sábado, 29 de junio de 2013

The angel oak tree, Charleston

the angel oak tree, charleston

nature photography Tags:

En la plurinación sudamericana, árboles como éste ya estarían hechos leña!

lunes, 10 de junio de 2013

Momordica charantia -Balsamina


Bitter melon
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Cucurbitales
Family: Cucurbitaceae
Genus: Momordica
Species: M. charantia
Binomial name
Momordica charantia
Descourt.
Momordica charantia often called bitter melon, bitter gourd or bitter squash in English, has many other local names. Goya[1] from the indigenous language of Okinawa and karavella[2] from Sanskrit are also used by English-language speakers.
It is a tropical and subtropical vine of the family Cucurbitaceae, widely grown in Asia, Africa, and the Caribbean for its edible fruit, which is among the most bitter of all fruits.[citation needed] Its many varieties differ substantially in the shape and bitterness of the fruit.
Bitter melon originated on the Indian subcontinent, and was carried to China in the 14th century.[3]

Description

Ripe fruit
This herbaceous, tendril-bearing vine grows to 5 m. It bears simple, alternate leaves 4–12 cm across, with three to seven deeply separated lobes. Each plant bears separate yellow male and female flowers. In the Northern Hemisphere, flowering occurs during June to July and fruiting during September to November.
The fruit has a distinct warty exterior and an oblong shape. It is hollow in cross-section, with a relatively thin layer of flesh surrounding a central seed cavity filled with large, flat seeds and pith. The fruit is most often eaten green, or as it is beginning to turn yellow. At this stage, the fruit's flesh is crunchy and watery in texture, similar to cucumber, chayote or green bell pepper, but bitter. The skin is tender and edible. Seeds and pith appear white in unripe fruits; they are not intensely bitter and can be removed before cooking.
As the fruit ripens, the flesh (rind) becomes tougher, more bitter, and too distasteful to eat. On the other hand, the pith becomes sweet and intensely red; it can be eaten uncooked in this state, and is a popular ingredient in some Southeast Asian salads.
When the fruit is fully ripe, it turns orange and mushy, and splits into segments which curl back dramatically to expose seeds covered in bright red pulp.

Other Names:

African Cucumber, Ampalaya, Balsam Pear, Balsam-Apple, Balsambirne, Balsamine, Balsamo, Bitter Apple, Bitter Cucumber, Bitter Gourd, Bittergurke, Carilla Fruit, Carilla Gourd, Cerasee, Chinli-Chih, Concombre Africain, Courge Amère, Cundeamor, Fr...
See All Names

Varieties

Bitter melon comes in a variety of shapes and sizes. The Chinese variety is 20–30 cm long, oblong with bluntly tapering ends and pale green in color, with a gently undulating, warty surface. The bitter melon more typical of India has a narrower shape with pointed ends, and a surface covered with jagged, triangular "teeth" and ridges. It is green to white in color. Between these two extremes are any number of intermediate forms. Some bear miniature fruit of only 6–10 cm in length, which may be served individually as stuffed vegetables. These miniature fruit are popular in India, Nepal and elsewhere in Southeast Asia.
Chinese variety
Sub-continent variety
Indian variety

Medicinal uses

Bitter melon has been used in various Asian and African herbal medicine systems for a long time.[6][7][8] In Turkey, it has been used as a folk remedy for a variety of ailments, particularly stomach complaints.[9][10] The fruit is broken up and soaked in either olive oil or honey.

