Print PageThe most unique feature of earth is the existence of life, and the most unique feature of this life is its amazing biodiversity. I hypothesize that the same forces that led to the speciation and coexistence of so many different taxa on earth are also the forces that determine how and why biodiversity impacts the functioning of ecosystems. Moreover, if, as often suggested, speciation has resulted from ecological opportunity, then the immense diversity of life would suggest that diversity should be the major driver of ecosystem functioning. I test these hypothesis via (1) analyses of paleontological patterns of species migration, coexistence and extinction for marine and terrestrial ecosystems, (2) results of eight long-term field experiments, all performed at Cedar Creek in Minnesota, that allow comparison of the effects of biodiversity versus numerous other factors or forces on ecosystem functioning.
Results/Conclusions
Ecosystem functioning is influenced by many factors including nitrogen loading, water availability, carbon dioxide enrichment, warming, herbivory, fire frequency and biodiversity. Comparisons of experiments that have manipulated one or more of these seven factors show that biodiversity had a larger impact on productivity than any other variable. The long-term effects of biodiversity were about twice those of nitrogen addition, which was itself about twice those of water, warming, herbivory, carbon dioxide or fire. The effects of diversity came about equally from interspecific complementarity and diversity-dependent feedback loops that increased soil fertility and moisture, decreased disease and herbivory, and increased parasitoid and predatory insect abundances. Finally, paleontological patterns of species accumulation suggest that species coexist because of interspecific tradeoffs, presumably the same tradeoffs that lead to complementarity.
