Growth, Part II

What is a weed?
-It's a bad plant.
-An ugly plant.
-Something that shouldn't be there
-It's non-native.
...
Not quite. If a Serviceberry bush crops up in a farmer's wheat field, it's the native shrub that's the weed, even though wheat is native to Mesopotamia. The concept of a "weed" is entirely determined by a human context, by our own placement of value on some species over others. So even though I'll warn the kid who said "bad plant" to not be so subjective, in essence the scientists base their work on a similar subjectivity.
In order to answer the question of "What is a weed?" we have to take a big step back, and consider the world in which we live, and how we want this world to be. We have developed much of the earth's surface for urban centers, suburban developments, and farming. We run cattle on many lands. We exploit vast areas by drilling and mining. We love our cities, our suburbs, our farms, and the products we get from natural resource exploitation. And we also love our "wild places," the Yellowstones and Yosemites and Grand Canyons, which we've set aside, protected from "the hand of man" so that we can enjoy the "unspoiled and timeless earthscapes" for many generations to come.
This is all fiction of course. All this land is touched by the hand of man. Many places were farmed or settled centuries ago. The act of preservation has often meant wildfire suppression, and this indirectly effects change on the land. And perhaps the largest way that we passively touch our earth- the second largest cause of species endangerment to date- we introduce exotic species.
With the ever-increasing rate of global travel and commerce, we carry around seeds and eggs and plants and animals, and constantly release species upon the land that don't belong. Since Pangea separated 250 MYA, isolation has allowed certain plants and animals to coevolve and develop balanced relationships. When an exotic species suddenly shows up off a Boeing 747, the danger stems from the fact that this newby did not coevolve within the ecosystem. So maybe there is nothing here capable of eating it. Even though back home it is just part of the mosaic of plants, maybe in its new context it is capable of pushing out native species, spreading quickly, and creating homogenous stands. If it can do that, we call it "invasive."
Now, what's a weed? As I've said, it starts with our intentions. In our protected, "wild" places, our intention is that the landscape represent a native, natural, "untouched" state. If a weed is a plant that we don't want, then in a National Park the exotic plants are weeds. So if we want to maintain the "natural" character of these places, we actually have to go in and proactively remove the exotic species. Some have the ability to become invasive and therefore take over huge areas of land, so they must be prioritized for removal.
It sounds counterintuitive, that we have to stomp around upon this land in order to leave it "untouched," but we have to realize that we've already touched the whole globe. Now it's ours, and if we want to keep some parts of it beautiful, inspirational, and powerful, we're going to have to work for it.