By Dr Peter JS Jones, Dept of Geography, University College London (P.J.Jones [at] ucl.ac.uk)
It is increasingly recognised that marine ecosystems that have a higher diversity of species are more resilient to impacts from non-native species, climate change, etc., but why is there a link between diversity and resilience and how can marine protected areas (MPAs) be made more effective in building resilience?
Species provide a variety of functional roles in ecosystems, such as nutrient recycling, population control, etc. The higher the diversity of functional groups and the higher the diversity of species and the population sizes within each functional group, the more resilient the ecosystem is, in that it can remain stable in the face of factors that could otherwise perturb it. This is because one species can replace the role of another species in the same functional group if that species is depleted by disease, over-harvesting, etc. Also, if environmental conditions change, a species that previously appeared to be redundant, in that it has no apparent functional role, can be better adapted to the new conditions and thereby is able to adopt a functional role, replacing the role of a species which is less well adapted to the new conditions. In these ways the ecosystem is able to remain in a relatively stable state, including the capacity to adapt to changing conditions. This capacity for resilience is increasingly recognised as being important, as the pressures related to human activities which can perturb marine ecosystems, e.g. greenhouse gas emissions and species introductions, increase, potentially shifting ecosystems to alternative states that provide fewer ecosystem services, e.g. food production, greenhouse gas sinks, genetic resources and tourism value.