Ecology: Breaking the chain

A study of ecosystem interaction chains in a remote atoll in the Pacific Ocean suggests that human disturbances, such as forest conversions, can corrupt the links that tie together ecological interactions and cause the chains to become radically shortened or go extinct. The research is published in the journal Scientific Reports.

Human impact on biodiversity is usually measured by decreases in species abundance or richness. Equally important, but harder to measure, is the anthropogenic elimination of ecological interactions. Douglas McCauley and colleagues conducted a focused study of ecosystem connections at the Palmyra Atoll in the central Pacific Ocean, which comprises both habitats that have been altered by human disturbances and relatively undisturbed areas, allowing the evaluation of anthropogenic influences on ecosystem chains. They report the persistence of a long ecosystem interaction chain, which links trees to manta rays via changes to seabirds, forests, soils, nutrient runoff and plankton communities. The results show this complex interaction chain is maintained by the relative lack of human disturbance in the better protected parts of the atoll, whereas in regions where native trees have been replaced by human-propagated palm trees, the chain readily breaks down.

Observations from other systems suggest that many long ecological interaction chains may be vulnerable to anthropogenic disturbances, although the effects will depend on the nature of the perturbation and the properties of the system. Further investigation of remaining pristine environments will add to our understanding of the implications of this type of environmental change on ecosystem connectedness.