Ecological Extinction and Evolution in the Brave New Ocean

JEREMY B. C. JACKSON

The great mass extinctions of the fossil record were a major creative force that provided entirely new kinds of opportunities for the subsequent explosive evolution and diversification of surviving clades. Today, the synergistic effects of human impacts are laying the groundwork for a comparably great Anthropocene mass extinction in the oceans with unknown ecological and evolutionary consequences. Synergistic effects of habitat destruction, overfishing, introduced species, warming, acidification, toxins, and massive runoff of nutrients are transforming once complex ecosystems like coral reefs and kelp forests into monotonous level bottoms, transforming clear and productive coastal seas into anoxic dead zones, and transforming complex food webs topped by big animals into simplified, microbially dominated ecosystems with boom and bust cycles of toxic dinoflagellate blooms, jellyfish, and disease. Rates of change are increasingly fast and nonlinear with sudden phase shifts to novel alternative community states. We can only guess at the kinds of organisms that will benefit from this mayhem that is radically altering the selective seascape far beyond the consequences of fishing or warming alone. The prospects are especially bleak for animals and plants compared

Center for Marine Biodiversity and Conservation, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0244; and Smithsonian Tropical Research Institute, Box 2072, Balboa, Republic of Panama.

6 / Jeremy B.C. Jackson with metabolically flexible microbes and algae. Halting and ultimately reversing these trends will require rapid and fundamental changes in fisheries, agricultural practice, and the emissions of greenhouse gases on a global scale.

About 10 years ago, several of us concluded that the global ecological condition of the oceans because of overfishing was as dire as that of tropical rain forests, and that future losses would be enormous and potentially irreversible if action were not taken promptly to reverse the trajectories of decline (Pauly et al., 1998; Jackson et al., 2001; Christensen et al., 2003; Myers and Worm, 2003). The scientific response was chilly, as evidenced by the statement of task for the recent National Research Council (NRC) report on the dynamics of marine ecosystems (NRC, 2006), which refers to our work in terms that emphasize the ''high profile'' of the articles (as if this were unseemly), the unconventional (and therefore suspect) nature of the data, and our assertions about the importance of shifting baselines and fishing down marine food webs, and that 90% of large predatory fish stocks are gone. In the end, the NRC report cautiously confirmed the conclusions it was convened to evaluate. But many scientists remain skeptical, apparently because (i) most conclusions are necessarily based on patterns and correlations using data gathered for many different purposes rather than experiments, (ii) the traditional emphasis in biological oceanography on bottom-up nutrient forcing rather than top-down control by predators, and (iii) the strong implication that most fisheries have been mismanaged for decades.

The focus of the NRC report (2006) was on fishing, but the problems are vastly greater because of the additional effects on marine ecosystems of biological, toxic, and nutrient pollution, habitat loss, global climate change, and the synergies among all of these different drivers of ecological change (Jackson et al, 2001; Knowlton, 2001; Riebesell, 2004; Pandolfi et al., 2005; Schmittner, 2005; Rabalais et al., 2007). There is also considerable uncertainty about the relative importance and interactions among local perturbations, such as fishing and pollution, versus global changes in climate and ocean chemistry that operate over very different and noncongruent temporal and spatial scales (Hoegh-Guldberg et al., 2007; Knowlton and Jackson, 2008). Trophic structure and biodiversity are also key components of the resistance and resilience of marine ecosystems to future perturbations (Bascompte et al., 2005; Worm et al., 2006), but we are only beginning to document how these parameters change across a broad spectrum of human and natural disturbance. The problems are complex because of the huge numbers of species and different kinds of perturbations involved, the nonlinear dynamics of interactions among them, and the infancy of the emerging theoretical framework required to interpret the results (Knowlton, 1992; Scheffer et al., 2001; Hsieh et al., 2005).

Much new data and analyses have appeared in the last 5 years, sometimes with sharply conflicting interpretations, about the magnitude and rates of change in abundance of particular species. Regardless of these uncertainties, however, it is increasingly apparent that all of the different kinds of data and methods of analysis point in the same direction of drastic and increasingly rapid degradation of marine ecosystems. Here, I examine some of the most important of these new results since the publication of my previous synthesis (Jackson et al., 2001), with emphasis on coastal seas and estuaries, continental shelves, the open ocean pelagic realm, and coral reefs, about which I am most familiar. The biology and substantial threats to the ecology of the deep sea have been recently reviewed by Koslow (2007) and are not considered here. I then discuss what I believe will be the future of marine ecosystems if the drivers of change continue unabated, and address the kinds of changes in patterns of consumption and energy use that will be required to turn the situation around.

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