Chapter 14 - Changes in Marine Biodiversity as an Indicator of Climate Change

Abstract

Biodiversity is commonly defined as the variability among living organisms from all sources. Over evolutionary time scales, there have been massive changes to the ocean's biodiversity, including several mass extinctions that have shaped planetary diversity over millions of years. Some, if not most of these events are thought to correlate with large-scale climate change that perturbed ocean temperature, chemistry, currents, and productivity. Most studies on the ecological effects of climate change, whether on land or in the sea, have concentrated on individual species. Biodiversity has three main components: diversity within species, between species and of ecosystems. The chapter discusses changes in all three components, but the studies to date have mostly focused on species composition and species richness, likely because these represent the most easily quantifiable aspects of biodiversity. Despite its taxonomic prominence, marine biodiversity is sometimes overlooked in the climate change discussion undoubtedly because much of it is little known and less understood than its terrestrial counterpart. It appears that indeed changes in diversity often indicate changes in climate, especially warming and increased climate variability. On a global ocean scale, it appears that, as on land, the tropics loose diversity, temperate regions show increased diversity, whereas polar environments so far mostly show declines in ice-dependent species as the climate warms.