In order to quantitatively predict the impact of loss of species number on the provision of ecosystem services therefore human well-being, it is necessary to evaluate the functional redundancy of ecosystem. However, the functional redundancy has been overestimated due to the insufficient appreciation on complexity and multidimentionality of ecosystem functioning. Associate Professor, Takeshi Miki, from Institute of Oceanography, with international research group (with Ehime University and Kinki University in Japan), developed a novel theoretical approach, using a bioinformatics model with the whole genomic information of diverse microbes, obtained from Microbial Genome Database for Comparative Analysis (MBGD), and proposed that the whole genetic functional diversity (=number of ortholog, evolutionary unit of genetic material) in microbial community as an index of multifuctionality of ecosystem. The model predicted that the functional redundancy of microbial communities is generally low; the initial loss of microbial species (less than 10%) can cause more than 5 % loss of genetic functionality, which in turn negatively affects the multifunctionality of ecosystem. The collaborators in Japan (Prof. Taichi Yokokawa and Prof. Kazuaki Matsui) leaded the microcosm biodiversity experiments using environmental microbes. These experiments confirm the linkage between the whole genetic functional diversity and the ability of microbial community to decompose diverse carbon substrates and also demonstrate that initial species loss (e.g. 5%) causes a detectable reduction of multiple ecosystem functions. This project is an example of successful marriage of bioinformatics, theoretical ecology, and biodiversity experiments. The proposed index serves as a scientific basis to determine an acceptable level of species loss for sustainable use of ecosystem services or to minimize adverse effects of anthropogenic impacts on ecosystem, which are addressed in the Convention of Biological Diversity (CBD). The article has been online published in Proceedings of the Royal Society B (http://rspb.royalsocietypublishing.org/content/281/1776/20132498.full).