“We” may “know” this. But that doesn’t necessarily mean it’s true.

Here is a table with year, world population in billions, hectares of agricultural land required per capita, and total resulting hectares of agricultural land required, for 1950 and 1980:

Year Pop. Area/capita Area, total
1950 2.2 0.47 1.2
1980 4.4 0.34 1.5

http://www-formal.stanford.edu/jmc/nature/node10.html#SECTION00910000000000000000

OK…so what? Population goes up, area required goes up…just as expected. But notice the area/capita went DOWN (and this occurred, even though people in 1980 were better fed than in 1950).

Sooo…the area/capita went down by 28% [(0.47-0.34)/0.47] in 30 years. Let’s say it continues to go down at a rate of 28% every 30 years, from 1980 to 2070.

In 2010, per/capita use is 0.25 hectares/person [i.e., 0.34*(1-0.28)]. Using a population of 6.8 billion (UN medium variant)…we get total use of 1.7 billion hectares…so more than 1980.

In 2040, per/capita use is 0.18 hectares/person [i.e., 0.25*(1-0.28)]. Using a population of 8.7 billion (UN medium variant) we get a total use of 1.6 billion hectares…still more than 1980, but less than 2010.

In 2070, per/capita use is 0.13 hectares/person [i.e., 0.18*(1-0.28)]. Using a population of 10 billion we get a total use of 1.3 billion hectares…LESS than 2030, LESS than 2010, and even LESS than 1980.

This is of course just a projection, based on 1950 and 1980 data. But it illustrates why it is not NECESSARILY true that more population means more acres devoted to farming.

P.S. My guess is that the actual trends will be even more positive than those I’ve sketched…especially for the long term. (For example, I think it was in MIT’s Technology Review where I read that chemical engineers were trying to actually create red meat (or maybe it was poultry) in a lab. Results didn’t taste very good yet, but give them a decade or two.)

http://resilience.geog.mcgill.ca/blog/index.php/2006/02/17/vapour-flows-soil-moisture/

And, as we know, with an increasing population forecast that means more land devoted to agriculture [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11303102&dopt=Abstract, http://www.pnas.org/cgi/content/abstract/96/11/5995 ], and more externalities with ag, esp. monoculture ag,; RS blog also has an entry on non-monoculture ag and how this will mitigate some of the environmental problems (esp. water quality and secondarily vapor transfer):

http://resilience.geog.mcgill.ca/blog/index.php/2006/02/17/evaluation-of-ecosystem-services-provided-by-multifunctional-agriculture-in-the-usa/

I’m an ecosystem services guy so there’s my bias.

Best,

D

Mark-

I’m glad you clarified the challenge of irrigating the ‘heart’ of the Sahel (and continental interiors in general). In my modest gratitude I realised I’d neglected to expound on that aspect of the logistical problem (perhaps because I feared being the butt of the Bahner ‘last word’ that it might generate…D’oh!) )

H

You write, “Mark – I stand corrected on the ‘Sweden to Sahel’ water transfer concept. Thanks.”

Omigosh. I didn’t know anyone “stand(ed) corrected” these days. (I can think of two people specifically…but no need to get into that…;-))

Anyway, you’re welcome. And thanks for thanking me.

But while we’re at it, you certainly weren’t completely wrong…if by “Sahel” you meant, “The heart of the Sahel.” Water pipelines are (presently) pretty expensive. So the water bags (or desalination plants) can get the water to the ***coast*** of Africa reasonably inexpensively (or somewhat expensively, for present desalination plants), but getting that water into the heart of the Sahel is certainly not economical at this point…especially for Africa.

However (see, I always have to get the last word ;;-)) the point I was making is still extremely solid. The “climate change community” routinely makes no attempt to take into account technological and economic trends. They routinely project 50 to 100 years (or more!) into the future, and pretend that the state of technology and wealth will be exactly as it is now. This is absolute and utter rubbish.

Does 2005 look like 1905? Well, the change from 2005 to 2105 is going to be much, much, MUCH bigger than from 1905 to 2005.

To take only one example, in my carefully researched and considered opinion, world economic growth in the 21st century is going to make world economic growth in the 20th century look like it was standing still.

In the 20th century, world per capita GDP increased from approximately $680 to approximately $6500 (in 1990 dollars, as estimated by economist Brad DeLong).

So even if the growth rate in the 21st century only MATCHED that factor of approximately 10, we could expect world per capita GDP in 2100 to be $60,000 to $70,000.

