For several days now this blog has explored twenty four obvious Earth environmental stressors which are worsening and projected each of them thirty years into the future in an attempt to estimate how bad they would plausibly become. That thirty year period seemed about right because these stressors are hard to measure and jump around too much on less than a ten year time scale to be reliably considered and no cares much about a hundred year time scale because it is too long. Except me, and you, because when thinking about these problems in the broad scheme of things and in the long run our personal relationship to them drops to below one part in six billion. With this post the attempt is to find those stressors that are likely to interact in a synergistic way and have the effects become noticeably greater than either of them acting independently.

Almost all of the items interact in an additive way and the real problem comes to the fore when the total agricultural support for humanity drops below some critical sustaining level and people begin searching for the last remaining sources of food. The following stressors add up for a while until some tipping point is reached: topsoil loss, desertification, deforestation, poisoned water, shrinking wetlands, overgrazing, species loss, lack of firewood, siltation of water storage reservoirs, cities built on farm land, dropping water tables, loss of stratospheric ozone, CO2 accumulation in the atmosphere, global warming, rising sea level, escaped nuclear waste contaminating farm land, acid rain ruining crops, plant disease destroying crops, human disease placing greater stress on everyone and endless human greed for energy.

A couple of items on yesterday’s list don’t affect the environment directly such as exhaustion of oil reserves and exhaustion of mineral resources but they very much affect human ability to create food and they may become the most unstable and most uncontrollable of all of the stressors. Most farm machinery is powered by petroleum products and most fertilizer has a large component of petroleum products somewhere in its chain of creation and then there is the power needed for transportation, bringing farm materials to and from the farms to the cities. When oil comes into a short supply and the price goes up it will be soon followed by a short supply of food and its prices will go up also. Many people in the world already spend more than half of their income on food and so when food prices double they starve.

Probably the most obvious and inexorable of the problems are going to come from lack of appropriate water and there is a synergistic effect to be found in several of those stressors: thin topsoil doesn’t retain water, desertification is an advancement of parched land to the point where it blows away, deforestation aggravates drought because mountain water flows away to the sea too quickly, salinization of the soil caused by low water flow through the soil lowers the land’s productivity, siltation of rivers and reservoirs prevents storage of rain runoff and then water isn’t available when it is needed, water tables become pumped out so low they can’t be used, and sea water encroaches on low countries. All of these factors interact in such a way as to lower overall food productivity of the land. And then global warming shifts wind patterns and rain patterns to new places which will not be as productive as present locations and will require the creation of whole new infrastructures which may not be possible.

All of those stressors are to some degree independent but they all go toward one outcome in the thirty year projection—less food producing capability of the land. As the population continues to expand the demand for more food will expand along with that living human mass. The huge number of children already living will create a tremendous inertia and drive the planet toward even greater populations.

The CO2 already in the air would take a hundred years to return to pre-industrial levels even if there was no new burning of fossil fuels. But there is a new big coal fired electric plant going on line every week or so and thus CO2 levels will climb even faster for most of the thirty years. The green plants like forests get a lot of attention as sequestering CO2 but in fact they are being cut down much faster than they are growing and they won’t be able to save us. They won’t be doing much when they are dead which in thirty years most of the big trees will be.

All of the above scenarios assume benign human beings doing their best to exploit their opportunities as best they can without injuring other people but sometimes that isn’t enough and their best option becomes destructive of other people’s well being. There is a lot of opportunity for malice in the modern world and with the internet it is becomes easy for people to exercise their negative proclivities. Thus the collapse of the social structure, war or economic collapse might well happen before the ecological failure. The problems with the world market the last couple of months shows how an accounting problem can cause chaos. What if the problem were a real physical one, such as being discussed in this post? What are the chances of finding a quick bail out by throwing pseudo money at the problem?

Not much! and the coming predictable disasters will probably combine their shortfalls for even worse effects. At some point this will become obvious and everyone will scramble to store up necessities and survive but that will be too late and the population curve when viewed from the future will probably look like the Doomsday chart.

There probably isn’t any way to prevent the worst of this from happening and so the EarthArk project seems like the best hope for humanity to recover something of its current prosperity and glory.