Nov 2, 2023 - Energy & Environment

Why acorns might be pelting you more this fall

Illustration of acorns with parachutes made of acorn caps.

Illustration: Shoshana Gordon/Axios

If your sidewalks are extra nutty with acorns this fall, certain species of oak trees in the region may be "masting," or producing enormous crops of seed.

Why it matters: There's a mystery at the center of why there are so many nuts, as scientists are unsure exactly what triggers "mast" events every few years or why many tree species — not just oaks — experience them.

  • That, of course, hasn't prevented them from proposing a range of explanations.

How it may work: Some scientists have suggested mast events could be set off by environmental factors, like temperature and precipitation, or chemical signals, such as pollen levels.

  • They've also proposed that they may be tied to the availability of resources like fertilizers and light, as producing a large volume of nuts is costly work.
  • Complicating things further, though, is that the mechanisms behind mast events may slightly differ for separate tree species or even between individual trees within the same species.

Though scientists still have to pinpoint the specific mechanisms behind mast events, they do know that they can have profound effects on the local environment.

  • Masts typically result in a sudden abundance of sustenance for a large variety of animals, which heavily alters the local food web.
  • The acorn, of course, is inseparable from squirrels, but the nuts are also an important energy source for bears, deer and many different types of birds and insects.
  • The glut of food then has several cascading effects, promoting the growth of many animal populations, including rodents and deer, which may go on to be consumed by other animals.

The fact that so many animals feed on nuts from oak, hickory, beech, witch hazel and black walnut trees may actually explain why they and other plant species evolved over millions of years to experience mast years.

  • By delaying seed production for a bumper crop, the trees may satiate predators' voracious appetites. That allows some seeds to survive the feast and eventually germinate into new saplings.

Of note: Raw acorns are toxic if consumed in large amounts, but cooked acorns have been a food staple for humans for thousands of years, so much so that there's actually a word for the practice: balanophagy.

The big picture: Tree masting varies widely from region to region.

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