mardi 9 juillet 2013

Peak Water et Peak Food ?

Global threat to food supply as water wells dry up, warns top environment expert
The Guardian, John Vidal, 06/07/2013 (traduire en Français texte en anglais )
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Lester Brown says grain harvests are already shrinking as US, India and China come close to 'peak water'

Wells are drying up and underwater tables falling so fast in the Middle East and parts of India, China and the US that food supplies are seriously threatened, one of the world's leading resource analysts has warned.

In a major new essay Lester Brown, head of the Earth Policy Institute in Washington, claims that 18 countries, together containing half the world's people, are now overpumping their underground water tables to the point – known as "peak water" – where they are not replenishing and where harvests are getting smaller each year.

The situation is most serious in the Middle East. According to Brown: "Among the countries whose water supply has peaked and begun to decline are Saudi Arabia, Syria, Iraq and Yemen. By 2016 Saudi Arabia projects it will be importing some 15m tonnes of wheat, rice, corn and barley to feed its population of 30 million people. It is the first country to publicly project how aquifer depletion will shrink its grain harvest.

"The world is seeing the collision between population growth and water supply at the regional level. For the first time in history, grain production is dropping in a geographic region with nothing in sight to arrest the decline. Because of the failure of governments in the region to mesh population and water policies, each day now brings 10,000 more people to feed and less irrigation water with which to feed them."

Brown warns that Syria's grain production peaked in 2002 and since then has dropped 30%; Iraq has dropped its grain production 33% since 2004; and production in Iran dropped 10% between 2007 and 2012 as its irrigation wells started to go dry.

"Iran is already in deep trouble. It is feeling the effects of shrinking water supplies from overpumping. Yemen is fast becoming a hydrological basket case. Grain production has fallen there by half over the last 35 years. By 2015 irrigated fields will be a rarity and the country will be importing virtually all of its grain."

'The real threat to our future is peak water'
The Guardian, Lester Brown, 06/07/2013 (traduire en Français texte en anglais )
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As population rises, overpumping means some nations have reached peak water, which threatens food supply, says Lester Brown

Peak oil has generated headlines in recent years, but the real threat to our future is peak water. There are substitutes for oil, but not for water. We can produce food without oil, but not without water.

We drink on average four quarts (4.5 litres) of water per day, in one form or another, but the food we eat each day requires 2,000 quarts of water to produce, or 500 times as much. Getting enough water to drink is relatively easy, but finding enough to produce the ever-growing quantities of grain the world consumes is another matter.

Grain consumed directly supplies nearly half of our calories. That consumed indirectly as meat, milk, and eggs supplies a large part of the remainder. Today roughly 40% of the world grain harvest comes from irrigated land. It thus comes as no surprise that irrigation expansion has played a central role in tripling the world grain harvest over the last six decades.

During the last half of the 20th century, the world's irrigated area expanded from 232m acres (93m hectares) in 1950 to 706m in 2000. This tripling of world irrigation within 50 years was historically unique. But since then the growth in irrigation has come to a near standstill, expanding only 9% between 2000 and 2010.

Today some 18 countries, containing half the world's people, are overpumping their aquifers. Among these are the big three grain producers – China, India, and the United States – and several other populous countries, including Iran, Pakistan and Mexico.

During the last two decades, several of these countries have overpumped to the point that their aquifers are being depleted and their wells are going dry. They have passed not only peak water, but also peak grain production. Their aquifers are being depleted, their wells are going dry, and their grain harvests are shrinking. Among the countries whose use of water has peaked and begun to decline are Saudi Arabia, Syria, Iraq and Yemen. In these countries peak grain has followed peak water.

3 commentaires:

  1. Lester Brown a toujours mis en avant le Peak Water et c'est tout à son honneur mais dire que le Peak Water est pire que le Peak Oil est étrange car le Peak Oil conditionne à mon humble avis tout les autres pic. En effet avec de l'énergie abondante tout peut être extrait, concentré, désalinisé ... etc ... surtout si on se fout du climat, ce qui est apparemment le cas!

    Chacun sa grille de lecture mais pour moi, le Peak Oil est le précurseur de tout les autres pics. Le Peak Oil engendre le Peak everything, et ce même si le Peak Water peut conditionner en retour le Peak Oil, il faut de plus en plus d'eau pour extraire du pétrole ... oui mais justement parce qu'on est déjà au Peak Oil.

    "Economic historians writing about this period may routinely distinguish between before peak oil (BPO) and after peak oil (APO)." - Lester Brown


  2. Je crois que tu fais une erreur d'analyse. Ces deux peaks ne sont pas équivalents... Le Peak oil peut être combattu avec pas mal de choses : énergies alternatives, mesures d'économie, etc.

    On peut en atténuer les effets en tout cas pour un temps.

    Mais le peak water ? Ca semble beaucoup plus redoutable... En terme d'usage (vital), de quantité, de masse. A part déssaler massivement l'eau de mer... et ensuite mettre en place une logistique de folie pour amener cette eau dans l'intérieur des terres... ?

    Enfin je ne suis pas certain que la quantité d'eau nécessaire pour l'extraction du pétrole... soit à la même échelle que l'eau pour l'irrigation des cultures.

    En revanche, au niveau macro, je suis d'accord avec toi : le Peak oil a permis un accroissement vertigineux de la population, et c'est bien cette population qui a entraîné le peak water.

    1. Non, ca ne fonctionne pas ainsi, le pic oil ne peut pas être combattu comme tu le dis.
      ca fait 30 ans en effet qu'on en atténue les effets ... sauf que la, cette période se termine.

      peak water, avec de l'énergie abondante, tu desalinise.


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