>Unexplained fertility decline in the last 40 years?

That's why human population has nearly doubled in last 40 years?

No, look at this: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6455044/

Decreased sperm count in the west. Could be due to a variety of factors.

But tie it together to microplastics: https://pubmed.ncbi.nlm.nih.gov/38745431/

And you got an interesting result.