Climate Change: Impacts on Fisheries and Aquaculture

Climate change has been recognized as the foremost environmental problem of the twentyfirst century and has been a subject of considerable debate and controversy.It is predicted to lead to adverse, irreversible impacts on the earth and the ecosystem as a whole.Although it is difficult to connect specific weather events to climate change, increases in global temperature has been predicted to cause broader changes, including glacial retreat, arctic shrinkage and worldwide sea level rise.Climate change has been implicated in mass mortalities of several aquatic species including plants, fish, corals and mammals.The present chapter has been divided in to two parts; the first part discusses the causes and general concerns of global climate change and the second part deals, specifically, on the impacts of climate change on fisheries and aquaculture, possible mitigation options and development of suitable monitoring tools.7 www.intechopen.comClimate Change and Variability 120anthropogenic greenhouse gas (GHG) emissions over the decades are major contributors to the global warming. Natural processes affecting the earth's temperatureSun is the primary source of energy on earth.Though the sun's output is nearly constant, small changes over an extended period of time can lead to climate change.The earth's climate changes are in response to many natural processes like orbital forcing (variations in its orbit around the Sun), volcanic eruptions, and atmospheric greenhouse gas concentrations.Changes in atmospheric concentrations of greenhouse gases and aerosols, land-cover and solar radiation alter the energy balance of the climate system and causes warming or cooling of the earth's atmosphere.Volcanic eruptions emit many gases and one of the most important of these is sulfur dioxide (SO 2 ) which forms sulfate aerosol (SO 4 ) in the atmosphere. Greenhouse gasesGreenhouse gases (GHGs) are those gaseous constituents of the atmosphere, both natural and anthropogenic, that are responsible for the greenhouse effect, leading to an increase in the amount of infrared or thermal radiation near the surface.While water vapor (H 2 O), carbon dioxide (CO 2 ), nitrous oxide (N 2 O), methane (CH 4 ), and ozone (O 3 ) are the primary greenhouse gases in the Earth's atmosphere, there are a number of entirely human-made greenhouse gases in the atmosphere, such as the halocarbons and other chlorine-and bromine-containing substances.Halocarbons such as CFCs (chlorofluorocarbons) are completely artificial (man-made), and are produced from the chemical industry in which they are used as coolants and in foam blowing.Increases in CO 2 are the single largest factor contributing more than 60% of humanenhanced increases and more than 90% of rapid increase in past decade.Most CO 2 emissions are from the burning of fossil fuels such as coal, oil, and gas.Rising CO 2 is also related to deforestation, which eliminates an important carbon sink of the terrestrial biosphere (www.ncdc.noaa.gov/oa/climate/globalwarming.html;Shea et al., 2007).Currently, the atmosphere contains about 370 ppm of CO 2 , which is the highest concentration in 420000 years and perhaps as long as 2 million years.Estimates of CO 2 concentrations at the end of the 21 st century range from 490 to 1260 ppm, or a 75% to 350% increase above preindustrial concentrations (WMO World Data Centre for Greenhouse Gases.Greenhouse gas bulletin, 2006; Shea KM and the Committee on Environmental Health, 2007) . Impacts of climate changeAlthough it is difficult to connect specific weather events to global warming, an increase in global temperatures may in turn cause broader changes, including glacial retreat, arctic shrinkage, and worldwide sea level rise.Changes in the amount and pattern of precipitation may result in flooding and drought.Other effects may include changes in agricultural yields, addition of new trade routes, reduced summer stream flows, species extinctions, and increases in the range of disease vectors (Understanding and responding to Climate Change.