Active substances

The plant contains several biologically active compounds, chiefly momordicin I and momordicin II, and cucurbitacin B.[11] The plant also contains several bioactive glycosides (including momordin, charantin, charantosides, goyaglycosides, momordicosides) and other terpenoid compounds (including momordicin-28, momordicinin, momordicilin, momordenol, and momordol).[12][13][14][15][16] It also contains cytotoxic (ribosome-inactivating) proteins such as momorcharin and momordin.[17]

Anticancer

Two compounds extracted from bitter melon, α-eleostearic acid (from seeds) and 15,16-dihydroxy-α-eleostearic acid (from the fruit) have been found to induce apoptosis of leukemia cells in vitro.[18] Diets containing 0.01% bitter melon oil (0.006% as α-eleostearic acid) were found to prevent azoxymethane-induced colon carcinogenesis in rats.[19]
Researchers at Saint Louis University claim an extract from bitter melon, commonly eaten and known as karela in India, causes a chain of events which helps to kill breast cancer cells and prevents them from multiplying.[20] [21]

Antihelmintic

Bitter melon is used as a folk medicine in Togo to treat gastrointestinal diseases, and extracts have shown activity in vitro against the nematode worm Caenorhabditis elegans.[7]

Antimalarial

Bitter melon is traditionally regarded in Asia as useful for preventing and treating malaria.[citation needed] Tea from its leaves is used for this purpose also in Panama and Colombia. In Guyana, bitter melons are boiled and stir-fried with garlic and onions. This popular side dish known as corilla is served to prevent malaria. Laboratory studies have confirmed that species related to bitter melon have antimalarial activity, though human studies have not yet been published.[22]

Antiviral

In Togo, the plant is traditionally used against viral diseases such as chickenpox and measles. Tests with leaf extracts have shown in vitro activity against the herpes simplex type 1 virus, apparently due to unidentified compounds other than the momordicins.[7]
Laboratory tests suggest compounds in bitter melon might be effective for treating HIV infection.[23] As most compounds isolated from bitter melon that impact HIV have either been proteins or lectins, neither of which are well-absorbed, it is unlikely that oral intake of bitter melon will slow HIV in infected people. Oral ingestion of bitter melon possibly could offset negative effects of anti-HIV drugs, if an in vitro study can be shown to be applicable to people.[24]

Cardioprotective

Studies in mice indicate bitter melon seed may have a cardioprotective effect by down-regulating the NF-κB inflammatory pathway.[25]

Diabetes

In 1962, Lolitkar and Rao extracted from the plant a substance, which they called charantin, which had hypoglycaemic effect on normal and diabetic rabbits.[26] Another principle, active only on diabetic rabbits, was isolated by Visarata and Ungsurungsie in 1981.[27] Bitter melon has been found to increase insulin sensitivity.[28] In 2007, a study by the Philippine Department of Health determined a daily dose of 100 mg per kilogram of body weight is comparable to 2.5 mg/kg of the antidiabetes drug glibenclamide taken twice per day.[29] Tablets of bitter melon extract are sold in the Philippines as a food supplement and exported to many countries.[29]
Other compounds in bitter melon have been found to activate the AMPK, the protein that regulates glucose uptake (a process which is impaired in diabetics).[30][31][32][33][34]
Bitter melon also contains a lectin that has insulin-like activity due to its nonprotein-specific linking together to insulin receptors. This lectin lowers blood glucose concentrations by acting on peripheral tissues and, similar to insulin's effects in the brain, suppressing appetite. This lectin is likely a major contributor to the hypoglycemic effect that develops after eating bitter melon.[citation needed] As bitter melon is extremely bitter if eaten raw, it must be cooked to make it palatable.

Weight loss

In combination with Chinese yam, bitter melon has been shown to contribute to weight loss. Over a period of 23 weeks, those eating the diet containing bitter melon lost 7 kilos.[35]

Other uses

Bitter melon has been used in traditional medicine for several other ailments, including dysentery, colic, fevers, burns, painful menstruation, scabies and other skin problems. It has also been used as abortifacient, for birth control, and to help childbirth.[7]

Cautions

The seeds of bitter melon contains vicine, so can trigger symptoms of favism in susceptible individuals. In addition, the red arils of the seeds are reported to be toxic to children, and the fruit is contraindicated during pregnancy.[36]
It is only potentially toxic only at an extremely large quantity,[37] such as possibly overdosing from concentrated bitter gourd capsules.[38] However, there has never been any case of toxic reactions reported after the vegetable is eaten as is normally prepared as food.[38]

