flow" by some researchers. A related, more general term "ecosystem service flow" is often used to describe the transmission of a specific ecosystem service to people.  

A research assessing water-related ecosystem services is recently done in northeast China by a research team led by Professors Yu Dapao and Dai Limin from the Institute of Applied Ecology, Chinese Academy of Sciences.  

The Northeast Forest Belt (NFB) covers large land areas of northeast China. With a number of essential ecosystem functions and services, NFB is vital for the plain areas where populations are concentrated. Considering that natural ecosystems are undergoing degradation worldwide, the researchers wondered whether water security issue has become severer than ever before in northeast China.  

The research team quantified annual water yield and the water demands by agriculture, industry, livestock and residents. They developed a dynamic model algorithm to delineate the flow path (i.e., spatial flow process) of freshwater services, which was obviously different from the static model algorithm used by previous studies. They also evaluated water security status in northeast China by calculating water security indices based on both static and dynamic flow models. 

Although the freshwater resources in northeast China were overall sufficient, the researchers found a downward trend in water security status between 2005 and 2015, largely because of the changes in precipitation and agricultural water consumption.  

By quantifying the trans-boundary flows of freshwater services, the researchers emphasized the importance of upstream watersheds in NFB as sources of ecosystem service provision. They also called our attention to agricultural and livestock water demands, as they may bring about risk of water shortage. 

The methodology of this study can provide technical support for future studies, and its results will be helpful for formulating inter-regional ecological compensation policies. 

The study titled "A framework of freshwater services flow model into assessment on water security and quantification of transboundary flow: A case study in northeast China" has been published in Journal of Environmental Management, and it was supported by the National Key Research and Development Program of China.