Thank you for sharing this, Nunik!
It seems the post you link is right to caution that lumping the low mercury and PCB claim together for small pelagics as is often done (even in our own post—prior to the update we just made!) is misguided.
I tried to do further research and it seems to me the following is true (I’m new to the topic, so please say if you know otherwise):
PCB concentrations are extremely geographically and temporally variable. Areas like the Baltic sea or SF Bay are very high in PCBs, but levels in the open oceans are much lower. Also, PCBs have been banned from the 80′s and levels in fish have been declining as more of the PCBs sediment to ocean floors, so it is becoming less of a concern.
PCBs are hydrophobic, thus they do accumulate in fishes, particularly their fat. As sardines/anchovies are fatty, they contain higher PCBs than less fatty fishes like Cod.
PCBs like most contaminants biomagnify. Predators consuming sardines will absorb the PCBs in their fat, increasing their PCB levels. Thus, sardines/anchovies may be less contaminated than equally fatty but longer-lived/higher trophic level fishes.
It really does seem PCB levels can be a health concern, something I was not as aware of before. However, health authorities still lean heavily towards promoting the consumption of oily fishes, often even singling out sardines/anchovies as top choices. I suppose the trade-off of higher PCBs but higher EPA/DHA + other nutrients is still a positive one, but I would love to explore this deeper! Let me know if you have any insights on this topic :)
Thanks for writing about such an important and neglected topic, Tandena! The EA community needs more people with ecology/biology backgrounds more generally, and perhaps writings like this on the forum will attract an increased diversity of academic backgrounds :)
Having written my thesis on Natural Capital Accounting which is adjacent to this topic, I wanted to share where I thought you downplayed too heavily the case for biodiversity in ensuring ecosystem services:
The portfolio effect is a well-studied, foundational benefit of diversity in many fields, from economics to ecology. Your claims that only a few dozen fish species would be needed to sustain wild fisheries or ~15 tree species would be needed for flood control maximises short-term efficiency at the expense of long-term resilience. So-called ‘functional redundancy’, where multiple species performing a similar role are treated as superfluous, is increasingly rejected in ecology, because species performing the same function often respond differently to shocks (e.g. one tree species may fail under drought while another tolerates it) so apparent redundancy becomes insurance against correlated failure—very similar to the portfolio effect on the stock market. This is already clearly seen in wild fisheries, where fishes occupying similar ecological niches respond differently to environmental shocks. Global fisheries exploit hundreds to thousands of taxa to stabilise overall yields.
With claims like “yes we lost a lot of benefits of natural flood control, but we gain greater benefits, else we would tear them back down,” you overlook several foundational problems in environmental economics:
ecosystem services are treated as externalities and systematically underpriced
people discount long-term benefits
ecological losses can be uncertain and only become apparent post fact
infrastructure creates sunk costs
ecosystem conversion is often irreversible or costly to reverse
Intact ecosystems have an option value because we can preserve them while learning more about their benefits, but cannot necessarily recreate them once destroyed.
3. I would also push back on the idea that preserving small existing populations in labs is sufficient, or that biodiversity becomes redundant once we have ‘gathered all their information’. Wild populations continue to evolve in response to climate change and other changing planetary conditions, generating biological information that does not yet exist, and would arguably be more beneficial for us as it reflects adaptation to the conditions we will increasingly face.
Very curious to hear your thoughts on these points! And thanks again for your work at ERI <3
Papers that might be interesting for you:
https://www.nature.com/articles/nature09060
https://onlinelibrary.wiley.com/doi/10.1111/brv.12756
https://www.nature.com/articles/s44185-023-00015-5