Gallery

The plant


See also

References


This Strange Little Melon May Cure Pancreatic Cancer
 
 
April Flowers for redOrbit.com – Your Universe Online
A new study from the University of Colorado Cancer Center reveals that bitter melon juice restricts the ability of pancreatic cancer cells to metabolize glucose, thus cutting the cells’ energy source and eventually killing them.
The findings of the study were published in the journal Carcinogenesis.
“Three years ago researchers showed the effect of bitter melon extract on breast cancer cells only in a Petri dish. This study goes much, much farther,” says Rajesh Agarwal, PhD, co-program leader of Cancer Prevention and Control at the CU Cancer Center and professor at the Skaggs School of Pharmacy and Pharmaceutical Sciences.
“We used the juice – people especially in Asian countries are already consuming it in quantity. We show that it affects the glucose metabolism pathway to restrict energy and kill pancreatic cancer cells.”
Argwal became interested in bitter melon juice by connecting the dots of existing research in new ways. Pancreatic cancer is typically preceded by diabetes, and bitter melon juice has been shown to effect type-II diabetes. It has been used for centuries in the folk medicines of China and India to combat diabetes. Argwal and colleagues wondered what would happen if they left diabetes out of the equation and directly examined the link between pancreatic cancer and bitter melon.
Argwal says the result is an “alteration in metabolic events in pancreatic cancer cells and an activation of the AMP-activated protein kinase, an enzyme that indicates low energy levels in the cells.”
Bitter melon also regulates insulin secretion by pancreatic beta cells. The mouse model of pancreatic cancer was fed bitter melon juice after studies of cell cultures were done. Compared to the control group, the mice fed the bitter melon juice were 60 percent less likely to develop pancreatic cancer.
“It’s a very exciting finding,” Agarwal says. “Many researchers are engineering new drugs to target cancer cells’ ability to supply themselves with energy, and here we have a naturally-occurring compound that may do just that.”
Argwal’s team is applying for grants to allow them to continue studying bitter melon in further chemoprevention trials in mouse models of pancreatic cancer.

viernes, 7 de junio de 2013

Cosecha sin dolor de espalda

Cucurbita argyrosperma -Pipián o ayote

Commons-emblem-notice.svg
Pipián
Cucurbita argyrosperma 1.jpg
Clasificación científica
Reino: Plantae
Subreino: Tracheobionta
División: Magnoliophyta
Clase: Magnoliopsida
Subclase: Dilleniidae
Orden: Cucurbitales
Familia: Cucurbitaceae
Subfamilia: Cucurbitoideae
Tribu: Cucurbiteae
Género: Cucurbita
Especie: C. argyrosperma
Nombre binomial
Cucurbita argyrosperma
Hort. ex L.H.Bailey
Sinonimia
Cucurbita argyrosperma (ayote o pipián) es una planta herbácea reptante anual, de la familia de las cucurbitáceas, oriunda del sur de México. Se la cultiva en América para su consumo, aprovechándose sus flores, brotes tiernos, frutos y sobre todo las semillas, que molidas y tostadas se emplean en numerosas salsas, moles y otras preparaciones. Es la menos difundida fuera de América de las especies cultivadas de Cucurbita, pero ha sido objeto de intenso estudio recientemente, y se ha difundido en los Estados Unidos con el nombre de Cushaw.

