I have been discussing population for the last few posts, and on my last installment in this series, I wanted to discuss the psychology behind why many of my readers still have difficulty grasping the message.

I don't mean this in a disrespectful manner. In fact, there is now an entire branch of psychology that deals with this sort of problem.

It emerged in 1982, when Professor of Human Ecology at Pitzer College in Claremont, California, the late Paul Shepard, extended James Lovelock's Gaia (developed while Lovelock was working for NASA, the idea earth is a giant interconnected superorganism) and Arne Naess' Deep Ecology (essentially the philosophical outgrowth of Gaia, sometimes called biotic egalitarianism) into the realm of the psychological, proposing in his book Nature and Madness that if there are profound and innate links between the planet and the human beings, those links extend to the human mind-and that by wantonly destroying the former we are simultaneously ravaging the latter-quite literally driving ourselves mad one clear cut forest at a time.

Shepard's arrived at this conclusion by thinking about how evolution shaped the human brain to shrink complexity by categorization. Our brains slot everything into small boxes. Part of this is our primate ancestry where divisions between ‘us' and 'them' were often critical to survival and part came about during the development of language, when the act of giving names to things required us to first put them in categories. Since those categories were based on what we saw around us, early language acted as our bridge to the natural world. The letter "A" comes from the Hebrew world "aleph" which means, among other things, oxen. Which is why, when you'll you turn an "A" upside down, you get a pictograph of an oxen head.

Overall, Shepard's work dealt with this process of categorization and how it affected the development of human . He realized it wasn't just that language was based on a connection to natural world, it was nearly everything else as well. Humans spent 99 percent of their existence as hunter-gatherers, which means the entire architecture of the higher cortex has been built atop the scaffolding of the great outdoors. When Shepard talks about humans being driven mad by environmental devastation, he's actually concerned with what happens when the very things that taught us how to think disappear.

Since publication, these ideas have been authenticated and expanded and now form the foundation of the multidisciplinary field of ecopsychology. Blending ecology, , sociology, psychology, environmental science- to name a few-ecopsychology concerns itself with everything from reestablishing our connection to the natural world to the emotional problem of confronting what Harvard psychiatrist and founder of the Center for Psychological and Social Change, John Mack, once called "the agonizing murder of the life systems on Earth."

Experimental validation for ecopsychology can now be found everywhere. In the wake of Hurricane Katrina, according to research conducted by the Hurricane Katrina Advisory Group, the rates of severe mental illness jumped from 6.1 percent to 11.3 percent among those who lived in the area. Mild-to-moderate mental illness also doubled, from 9.7 to 19.9 percent.

But it's not only reactions to environmental disaster triggering such emotions. Most eco-psychologists have come to feel that the nearly 10 percent of adult Americans who suffer from mood disorders do so because of a lack of contact with wilderness. One of the studies backing this up appeared in the October 2008 in the journal Nature, when researchers at the University of Illinois found a 20 minute walk in the woods out-performed all the drugs currently on the market for the treatment of (ADHD) in children.

But if there are profound links between ourselves and our eco-systems, one of the difficult questions for eco-psychology to answer is why aren't more of us insane. After all, as James Gustav Speth, Dean of the Yale School of Forestry, recently pointed out: "Half of the world's tropical and temperate forests are now gone. The rate of deforestation in the tropics continues at an acre a second, and has for decades. Half of the planet's wetlands are gone. An estimated 90 percent of large predator fish are gone, and 75 percent of marine fisheries are now overfished or fished to capacity. Almost half the corals are gone or are seriously threatened. Species are disappearing at rates 1,000 times faster than normal. The planet has not seen such a spasm of extinction in 65 million years, since the dinosaurs disappeared."



The answer seems to be that we are all slightly insane, only not perceptive enough to notice. This happens because of the familiar trait: denial. In her essay The Skill of Ecological Perception, the visual psychologist Laura Sewall examines this denial, which she calls our "psychic numbing," a sort of collective that "shields us from fully experiencing the latest reports on ozone depletion, increasing pollution, toxicity, poverty, illness, and the death of species." Not surprisingly, this condition has been repeatedly linked to the pathology -which is both a case of massive self-aggrandizement and an inability to understand that the boundaries of self frequently extend beyond the confines of skin.

One of the ways this denial has been found to work is in our evaluation of gradual change, like the kind produced by . Humans and frogs are not too different in that if you put either of species in the proverbial pot, and bring it to boil slowly enough, because the brain is so well-designed to notice rapid and sudden changes in its surroundings, it often fails to notice gradual increases in danger until it's mostly too late.

Recently, the magazine New Scientist asked British biochemist James Lovelock, both the man who created the Gaia Hypothesis and the man whose work on atmospheric chlorofluorocarbons led to the global CFC ban that saved us, literally, from ozone layer depletion, if there was any hope for humanity now.

"I'm an ," said Lovelock. "I think it's wrong to assume we'll survive a 2 degree warming: there are already too many people on earth. At 4 degrees we could not survive with one-tenth the current population. The reason is we would not find enough food (for every one degree the globe warms rice, corn and grain yields will drop by 10 percent), unless we synthesized it. Because of this, the cull during this century is going to be huge, up to 90 percent. The number of people remaining at the end of the century will probably be a billion or less. It's happened before: between ice ages there were bottlenecks where there were only 2000 people left. It's happening again."

Ecopsychologists believe to heal ourselves, we simultaneously need to heal the planet. The first step of this, as Sewall examines in a great essay called The Skill of Environmental Perception, is in learning to pay to the natural world. We have to start to notice the tiny details, so we can start to notice the awesome danger those details are adding towards.

So we can act.

For the past four blogs, I've been proposing a Five Year Ban-a voluntary, grassroots-based, worldwide five year moratorium on childbirth. Five years lowers the earth's population by a billion people. It means the food that we're going to run out of will go a lot farther. It means the carbon we're pumping into the earth's atmosphere will be pumped slightly slower-maybe even giving us time to figure out how to slow it down further, or perhaps reverse the effects. Five years to buy us some time.

Why do we need such a radical solution? because Lovelock's not alone out there. One of the main reasons I decided to put forth the idea of a five year ban is because I'm not like most of my fellow PT bloggers. They are primarily academics and clinicians. I am a science writer and environmental reporter. I spend most of my day talking to academics, clinicians and researchers-all scientists at the top of the fields. For the past five years, in talking to these people-and I talk to as many ecologists as I do weapons designers so my inquiries cut across all political lines-researchers familiar with the facts have nearly unanimously echoed Lovelock's concerns.

In proposing a Five-Year Ban what I'm asking is for people to make a choice. Do we want to lower our current population numbers voluntarily, or do we want nature to do it for us?

And I've been asking this because really, there's no other choice.