But my estimate for world per capita GDP in 2100 (in year 1990 dollars) is…

…..over $10,000,000!

(And I am NOT kidding.)

http://markbahner.typepad.com/random_thoughts/2003/11/i_solicited_pre.html

http://markbahner.typepad.com/random_thoughts/2004/09/second_thoughts.html

http://markbahner.typepad.com/random_thoughts/2004/10/3rd_thoughts_on.html

http://markbahner.typepad.com/random_thoughts/2005/11/why_economic_gr.html

Best wishes,
Mark

Mark – I stand corrected on the ‘Sweden to Sahel’ water transfer concept. Thanks.

Hugh, you and Dano have convinced me that I don’t write as clearly as I delude myself into believing – one more cherished notion out the window!

I am not sure that we have any fundamental disagreements, but additional clarification is in order from my end. Following are specific responses to your comments.

Hugh: You suggest that 1,000 cubic metres pa/pc is the basic human need.
Response: I offered this as an “e.g.” rather than a definitive threshold to help me think through how impacts may be counted — or not counted (see below). By the way, the 1,000 cubic m/person/yr is one of the measures that Arnell refers to [other candidates are 500, 1,700 etc., all in cubic meters/person/yr]. My understanding is that this number was originally tossed out a few years ago by a Professor Malin Falkenmark. It certainly looks good on paper, is easy to remember, is in tune with the metric system, but I can’t vouch for its sociological and biophysical underpinnings. In fact, it’s not clear to me that this should be a “universal constant” like Planck’s constant. There is probably a different number appropriate for each (sub)society depending on history, culture, dependence on agriculture, and even available water resources, etc. Thus we could have one number for the urban Germans, another for the French farmers, etc. – but let’s not go there.

Hugh: I do understand your argument against measuring good *and* bad impacts of CC.
Response: Thanks, that was the basic point I was attempting to make.

Hugh: Why do we need to worry about the areas that, under CC, will receive increases in AWS over that threshold?
Response: We only need to worry about this when keeping score of the good and bad outcomes. If, because of CC an area’s AWS (actually AWS/person/yr) goes from below the threshold to above it, it should go into the “good” column and (its population) should be subtracted from a population that goes from above the threshold (whatever it is) to below it [the latter is clearly a bad outcome]. I recognize this doesn’t address the issue of a population whose AWS is below the threshold and for which matters get worse. That’s why in my post I alluded to weighting different outcomes differently [see above]. On the other hand, if AWS substantially exceeds the threshold before and after CC, I would, along with you, not be too concerned about it. {I think the appropriate method of estimating “total impact” would be to estimate the marginal change in utility for an average population for a marginal change in AWS for each level of AWS and integrate over populations and AWS, etc. [Quite possibly, some water economist has done this kind of stuff.]

Hugh: Water is not economically transportable over large distances, and the distance between Sweden and the Sahel … is indeed large.
Response: That’s only partly true today, and may not be true in the future, especially if shortfalls are large and technological innovations change transportation costs over the next several decades(see Mark’s post, for instance). Even today, rich populations pay quite a lot for water that has been transported directly (as bottled water). In fact, the price of bottled water in my local store substantially exceeds that of gasoline. Rich populations also import water indirectly, e.g., in the fruits, vegetables, timber and flowers that the come from poorer countries. Similarly, rich countries export water in their wheat, corn and other grain. The real issue is whether the (implicit) water in these products is appropriately priced. And generally they aren’t because more often than not water is, unfortunately, not dealt with as an economic commodity [under the misguided notion that water is too important to attach a price to, but that's precisely why it ought to be priced -- how else to best stimulate conservation?] Doing so would help populations adjust better to changes that might be wrought by climate change, not to mention the vagaries of nature. If we can move 85 million barrels of oil and gasoline around the world each day, surely we can move water around if the incentives (and prices) are right. By the way, there are other options than moving water from Sweden to the Sahel, as Mark notes.

Hugh: Is your argument really that it’s okay for us not to worry about future disparity in AWS because the populations of the more temperate latitudes will be getting more water than they really need…so who cares about everybody else? …Having a high global MEAN AWS is no good to those people with none to drink.
Response: No, that’s not my argument. My remarks were about how one tallies the impacts of climate change (see above). And I do agree that a high global AWS doesn’t mean that there are no localized problems, or that we shoul ignore those problems. Your example, however, underscores the point that models should allow for adaptations, which goes back to Richard Tol’s original post (and Mark Bahner’s, as well).

