Now we come to possible projects that require global investment support and are essentially large enough to be seen as terraforming in their own right. My primary focus is the deserts of the world, which represent 30% of all land surfaces. These can be restored to woodlands by farming water from the atmosphere. It is entirely obvious also that successfully turning the major deserts of the world into productive growing environments will have a significant moderating effect on the global climate.
The areas of interest include all tropical deserts and much of the temperate deserts. In practice, the techniques also apply to major areas deemed as outside the desert zones, yet suffer from droughts and seasonal aridity. In fact there are few places in which agriculture as practiced could not benefit from having alternative water supplies on hand.
In the early stages, we expect that these techniques will be applied in the US southwest and inter mountain region, Northwest China including the Gobi desert and the Sahel in Africa on the edge of the Sahara. All these areas have ample humidity during the dry seasons and a season of rain. Building tree cover that holds that rain and the soils is attractive in terms of expanding the agricultural utility of these regions.
The Sahara Mediterranean ecosystem
The Sahara, the largest single desert on Earth, is possibly the easiest major desert to substantially recover as a successful growing environment. There is good evidence that traditional herding and agricultural deforestation probably accelerated or even caused the original desertification in the first place. Similarly, extensive grazing damage as well as deforestation has caused massive environmental degradation throughout the Mediterranean and the Middle East. Restoring the agricultural potential of the Sahara and the Sahel could easily create millions of new economically viable farms directly employing at least 50,000,000 people with an equal number indirectly engaged. This would be in the early going when urban development is still concentrated on the periphery. In practice I would expect close to a billion people to depend on such a development within two generations.
The primary thrust of any such program is to focus on restoring ground cover, preferably in the form of forest cover, but perhaps more practically early on in the form of commercially valuable scrub plants such as jojoba, which produces a valuable oil berry. The first priority in this program would, through the process of establishing proper tenure, be to finance and generally encourage a recovery where nature can naturally support it.
I recall a report from the Sahel twenty years ago that the simple expedient of putting up a fence was sufficient to establish a green zone. Since then, communities have been making the types of investment necessary to preserve available moisture. This is still an example of cleverly pursuing short-term interests. Growing trees requires some form of effective internal subsidy to carry the tenure holder over in the face of long-term economic benefits and the critical ecological benefits, of which he may simply not live long enough to realize.
[more recently the locals have discovered that encouraging and protecting the growth of acacia trees in combination with cattle raising is hugely beneficial to establishing better fodder and soil conditions]
This is particularly true in areas such as the Mediterranean were hillsides have been totally denuded for a thousand years and forest recovery must be permanent just to restore the soils. Any nominal and sustaining economic benefits will arrive a century hence.
The key technical point to remember is that it is in the nature of things for moisture to be exhaled from plants into the atmosphere. This same moisture can be recycled over and over again as rainfall. We need to help this natural process along.
If we take advantage of the fact that even in the driest desert, the moisture content of the atmosphere is in excess of 13%, it is possible to use refrigeration cycle systems to strip moisture from the air and collect it. If this is used massively, the local environmental moisture itself will be raised, sharply reinforcing the efficiency of the process and improving the water production rate. It is probable that if the Sahara were covered today with the right type of vegetation, that the recycling of atmospheric moisture would be sufficient to sustain the majority of the ground cover with no additional help. This is not true for most deserts which are created in the rain shadow zone of a mountain range.
Modelling water uptake from that of mature apple trees, which are hardly well adapted to the extreme conditions experienced in the desert, we can generate a conservative development model. It is known that such a tree will use and transpire around 70 litres of water per day. We can also reasonably assume such a tree will occupy a footprint with a radius of fifteen feet, which translates comfortably into about fifty trees per acre.
Now it is possible to manufacture and operate a solar driven refrigeration cycle water collector capable of producing 70 litres of water per day. With mass production, such a unit can ultimately cost well below $1,000 and last with minimum inputs for twenty years. Initially it could support a battery of four young trees and as water demand rises, additional units can be added. We have already commented on the advent of solar energy production whose cost per installed watt can be expected to drop below fifty cents per installed watt. Several additional innovations and fixes are also readily available for mass application in the desert environment. We can actually do this.
