New Geoengineering Idea: Turning Deserts into Forests

Leonard Ornstein, a cell biologist at the Mount Sinai School of Medicine in New York, and Igor Aleinov and David Rind, two climate modellers at NASA, argue that foresting the Australian outback and Saharan Desert would “solve climate change.” While numerous geoengineering schemes have been proposed to mitigate the adverse effects of greenhouse gas (GHG) build-up, many of the more ambitious ideas, including ocean-based aerosol sprayers, space mirrors, C02 air scrubbers, or artificial C02-capturing “trees,” have been examined and labeled cost-prohibitive or dangerous (see earlier post). Others ideas will work, are much cheaper on a small-scale, but require significant investment and regulatory changes to scale up worldwide (see Steven Chu’s call for reflective cool roofs, and more on the idea of creating reflective crops). These researchers, however, argue that massive forestation in equatorial deserts  “provides the best, near-term route to complete control of greenhouse gas induced global warming,” and would be cost-effective in comparison with carbon capture and storage (CCS) plans now receiving massive investment (see earlier post). 

The scientists outlined their plan in a recent article in the Journal of Climatic Change. According to The Guardian (UK), the plan would involve planting “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 8bn tonnes of carbon a year, about the same as emitted from fossil fuels and deforestation today.”

While the costs of planting a forest in the Sahara would be high (around $1.9 trillion per year), Ornstein argues the plan is cost effective when you consider the cost of CCS and compare the amount of C02 emissions sequestered.  In comments to The Guardian (UK), he said: “when that’s compared to figures like estimates of $800bn per year for CCS, our plan looks like a loser. But CCS can address only about 20% of the problem at the $800bn 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.”

According to The Guardian (UK),  Saudi Arabia, Libya, Tunisia, Morocco, and other northern African countries, along with central Australia, would all be suitable sites. Forestation must occur in sub-tropical areas where there is little chance of darker forested landscapes soaking up more sunlight and therefore warming the earth’s surface. “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.” The plan would also yield economic and social benefits through new green jobs. Sustainable wood industries could take hold.

Some critics argue the Sahara is already a functioning ecosystem, which locals rely on, and planting forests would destroy it. Ornstein responded: “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 part of the 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. If sacrifices are required to stem global warming, the almost non-existent ecosystems of the central Sahara and the [Australian] outback seem like reasonable candidates compared to the alternatives.”

Read the article 

In other news, the Prince of Wales announced a new fund to prevent additional deforestation in tropical developing countries like Brazil, Malaysia and Indonesia. The Guardian (UK) writes that a global emergency fund has been set up to “drastically reduce the destruction of tropical rainforests over the next five years.” Some 35 governments of the Informal Working Group (IWG) agreed to the plan.

“The IWG hopes to achieve a 25 percent reduction in annual deforestation rates by 2015. The felling of forests causes almost a fifth of global carbon emissions.”

The U.S. government has pledged $275 million towards rainforest protection. The plan is expected to cost between £13.5bn and £22bn over the next five years. Read the report

Lastly, check out UNEP’s BillionTree campaign, an ambitious global reforestation program, which aims to plant seven billion new trees worldwide in 2009. Companies, organizations or individuals can pledge and register their new trees through the program.

14 thoughts on “New Geoengineering Idea: Turning Deserts into Forests

  1. luke 11/20/2009 / 1:43 pm

    In addition to a major concern for proper bio-diversity, the entire concept of foresting the Sahara seems to shove the world’s issues onto a population that has contributed seemingly little to the problems of greenhouse emissions compared to say the US or China. Perhaps these countries should take it upon themselves to remediate their portion of greenhouse gas contribution on their own soil and take responsibility for their own actions, using their own resources to fix a problem they created in the first place.

  2. Mason Inman 11/21/2009 / 4:27 am

    Throughout the article, it mistakenly says C02, not CO2.

    That is, it should be “C-oh-2,” not “C-zero-2”. The “O” stands for oxygen.

  3. Justin 11/23/2009 / 9:03 pm


  4. Matt 11/23/2009 / 9:50 pm

    You forgot to add in the cost of protecting all those trees from being cut down and used for shelter/firewood. Lets face it, the locals are going to use this resource if it is there. Wood is much more useful than sand. Last time I checked, when all you have is sand, all you can make is… sand.

