The calculation of productivity factor for ecological footprints in China: A methodological note

The ecological footprint (EF), a physical indicator to measure the extent of humanity's use of natural resources, has gained much attention since it was first used by Wackernagel and Rees in 1996. In order to account for differences between countries in productivity of a given land type (i.e., arable land, pasture, forest and water/fishery), productivity factor was introduced to relate the regional primary bio-productivities of the 4 types of land to the integrated average primary bio-productivity of the corresponding land types. Hence, the productivity factor is an important parameter in the EF model and it directly affects the reliability of all results. Thus, this article calculates productivity factor on the national and provincial level in China based on Net Primary Production (NPP) from MODIS 1 km data in 2008. Firstly, based on the Light Utility Efficiency and CASA model, the NPP of different biologically productive lands of China and of different provinces was calculated. Secondly, China's productivity factor for a given land type was calculated as the ratio of national average NPP of that land type and world-average NPP of that land type. Finally, productivity factors of each province in China for a given land type was calculated. The NPP of each ecosystem type varies along with the productivity factor in different provinces. However, the ranking of the productivity factors remain the same, with that of arable land being the largest, and the water/fishery being the smallest.