Índice

Características

C. argyrosperma es una hierba anual caulescente, reptante o trepadora; su tallo muestra tricomas cortos, duros y angulosos. Varía desde lo ligeramente velloso hasta lo hirsuto. Las raíces son fibrosas y superficiales, y zarcillos apicales la fijan a la vegetación y al suelo. Las hojas son anchas, cordadas a ovadas, ligeramente trilobuladas con lóbulos elípticos o triangulares, de hasta 30 por 40 cm de superficie, de márgenes serrados o dentados y superficie moteada de blanco, ubicadas al cabo de un pecíolo elongado de hasta 30 cm.
La planta es invariablemente monoica; las flores son solitarias, axilares y pentámeras, de pétalos carnosos y suculentos. Las masculinas alcanzan los 35 cm de largo, con cáliz de forma campanulada, y sépalos lanceolados o foliáceos; la corola es tubular o campanulada, amarillo-anaranjada, pentalobulada, con tres estámenes. Las femeninas tienen un pedicelo ancho y robusto, y el ovario globoso a cónico, botuliforme o piriforme, multilocular. Los estigmas son tres, lobulados.
La forma del ovario determinará la del fruto, un pepónide (baya modificada) de hasta 50 cm de largo. Suele ser lisa, normalmente piriforme, con la parte delgada recta o ligeramente curva. La corteza es verde o blanca, normalmente irregular. La pulpa es blanquecina, amarilla o verdosa, de textura firme. En el interior del fruto hay hasta 200 semillas elípticas, achatadas, blancogrisáceas o amarillentas, de hasta 1,5 x 3,5 cm, con un núcleo blanco, dulce y rico en aceite.

Hábitat y distribución

C. argyrosperma presenta tres cultivares de distribución bien diferenciada, pero en general se cultiva en zonas cálidas, relativamente secas o con estación lluviosa claramente delimitada; se da hasta los 1800 msnm, pero tolera mal las bajas temperaturas. Requiere suelo fértil, bien drenado, rico en humedad, y una ubicación soleada y protegida del viento. Resiste mal las heladas y la sequía; las raíces sufren también en caso de exceso de lluvias.
La domesticación del pipián se estima producida en México hace más de 7000 años. De las dos subespecies identificadas, C. argyrosperma subsp. sororia (sin. C. sororia) y C. argyrosperma subsp. argyrosperma, se cree que la primera es la más próxima al ancestro silvestre; crece en estado natural entre México y Nicaragua. La segunda crece en estado silvestre en el noreste mexicano (sin. C. palmieri), e incluye a las tres variedades cultivadas: C. argyrosperma subsp. argyrosperma var. argyrosperma, C. argyrosperma subsp. argyrosperma var. stenosperma y C. argyrosperma subsp. argyrosperma var. callicarpa, de acuerdo al presunto grado de selección.
De éstas, la primera (conocida comercialmente como 'Silverseed') se cultiva sobre todo por su semilla, y se produce en el norte mexicano y Florida; la segunda se cultiva en México por la pulpa del fruto, mientras que la última ('Cushaw' o 'Green-stripe') se cultiva en Estados Unidos y Japón por sus frutos. Variedades similares a ésta última, pero incertae sedis, se cultivan en Perú y Argentina. En el viejo mundo su presencia es mínima.
C. argyrosperma no forma híbridos espontáneos con otras especies del género.

Galería

Cultivo y uso

Las flores, brotes, tallos y fruta inmadura de C. argyrosperma se utilizan como verdura. En el sur de México, las variedades silvestres, más amargas, también se emplean a ese efecto una vez cuidadosamente lavadas y curadas para eliminar la cucurbitina. El fruto maduro se asa para preparar tartas o emplea como forraje para animales de granja. Mayor uso tienen las semillas, que se asan o tuestan e incorporan a salsas como el pipián de carne y el mole verde. La pulpa se utiliza medicinalmente como tópico para quemaduras y eczemas.
C. argyrosperma se propaga únicamente por semilla. Se planta a comienzos de la estación lluviosa; el plazo para la recolección varía según el uso al que se destine y las características del cultivar. Va de tres meses para los brotes y frutos verdes hasta siete para el fruto completamente maduro. En regiones donde el suelo lo permite —como Oaxaca y Sonora—, al retener la humedad, se la planta a veces en la estación seca y se irriga ligeramente. Puede germinar con mucha menos humedad que otras cucurbitáceas, por lo que en algunas regiones se planta inmediatamente después de la quema de la cosecha precedente, y antes de que las lluvias favorezcan la aparición de malas hierbas. Comparte parcelas con el maíz (Zea mays) y los porotos (Phaseolus vulgaris).

