Islands as model systems for understanding how species affect ecosystem properties

Aim To evaluate the potential of island systems as tools for investigating how species affect ecosystem properties. This is done by first reviewing the available literature, and then by focusing on a study in an archipelago of lake islands in northern Sweden. Location Islands in lakes Uddjaure and Hornavan in the northern Swedish boreal forest. Results The available literature suggests that islands offer two types of opportunities for investigating how species affect ecosystem properties. The first emerges from the fact that island biotas are often relatively depauperate compared with corresponding continental biotas. This enables the effects of species to be assessed against a less complicated background. The second involves the use of islands as spatially independent replicate ecosystems, which can be used to evaluate the effects of ecosystem drivers over larger spatial scales than is possible through most other approaches that allow proper replication of ecosystems. Examples are presented of the use of each approach. The Swedish lake island system is based on fifty independent islands. A wildfire frequency gradient across these islands favours different plant functional types on different islands; this leads to plant species effects influencing a range of properties both above‐ and below‐ground. Two examples are presented of ecological issues that can be investigated using this island system. First, the difference in fire frequency across islands enables assessment of the effects of fire (and hence fire suppression) on terrestrial carbon storage, and the global change implications of this. Secondly, the system can be used to address theories about the importance of plant community composition and biodiversity in driving ecosystem properties at the across‐island spatial scale. Conclusions Islands provide real opportunities for investigating biological drivers of ecosystem functioning, although they have been vastly underused for such purposes. Further, island studies have significant potential for investigating the effects of global change phenomena on terrestrial ecosystems, ranging from the impacts of biodiversity loss and invasive organisms to issues relating to terrestrial carbon sequestration. Island ecosystems enable questions to be addressed about ecosystems over ecologically meaningful spatial scales that can be addressed in no other way.