Marine Reserves May Ameliorate the Negative Consequences of Both Local and Global Stressors of Sea Life
Micheli, F., Saenz-Arroyo, A., Greenley, A., Vazquez, L., Montes, J.A.E., Rossetto, M. and De Leo, G.A. 2012. Evidence that marine reserves enhance resilience to climatic impacts. PLoS ONE 7: e40832.
The seven scientists begin their narrative by noting that highly valuable abalone harvesting enterprises that came into existence in the mid-1800s in various places around the world have subsequently collapsed, and that in California (USA), "total catches dropped from a peak of 24,000 tons to 115 tons by 1995, culminating in the 1997 closure of all commercial and sport fishing south of San Francisco." In 2006, however, they note that "the fishing cooperative of Isla Natividad, along the Pacific coast of Baja California, established two marine reserves, excluding all take from 8% of the fishing grounds surrounding the island," with the hoped-for goal of recovering depleted abalone populations and fisheries through larval spillover from reserves to fishing grounds.
In the spring of 2009, however, fishermen reported unusually high mortality of abalones and other benthic invertebrates, which was presumed to be due to an unmonitored hypoxia event at sites in the Isla Natividad. Fortunately, between 2006 and 2010, Micheli et al. had monitored "the abundance, size structure, reproductive output and post-larval recruitment of pink abalones (Haliotis corrugata) within the reserves and in adjacent fished areas with similar habitat characteristics," which allowed them "an unprecedented view" of the demographic effects of the mortality event, "both within reserves and in fished areas."
So what did they learn?
First of all, annual biomass estimates conducted by fisheries indicated that mass mortality due to the presumed hypoxia event in the spring of 2009 caused an estimated 75% reduction in abalone biomass within the fishing grounds, but a much smaller 50% reduction in the marine reserves. And following the mortality event, Micheli et al. report that "estimated reproductive outputs in the reserve were 1.6 and 2.6 times greater than in fished areas in 2009 and 2010, respectively." In addition, they state that in the spring of 2010, 92% of individual abalones encountered in field surveys were above the reported size of sexual maturity and 45% above the minimum legal size within reserves, as compared to 81% and 35% in fished areas, respectively.
In discussing the implications of their findings, Micheli et al. say they "indicate that management actions aimed at alleviating local stressors, such as protection in marine reserves, can increase the ability of populations to resist climate disturbances through maintained reproductive output (resistance), thereby preventing local extirpation, and possibly also their ability to reverse the effects of such disturbances (recovery)," additionally citing Cote and Darling (2010) in this regard. And so they conclude that "under future scenarios of frequent and/or persistent disturbance, increasing resilience to climatic impacts through networks of marine reserves may be the most effective tool that local communities and nations worldwide have to combat the negative impacts of global climate change on marine ecosystems and livelihoods."
And so it would seem to us that both climate alarmists and skeptics alike would deem it wise to establish more marine reserves throughout the world's oceans, in order to help prevent the deleterious effects of (1) verified local threats and (2) postulated global threats to the well-being of Earth's marine life. If each person, city, state and country took care of their own piece of the planet, all would be as well as we could possibly make it.
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