To Benny — I suspect you are right about the spin different sides will put on the Gedney et al. results. [In the days of yore, when we had a little money for extramural research, the first study I funded on CC was to look at the effect of higher CO2 levels on water use efficiency in plants and what that meant for runoff.] However, I think this latest study, if it stands up, will be specially significant for prognostications of soil moisture, and what that means for ag productivity in arid and semi-arid regions (because they have been among the foci for CC concerns). [Remember, it is the developing world in general and Sub-Saharan Africa in particular, which are most vulnerable to CC.] Moreover, despite the increased potential for floods, higher run-offs could also have some benefits, e.g., increased potential for hydroelectric (and white water rafting to compensate for declines in skiing perhaps?). I suspect, but can’t prove offhand, that it’s probably easier to do something about a situation with too-much-water than one in which there’s not-enough-water-to-grow-things-with, but of course it all comes down to costs.

Dano, Thanks.

Regards to all.

As I think you infer with your ‘Sahel’ acknowledgement and your footnote, transnational migration for many under AWS is impossible; indeed, as Americans are now seeing, those who flee environmental catastrophe stress the social fabric of the place they fled to.

My reading of your well-constructed comments is that simply tabulating single indicators is an insufficient metric for assessing future policy options [says the ecologist]. Ecological impacts of, say, attempting to sequester increased precipitation must be considered as well. The reduced agricultural production in drier areas will lessen AWS temporarily if people migrate to other areas.

But, certainly, the AWS and PAR metrics are excellent indicators and I can easily picture how they could be well-utilized in an adaptive management strategy, and thank you for taking the time to explain them to me. I appreciate it.

Best regards,

D

Yes, and this completely ignores the potential for desalination. The simple facts of desalination are:

1) Two-thirds of the planet is covered with water (the only problem being it has salt in it),

2) 39% of the world’s present population lives within 100 km of the sea,

3) Worldwide water desalination increased from 2 million cubic meters in 1972 to approximately 24 million cubic meters in 2000,

4) At least two countries (Qatar and Kuwait) already get 100% of their water from desalination,

5) The costs for water desalination–particularly reverse osmosis, which is rapidly displacing thermal desalination–are dropping steadily. In 1960, the cost of conventional water treatment systems (i.e., for freshwater, prior to retail sale) were $0.10 to $0.50 per 1000 cubic meters. In contrast, the cost of thermal desalination of seawater averaged approximately $2.20 per 1000 cubic meters, and reverse osmosis desalination was not even commercially available. By 2000, the average cost for both thermal desalination and reverse osmosis desalination had dropped to $1.20 per 1000 cubic meters.

http://www.mwi.gov.jo/home/Thursday/medrc.pdf

In another 40 years, it’s easily conceivable that desalination costs will have dropped even closer to the cost of supplying treated freshwater. Does any analysis of water availability by anyone in the “climate change community” take into account the likely progress in desalination technology 40, 80, or 100 years into the future?

That’s a semi-rhetorical question. I’m virtually certain the answer is “No, of course not. How could they scare people if they did that?”

P.S. And I’m absolutely positive no attempt has been made by the “climate change community” to assess the possible progress (i.e., cost reduction, and increase in freshwater delivery) over the course of the 21st century for technologies like this:
“Several companies around the world are developing technology whereby large quantities of freshwater would be loaded into huge sealed bags and towed across the ocean for sale. The Nordic Water Supply Company in Oslo, Norway, has signed a contract to deliver 7 million cubic meters of water per year in bags to northern Cyprus. During the Gulf War, Operation Desert Storm used water bags to supply water to their troops.”
“Aquarius Water Trading and Transportation Ltd. of England and Greece has begun the first commercial deliveries of freshwater by polyurethane bags, towed like barges through waterways. The company, whose corporate investors include Suez Lyonnaise des Eaux, delivers water to the Greek Islands where a piping system links the bag to the main water supply on the island. Aquarius predicts that the market will soon exceed 200 million metric tons per year. The company’s bag fleet consists of eight 720-ton bags and two 2,000-ton versions. The larger bags hold two million liters of water each. Aquarius has completed research and development on bags ten times larger and is searching for the capital investment to produce them. The company has its sights set on Israel, and claims to have the interest of several major water companies.”

http://www.thirdworldtraveler.com/Water/Global_Trade_BG.html