National Geographic December 2013, Part 3

The Unexpected Walrus, by Jeremy Berlin, photographs by Paul McNicklen

I am unclear on what is unexpected here.  The Unexpected Walrus is a brief sort of biological sketch of the species and the effect that human activity can have on their numbers.  Walruses’ whiskers are apparently very sensitive and they can hoover up food from the ocean floor like no one’s business.

It’s an ill wind that blows no one any good, however, and apparently global warming is exposing more clams, which are a main source of food, than the walruses would normally have been able to get to.  So as difficult as humans have made the life of the walrus, at least the walrus is finding food more plentiful than in the past.

The Weed that Won the West, by George Johnson, photographs by Diane Cook and Len Jenshel

The Weed that Won the West is a quick read about the history and lifecycle of the tumbleweed, more formally known as “Russian thistle” and also of Johnson’s history with said plant. Johnson, who has been fighting tumbleweeds ever since he and his wife bought a horse ranch in New Mexico, compares the tumbleweed to a The Outer Limits episode, “Cry of Silence,” in which a young couple are menaced by sentient tumbleweeds.

Turns out tumbleweeds don’t actually need sentience to be menacing, because they are pretty much optimized* to reproduce.  As tumbleweeds tumble along, they are shedding seeds.  Then the seeds can lie dormant for years, but can germinate in as little as 36 minutes. The plant also has a taproot which can reach a depth of six feet.  This means that you can pull all of the plants out of the ground and it can still grow a new plant from the taproot.  And even after you think you’ve gotten all of the plants off of your property, there still can be seeds in the dirt waiting to sprout. The only defense I have been able to find is that the seeds cannot germinate in packed dirt, which is kind of impractical.  In order to use this defense, every square foot of land in the area must somehow be packed down perfectly and remain packed down until all of the seeds have lost their ability to germinate.

Before I moved to San Antonio, I imagined that it looked like an old west city, like Dodge City in the old movies, with tumbleweeds tumbling down the streets.  Thank goodness it isn’t. I have enough fun trying to keep on top of the runners that my live oak trees put out.  I don’t want to have to wrestle with tumbleweeds on top of that.

*You have no idea how much time it took me to find the word “optimized” — I almost went with “maximized,” because it was pretty close.  I also researched “tribbles,” even though I’m not terribly gung-ho on Star Trek (I’m more of a Babylon 5 girl, myself) in hopes that I’d stumble across the right word.  Finally I stuck “maximized for reproduction” into Google and the second hit was titled, “Optimal Reproduction Tactics,” and the rest was history.