We can then project in the early going that each developed acre will have an all-in capital investment base somewhere around $50,000. This assumes that each tree ultimately requires one collector. This will also be true only if humidity stays at very low levels. In a large-scale regional development we would expect instead a steady rise in the availability of humidity and even of precipitation, quite capable of increasing production efficiency four fold. The cost per acre could then drop to under $20,000 without additional clever inputs.
I also observe that the initial buildout will usually take place were humidity is already quite high (such as the Sahel) and some distance from the margins of the true desert. As the build out advances into the desert, it will then bring the high humidity and diurnal rainfall with it.
We can plan for full site development, particularly were labour is readily available and cheap as in a home-steading economic model That means clearing a twenty-foot diameter circle by excavating somewhat so that any surface water flows toward the centre. Also a thick layer of organic material, if available, is dug into the circle before been covered slightly with local soil or sands. Water would be delivered from the collector by seepage lines possibly buried in the soil. In the early stages some of this moisture can probably be used to even support a surface cover of grass or alfalfa, which will do an excellent job of binding the soil together and increasing organic content.
This is all initially labour intensive. However, once done it is cheaply maintained. Sudden rainfalls can be captured by these small catchments and absorbed by the imported organic base. Proper design can ensure that the rainfall is concentrated and retained by the roots increasing effective rainfall efficiency. This will augment the solar driven collectors and provide additional security. The manpower needed to maintain such an operation will probably run at one family per twenty acre orchard, particularly if there is the capability to gather unneeded water to support additional small garden plot growing and animal husbandry. Since the maximum base capital investment is about $1,000,000, annual gross sales should reach $100,000 at least. There are crops for which this is possible. A regional program in which water productivity has hugely increased would bring the base capital cost down to under $200,000. This would allow ownership to jump easily to perhaps fifty acres for a family operation with the ability to handle lower value crops. Since the environment is conducive to rapid growth, higher than average productivity can also be expected. The point made is that the putative economics are close enough to feasibility that a massive build out can be entertained, supported by a combination of low interest loans, production subsidies and market stabilisation programs.
From a conventional investment perspective, the asset may take as much as fifty years to pay itself out, though I think this rather unlikely. On the other hand, once created, the asset has a lifespan of thousands of years.
The key aspect of this exercise is that it is technically feasible to cover much of the entire Sahara with trees and the resultant agriculture without irrigation engineering. The technique can also be deployed in any arid environment around the globe creating livelihoods for hundreds of millions of families. This is even true in the tropics were uncontrolled deforestation has induced droughts and falling yields.
This is just the beginning. The whole purpose of covering the arid desert with a tree based vegetation cover in the first place is to increase the total humidity to about one hundred percent. This will cause a diurnal cycle of daytime atmospheric moisture build-up followed by heavy night rain. The real magic of a great forest is that the same water returns as precipitation many times. Thus we can expect that all the great deserts can be turned into hot wet climates, possibly within a generation of the completion of the build out. This means that wild vegetation will actively return to even the truly barren areas within the desert, and the newly developing soils will begin to capture and hold water. Aquifers will replenish and new springs and active riverine systems will emerge. And the agricultural enterprise itself will be partially weaned of the need to use humidity collectors over substantial areas.
There are other technical tricks that can also be used in specific locales. Dewponds can occasionally be built profitably in certain locations, perhaps as a supplemental source of water. Again this is low tech. The stony dessert areas can we windrowed with the surface stones at right angles to the prevailing winds. These windrows can also act as dew catchers as well as unconsolidated roadbeds. The exposed areas between will usually have some sands exposed as a result of the removal of the cover. Additional sand will also blow in with each dust storm. This becomes the growing area for supported trees.
In addition, on the coasts it is possible to build massive greenhouses that integrate seawater as an evaporating water source for supplying ample fresh water for plant growing. Occasional flash floods can also be locally contained and redistributed. As the program matures we will see an expansion of surface runoff and riverine gathering of these waters that can be captured and used to support additional open field farming.
