- 1 kg of plastic is emitted to the ocean per capita per year.
- 0.0001 seabirds and 0.00001 sea mammals are killed by marine plastic pollution per capita per year.
- 200 wild fish are caught per capita per year.
- The catch of wild fish is 2 M times as large as the number of seabirds, and 20 M times as large as the number of sea mammals killed by marine plastic pollution.
The data and calculations are presented below.
- The plastic emitted to the ocean in 2010 was 8 Mt (PEO) according to OWID.
- The world population in 2010 was 6.92 G (WP) according to The World Bank.
- Marine plastic debris kills up to 1 M seabirds (SB) and 100 k sea mammals (SM) each year according to the United Nations.
- The catch of wild fish is 0.97 T/year (WFL) to 2.7 T/year (WFH) according to fishcount.org.
- Plastic emitted to the ocean per capita in 2010 (PEOpC): PEO / WP = 8 Gkg / 6.92 G = 1.16 kg.
- Plastic emitted to the ocean to cause one death of a seabird (PEOpDSB): PEO / SB = 8 Mt / 1 M = 8 t.
- Plastic emitted to the ocean to cause one death of a sea mammal (PEOpDSM): PEO / SM = 8 Mt / 0.1 M = 80 t.
- Seabirds killed by per capita plastic marine pollution in 2010 (DSBpC): PEOpC / PEOpDSB = 1.16 / 8 k = 145 μ.
- Sea mammals killed by per capita plastic marine pollution in 2010 (DSMpC): PEOpC / PEOpDSM = 1.16 / 80 k = 14.5 μ.
- Wild fish caught per year (WF): (WFL * WFH)^0.5 = (0.97 * 2.7)^0.5 T = 1.62 T.
- Catch of wild fish per capita per year (WFpC): WF / WP = 1.62 T / 6.92 G = 234.
- Ratio between the catch of wild fish and the number of seabirds killed by marine plastic pollution: WFpC / DSBpC = 234 / 145 μ = 1.62 M.
- Ratio between the catch of wild fish and the number of sea mammals killed by marine plastic pollution: WFpC / DSMpC = 234 / 14.5 μ = 16.2 M.
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Do you have any thoughts on the effects of plastic pollution on wild fish?
According to this section from OWID:
However, it is worth noting that reduced food consumption tends to decrease the size of the fish population, which might be beneficial if fish have net negative lives.
Sorry, but I don't understand the meaning of this article because I am having trouble understanding the measurements. kg is kilograms, t is tonnes, but what is u and what is M? Also, is the conclusion that catching wild fish does more damage to the ecosystem than throwing plastic into the ocean? How should I interpret the sentences?
They are SI Prefixes: M stands for mega or 1 million, 10^6.
u (for μ) stands for micro or 1 millionth, 10 ^ -6.
If I understand correctly, the conclusion is that the direct effects of marine plastic pollution on seabirds / marine mammals are probably much smaller than the effects of fishing on fish.
Thanks for noting that, Raluca! Thanks for clarifying, Lorenzo!
I have now added links to the 1st instances of each of the prefixes.
Yes, I think this is exactly the right conclusion to take. We should be careful not to extrapolate to other animals. I have now updated the title to better reflect this.
I think it is crucial to point out that while there may be little direct effect of plastic pollution on morality of animals, plastic (mainly microplastic) is a vessel for pollutants and can therefore transport in chemicals, which can cause death in the organism. Therefore the effect of plastic is indirect, while clearly still playing a very crucial role.
I really appreciated this short, clear post. Thank you!
Thanks for the post. I learnt about the size of the plastic pollution problem for animals.
I can't entirely agree with the framing of the article. 1M seabirds dying per year from plastic is not "small". It makes me think that this is not a big problem, and I shouldn't worry at all about it.
I would frame it as "1M seabirds die every year from plastic pollution, so it's a big problem (malaria kills 0.5M people per year), but it's still 1 million times less than 1T fish slaughtered per year."
Great to know that you found it useful!
In my mind, the meaning of words such as "small" and "large" is always context-dependent. In this case, I think it is fair to say that the impact, measured as the number of deaths, from marine plastic pollution on seabirds and marine animals is small in comparison with the impact of catching fish.
In order to make comparisons between species, I think it is worth having in mind the number of neurons (a proxy for sentience) respecting each death toll.
Estimates for the number of neurons:
Number of neurons respecting each death toll:
Consequently, the number of neurons regarding:
From the above, it naively seems that:
However, this is not by all means a definite analysis:
I didn't know fish had 10M neurons. Thanks!
I appreciate your quantitative thinking. But I believe it's unfair to say that a fish is 10,000X worth less than a human because a fish has fewer neurons. What if suffering has a minimum threshold of neurons and then declining marginal suffering after that? We don't know (as you point out in your last paragraph).
"Not everything that can be counted counts and not everything that counts can be counted."
Yes, I agree, there is lots of uncertainty! Moreover:
Thanks for sharing this!