Weeds

There was a podcast on Science Friday that originally aired on July 15th of 2011. It was about Weeds and Invasive Species. I listened to it again around the end of December 2011 and put an outline here on my blog, and now am sitting down to complete the entry in May of 2012.

The subject was weeds. This is usually a plant, and sometimes an invasive species. Simply put, it is a species that is in a place you don't want it. By this definition, you might include some animals, although you wouldn't call them weeds. Many people would treat them the same, though. If it's something you don't want, many people try to eradicate them.

The discussion between the two guests, one a Professor of Biology, and the other an author, was interesting and struck a chord with me. I've often been a fan of plants that other people are always trying to kill (animals, too, for that matter). I've had a hard time whenever I tried to explain the virtues of a species to someone who had a deep hatred for whatever it was. I often wondered where they got their idea and how you could ever change their minds.

At the core of my belief is the thought that biodiversity is important. Not just the liberal activist, knee jerk recitation of "biodiversity" as a way of sounding hip and trendy without really thinking about it. I've always thought that life on Earth forms a web, a rich tapestry made of many ingredients. When you start knocking out certain strands of the web or certain patterns or colors of the tapestry, you run the risk of making the structure fall apart and causing it to stop functioning. You never know what other species might be depending on that particular plant or animal, so it's best not to make an arbitrary decision that it's "undesirable" and try to wipe it out. If you find out later that you needed it, it could be too late. Nature evolved in equilibrium with each species as part of the mix, it's insane to think that removing some of them at random won't have an effect on the rest.

Another thing I've always suspected is that there will be value in most species, if studied close enough. This is beyond the way that this species impacts others, or the exact role it plays in nature. I believe that most species have one or two molecular tricks that their DNA perform that we can learn from. It seems that each time we really study a life form in detail, we find something biochemically about it that is unique. We will need all these tricks if we are to survive in a resource starved and overpopulated world. The obvious example of this is the search for medicines and other pharmaceuticals in plants, but what if the thing you find is an adhesive or a natural plastic? It's still valuable.

One of the interesting points the podcast guests made was that many species tend to rapidly colonize and thrive in environments where we have disturbed the soil. There are natural disturbances, volcanic eruptions, landslides, erosion or deposition of soils, and these events all are followed with a series of plant species that come in to perform specific tasks. The first colonizers anchor the soil and provide ground cover and deposit nutrients when they die and decay. Eventually, a series of species take their place in the recovery of a disturbed area, sometimes crowding out the early weedlike species, sometimes living side by side. Ultimately, a dominant species like trees come to take over the area, forming a mature and stable landscape rich with niches for other species to inhabit.

The other interesting aspect of many plants that are considered weeds is that they could have a beneficial function that is not obvious. Some "weeds" condition the soil. I recently discussed this with a friend. He will have to regrade and reseed a recently completed yard because of buried septic and ground source heating systems. I suggested clover to nitrogenate the soil, but he was concerned that he would not be able to wipe it out once it was established. I suggested he let it stay to feed the honeybees, which are having a hard enough time struggling for survival.

We often become dismayed when a nonnative species takes over an ecosystem. I'm not sure we can be certain that this is a bad thing. The Great Lakes were so polluted that they were a tragedy just a few years back. With the invasion and profusion of the tiny zebra muscle, the lakes are now so clear that you can see down for 30 to 40 feet in some places. It just sits there with it's little shell open filtering the water. They determined that cattails remove heavy metals from marshlands. Some people have considered actively using them for remediation of polluted waterways. I saw a road crew spraying some kind of herbicide on roadside cattails just yesterday.

Another point that the guests made is that you might as well find a way to live with unwanted species, as it is virtually impossible to eradicate some. I know most people have heard that dandelions can be used to be in salads, so that is a direct use (which I have often thought would be to my benefit if civilization fell, I'd be able to eat the greens out of my yard). But there are other issues, such as the Asian Carp, an highly invasive species that it spreading in the rivers outside of Chicago. Apparently, these fish could be harvested without limits and would still thrive, and there is supposed to be a huge market for their meat in China. I heard that the Kudzu grass that is taking over in Australia is causing some to consider importing elephants from Africa to come and graze it back down to manageable proportions.

I liked the way the podcast guests described weeds. One quoted Ralph Waldo Emmerson, who said a weed is simply a plant whose virtues have not yet been discovered. Another noted that a common definition of a weed is a plant in the wrong place. He then asked, "What is the right place? Who makes the decision?" He noted that these answers are entirely subjective. A weed is a plant that gets in the way of your plans. Why not change your plans?

Their discussion of Invasive Species was interesting. They noted that the northern parts of our continent were scoured clear of all life during the ice ages. That means that everything we see is new as of 25,000 years ago. So invasive and non-native classifications beg the question of how do you declare the cutoff date for when such a distinction began. Most people do not know that many state flowers and insects are not native. Vermont has the Purple Clover and the Honeybee as the state flower and insect, when neither were here when the state was colonized by Europeans. For many people non-native species have always been there and are not considered an invader.

One of the guests remarked that all weeds are trying to do is green over empty ground, and for that, we should give them a second chance. A caller in to the program tried to counter that many native species are dangerous, poison ivy, trumpet vine, and the plant responsible for milk sickness. The author remarked that the berries of poison ivy are the most important food of Chickadees. He proposed that we need to take a planet centric view of all species and try to answer how they fit into the whole environment.

There was an interesting discussion of perception. The guest said that we should not embrace the native versus non-native difference, which is exceedingly emotional for some people. People like to dislike certain species. When altruism evolved, along with that was a distrust of people outside your own group. Maybe people were predisposed to have an us versus them viewpoint on the world. We just fall into this trap when it comes to species, we embrace the natives and we love to hate the non-native. It's a natural instinct of humanity, but not necessarily a useful one.

Another more recent podcast that I listened to says that we absorb and hold all kinds of micro RNAs from plants. They speculate that this enables us to make proteins with bigger building blocks and makes for an efficient metabolism, but also that we may have co-evolved with certain plant species whose chemical contribution gave us an edge. It's not just raw building blocks or minerals or other simple chemicals that are part of a good diet, it's part of the unique substance of a particular plant that can be quickly used by our bodies. Wouldn't it make more sense to figure out what there is out there before we arbitrarily wipe it out?

[NOTE: the field of yellow flowers that was thick with bees and butterflies was sprayed with a herbicide shortly after the pictures were taken.]