Sunday, July 23, 2017

Invasion!


I took this picture on the train station on my daily commute. There are four problem species in the picture: Asian bittersweet, Japanese knotweed, bamboo and Concord grapes. Of the four, only the grapes are native.

For us, this year is a particularly bad one for bittersweet. We’re finding it everywhere. They Gypsy moths, which seemed to like everything, leave bittersweet alone. We’re finding it pretty much anywhere there’s any kind of shrubbery.

Different vines use different methods of gaining a foothold. Grapes have tendrils that curl around a base. Poison ivy—one of my particular favorites—actually bores its roots into the barks of the trees it parasitizes. I don’t know if it actually vampirizes the tree but it’s creepy to watch a poisonous plant stick itself right into the bark like some snarling alien.

Bittersweet is just as nasty. It grows around whatever it’s based on, encircling and eventually strangling it. It’s quite prevalent up here in the northeast. I’ve driven sections of highway where both sides are covered in rounded mounds of bittersweet, their searching tendrils sticking out like triffids.

The good news is they’re non-toxic so you can pull them up by hand—and you have to pull them up. They’re like Hydra: cut off a limb and two more shall take its place.

But these are just the visible aspects of a larger problem. The US has a real problem with invasive organisms. In large part, it’s a self-inflicted wound.

This goes back to the very beginning of the United States. Earthworms were not native to the northern US since the last ice age.  The result was deep beds of leaf litter and a rich understory. Enter the lowly earthworm brought over by English colonists in their fruit trees. Notice the lack of deep leaf litter in the area.

Not to mention sparrows and starlings. Sparrows were at least introduced here in an ill conceived attempt to control the linden moth. Ah, but the starling, a relatively ugly bird with noisy habits, was introduced because the American Acclimatization Society thought the USA should have all of Shakespeare’s birds. 

There is also the Burmese python. Who would have thought it would have thrived in Florida? I used to have a Burmese but I, like a lot of other people, found it got too big and so I gave it back to the guy I bought it from. He had a 23 and 24 foot pair. They lived in the first floor of his house. These were big enough to eat him.

But my own personal favorite is pampas grass—which you can still buy! Up here if you drive by a marsh that should have an abundance of native grasses and cattails, you’ll see unbroken pampas grass. Nothing eats it. Nothing nests in it. It’s the Styrofoam of the plant kingdom.

It’s interesting that we in the New World seem to get the short end of the stick with invaders. It turns out that the New World has a significantly shallower evolutionary history than the Old World. See here and here.)  I’m not sure why that is. When I read the original article I didn’t see an explanation. Could it be that the New World is the site of the Cretaceous meteor extinction event? Is it size—the Old World has Europe, Asia and Africa. We have North and South America connected by a fragile thread. Not clear.

Invasions are rarely pleasant for the invaders. For example, the brown marmorated stink bug destroys fruits and vegetables because it can reproduce without problems. Why? Because back in China, the bugs original home, there’s a parasitic wasp that lays its eggs on it. The larva hollow out the bug like United Fruit did Central America. 

This is a pattern. Species get transported here and do well because they do not have the same predators they did back home. Birds and turtles will eat Gypsy moth larva but with the numbers produced, they can’t keep up. Thank you, √Čtienne Trouvelot

Sometimes, I find this sort of thing discouraging. Okay, we’re poisoning the planet but putting out CO2, methane and mercury introduces passive problems into the system. Sure, it’s bad. But the CO2 molecules don’t go out there and make more CO2 molecules. Starlings and pythons are active agents. They’re the equivalent of Von Neumann  or Berserker machines. 

But from bittersweet to buckthorn to bullfrogs, human beings are one of the most successful couriers in biological history.  We’re just going to have to live with it.

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