Human population size needs to be back on the agenda for discussion. Not ignored because of the rate of growth in numbers may be declining. Absolute numbers continue to grow far faster than was the case with a larger rate of growth on a smaller base. The problem is here and now.

Nor ignored because of the the theoretical possibility that this or that technology or life style change could lead to an end to non-renewable resource depletion, or reduce pollution to a level that could be absorbed by the earth system.

Nor yet should it be a taboo subject because you can envisage ‘solutions’ that are unacceptable to you. A discussion of population does not have to presuppose any particular solution until the problem has been clearly defined.

So what are the problems with the number of people on the planet. We need to separate this question from any particular solution to the problem, if there is indeed a problem. The question relates to the situation as it exists today with the current patterns of distribution and consumption, not to some theoretical state where everyone lives a ‘sustainable’ life.

The obvious overall problem is that current humans are consuming physical resources (animal, vegetable & mineral) at an unsustainable rate and are turning those resources into human waste (pollution) at a rate  faster than the whole earth system can absorb.

But that is only one part of the story, the physical human part. There are several other dimensions.There is the impact on our own collective mental well-being. There is our impact on other living things from their point of view. There is the impact on a spiritual plane that we can only dimly perceive. There is the impact on the balance of the whole earth system which could be nudged into a new state.

The usual focus for discussions about human population is the human physical dimension, and very quickly moves on to debate about particular “solutions” – everyone go vegan / better education / better healthcare /… – it then rapidly spirals into binary choices and name calling. Which has resulted in the whole topic becoming taboo in many green circles.

This is simply inadequate. For a start the focus on the human dimension is simply attempting to deal with effects, proximate causes, symptoms that we could stick a plaster over. We actually need to start to look at the bigger picture in order to get a fresh handle on the problem.

Overcrowding is a very subjective and context dependent feeling. At one extreme when walking on Dartmoor, the sight of another hiker a mile away on a crest may make it feel like the moor is a bit crowded today – or it may be a blessed relief from the interminable loneliness of what can seem like a barren landscape. At the other extreme the crush in front of the stage where you are all moved together by the same music may not seem over-crowded at all.

Where-ever your personal line between companionable and overcrowded lies in any given situation it is obvious that increasing total numbers is going to increase the number of occasions where you personally experience feelings of being crowded.

It is a very common experience among those who have moved down to the Westcountry from the cities or the South-East to find that when they return to visit friends or family left behind, the rush and bustle and sheer pressure of numbers is overwhelming.

It is often observed that people who live in more isolated, less crowded, conditions have a different perception of inter-personal space. They will typically stand further apart when conversing with someone.

This is not necessarily to say that one is better or worse than the other, but the fact is that for the bulk of our historical cultural experience we have lived in a less densely populated by humans world. 50,000 generations as nomadic hunter gatherers followed by 500 generations as sedentary farmers followed by a mere 20 generations developing industrial civilisation and finally the doubling of human population within only 2 generations (and the next doubling within a generation) has hardly equipped us emotionally to deal with current levels of crowding.

To this extent increasing population leads to a decrease in quality of human life. The impact on our collective mental well-being provides a compelling reason why the issue of human population size must be on the agenda for any green discussion of the future.

Even if we could technically create a world capable of supporting 12 billion people would that be a world you would want to live in? Even if you love the life of the city (or mega-city) are you prepared to live there without the holiday (that you _so_ deserve) to the deserted beach every year?

When we consider the impact of human numbers on other living forms the situation is just as urgent. As our numbers increase then inevitably we are crowding out other species. One of the most powerful experiences I had at the Bonn COP23 talks last November was the session Euan and I attended of the UN Rights of Nature tribunal.

Of course humans have been having an impact on other species since time immemorial. The fate of the large mammals of the North American continent following the influx of hunter-gathering humans spreading South from the Alaska was that they were effectively wiped-out. The blowback for the human population was that when food production (as opposed to gathering) developed independently in parts of North America there were no animals left suitable for domestication either as sources of food (cows, sheep etc) or as beasts of burden (oxen, buffalo, horses etc). This delayed the development of farming and the package of subsequent developments enabled by the production of surplus food, to the extent that the North Americans were simply overwhelmed by the arrival of the European people – see Jared Diamond’s “Guns, Germs and Steel” for a detailed account of human development – much richer than implied by the book’s title.

