Climate Change and Marine Capture Fisheries

R.I. Perry’s paper Potential impacts of climate change on marine wild capture fisheriespublished in the Journal of Agricultural Science (Perry 2011) reviews data regarding climate change and its effects on marine wild capture fisheries.  Climate change in marine ecosystems is a broad and inclusive matter; understanding its synergistic effects on both the marine world and human world is crucial to taking the next steps of reducing the uncertainties of climate impacts while creating adaptive, resilient ecosystems that can benefit both social-environmental systems.–Alyshia Silva  
Perry R. 2010. Potential impacts of climate change on marine wild capture fisheries: an update. The Journal of Agricultural Science 149 63–75

          About 20% of the world’s population relies on marine wildlife capture as a means of subsistence­­­­­—a factor in much of the developing world’s economy—and for jobs in the marketing and processing sectors.  However, due to growing pressures ranging from human to environmental stressors, the ability of marine ecosystems to continue meet the world’s needs is becoming questionable. 
          Many studies have shown that climate change is directly affecting fish abundance and location.  The warming of waters near the equator causes a shift in marine populations pole-ward, encouraging their seasonal migrations sooner and for longer periods of time, while moving them away from historical fishing grounds.
          Using a range of physical conditions, modeling studies have projected ranges shifts of 45–60 km per decade.  Using a high CO2 emission scenario, an estimated 80% of species will move towards the poles, resulting in local extinctions of fish in sub-polar, tropical, and semi-enclosed bodies of water.  Overall, however, little change in global maximum catch potential will occur, meaning higher-latitude areas will increase on average 30­–70%, while the average of the tropics dropped to 40%.  It is developing countries nearer to the equator that will be most harmed by the pole-ward shift of fish population while developed countries to the north will benefit from increased fish populations.  The low-emission scenario produced less clear results, but in a similar nature.  
          Primary production within marine ecosystems plays a vital, yet at times confusing, role within climate change modeling systems.  Coupling complex food webs (predator and competitor interactions), biology, and physics, model formulations of increased primary production led to unexpected declines in more abundant catches and increased populations for some threatened species. 
          Declines of phytoplankton biomass in eight out of the ten oceans were attributed to increasing sea surface temperatures and observational increases in surface air temperatures of 6°C over the past 50 years is leading to loss of perennial ice, coral bleaching, retreating glaciers, and a net decrease of primary production.  
          Zooplankton play a crucial role within the marine ecosystem, shifting their range to a greater extent and faster than any other marine or terrestrial group.  Within an experimental and simplified marine food web that included both zooplankton and phytoplankton, increased temperatures led to blooms of zooplankton and decreases in primary productivity of phytoplankton.  This led to an overall decrease in marine biomass; these studies conclude that even small temperature shifts can lead to huge impacts on the ecosystem. 
          The combined pressures of fishing for an increasingly demanding human population and global climate change appear to be too much for the marine ecosystem to adequately recover from.  The potential costs of adapting to a 2°C warmer world by 2050 include estimated global losses in landed catch value of $7–$19 billion for developing nations and $2–$8 billion for the developed world.

          Climate change will have a direct impact on marine ecosystems, food security, economics, and politics.  Climate change and its effects will directly negatively impact the developing world while possibly benefitting the developed world, a problem of environmental justice.  To better handle the currently stressed marine world we must couple social-ecological systems to develop a resilient yet adaptive human and ecological system that can adequately respond swiftly and effectively.  

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