Sunday, September 30, 2007

Weeds?


Rob Hardy, on his recent return to Northfield from the UK, wrote about pulling weeds from around his garage. He mentioned that the now-reviled buckthorn was sold to Midwesterners as an effective hedge. In yesterday’s mail came St. Olaf College’s newsletter “Posten” and the cover story was about an artist who wants to help eradicate buckthorn and is using dead buckthorn stems to build a sculpture resembling giant dandelions. Last week, the Minneapolis newspaper carried a story about an exotic aquatic plant growing in Powderhorn park. This plant is sold in pet stores to decorate tropical fish tanks. Apparently, someone dumped a tank and a plant into Powderhorn lake. To everyone’s surprise, the plant appears to have survived a couple of Minnesota winters, is in fact thriving, and may even push out other plants. This has lead to some fear that the plant – considered invasive, just like the buckthorn – may spread to other lakes. Then, to top off the week, the following announcement appeared on Grants.gov:

Department of the Interior
Bureau of Land Management
County Weed Assistance Program within Grand, Larimer, and Jackson County, Colorado


I don't know what kind of weed problem they have in those three counties or why a federal grant is needed to help the weeds (or the counties), but the events of the week seemed to demand some thinking about weeds and more generally about our desire to control the environment and our often competing desire to control each other.

A weed is, broadly, any unwanted plant. A soybean plant in my cornfield is a weed, and a volunteer corn stalk growing in my soybean field is a weed. Lawnophiles regard the dandelion as a weed (though some might turn right around and plant yellow mums in the garden).


The buckthorn (that's a picture of glossy buckthorn on the left) and the Powderhorn exotic are different kinds of weeds than the common dandelion or the stray cornstalk. They are said to be invasive because a) they are non-native and b) they are robust and therefore tend to push out the plants that were there before. Here is where I get a little confused. When a plant is spread by the wind or by animals, that’s natural; when it’s spread by humans (as in a tropical fish aquarium or the ballast tanks of a ship), that’s invasive. But if the plant thrives in its new environment, isn’t that natural? If I eat some fruit in the wilds of Borneo, and deposit the seed back in Minnesota, and that exotic fruit takes root and spreads, how is that invasive? Or how is it more invasive (coming from a human vector) than if that same seed had come in on the wind or in the bowls of a bird?

John McPhee has written about volcanoes and about the ways in which barren lava fields are gradually (and sometimes not so gradually) filled with plants and animals. In his beautiful essay “Cooling the Lava,” he describes the volcanic island of Surtsey, which formed off the southern coast of Iceland between 1963 and 1967 in a more or less continuous eruption (that's a picture of Surtsey at the top of this entry). Scientists watched eagerly for the first plant to appear as the lava cooled. The first shoot turned out to be a tomato plant, presumably deposited in a hunk of bird scat. But the seed could just as easily have been washed ashore from a garbage scow or been tossed there from a passing pleasure boat. Is a tomato on Surtsey invasive or exotic? Does it matter how it got there?


If buckthorn has been around here for generations, and if it seems to thrive, and if it’s not doing any harm, then why are we so eager to get rid of it? Why is the prairie as it was in, say, 1650, preferable to the prairie as it was in 1950? Or as it is today?

I pity the poor buckthorn, with the forces of artists, historic preservationists, ecologists, and sentimentalists allied against it. The buckthorn needs some defenders. I hereby volunteer.

The opening salvo in the Great Minnesota Buckthorn Skirmish is…a poem!



Endangered

I grow.
This is all my creator ever asked of me. My
leaves are green, my berries moist, my roots deep.

I reproduce.
This is nothing but simple biological necessity, an imperative shared with every
other living thing. I’m good at it. Too good, I guess.

I adapt.
There are hundreds of varieties of me because I have learned the tricks of
transformation and adaptation, the lack of which has caused lesser plants to die
off. This is also a completely natural thing.

I look down the hill and
see enemies amassing – humans who want to stop time, who want to change the
natural course of history by killing me and my progeny. They are on the march,
with weapons named Weed Wrench and Husqvarna. They arm themselves with
poisons named triclopyr and glyphosate. They may as well carry M-16s or spew Agent Orange.

Some are grimly determined, like
religious zealots. Others smile beneficently, like flower children from the
1960’s.

If they succeed, and my numbers shrink, and I become rare – even
endangered -- who will sound the alarm then? Will my few remaining successors be
protected?

5 comments:

Rob Hardy said...

Jim, I think one of the major problems with aggressive invasives like buckthorn is that they crowd out biological diversity. The balance of most ecosystems depends upon diversity, on the complex interrelationships between diverse members of an ecological community. Often, organisms in a native community have co-evolved, and need each other to survive. Take away one native species and substitute an aggressive invasive species, and other native species may begin to fall like dominoes.

Bleeet said...

What the hell, Jim?! Why am I learning things from your blog? What the shit is going on? This ain't right. I'm learning things from you? I thought you were some sort of harmless potter.

Great post. They won't be able to get rid of the buckthorn. Just wait for them to "clear" an area, then take some clippings, berries or whatever and bury them when the people are out of the cleared area.

(Evil Laugh. Evil, Evil Laugh)

Jim H. said...

Rob:

My question about biodiversity is: who gets to decide how diverse a given chunk of land should be? You've written about the oak savannah. Could there have beeen too many oaks on the oak savannah?

And if a state of biodiversity (however defined) can be maintained only by force, should it be?

Rob Hardy said...

The oak savanna is an interesting case, since it did rely on fires (often set by humans) to maintain its distinctive features. Once the fires stopped, there often were too many oaks in the savanna, and it just became woods. But in general, I think diversity evolves, just as individual organisms evolve. So, ideally, nature decides.

Rob Hardy said...

I've posted a long-winded piece, addressing some of these issues, on my own blog.