A change in statistical distribution of temperature and rainfall over periods of time ranging from decades to millions of years is called climate change. This is a naturally occurring phenomenon but since the middle of the 20th century, human influence on global climate has been substantial and much of the change has been attributed to human activity.
These effects or influences are called anthropogenic or man-made. This term is often used when describing polluting emissions produced by human activities - all major human impacts on the environment like chemical or biological wastes produced as by-products of otherwise purposeful and useful human activities.
This change in global climate has been observed as an increase in average global temperatures and hence the term global warming.
The impact of climate change and harmful human emissions of CO2 on the oceans of the world is substantial. The ocean has the capacity to absorb CO2 from the atmosphere and is called a natural carbon sink – a place where CO2 is absorbed and retained. However, if too much CO2 is absorbed, the ocean turns acidic which is not good for marine life and reduces its capacity to act as a carbon sink.
So we have two major issues directly affecting oceans and marine life – rising temperatures and acidification – both caused largely by human activity post industrialisation. Another issue affecting oceans is the increase in frequency of storms and cyclones due to global warming.
Rising temperatures:
When global temperatures rise, polar ice caps will melt causing a rise in sea levels that directly affects fishing communities living in the front line of coastal areas. Sea incursions into the coast will increase and low lying islands and coastal lands like the Maldives and Bangladesh
Salt water intrusions from rise in sea levels, into fresh water bodies will cause salinity and affect communities of inland fishermen who are dependent on fresh water fish and river water for drinking.
Also, fish are adapted to specific temperatures of water and any change in water temperature will mean they have to migrate to areas where the water has the right temperature. This means fishing grounds will change and some of them may be lost forever. Fishermen may have to go greater distances in search of fish which means they burn more fossil fuels – both expensive and harmful.
Rising sea temperatures also result in frequent storms and cyclones which further endanger the lives and livelihoods of traditional fishermen who have poor safety at sea facilities.
Acidification:
Rise in the acidity of oceans makes it difficult for marine organisms like corals, oysters or shrimps to form shells – a process called calcification. Many vital organisms like the zooplankton which form the staple food of marine life have calcium shells so acidification will affect the marine food web and cause unpredictable changes in the production, distribution and species composition of marine life. All marine life is interconnected, this means coral reefs, mangroves, sea grass beds etc that provide habitat for marine organisms will also be affected.
If acidification continues unchecked, marine life will degrade and change in unpredictable ways affecting coastal communities adversely.
Adaptation to climate change:
Several international agencies like the FAO and the World Bank have programs to help communities in the developing world adapt to the effects of climate change on their livelihoods. Reducing capacity of fishing fleets, fisheries co-management, creation of marine protected areas are among those that help fish stocks recover and increase economic returns from the harvest of marine resources.
Climate change is a widely discussed topic in the media as well as in scientific circles. There are those that believe climate change is happening and those that do not. The controversy exists more in the media than in scientific circles and political influences have also played a leading role in shaping opinions. However, more and more scientists and scientific organizations are endorsing man-made influences on climate and have joined the call for mitigating action.
There is no immediate danger to coastal communities and ecosystems but all projections into the future look bleak so now is the time for action keeping in mind that fishing needs to be maintained as a viable occupation while adapting and mitigating the effects of climate change on marine ecosystems.