Referencias

  1. Sinónimos en Tropicos
  • Hernández Bermejo, J. E.; León, J. (eds.) (1994). Neglected crops: 1492 from a different perspective. Roma: FAO. ISBN 92-5-103217-3 [1].

Enlaces externos

Reverdeciendo desiertos

To green the deserts, just add... seawater?
30 May 2013 by Fred Pearce
Can desert be turned into fertile oases using nothing but seawater and sunshine? Yes, but at a price
THE smell of ammonia wafts past me as I stand next to the world's largest urea and ammonia factory, clutching the gas mask I've been issued as a precaution. Gas flares glint through the desert haze. This is Mesaieed, a closed industrial city ringed by security cordons in the Gulf state of Qatar – and the unlikely setting for a remarkable oasis.
The heart of this oasis is a greenhouse full of cucumbers. But this is no ordinary greenhouse: it is delightfully cool inside, despite the desert heat. Surrounding it are a series of small garden plots growing desert plants, each walled in by what look like cardboard hedges. Their effect is startling. When I step downwind of a hedge, the air temperature instantly drops, as if I have set foot in front of a powerful air conditioner. And next to the plots is an array of mirrors for concentrating the power of the desert sun.
The most remarkable thing about this little island of glass and greenery (see "A briny business: How to green the desert") is that there is no external supply of either water or electricity – the plants are kept cool and watered using only sunlight and seawater.
Some see this pilot project as the first step towards turning hundreds of square kilometres of parched coastal desert into fertile farms (See "When desert meets sea"). The head of the project, Norwegian biologist Joakim Hauge, has an even bigger dream. He wants to do nothing less than revegetate the desert. And the claim isn't as crazy as it might sound.
The heart of this prototype is the greenhouse. Worldwide, greenhouses are an ever more popular way to grow high-value vegetables and flowers. In their controlled environment, it is possible to get much higher yields than outdoors, making up for the higher costs. But with their insatiable thirst for water and need for heating in winter, most greenhouses are not very green.
This greenhouse is different. For starters, whereas greenhouses in temperate lands are mostly for keeping crops warm, here in Qatar the main task is keeping them cool. This, says Hauge as we tour the site, is done by evaporative cooling.
At the front of the greenhouse, facing into the prevailing northwesterly wind, is a wall of honeycombed cardboard. It is kept constantly wet, cooling and moistening the air that enters the greenhouse. The clever part is that no precious fresh water is wasted on this task; instead, it is done with seawater. The owner of this industrial complex and one of the project's funders, the Qatar Fertiliser Company (QAFCO), has built a network of pipes to deliver seawater for cooling, and the greenhouse taps into that supply.
Inside, in the cool created by the wet cardboard, I met Stephen Clarkson, who grew cucumbers in the UK for 40 years before heading to Qatar. "We plan to grow 1200 cucumbers per square metre per year in here," he says. So far it's going well – Clarkson was about to harvest his second crop of baby cucumbers.
Explore our interactive diagram: "A briny business: How to green the desert"
The ultimate test has yet to come. During my visit, in March, temperatures outside were in the 30s, but in the low 20s in the greenhouse. In August, it can reach 50 °C outside, but the greenhouse needs to stay below 30 °C for crops to thrive. Hauge is confident that it will. As head of the rather grandly named Sahara Forest Project, the private Norwegian company that built and runs the prototype, he has a lot riding on its success.
Keeping the greenhouse cool and humid reduces the plants' need for fresh water, but it still has to come from somewhere. The answer again is seawater. A concentrated solar power system provides the heat and electricity needed to desalinate seawater for irrigation, as well as power all the pumps, fans and other machinery. This is the purpose of the 300 square metres of parabolic mirrors, which track the sun and focus its rays onto a pipe containing oil.