  5. Wahday 11/24/2009 / 2:26 pm

    An interesting idea, but I think the largest obstacle may be that much of the infrastructure would require growing on or traversing territory that is experiencing tremendous conflict, turmoil and displacement. It is likely that such a large scale project would be met with sabotage (for political purposes) or simply raiding for materials that can serve a more immediate needs in local, struggling populations. This has been the case with other large scale, multinational projects, particularly in Saharan Africa where a great deal of turmoil is taking place. I have a hard time seeing any of this taking place in Sudan or Somalia, for example.

    But the concept is interesting. It was only a little more than 10,000 years ago that the entire Sahara was a lush grasslands that served as a center for instrumental crop development such as sesame, sorghum and millet.

  6. lyle 11/24/2009 / 6:28 pm


    Parts of the Sahara were quite lush at one point in time. Overgrazing, and deforestation for firewood brought down more than a few north African or middle Eastern society.

    The current generation may not have been responsible for what their ancestors did, but they’ve certainly paid the price. Reforestation would only be giving back to them what their own forebears took away.

  7. Craig Hullinger 11/26/2009 / 5:14 pm

    Interesting Idea. It could be combined with a major effort to create additional agricultural areas for the poor parts of Africa – a major need.

    Would likely require nuclear plants to power the desalinization and pumping of sea water into the interior.

    Would be much easier to do politically in Australia – Get it started there, and expand into other deserts when it is proven.

  8. Mark 11/26/2009 / 5:42 pm

    In framing this topic in terms of social inequity and a zero-sum calculation, I think Luke misses a critical opportunity for these regions, areas that have been naturally (though only episodically) forested in the past – or at least that were rangeland rather than desert.

    Not only would there be significant transfers of wealth to these regions in the form of land rents, but new natural resources and habitable areas would be created for the people there. At the same time, biodiversity would be significantly increased (even as certain desert species would be marginalized). The same trend would apply for economic diversity.

    For me, the critical social issue in an equatorial forestation plan is instead assurance of democratic governments in these areas, so that profits from such massive annual investments are not squandered or held by a minority of the population (as so often with oil profits today), and so that the transfered wealth truly reaches and benefits great numbers of people in these regions.

  9. luke 11/30/2009 / 10:04 am

    All very good points. The challenges of such a project are on a scale unparalleled by any other, and would require the administration, funds, and management from many countries, rather than strictly local governments. This type of restoration would be forced to reform the political ecology of this region as well in order for these proposed efforts to sustain themselves.

  10. linda barbero 11/30/2009 / 11:40 am

    Check out this permaculture solution for greening the desert through swales and rain harvest

  11. Randy Hayes 12/01/2009 / 8:46 pm

    Carbon offsets like this reforestation idea should be done at (say) a 3 to 1 ratio. An example: for every one ton of polluting coal power plant GHG emissons that are not shut down the comany owners would have to finance three tons of carbon offsets. The reason for this is to maximize the pressur to “first do no harm”. If you don’t like offset programs imagine 3 to 1 or 10 to 1 or 1,000 to 1 ratio. If someone destroyed (say) one square mile of wetland but restrored 1000 would that feel OK to you?

  12. kevin dwan (@THE_ST0RY) 02/27/2014 / 7:11 pm This is an amazing idea check it out. Create massive inland mangrove swamps in the sand seas of Algeria with water pumped over the Atlas mountains near Tan Tan in Morocco. Once over the mountains the water will pool in shallow seas that can be planted with mangrove, plant enough and we’ll create weather and fresh water over the entire Sahara. That means savannah and forests and sustainability. Please like and share the page if you can!

  13. picoallen 12/12/2016 / 6:19 am

    So how come having oceans west of the desert zones of Africa, Australia and the Americas do not cause high rainfall on their west coasts? Answer: the Hadley Cells in which air rising in the tropics, release their moisture there as rain, then descend on the subtropics desiccating the desert zones. You will never grow forests there because you can never stop this circulation, unless perhaps you can build an artificial mountain range the height of the Andes to disrupt it.

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