Poison Ivy Isn't Poison

Yes, you heard that right. Poison ivy is not poison. I recently posted a YouTubevideo in which I cuddle up next to a poison ivy plant (they are ubiquitous in Oklahoma) to address this topic.

Plants—all plants, all the time—are engaged in a silent struggle for existence. You cannot see it, especially in a peaceful forest, but you can imagine it. Leaves contain thousands of different chemicals that are mildly or very toxic to herbivores. This makes perfect sense, because any plant that did not defend its leaves against herbivores—any leaf that said, “Come and eat me!”—would quickly disappear down the gullets of extinction. Each kind of plant has its own cocktail of poisons.

But when a plant defends its leaves, it is an investment decision. Plants that produce too much defensive chemical, and thus waste their precious resources, risk extinction just as surely as a plant that produces too little. A leaf has to pay for itself by photosynthesis, but also by not having excessive maintenance costs, including defense.

None of this, however, explains poison ivy. In poison ivy and related species within the genus Toxicodendron, a set of chemicals collectively called urushiol harm humans, but not most other mammals. According to this scholarly article (which can be downloaded here), “Deer, goats, mice, and other mammals readily eat poison ivy foliage without apparent discomfort.” I have seen squirrels eating the berries. Clearly, urushol is not a metabolic poison.

The human immune system reacts to urushiol as if it is a pathogen. That is, urushiol is an allergen, not a poison. Poison ivy itch is a massive allergy. Some people are more allergic to urushiol than others, just as is the case with other allergens such as pollen (hay fever), gluten, etc. But why does poison ivy affect only humans? It seems incredible to me that humans might have exerted an evolutionary pressure on poison ivy sufficient to select for the urushiol response.

As far as I can tell, no one has explained why poison ivy plants produce urushiol. It must have some function unrelated to defense. There will always be mysteries and unanswered questions in science!

I am working on a book, tentatively entitled Silent Struggle: The Hidden World of Plants. Watch for it!

The Allure of Science

In the eyes of most people, science has a lofty allure. Even people who do not like the conclusions and beliefs of scientists feel this way. Why is this?

The ideal scientists zealously pursue the truth about the natural world, relentlessly cutting away the prejudices that they and others have, and demanding only the best evidence. No sloppy thinking allowed, no reliance on hearsay or single observations. To be a scientist is, in some ways, like being an athlete. Scientific thinking is a discipline. It is available to anyone, but it is usually only professional scientists and science educators who take on the discipline consistently. A scientist exploring the depths of nature, and an athlete running the course, have a kind of golden shimmer quite unlike the sloppy thinker or the armchair athlete.

This is why anti-scientists want to look like scientists. There are numerous anti-scientific think tanks that announce their seriously flawed beliefs in sciencey-sounding jargon. And some religious groups have even started up their own pseudo-scientific journals. They imitate the very appearance and structure of scientific articles: an objective-sounding title; an abstract; a text that cites evidence and analyzes it with reason; a conclusion; and references to other articles previously published on the same topic. They want everyone to think that they are scientists, even as they discredit scientists.

One example is an article in “Answers Research,” the pseudo-journal started by Answers in Genesis, that purports to show that the speed of light has decreased over the last few thousand years. Therefore the red shift does not indicate the universe is billions of years old but that light used to travel a lot faster than it does now. From the link you can download the PDF. The PDF of the article looks exactly like a scientific article, down to the most minute detail of its appearance.

One hallmark of scientific papers is that they are “peer-reviewed,” which means that other competent scientists anonymously review the paper and pass judgment—sometimes fair, sometimes unfair—on whether the paper should be published. If religious pseudo-science articles have “peer review,” it only means that people who share the same delusion have read it prior to publication.

Remember that in such pseudo-journals, anyone can be a peer (in the sense of micturator).

Of course, it is not just creationists who produce fake scientific articles. There are numerous online journals that will print anything so long as it has a sciencey appearance and you pay them. There is no peer review. I discuss this in Chapter 14 of my book Scientifically Thinking. I end that chapter, “I’m thinking about starting a science journal. I only charge $10,000 per article. If you are interested in publishing there, let me know, and remember I’m a peer.”

I suppose I am flattered to be a legitimate member of the scientific community. But, with ever more fake scientific journals, I fear that the public will begin to disbelieve true scientists along with the fake ones. With this, society can no longer benefit from true scientific research.

