Santiago, Chile.- During recent decades, the Humboldt Current System produced more fish by surface unit than any other marine system; however, climate change could shift this system out of its current favorable state of productivity, warns a new FAO study published today.
This could mean significant changes for the countries that benefit the most from this system -Chile, Ecuador and Peru- since El Niño and El Niña events may become more frequent in a warming climate, with major regime shifts in fisheries and an overall decrease in plankton abundance.
While the FAO report Impacts of climate change on fisheries and aquaculture: Synthesis of current knowledge, adaptation and mitigation options warns that these projections have a high level of uncertainty, their potential consequences are considerable, and countries should consider a series of policy changes to face them.
Institutionalizing participatory governance systems, promoting dedicated scientific studies and improving monitoring, for example, would increase the adaptive capacity of small-scale fisheries to cope with climate change, while strong control and enforcement and a reduction of fishing capacity to sustainable levels, particularly in marine fisheries, could have a short-term negative social effect, but are indispensable measures to safeguard their long-term sustainability.
Increasing the share of fish dedicated to direct human consumption would increase food security and social and economic development, while fostering sustainable aquaculture, stopping fish discards and waste through relevant policies, would mitigate the projected reduction in fish productivity.
The study also highlights that the use of natural gas instead of heavy fuel could help to mitigate the carbon footprint of the fisheries sector; as will do the introduction of renewable sources of energy.
A key marine ecosystem
On average, 9.35 million tonnes of marine fish, molluscs and crustaceans were landed each year in Chile and Peru during 2005 to 2015, with a noticeable decreasing trend, primarily because of the implementation of stricter management plans but it also reflects climate variability and, in some cases, increased overexploitation.
The Northern–Central Peru region accounted for 75 percent of the total catches, Southern Peru–Northern Chile for nearly 20 percent, and central Chile represented less than 5 percent of the national fishery production.
The FAO publication indicates that global models predict a moderate decrease in catch potential by 2050 in Chile and Peru, since climate change may significantly reduce the spawning success of small pelagic fish exploited by the industrial sector.
Troubling changes to the Humboldt Current System
According to the FAO report, in the Humboldt Current System (HCS) fish productivity is mostly controlled by climate and its effect on the production of phytoplankton (the basis for the entire marine food chain)
An overall decrease in phytoplankton and zooplankton abundance is projected for HCS as a result of large-scale nutrient depletion in subsurface water due to a warmer climate. The mean offshore extension of the zooplankton-rich area is expected to decline by approximately 33 percent in the northern and central HCS, and about 14 percent in the southern HCS.
Increased stratification (when water masses with different properties form layers that act as barriers to water and nutrient mixing) and a strong surface warming of Peruvian waters (and to a lesser extent of Chilean waters) is forecast.
Another key feature of this system is the presence of an extended subsurface oxygen minimum zone; a thick layer of water a few tens of meters below the surface where oxygen concentration is so low that, except for bacteria, only some species can temporarily survive. This layer could also expand in a warming world.
More frequent El Niño and El Niña events
The HCS is also the region where the effects of El Niño and La Niña events are most notable. Although there is no consensus concerning El Niño changes in frequency or amplitude, extreme El Niño and La Niña events are expected to become more frequent over the whole region in a warming climate, while evidence from the early Pliocene (23 million to 5.3 million years ago), when temperatures were higher than today, suggests permanent El Niño conditions for this region.
Reference (open):
Barange, M., Bahri, T., Beveridge, M.C.M., Cochrane, K.L., Funge-Smith, S. & Poulain, F., eds. 2018. Impacts of climate change on fisheries and aquaculture: synthesis of current knowledge, adaptation and mitigation options. FAO Fisheries and Aquaculture Technical Paper No. 627. Rome, FAO. 628 pp http://www.fao.org/3/I9705EN/i9705en.pdf
