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VariableFigureSource or reasoning
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Fishes in the world1000000BBar-On, Phillips, and Milo (2018, "Supplementary"), Table S1
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Planned seismic survey area, km2854,779Bureau of Ocean Energy Management (2014, p8)
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World’s water surface area, km2361,500,000https://www.indexmundi.com/world/area.html, http://www.physicalgeography.net/fundamentals/8o.html
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If fishes were distributed equally throughout all the world’s water surface area, then the survey area would contain this number of fishes2365BCalculation
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Fish in the survey area (guess based on map of primary production or the map of teleost fish biomass)525BIf you look at the world’s map of primary production or the map of teleost fish biomass and compare it with the planned survey area (see the map here), you can see that most of the survey area has low biomass and teleost fish concentration, though some part of the area has very high biomass. I don’t know if teleost fish biomass is indicative of all fish biomass. For the sake of simplicity I assume that biomass in the area is proportional to the number of fishes but I don’t know if this is an appropriate assumption, I don’t really know what I am doing. To account for possibly lower fish population, I assume that the survey area has 4.5 times lower number of fish per square kilometer than average
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Dolphins and whales in the survey area in BOEM estimates865,000BOEM estimates how many dolphins and whales were exposed using a seemingly complex modeling that takes into account the movement of these animals, time of year, the ocean floor type, and many other factors. They don’t have a single estimate of dolphins and whales in the survey area. Instead, they use a density table (BOEM (2014, p260)) that shows how many marine mammals are on average in each zone and for each time of year. For the purpose of my quick estimate, I assumed that all zones are of equal size, even though they are not. In this spreadsheet I summed up the numbers of marine mammals per square nautical mile in each zone and multiplied it by the number of square nautical miles of the area of the surveys. The zones cover the area four times because zones 1-5 are for winter, zones 6-10 are for spring, and so on. Hence, to get the average number of dolphins and whales in the survey zone at any given time, I divided the result by four and got that the estimate assumed that there are very roughly 865,000 dolphins and whales in the area.
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Dolphins and whale exposures to 180dB airgun sounds (BOEM estimate)138,500Bureau of Ocean Energy Management (2012) (aggregated by Huelsenbeck and Wood (2013)) found that the planned seismic surveys along the East Coast in the U.S. would have caused estimated 138,500 injuries to marine mammals and 13.5 million disturbances to vital behaviors like foraging, communicating and mating to marine mammals. The only marine mammals included in the estimate were dolphins and whales.
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Dolphins and whale exposures to 160dB airgun sounds (BOEM estimate)13.5M
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A multiplier to account for BOEM likely overestimating the number of dolphins and whales exposed to airgun sounds0.1In BOEM (2014, p104) you can see that the estimates in the two rows above are actually upper bounds. According to BOEM (2014a, p294), “each of the inputs into the models is purposely developed to be conservative, and this conservativeness accumulates throughout the analysis.” My analysis avoids some of the conservative assumptions but not all of them. Hence, I multiply results by 0.1 to get more realistic numbers. I don't know what this multiplier should be. Based on descriptions in BOEM (2014), it would be reasonable to choose a higher multiplier. At the same time, BOEM has been accused of being corrupt (a claim I have not looked into). Hence, it's also possible that they underestimated the impact on mammals in some way. Also, Huelsenbeck and Wood (2013, p11) claim that BOEM "likely underestimates the cumulative impacts since it is using outdated science." So I didn't choose a very low value for this variable.
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Fish exposures to 180dB airgun sounds8.4BCalculation
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Fish exposures to 160dB airgun sounds820BCalculation
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Percentage of fish stressed by exposures to 180dB airgun sounds25%The choice of these values is very arbitrary. I collected evidence that 180dB and 160dB airgun sounds may affect some species of fish here. However, as I explain in the appendix of my EA forum post, some other research found that such sounds did not seem to significantly affect fish. The values I've chosen are simply my best guesses based on having read over a hundred papers on the subject. I'd find quite a wide range of values here defensible and I'm not at all confident in my choice of values. It's also unclear what should be considered a stressful event but this is the best way I came up with modeling the impact.
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Percentage of fish stressed by exposures to 160dB airgun sounds3%
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Fish stress events caused by 180dB airgun sounds2.1BCalculation
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Fish stress events caused by 160dB airgun sounds24.6BCalculation
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Time stressed after an exposure, minutes20Based on McCauley et al. (2000) claim that “a return to normal behavioural patterns some 14–30 minutes after air gun operations ceased”, I assume that fish are disturbed for an average of 20 minutes. I think that this figure is most likely higher as I don’t even know how long the exposure is. It could also be shorter as it’s possible that fish are only briefly startled but then return to their normal behaviors without much stress. Note that I exclude longer term exposure effects like temporarily increasing sound threshold levels which could be most important.
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Minutes in a year525,600
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Years of stress averted by preventing seismic surveys1,016,188Calculation
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Costs needed to avert seismic surveys along the east coast of the US, USD1.0MAs this blog post by Michael Stocker says, plans to do these surveys were abandoned and this was likely due to a 2015-2020 campaign by Ocean Conservation Research, Southern Environmental Law Center, Surfrider and some other organizations. I asked Michael what the very approximate costs of the campaign were and he said that it was maybe $250,000. However, he added that he was raising concern about this for many years prior and that “there may have been many other campaigns that hinged off of this one that expanded both the reach, and the effectiveness of this campaign which did not figure into the calculus of your estimate.” And I can see that organizations NRDC and Oceana also have articles on the issue (and hence likely worked on it). To account for this, I increased the costs to $1.5 million. It also seems to me that the campaign was successful in raising public concern for the amount of money spent which suggests that similar efforts in the future may be less cost-effective.
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Years of stress averted per dollar1.02Calculation
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For an explanation of this estimate, please see this textual description.
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