14 - Conjectures on future climate effects on marine ecosystems dominated by small pelagic fish  pp. 312-343

Conjectures on future climate effects on marine ecosystems dominated by small pelagic fish

By Pierre Fréon, Francisco Werner and Francisco P. Chavez

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Summary

Direct effects of humans on the environment (agricultural practices, fishing) have been evident for hundreds of years. Some of these direct effects (increased carbon dioxide in the atmosphere) are now spilling over into the climate system creating uncertainty regarding the future of marine ecosystems. Here, we review possible scenarios of climate change (CC) and physical oceanography in the SPACC context. Three predicted avenues of ecological change are discussed: (1) changes in productivity and composition of lower trophic levels; (2) distributional changes of marine organisms; and (3) changes in circulation and their effects on recruitment processes. Research gaps are identified with special attention to current limitations of available data, models, and projected scenarios. We identify significant gaps in the knowledge of processes and interactions between changes in climate and other ecosystem stressors. These other stressors, such as ocean acidification, eutrophication, and overfishing, constitute additional anthropogenically induced components of global change but are not the focus of this review. The main conclusion is that, although more information is needed before the scientific community is able to make reliable predictions regarding the future state of marine ecosystems, there is already evidence of sensitivity of pelagic species and pelagic ecosystems to CC and of decreased resilience of natural ecosystems caused by overexploitation.

Introduction

Fishers have known for centuries that climate fluctuations are both important and normal. Climate varies on daily, weather-system, and seasonal time scales, and over the past several decades scientists have learned about longer-term fluctuations that occur within the bounds of “natural” variability (e.g. El Niño, Pacific Decadal Oscillation, and ice ages).