Chapter 21 - Marine biodiversity and climate change

Abstract

Ambient temperature is a leading environmental factor determining the distribution and diversity of life in the oceans. Hence, climate change is fundamentally changing marine biodiversity on a global scale and will continue to do so into the future. Here, we review observed and predicted effects of climate change on the diversity of marine species. An increasing number of studies demonstrate that effects of climate change on marine biodiversity are already apparent from local to global scales. So far, long-term fish and plankton monitoring data have provided the most compelling evidence for climate-driven changes in species distribution and diversity, but studies involving other groups such as corals, seaweeds, and mammals are increasing. As a general pattern, tropical regions often experience a loss of species due to elevated heat stress, whereas temperate regions increase in diversity, as species migrate poleward. Large increases in diversity through invasion of southern species are expected in the polar regions, but so far there are few observations to support this. Complex patterns of change emerge where ocean warming is accompanied by the effects of sea level rise, acidification, habitat alteration, changes in ocean circulation, stratification, and other aspects of global change. Projections from climate-driven ecosystem models highlight a loss of primary production from lower and midlatitudes as a major factor that could drive changes in marine biomass and likely diversity, particularly at higher trophic levels. From a management perspective, the conservation of biological diversity will provide insurance and resilience in the face of rapid global change, but conservation strategies need to be adapted to take shifting species distributions into account. Cumulative impacts of exploitation, habitat destruction, and other threats to biodiversity need to be minimized to maintain the adaptive capacity of marine ecosystems in the present and coming centuries. This might be particularly pressing in tropical regions and developing countries, which already face exceptional socioeconomic and climate-related pressures, as well as in polar regions, which are experiencing the most rapid rate of environmental change.