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Sowing seeds in the sand

A staggeringly ambitious plan to mitigate the effects of climate change would see the Sahara and Australia’s outback planted with forest – and cost US$2 trillion. David Adam looks at a US researchers’ scheme.

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Some talk of hoisting mirrors into space to reflect sunlight, while others want to cloud the high atmosphere with millions of tonnes of shiny sulphur dust. Now, scientists may have dreamed up the most ambitious geoengineering plan to deal with climate change yet: converting the parched Sahara desert to a lush forest. The scale of the ambition is matched only by the promised rewards – the scientists behind the plan say it could “end global warming”.

The scheme has been thought up by Leonard Ornstein, a cell biologist at the Mount Sinai School of Medicine in New York City, together with Igor Aleinov and David Rind, climate modellers at NASA. The trio have outlined their plan in a new paper published in the Journal of Climatic Change, and they modestly conclude it “probably provides the best, near-term route to complete control of greenhouse-gas-induced global warming”.

Under the scheme, planted fields of fast growing trees such as eucalyptus would cover the deserts of the Sahara and Australian outback, watered by seawater treated by a string of coastal desalination plants and channelled through a vast irrigation network. The new blanket of tree cover would bring its own weather system and rainfall, while soaking up carbon dioxide from the world’s atmosphere. The team’s calculations suggest the forested deserts could draw down around eight billion tonnes of carbon a year, about the same as emitted from fossil fuels and deforestation today. Sounds expensive? The researchers say it could be more economic than planned global investment in carbon capture and storage (CCS) technology.

“The costs are enormous but the scale of the problem is enormous,” says Ornstein, who is best known for pioneering a cell biology technique called polyacrylamide gel electrophoresis in the 1950s. “It’s a serious suggestion, in that I believe it is the most promising and practical option in terms of current technology to solve the biggest parts of the problem.”

The scheme could cost US$1.9 trillion a year, he says. “When that’s compared to figures like estimates of $800 billion per year for CCS, our plan looks like a loser. But CCS can address only about 20% of the problem at the $800 billion price. Mine addresses the whole thing. And CCS would involve a network of dangerous high-pressure pipelines coursing through the most developed neighbourhoods of our civilisations, compared to relatively benign water aqueducts in what are presently virtually uninhabited deserts.”

Planting trees to combat rising carbon-dioxide levels is controversial on a large scale, because most places where it has been suggested, such as Canada and Siberia, are in the northern hemisphere where the resulting change in surface colour, from predominantly light snow and rock to predominantly dark trees, could soak up more sunlight and cancel out the cooling benefit.

Ornstein says subtropical regions, such as the Sahara and the Australian outback, do not have this problem. The areas have only minimal “human occupation, agricultural food and fibre resources and competing natural biomes”, the team says. “We must bite the bullet; global warming will not go away by itself ... solar, geothermal and wind power can make modest contributions. All of these are other parts of a fix. But the quicker a forest can be grown, the more time will be available to choose among and to implement such adjustments, and perhaps to develop more attractive substitutes.”

Ornstein says several desert-heavy countries are suitable, including large chunks of Saudi Arabia and a string of African nations west of Egypt. The scheme would provide jobs and investment, he says, as well as a long-term source of sustainable wood that could be used as a biofuel to replace fossil fuels. Other plans for the desert region, such as the installation of giant arrays of mirrors and solar panels to generate electricity would not be affected, he says. Tree-planters, and the resulting clouds, would stick to the flatter regions further south.

Since the paper was published recently, Ornstein has attempted to seed serious discussions on specialist websites, with little success. Critics have pointed out that the deserts are not total wildernesses, but rich and diverse ecosystems in their own right, which would be destroyed. Ornstein says: “If sacrifices are required to stem global warming, the almost non-existent ecosystems of the central Sahara and the outback seem like reasonable candidates compared to the alternatives.”

The scheme does have some support. “It is incredibly important and definitely worth taking seriously,” says Rick Anthes, president of the University Corporation for Atmospheric Research (UCAR) in Boulder, Colorado. “While there are many practical and political difficulties of afforestation of regions this large, the benefits could be enormous and go well beyond carbon sequestration.”


www.guardian.co.uk

Copyright Guardian News and Media Limited 2009

Homepage image by alex lichtenberger
 

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Default avatar
匿名 | Anonymous

火灾

作者忽视了森林火灾的危险。无论火灾是由闪电还是由纵火还有那些以内政治原因引起的。
森林火灾的危险一定要考虑因被提议的地点都是在非常干旱的地区。任何的收获可能都会被火灾毁掉,这样森林中储存的二氧化碳又将被释放到大气。
最重要的还是不要排放二氧化碳

Fire

The authors ignore the very real risk of fire, whether by lightning or arson - including by those with a political agenda.

That risk is particularly great given that the proposed plantations would be in very dry parts of the world. Any gains would be lost by fire - carbon stored in the trees being released back to the atmosphere.

It would be much better not to emit the carbon in the first place.

Default avatar
匿名 | Anonymous

人类与其他物种

这篇文章隐含着作者认为人类比其他物种(以及土著居民)都要优越的观点。
人类无权进行不可持续的生活,或者说无权让其他物种灭亡。
我们的价值体系必须改变,更加注重生长的质量,还不是数量。

Humans V Other Species

This article implies that the authors regard themselves as superior to other species (and indigenous peoples).

Humans have no right to live unsustainably - or knowingly to cause other species to become largely extinct.

Our value system must change, focussing more on the quality of growth rather than the quantity.

Default avatar
匿名 | Anonymous

特拉菲古拉公司掩盖污染真相

以下是特拉菲古拉公司删除的一段视频。 这段视频来自《BBC受法律威胁,删除在象牙海岸倾倒废物的重要新闻》。

注:请Windows Media Player免费安装FLV视频格式插件“鲨鱼编解码器”。http://bit.ly/6ZTqsk

Trafigura Poisoning Coverup

Here is the deleted Trafigura.flv video from the "BBC deletes important story on toxic waste dumping in the Ivory Coast after legal threats". Note: the free "Shark Codecs" software program installs the video file format FLV in Windows Media Player. http://bit.ly/6ZTqsk

Default avatar
匿名 | Anonymous

森林

比起在沙漠里播种植被,保护和扩大森林和雨林则容易和便宜得多。在森林里,树木在肥沃土壤中更易生存。相反,盲目砍伐树木现象非常严重,同时也给环境带来了巨大伤害。由于森林的规模逐年下降,我们坚信提高对森林的重视至关重要。--Morning

forest

It's more easier and inexpensive to keep and expand the forest or rainforest than to plant trees in sand.In forest,the trees survive easier with the fertile soil;on the contrary,the abuse of cutting trees is severe and brings harmful impact to environment.As the scale of the forest decreases year by year,we are convinced that it is wise to place great emphasis on the forest. Morning

Default avatar
匿名 | Anonymous

态度

与其大规模改变现有的生态环境,不如去保护正在拥有的!大自然所赋予的,是属于我们自己生存最好的!妄加改变,只会让环境变得越来越可怕!请专家、政客在做出决策时,为人类长时间的生存、可持续的发展所考虑,而不只是为了一时的冲动!

Attitude

Try not to change the current entironment but rather protect what we are having now! That which nature gives belong to the best that for us to live with! Changing without close thought can only make the environment increasingly horrible! Please think about the survive and sustainable development of human before you experts and politicians make decisions not just merely a impulse!