As first suggested fifty years ago the engineers can do one more major trick in the case of the Sahara. It would be feasible to divert a substantial part of the waters of the Congo north into the Lake Chad Basin and on through into the Libyan Desert. This would have a nominal effect in the Congo Basin itself since it is rainforest and is not dependent on the river system maintaining groundwater levels. The Lake Chad Basin could be partially refilled and the surrounding countryside could be fully irrigated, perhaps creating a major rice bowl supporting 100,000,000 people. The evaporating moisture from the huge area covered will also increase precipitation in the direction of the prevailing winds. Surplus water flowing into the Libyan Desert can readily support irrigation farming with enough left over to run into the Mediterranean.
Most irrigation technology is essentially temporary, even if temporary means two thousand years. Shifting to humidity collectors and inducing precipitation will recover even those soils ruined by the salt build up from long-term irrigation. And the trees so chosen should be capable of initially absorbing this overabundance of minerals.
The elimination of arid and desert areas around the globe will lead to a general increase in global precipitation and to a moderation of the climate in both the formerly dry areas and the surrounding climate zones. The absorption of solar energy will also induce a slight drop in average global temperatures. Huge amounts of carbon dioxide will also be taken up and huge amounts of water will be stored in these new ecosystems.
The evolution of this form of water husbandry should be directed toward using the evolved forest as a water retention system and a producer of a water surplus, which finds its best economic expression in supporting irrigated crops of high value. It is not hard to imagine a hundred-acre forest comfortably supporting perhaps twenty acres of cash crop and a small piggery for consuming waste produce. The economic productivity of forests, with the exception of specific orchard plants has a long realization cycle. Shifting the maintenance burden onto the local operator is critical and will require continuous fine-tuning and regulatory guidance. The onset of predictable rains will eventually relieve these operators of much of this burden since fewer collectors will be required.
I expect that a band as narrow as one hundred miles wide to the windward will be sufficient to initiate and sustain the natural precipitation cycle. The degree to which this will augment water requirements down wind can only be guessed at, but it can be expected to be significant. Losses will continuously occur because much rain will fall on barren rock and unusable highlands. Any that falls on the farms will be largely recaptured.
Northwest China and the Gobi
This area is now stricken with advancing desertification and major dust storms. Yet the land area involved that could be potentially recovered for agricultural purposes is probably over 100 million acres eliminating the dust storms forever. China also has the advantage of having a huge peasant population who would be natural operators of the derivative farms, already having the requisite skills. In addition effective mass production of the humidity collectors in China should quickly reduce the per-unit cost to the lowest possible level. A homestead type program can be envisaged that could mobilize millions of Chinese peasants to work for the opportunity to own a large farm.
A typical farm could consist of fifty acres, out of which forty acres are covered with economically valuable trees supported by humidity collectors. A gathering system, even if the farm starts with only 400 collectors will produce 20,000 to 40,000 liters of water per day plus a substantial amount of electrical power, which can be stored in various batteries. Cheap industrial grade lead-acid batteries, which last forever, come to mind. This provides water for the growing of the trees, but will also diverts surpluses to a central storage for use on the ten-acre plot. Unused water production on the off-season can be stored and used to support wet season field crops and the small garden. Animal husbandry can be steadily integrated into the operation, particularly if the trees are productive in fruits and nuts, as a consumer of waste organics. The wet season should also permit the growth of forage crops in the orchard. The numbers quoted are for illustration purposes. Each district will be engineered at first for the best likely configuration and inevitably modified greatly as the system matures.
China is currently under one political system, which means that this program could be implemented now. The reality is that most prospective terraforming initiatives require the cooperation of several governments. The idea of diverting water from the Congo to Lake Chad is today a near political impossibility. Feasibility is thus irrelevant.
Undoubtedly, once the human imagination recognizes the possibility of constructively terraforming the Earth we will have a flood of great ideas. I personally have no doubt that covering the deserts and semi arid zones with trees as well as restoring former woodlands with economically valuable trees and simultaneously integrating the work with the best agricultural practice will be the single best gift this generation can give the generations of the next millennia.
No comments:
Post a Comment