Trust the Mother

One of the most divisive political issues is abortion rights. I am a scientist, and I can tell you that there is no single point in embryonic or fetal development in which the unborn child “becomes human.” It depends on the indicator that you use: heartbeat, brain activity, etc. all begin at different times. There are even three events that occur during “the moment of conception.” As a result, I have no scientific opinion about “when life begins.” Nor will I speculate about morality or politics. But I do have some scientific insights that you might find useful.

Love evolved. Love is, from the evolutionary point of view, the instinct for helping and protecting other animals in your species. Natural selection has favored animals that protect their offspring. In this way, they maximize their reproductive success. If you want to know more, search for information about inclusive fitness. The most famous examples are from insects such as bees, ants, and termites, and among mammals such as ourselves.

The strongest love in the natural world is the love between a mother and her offspring. It is a force of nature. If you get between a mother bear and her cubs, it might be the last thing you do. This is because the cubs are the mother bear’s entire genetic future. Human mothers are no less motivated to protect their young, including those not yet born, than any other species of mammal.

In the animal world, a mother’s love is, on the average, stronger than a father’s love. The reason for this is because the mother always knows which offspring are hers, but the father cannot be certain. Every ounce of effort that a mother puts into nurturing and defending her young is well spent, but for the father, there is the lingering subconscious question about whether the offspring are his. (“Mommy’s baby, Daddy’s maybe.”) Genetic tests, in humans and birds, show that some of the offspring in the nest or the home, which the father supposes to be his, are not. The offspring may not be the father’s entire genetic future. Most of us fathers love our children, but on the average, mothers love their children more.

And a mother loves her offspring, including those not yet born, more than politicians do.

Given that a mother’s love is the strongest love in the natural world, I believe we should trust the instincts of an individual mother. The idea that pregnant women are eager to kill their unborn children unless white men pass laws and tell them not to is ridiculous. Maybe we should trust the mother to make the right decision regarding her unborn offspring.

What Is a Forest Worth? More Requiem for Nature

Whenever I write about somebody else’s book, I fear that I might have represented it. I sent the link to the previous essay to John Terborgh, author of Requiem for Nature. He responded that my summary was essentially correct. He added, reprinted with his permission:

“The world has moved on in a way that is predictable but not conducive to protecting nature. I say predictable, because the fundamental economic goal of nearly every country on the planet is to maximize economic growth. With this as the background to nearly all important policy decisions, nature doesn't have a chance. It is the empty chair at the conference table.

Perhaps the most memorable lecture I heard in college was one delivered by my Freshman biology professor in which he laid out in vivid terms the consequences of unchecked population growth. That, my friend, was in 1955. Here we are, 64 years down the road, and putting the brakes on the human population is still a topic that can't be mentioned in polite company - much less in open political debate.”

One issue in my essay remains unresolved. Terborgh said that a tropical forest is worth more dead than alive. In my book Green Planet, I said that a forest is worth more alive than dead. Which of us is correct? I realized that it depends on who is making the decision. For people collectively, as in a community or a world, a forest is worth more alive. But for individuals or corporations whose only goal is short-term profit, a forest is worth more when it is dead. Alas, evolution (biological or cultural) rewards individual, not collective, benefits. Collective benefits accrue only when they provide a direct and immediate benefit to individuals. For example, altruism within a group of animals offers immediate benefits to most, even if not all, of the individual animals in the group.

In the first photo, I am leaning against a rainforest tree (I have no idea which species, there are so many!) in 1989; in the second, I saw an area in which the rainforest had been hacked away, exposing soil to erosion.

Meanwhile, all I can do is to teach and to write. I continue to do these things even if they are likely to have little effect on the course of the future. As John added at the end of his message, “Carry on with your efforts to prod students into thinking out of the box. It's the only way we'll get out of this mess.”

Requiem for Nature?

In 1999, ecologist John Terborgh, of the Duke University environmental program, published a book, Requiem for Nature, in which he convincingly made the case that few of us wanted to hear: There is no hope for the survival of wild nature or wild biodiversity. The conclusion was similar to that of Diane Ackerman, whose book I reviewed in an earlier essay, only Terborgh shows us the dark side.

In 1999, every indicator showed that the forces of destruction, especially in the tropical rainforest, were accelerating. But Terborgh presented plenty of examples from the United States, as well.

Yes, there were many tropical national parks. But many of these parks were “paper parks,” that is, they existed only as designations on maps. (You could now call them “Google parks.”) Many of them had no guards, some had just one guard. Settlers encroached on the parks. The government could take credit (and possibly receive foreign aid) for protecting nature, without spending anything on it. Many of the parks, far from being located in biodiversity hotspots, were in areas that were unsuitable for agriculture and low in biodiversity: they were the easy ones to “protect”.

