Abstract: How to make a balance between reducing sampling efforts and gaining accurate information is a central problem in broad-scale biodiversity assessment. This article tries to address this question by introducing multiscale methodology. We first provide a definition of broad-scale assessment, then highlight this problem after reviewing the history of global assessments. In the third part, we summarize the methodology of assessment design from five aspects: sampling strategy, surrogate species, rapid assessment technique, indicators and remote sensing techniques. Finally, a hierarchical multiscale method is described that provides a better balance. In a typical multiscale assessment, biodiversity is characterized at a series of spatial scales, thus it is different from the traditional sampling design. Correspondingly, multiscale planning can be simply divided into two categories: one comprises sampling designs with loosely-defined scales, and the other comprises those with strictly-defined scales. The former has the advantage of synthesizing information more easily among multiple scales. In our view, the essence of this method is construction of a middle-scale, which can be realized by “top-down” and “bottom-up” approaches. The ideal method for biodiversity conservation based on this multiscale methodology is to plan in the broad-scale context, to integrate at the middle scale and to act at the local, manageable scale.

Key words: China, marine biodiversity, current status, prospects