Clearing out the large mammals from North America reduced the resilience of the North Americans in ways that they could not have foreseen. In the same way the consequences for our, now global, population of squeezing out other species will surely have unforeseeable consequences.

We can guess that our development of pesticides to exterminate locally unwanted species may have knock-on effects on the bee and other pollinator populations that we might regret. And so we may be able to tackle that particular issue and think the battle won. But the war against other species goes on, the collateral damage continues, and the consequences are unknowable.

All we can be sure of is that we exist on a world that has been resilient to most of the impacts of a human population of less than 100 million during the first 49,950 generations of human development. The consequences of the 10 fold increase over the next 40 generations and the eightfold increase over the 10 generations since 1800 AD are as yet unknown. We can, however, be pretty sure from looking at what has happened so far that the living world, even as it was in 1800, is not capable of co-existing with current human numbers.

Does the fact that we can envisage living in a world where we have squeezed out many other life forms make it desirable to do so? We may think that we can invent technology to support ourselves without them, but even if you believe that we have a right to do that, and that the natural world has no right to exist, does that make it a desirable situation?

This can become a “religious” question, so perhaps time to consider the next non-physical aspect of human population and that is the affect on spiritual health, and the impact on a possible spiritual plane.

As self-conscious beings we are also conscious of other conscious beings – animals, we are conscious of other non-animate beings – plants, and of in-animate discrete objects – rocks, clouds and so on. Consciousness may be an aspect of all of these, most likely it seems to me that it is a continuum with increasing depth as we move from the simplest material through organised matter, to living matter, to animate matter, to communities of animate matter (complex bodies) which in some species, including ours, acquire self-awareness and consciousness of being conscious.

What we glimpse only dimly, as maybe a dog perceives the social and emotional lives of the humans it lives with, is a next plane of hyper-conscious being which may or may not have a physical presence in our world.

This is the territory of what christian religion calls angels, and older traditions call spirits or minor gods. Beyond them there  may be more. Monotheistic religions stop with a single god-head, pantheism goes beyond with a hierarchy of gods – back to shadowy figures whose purposes we can far from divine.

Given that the purpose of life is self-realisation (quite a big ‘given’ that I’ve run out of time to consider in this post although I touched on it here: limits-to-rights ) we are inevitably engaged in a struggle with all the other forms of life that we co-exist with to thrive in our own niche. The problem that we have is that we have been expanding the size of our niche to the exclusion of others, and we must recognise that there comes a point where we may be damaging ourselves.

More than that, just as if an out of control, ever-expanding, algal bloom threatened to suck all of the oxygen out of the oceans and turn them into a toxic soup and the atmosphere back into an acidic cocktail we would feel quite entitled to limit the right of this bloom to self-realisation in the face of its impact on us, so we can reasonably expect that the human bloom spreading over the face of the planet may be seen as threatening to the actualisation of the hyper-conscious plane of spirits and gods.

The spiritual damage that we are doing through our ever increasing impact on the material world may yet have blow-back on our own existence.

Or maybe there is nothing beyond us. I’m not certain I would want to gamble on that simply to allow my species to take down its own life support systems through pressure of numbers.

As self-conscious earthlings we exist as part of the web of life on this planet, and being self-conscious we can know, if we choose to look, that we cannot fully exist independently of that web. We are a part of the whole, and the whole is part of us.

Without self consciousness, like an algal bloom we would continue to grow until our exhausted environment could no longer support us.

With self-consciousness we have a choice. We can either have a serious discussion about our population and take steps to reduce the ultimate cause of our problems, or we can continue to argue about what brand of sticking plaster to use meanwhile allowing the infection which will destroy us to enter the wound.

Our world is wounded. We need to heal it, not fix it.