Biodiversity is composed of interconnected species within food webs that exchange matter, energy and information and form complex systems. This chapter describes ecosystem functioning as the processes, activities and properties of ecosystems influenced by biodiversity. In the central Pacific, the Hawaiian archipelago can be divided into two areas: the Main Hawaiian Islands (MHI), which have been heavily exploited; and the North-Western Hawaiian Islands (NWHI), which are unaffected, conservation area. Local/global stability occurs when a system can resist to a small/large perturbation, respectively. A first criticism is that biodiversity and ecosystem functioning (BEF) experiments are biased because they cannot account for all processes occurring in nature. Meta-analyses of controlled experiments provided evidence that a diverse diet increases growth, survival and fecundity of species. Marine biodiversity moves a large quantity of elements and compounds, and it is likely that current alteration in marine biodiversity due to both direct and indirect effects of human activities will affect global biogeochemistry.