But the prototype is more than just a souped-up greenhouse. The aim is to use seawater to maximum effect, Virginia Corless, an astrophysicist recruited as the project's science manager, told me as we headed outside. "What we have is a cascade of uses for the seawater."
Some goes straight into ponds for growing marine algae. Algae farms are in their infancy, says Patrick Brading, a marine biologist fresh from the University of Essex in the UK, who was preparing a batch of algae for release into a pond. "A lot of basic things are still unknown. I am trying to answer those questions, and it is brilliant to work here with a constant supply of brine to do open-air experiments."
In theory, the algal ponds could provide anything from feedstock for pharmaceuticals and food supplements to food for livestock and farmed fish, Brading says. There are also plans to use seawater to grow a range of native salt-tolerant plants, which could be used for a similar range of purposes.
The leftover brine from all these processes – with a salt content of 10 to 15 per cent – is used to wet the cardboard honeycombs around the small garden plots. "We call them evaporative hedges," Corless says. Their cooling effect allows desert plants and a few tough herbs and crops to grow where none would grow before. The plots are planted with a variety of grasses, as well as barley, rocket and medicinal plants such as aloe vera. The aim is ecosystem rehabilitation, not just desert farming. The long-term plan, she says, is to grow trees as well, which should eventually take over the cooling role of the cardboard hedges.
Brine from the hedges, now with a salinity of around 30 per cent, is pumped to evaporation ponds to produce salt. This can be sold, and also avoids the need to dump extremely salty waste water back in the sea, which can harm marine life.
None of these technologies is new, says Corless, but they have never been put together before. Well, not quite like this. The seawater greenhouse was actually devised two decades ago by British inventor Charlie Paton, who set aside a successful career devising special lighting effects for films and theatres to pursue a vision of growing crops in deserts. I have written about his work before, and before I left for Qatar I visited him at his lab-cum-home in east London.
Paton has built several pilot greenhouses to test his ideas. They have won architectural and environmental prizes, but so far they have failed to catch on. Two – including the first ever seawater greenhouse, built on Tenerife in 1992 – have since been abandoned. Only one, built in Oman in 2004 on land vacated by farmers for want of fresh water, still produces crops – and occasional research papers.
Most recently, Paton's company helped design the Qatar project and was also involved in building a separate project, a trial seawater greenhouse in South Australia that is now selling tomatoes to supermarkets in Adelaide. But he disagreed with some of the changes made by his partners and severed his links with both projects last year.
One change in particular concerned him. Paton came up with his idea during a holiday in the Moroccan desert, when the windows inside his bus steamed up during a rainstorm and left a towel he was using as a pillow soaking wet. His greenhouse design exploits this effect for desalination: cool seawater is pumped through a maze of pipes in a roof cavity, and fresh water condenses out of the air – made humid by the seawater evaporators – onto the outside of the pipes. The system can produce up to 20 litres of water a day per square metre of greenhouse – more, says Paton proudly, than falls in a rainforest.
But this elegant scheme failed to impress his partners. The Australians say that the condenser pipes were a nightmare because they sprang leaks. Both projects ditched them in favour of desalination using concentrated solar power, though the Qatar greenhouse does also collect moisture that condenses on the inside of the roof at night. Solar desalination is simply more efficient, Hauge told me as we watched the sun beat down on the mirrors.

