Some things worth bearing in mind. These studies come from the field of epidemiology, which is notorious for low quality studies that rely on flawed assumptions to create apocalyptic scenarios. Everything coming out of this field has to be assumed to be suspect until thoroughly vetted by outsiders.

At least, that's my personal belief. Let's do a quick literature review to check if there's disagreement with the claims of the researchers.

Firstly, are sperm counts actually falling at all? The article says:

"Sperm quantity and quality have dramatically declined across Western countries in recent decades, with research suggesting sperm counts have been more than halved in the space of 40 years."

But Tong2022 [1] says:

"Concerns regarding declining sperm counts have existed for over 50 years, and even predate the use of a standard means to assess semen characteristics ... in the field of reproduction, the contention that sperm counts are declining is not universally accepted and has been a hotly debated topic over the last several decades.1,5-9"

If they are falling, does it actually matter?

"... our review suggests that a decline in sperm counts does not necessarily translate to a decline in male fertility"

A New York Times report [2] on their study stated:

"Now a group of interdisciplinary researchers from Harvard and the Massachusetts Institute of Technology contend that fears of an impending Spermageddon have been vastly overstated. In a study published in May in the journal Human Fertility, they re-evaluated the 2017 review and found that it relied on flawed assumptions and failed to consider alternate explanations for the apparent decline of sperm ... even the data that passed muster was geographically sparse and uneven and often lacked basic criteria like the age of the men. Moreover, its authors took for granted that a single metric — sperm count — was an accurate predictor of male fertility and overall health ... no one knows what an “optimal” sperm count is ... as methodologies for counting had improved and been standardized since the 1980s, sperm counts had appeared to fall. In other words, it may simply be that earlier scientists were overcounting sperm."

A lot of this stuff originates in a 2017 meta-study by Dr Swan et al. Tom Chivers reviews Swan's book on the "spermogeddon" [3]:

"the book does not seem sensible. Because for Swan, everything causes fertility problems, not just phthalates. Sugar, beef, cycling, stress, watching TV, doing too much exercise, doing too little, eating the wrong diet; you can barely get out of bed in the morning without sabotaging your chance of having a baby ... I half expected her to say we ought to wear ray-shielded underpants ... She even suggests that the growth in intersex conditions and perhaps the rise of gender dysphoria, and even changes in gender identity, could be because of EDCs (and taking paracetamol in pregnancy!)

This hyperventilating about human extinction, and rolling everything bad into a ball labelled “fertility and phthalates”, makes no sense if you think Swan (a respected epidemiologist) is trying to give a dispassionate assessment of fertility issues. But she’s not. This is a polemic."

A key problem with Swan's argument is that she and others like her define fertility as how many babies women have. This makes it easy to draw a correlation between falling sperm counts and falling fertility, but eliminates the impact of free choice. Women prefer to have fewer children as their countries get richer and child mortality falls, but as far as these "respected epidemiologists" are concerned that's apparently out of scope.

[1] https://bcmj.org/sites/default/files/BCMJ_Vol64_No3_bcmd2b.p...

[2] https://www.nytimes.com/2021/06/04/health/sperm-fertility-re...

[3] https://unherd.com/2021/03/the-truth-about-spermageddon/