Last year, the global population celebrated its 7 billionth person to the planet. We hardly seem to be having a fertility crisis, by all indications. But most of that growth is in developing countries, while developed countries, like in Western Europe, have seen falling birth rates. Now, experts are drawing attention to an issue that seems to be growing: sperm quality is declining in quality and quantity.

The Los Angeles Times has published an article in which they have highlighted the plights of two fertility clinics in Israel. One, the Cryobank Israel, is the country's largest sperm bank. The clinic features sperm from tall, handsome soldiers whose sperm passed rigorous genetic tests. Today, only 1 in 100 donors make the cut, down from 1 in 10 a decade ago. The Hassadah Sperm Bank has had to relax its own stringent selection criteria that it implemented in the beginning of its existence in 1991. Then, 1 in 3 men were rejected. If the same criteria were used today, the clinic would reject 80 percent of potential donors. The sperm bank currently rejects two-thirds of donors today.

Scientific experts seem to confirm that the plight of sperm banks in Israel are not isolated incidents. Grace Centola, a sperm bank consultant and president-elect of the Society for Male Reproduction and Urology, analyzed 8 years of sperm donor data in the Boston area. She found a significant decline in volume, mobility, and count over the years, even though the age of applicants remained the same. A study published in the British Medical Journal found that sperm counts had halved, going from 113 million sperm per milliliter to 66 million.

Admittedly, that number is still well above healthy; the World Health Organization says anything above 15 million sperm per milliliter is considered normal. And, globally, we do not have a fertility crisis on our hands. In the United States, our birth rate is healthy at 2.06; even Israel's fertility rate is 2.67.

Other U.S. sperm banks contacted by Live Science did not report a drop in quantity or quality of sperm, and other studies are inconsistent. And, as some researchers have pointed out, all the studies about this topic have been conducted in high-income countries, provoking bias.

Regardless, the issue may be symptomatic of larger problems. People are blaming everything from estrogen levels in milk, cell phones, pesticides, diet, water contaminated by birth control pills. But, though there is no consensus on the root of the issue or even if there is an issue, it is clear that such a rapid environmental change warrants further examination.