Costly cucumbers

But this high-tech approach does add to the considerable price tag. Back in Doha after our day in the desert, I went through some back-of-the-envelope sums with Hauge. The Qatari greenhouse cost $6 million to build, with the money coming from QAFCO and the Norwegian agrochemicals company Yara. Given the anticipated annual harvest of 720,000 cucumbers for 10 years, that would work out at a capital cost of almost a dollar per cucumber, even without overheads. That is spectacularly expensive: cucumbers were on sale in the Doha souks for a fifth of the price.
Together with the fact that the pilot project was hurriedly constructed to showcase at the UN climate conference in Qatar last December, some might wonder if the project is just an expensive publicity exercise, I suggested to Hauge. No, he insisted. His partners were serious. Of course the cucumbers from the prototype are expensive, but it was built to carry out research, not to make money. "Economically, this kind of farming is only feasible at a large scale."
And there are plans to go large in Jordan, which is one of the most water-stressed countries in the world and increasingly reliant on food imports. Later this year, the Sahara Forest Project hopes to start building a facility near the Red Sea 20 times larger than the Qatar pilot. If all goes well, the idea is to expand to 200 hectares, and eventually to 3000.
In such a billion-dollar megaproject, the vision is that up to half of the area would be devoted to vegetating the desert (see diagram)with everything from dune grasses to native trees, such as the nitrogen-fixing thorn acacia (Acacia tortilis). Over time, as trees grow and the soil improves, these plots will need less assistance, allowing resources to be switched to other areas. "This is not just about sustainable agriculture. It is about restorative ecology," says Hauge.
There is no doubt that it is possible to green desert plots that are actively cooled and irrigated, and that planting trees can have all kinds of benefits for the immediate vicinity, from preventing erosion to providing shelter from the sun and wind. What isn't clear is what will happen to the untouched land a little further away. Simple modelling done for the Sahara Forest Project in 2009 suggests such greening will not produce significantly more clouds or rainfall in the vicinity. However, downwind areas will be cooler and more humid, and the hope is that this altered microclimate will encourage more vegetation to grow naturally, with the effect spreading as positive feedbacks kick in.
This is plausible, says Paul Valdes of the University of Bristol in the UK, a climate modeller who has studied why the Sahara abruptly flipped from a green state into desert around 8000 years ago. "But there is probably a threshold before the effect really starts having an impact," he says, and this threshold will vary from place to place. "This would not happen in all deserts." In other words, in some places greening a relatively small area might greatly boost natural vegetation in the surroundings, but in other places even greening a very large area would make no difference.
Finding out what the threshold might be will require both fieldwork and detailed modelling. Complicating matters further is global warming, which is expected to make dry areas even drier.
There are cheaper ways to revive desert ecosystems and turn back advancing deserts. In Niger, on the edge of the Sahara, simple measures such as protecting trees and digging ditches to catch rainwater have had a dramatic effect. Then again, these approaches won't work in drier regions, or deliver cash crops.
In 20 years, Hauge thinks, seawater greenhouses could be sprouting everywhere from the Atacama desert of northern Chile to California and North Africa, where some coastal aquifers have already been pumped dry. In the Egyptian desert, the 19,000-square-kilometre Qattara depression could be exploited. It is around 100 kilometres from the coast, but could receive seawater by gravity as it is below sea level.
Paton has a similar vision. He says the technology could save 20,000 hectares of greenhouses in Almeria in southern Spain, which supply fruit and vegetables to much of Europe but are now running out of underground fresh water. (Another possible solution is setting up closed greenhouses which recycle most of their water).
And seawater greenhouses could link up with Desertec, the European plan to harvest solar energy in the Sahara desert. A small fraction of that energy could be kept in Africa to desalinate seawater for growing crops. Placing solar plants near greenhouses could have several advantages, such as helping protect them from wind and dust – this is one of the aspects being investigated in Qatar.
But will investors stump up the vast amounts needed to realise these dreams? Perhaps. The financial crisis has dented enthusiasm for grand projects, yet the bottom line has changed since Paton first came up with his idea. Food prices are soaring, world demand for greenhouse-grown fruit and vegetables is rising by 10 per cent a year, and more and more countries are running short of fresh water. The owner of the trial project in Australia, Sundrop Farms, this year got approval to build a 16-hectare, commercial-scale seawater greenhouse, with construction due to start in August. If it can turn a profit, heads will turn.
Sundrop, though, is focusing on growing cash crops – its facility has no desert plots or algae ponds. And perhaps that's telling. My trip left me unconvinced that I will ever see vast areas of the Sahara turn green as massed ranks of cardboard hedges advance across the sands. On the other hand, people have talked for decades about how desalination could be the solution to producing more crops at a time of growing water shortages. With the seawater greenhouse, there might at last be a practical way to do so.
Fred Pearce is a consultant for New Scientist based in London