Even the parks that were protected suffered from “empty forest syndrome.” The adult trees still stood, but (1) young trees did not germinate to replace them, and (2) many animals were missing, producing an eerie silence. The parks existed, they had a certain area, but they were oddly shaped. In 1989, I visited Jatun Sacha in Ecuador, and it was a skinny corridor of land. As a result, most of the forest in the preserves is very close to human-dominated landscape. The human effects therefore penetrated into the protected area, making it unnatural. The landscape was fragmented. Strange ecological imbalances happen in small parks, and on small islands (such as an explosion of leaf-cutter ant populations) that would not happen in a large protected area.

In this photo, a graduate student from Europe classifies orchids rescued from the branches of rainforest trees that had been cut down. There was no time to do anything else at Jatun Sacha except make records of what was killed.

Terborgh used examples from all over the tropical world, and the story is everywhere the same. There were a few exceptions—some nature preserves on Madagascar were respected and protected by local people—but such examples were rare. Wild nature is threatened even in countries that have “charismatic megafauna” wildlife, in Africa and in Nepal, where tourists spend a lot of money.

Many proposed solutions were not working. One idea that was popular in the 1980s and early 1990s was to support the rubber tappers, who made a sustainable living off of wild rubber trees, without killing them, and without plantations. These were the people championed by the charismatic Chico Mendes, who was assassinated in 1988 by a gunman hired by a large land-owner. But the rubber tappers remained poor, and their product could not compete in the marketplace with commercially-produced rubber. Another failure has been forest protection by edict. When the Thai government, alarmed by the loss of watershed forests, prohibited logging, the price of lumber increased, thus making illegal logging more profitable.

In some cases, land degraded by human activity can recover. The processes of ecological succession are amazing and were among the earliest things that inspired me, as a child, to be interested in nature. But it doesn’t always work. If a tropical forest is cut down, and is then invaded by alang-alang grass (Imperata cylindrica), a cycle of fires can then prevent the forest from ever growing back, that is, in a time frame meaningful to humans.

For many of us, the modern mantra is “sustainable development.” But sustainable development does not require biodiversity. Agroforestry and plantations can be sustainable, even when dominated by just a few species. The conclusion Terborgh reached is that the human future does not depend on biodiversity; humans, and human civilization, can survive just fine without the high levels of biodiversity found in nature. We cannot honestly use “human survival” as a justification for protecting biodiversity. There is no shortcut: we have to save it for its own sake, not ours. “Whether we like it or not, tropical forests are worth more dead than alive,” Terborgh wrote. In strict economic terms, that is—which are the only terms that matter to most governments.

Things have only gotten worse, at rates and in ways that Terborgh did not, apparently, imagine. He wrote, “I am confident that objectivity and popular opinion will eventually prevail in the United States to bring conservation and development into balance.” But even if the Obama Administration might have encouraged this, Donald Trump proclaims loudly that conservation is the enemy of prosperity. Whatever hopeful trends Terborgh saw have been deliberately smashed by people who, perversely, call themselves conservatives. Terborgh called for a redesigning of democracy. Well, we’re getting it: it is being redesigned into a system in which the president can do whatever he wants with no constitutional restraints. I don’t think that’s what Terborgh meant.

The situation can only get worse, as populations increase and conflict over resources escalates.

This does not necessarily mean that the world will go as far as it did in René Barjavel’s novel Le Voyageur Imprudent, in which the human species 100,000 years from now evolved into males with claws, with which they had dug away all mountains and valleys and made the Earth into one vast plain, and females as large as mountains, with thousands of teats, from which the males fed. But a few generations from now, the phrase “natural world” may simply mean a municipal park. “I hope I am wrong,” Terborgh wrote, “but if I had to bet, I would wager that the last gorilla will die in a zoo.”

It is not good news, but Terborgh wanted conservationists to be honest about the problems and not pour time and other resources into lost causes.

To find good news, you can only, at best, read about individual success stories. The United States government refused to protect an endangered species of beetle in Oklahoma. So, the Cherokee tribe stepped in and did it. And, as I took a break from reading Terborgh’s bad news, I opened the May 2019 National Geographic and read about Gorongosa National Park in Mozambique, where nature is thriving, full of wildlife, because of the support of local people, 180 of whom it employs. Sometimes human ingenuity can surprise us (this was the same issue that had a long article about Leonardo da Vinci). An isolated example the Gorongosa may be, but what else am I supposed to think about? As a writer, I look for the individual stories. It is too depressing to do otherwise.