The Plant Superhighway!

I recently posted a video about the Plant Superhighway. In this video, I am in a weedy field which is turning into a young forest very near a busy highway in Oklahoma. The young forest seems so calm and serene in contrast. But, silent and underground, the plants have superhighways that are just as busy as those built by humans.

For much of my professional life, I considered ecological succession to be a process of shading out: trees such as many oaks in Oklahoma shade out the smaller trees such as honey locust, black locust, and persimmon, which shade out the bushes such as sand plum, which shade out the herbaceous perennials such as goldenrods, which shade out the annual weeds. That was pretty much the story as I told it in three of my books.

As far as this story goes, it is true. But I now realize there is so much more to the story than this. One reason that herbaceous perennials, such as goldenrods, displace the annual weeds is that the annuals have to sprout from seeds, while the perennials have already built up underground reserves and can grow faster in the spring. Bushes shade out herbaceous plants because their stems are higher up in the air; trees, higher yet. But the early-successional weeds, shrubs, and trees have another strategy (in the ecological sense) that promotes their survival and evolutionary fitness. They form underground connections.

When a goldenrod gets established, it not only puts down its roots and stores up food, but it sends out underground stems to new locations, where they become new plants, genetically identical to and connected to the mother plant. Through these underground stems, food can travel from one plant to another. Any plant that happens to be lucky can send nutrients to the less lucky plants, allowing them to form an integrated whole that secures resources for its use. I first learned of this from the research of David Hartnett and Fakhri Bazzaz at the time when I was in their lab at the University of Illinois.

This integration may be absolutely essential to the survival of early-successional plants; at least, most of them do it. In the video, we see goldenrods and false-goldenrods; sand plum bushes; and even trees such as persimmon, black locust, and honey locust that connected into large, integrated systems. It looks, at least, like individual, unconnected early-successional plants do not stand a chance on their own.

There might also be connections among different kinds of plants, via shared mycorrhizal strands. The “wood wide web” of inter-plant connections may be as important of an explanation of ecological succession as the process of one kind of plant shading another (as explained in an earlier essay and video. These connections dampen the variability of light, moisture, and nutrient conditions. They do this by forming underground superhighways.

 

Plants Will Save the World! Or Not

An old acquaintance of mine (well, no older than I am) responded to a message that I had posted on Facebook, in which I said I had my students do a project in which they increased their health and reduced their carbon footprints. My friend wanted to know why anyone would want to reduce their carbon footprint. Plants need carbon dioxide, so if we put as much carbon into the air as possible, we are feeding the plants, right? He was puzzled that I, as a botanist, did not seem to understand this.

He even had a scientific source for his views. He referred to the work of Sylvan Wittwer, a horticulturalist whose research showed that plants grow better in higher carbon dioxide. From this, Wittwer concluded that rising carbon dioxide levels in the air was a good thing.

In the narrow sense, Wittwer was right. Back in graduate school, I worked on experiments with Fakhri Bazzaz (University of Illinois, later Harvard) that proved this very thing. They were greenhouse experiments. But later outdoor experiments, using Free Air Carbon Enrichment (FACE) reached similar conclusions. What happened is that, at first, plants grow more when they have more carbon, but then the growth enhancement slows down. Just one example of this is a 2006 article by Stephen Long and Donald Ort, from the University of Illinois where I got my Ph.D. Unfortunately, I cannot provide the full text, since it is available only to members of AAAS. But you can read the abstract. Here is a photo of one such experiment. It was led by my fellow graduate student from Illinois in the 1980s, Rick Lindroth.

The problem with saying that plants will grow more and cleanse the air of excess carbon is that plants need lots of things other than carbon dioxide in order to grow. They need light, which on this planet is usually abundant. But they also need soil with water and nutrients. A lot of places on Earth have droughts and soil erosion, and in those places the plants cannot make use of any extra carbon dioxide. Most of all, plants need to not be destroyed if they are to grow and absorb carbon dioxide. A lot of forest and grassland is being destroyed. Forests grow back, but we are destroying them faster than they can grow back. Apparently the plants grew quite well in Wittwer’s greenhouses, but in the great outdoors, they frequently do not.

The results are clear. Carbon dioxide levels have been increasing. When measurements began in the 1950s, carbon dioxide levels were less than 300 parts per million. Today, they exceed 400. These numbers sound small but carbon dioxide is very good at holding in the atmospheric heat. Carbon dioxide is the main reason that Venus is hotter than Mercury despite being further from the sun.

If plants are going to save the world, why are they not doing so now? They seem to be totally incapable of absorbing the surplus carbon dioxide we have already put in the air. If plants are going to save the world, when are they going to start?

Plants need carbon, and we need water. But you can’t make us healthier by drowning us in water. You can’t make plants grow more by gassing them with carbon, except sometimes in a greenhouse.

Another problem is bias. Wittwer helped to start two major think tanks. One of these is the Greening Earth Society, which is sponsored by the Western Fuels Association. The other was the Center for the Study of Carbon Dioxide and Global Change, which does not reveal its funding sources but IRS records showed that at least one source was ExxonMobil. The very purpose of these think tanks is to convince people, mainly politicians, that global warming is nothing to worry about and we should use as much oil as possible right now. They fund only research that is consistent with this view.

Having bias does not mean that you are a liar. We all have biases, as I explain in Chapter 13 of my new book, Scientifically Thinking. But there is certainly pressure for scientists whose work is funded by oil companies to reach conclusions those companies would like. You would have to be nearly superhuman in your fairmindedness if your funding sources did not influence your conclusions.

One would think that the Center for the Study of Carbon Dioxide and Global Change would gleefully promote the conservation and replanting of forests and grasslands, in order to get them to grow back faster and absorb more carbon dioxide. I asked the lead scientist of that organization if his organization promoted conservation and reforestation. He answered that taking a stand one way or the other on reforestation was outside the mission of his organization. I took this to mean that his oil donors did not want him to say that we should save and replant forests, even if he personally believed it. Your funding sources not only influence your conclusions but limit what you can say. This man struck me as being honest, as honest as he was permitted to be.

My own research shows that buds of deciduous trees in Oklahoma have opened earlier in the spring by about one to three days per year over the last dozen years. This is associated with one component of global warming. Earlier budburst is not necessarily a bad thing, but it is a sign of global warming. This graph shows the earlier budburst dates in four major species of deciduous trees. Lower numbers on the y axis mean earlier budburst.

Budburst did not occur earlier each year, but over the twelve year period, the odds of this result occurring by chance were (by statistical analysis) less than one in ten thousand.

I have received no funding for this research, not from science agencies, nor from environmental groups, nor from oil companies.

So, what is my bias? Of course I have one. But it is not what you might think. I am a botanist. I love love love plants, starting with the green chlorophyll that absorbs sunlight all the way up to the whole organism and the whole forest.

In the photo on the top, green chlorophyll glows red because it absorbs visible white light but emits red light by fluorescence. The photo on the bottom is a water oak leaf, which is a photosynthetic factory filled with veins that deliver water and take away precious sugar.

I would love to be able to tell everyone, plants will save the world! They will scrub the excess carbon out of the air. Unfortunately, I have to dejectedly accept the conclusion that they will not. This is the conclusion I reached in Chapter 3 of my earlier book, Green Planet. The subtitle of that book shows clearly that I really hoped that plants would rescue us from the greenhouse effect: How Plants Keep the Earth Alive.

It is with a heavy heart that I must report to you that the research conducted by a handful of oil-funded scientists is incorrect, and global warming is real, getting worse, and very dangerous.