Effects of species and functional group loss on island ecosystem properties

It is well known that large islands support more biodiversity than small ones. Now a seven-year study of a group of islands in lakes Uddjaure and Hornavan in northern Sweden shows that the size of an island is also important in determining susceptibility to biodiversity loss. Considerable recent attention has focused on predicting how the losses of species and functional groups influence ecosystem properties1,2, but the extent to which these effects vary among ecosystems remains poorly understood3,4. Island systems have considerable scope for studying how biotic and abiotic factors influence processes in different ecosystems, because they enable the simultaneous study of large numbers of independent replicate systems at ecologically meaningful spatial scales5,6,7. We studied a group of 30 islands in northern Sweden, for which island size determined disturbance history, and therefore vegetation successional stage and biotic and abiotic ecosystem properties. On each island we conducted a seven-year study that involved experimental removals of combinations of both plant functional groups and plant species. We show that although losses of functional groups and species often impaired key ecosystem processes, these effects were highly context-dependent and strongly influenced by island size. Our study provides evidence that the consequences of biotic loss for ecosystem functioning vary greatly among ecosystems and depend on the specific abiotic and biotic attributes of the system.