A sweltering, record-breaking heat wave throughout Europe this summer is causing widespread drought, and river levels, such as along the Elbe, are reaching critical lows. The crisis has gotten so bad that many large river stones that have been underwater for centuries are now being exposed, and many of them are inscribed with grim, dire warnings.

"If you see me, weep," reads one.

Another reads: "If you will again see this stone, so you will weep, so shallow the water was in the year 1417."

Known as "hunger stones," these ancient boulders only get exposed in times of severe drought, and over the centuries they have been carved with woeful messages that tell not of the past, but of prophecy, of desperate times ahead, reports NPR.

At least a dozen hunger stones can now be seen in and near the northern Czech town of Decin, near the German border, according to an Associated Press report. It is likely to mean what it has meant for centuries: bad harvest, scarce food and higher prices. It also threatens transportation along the river, further stagnating local economies. In the past, these conditions could have led to famine.

While there are safeguards against such extreme hardship today, those safeguards are only temporary. And droughts like the one this summer could become a regular occurrence across Europe due to global warming. In fact, recent droughts, including this one, have been strongly linked to rising summer temperatures. So drought could soon become a trend rather than an aberration.

And hunger stones aren't the only ominous artifacts emerging from the shallow waters. Unexploded bombs and hand grenades that have been corroding in this waterway since World War II have also become exposed for the first time in over 70 years. It makes wading in the already-diminished waters even more precarious.

It goes to show that our demons are always lurking, just beneath the currents. We'd best take care of our environment for the sake of the future; otherwise, we'll be doomed to relive the worst of our past.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

Ancient European stone inscriptions revealed by low river levels carry grave warnings
'If you see me, weep,' reads one of these so-called 'hunger stones.'