x Abu Dhabi, UAETuesday 25 July 2017

Carbon farming: UAE deserts ideal for saving the earth

Hot, dry coastal regions such as the UAE may actually be ideal for a technique scientists are calling "carbon farming".

Pupils at Repton School plant trees at their school campus in Dubai. A project to plant trees on “carbon farms” in the desert could bring more rainfall to the area and absorb tonnes of atmospheric carbon dioxide. Pawan Singh / The National
Pupils at Repton School plant trees at their school campus in Dubai. A project to plant trees on “carbon farms” in the desert could bring more rainfall to the area and absorb tonnes of atmospheric carbon dioxide. Pawan Singh / The National

It's a nice idea - plant a tree, save the planet.

And it certainly seems to resonate with young people. Last month, a UAE youth group led by its 14-year old founder, Simran Vedvyas, planted dozens of trees on a landfill site in Dubai as their contribution to the Plant-for-a-Planet campaign, which aims to plant a trillion trees around the world.

Cynics may dismiss all this as pie in the sky, yet some simple arithmetic suggests otherwise. If everyone planted 150 trees over the next 10 years, the total of a trillion would be reached with ease. The Chinese alone planted 2.7 billion trees in 2009 as part of a United Nations tree-planting campaign.

Even so, it is hard to imagine that places such as the UAE will ever play host to vast acres of planet-saving trees. Yet some new and not-so-simple ecological research suggests that it just might be possible.

Hot, dry coastal regions such as the UAE may actually be ideal for a technique scientists are calling "carbon farming".

It is widely known that our planet is undergoing climate change as a result of the increasing carbon dioxide concentration in the atmosphere. Plants mop up this greenhouse gas, and that - in theory - makes planting trees a natural means of so-called carbon sequestration, in which the gas is locked up out of harm's way.

Studies of forests and plantations show that the mere presence of trees can alter the local climate, bringing more rain and making regions more hospitable.

In environmental issues, however, simple solutions have a habit of turning out to be anything but.

After the biofuels debacle, where food crops were bulldozed to make way for "eco-friendly" fuel crops, it has become clear that a more nuanced approach is needed towards the use of land to combat climate change.

And it is this that makes desert regions the focus of interest in carbon farming with trees. Most of the land in such regions is not much good for anything else.

Using computer models of the climate, researchers have found that planting trees capable of thriving in such areas, such as eucalyptus, can bring about the twin benefits of carbon sequestration and increased rainfall. Until now, however, these global models have been regarded as insufficiently reliable to act as the basis for policy decisions.

What is needed is a far more detailed computer model - plus detailed input from experts in crop behaviour, irrigation and economics.

Now scientists based in Germany have published what they claim is the first such study of the feasibility of using trees in desert areas. And the results are intriguing.

Led by Professor Klaus Becker of the University of Hohenheim, Stuttgart, the team has focused on Jatropha curcas, a shrub native to Central America able to cope with very arid conditions - and for which there is already a wealth of data from plantations in Egypt, India and Madagascar.

Combined with the results from various computer models, the team has come up with figures for both the effectiveness of Jatropha "carbon farms" and their cost effectiveness.

Publishing their results in the online journal Earth Systems Dynamics, the team estimates that one hectare of Jatropha could capture up to 25 tonnes of atmospheric carbon dioxide a year over a 20 year period.

To put that into context, a plantation taking up only a few per cent of the Arabian Desert could in that time absorb all the carbon dioxide produced by motor vehicles in Germany.

The team estimates that globally about a billion hectares of land is suitable for carbon farming, so the same shrubs could mop up a significant portion of all the CO2 added to the atmosphere since the Industrial Revolution.

The scheme makes economic sense too, says the team. They estimate that carbon farming costs between US$80 and $120 (Dh290 and Dh440) per tonne of CO2, making it competitive with other sequestration techniques such as carbon capture and storage.

After a few years the plantations could be the source of bioenergy, in the form of tree trimmings. The resulting biokerosene is clean and could be used to power the desalination and irrigation systems, whose cost would be kept lower still by basing the plantations in coastal regions.

Now the team wants to start real-life trials of carbon farms in Oman and Qatar. Computer models of these sites suggest that 10,000 square-kilometre plantations would produce significant cooling over the region while boosting summer rainfall by about 11 millimetres.

There are, however, clouds hanging over the idea - especially the focus on Jatropha. The shrub was extensively used during the biofuels boom earlier this century, specifically because of its supposed hardiness. India and China planted huge areas of marginal land with the crop, but it failed to thrive. Many plantations have since been abandoned.

Whether this underperformance will undermine the biofuel yield of Jatropha - and thus its ability to power the desalination plants, and remain economic - remains unclear, along with the reliability of the computer models on which the predictions are based.

Vegetation cover affects the reflectivity of the Earth, and thus its ability to bounce the sun's heat back into space. Covering large swathes of light ground with dark trees could thus lead to more heat being absorbed, boosting temperatures.

Previous studies have shown that trees planted too far from the equator can produce a net gain in solar heating - precisely the opposite of what is required. What is not clear is whether desert regions such as the UAE are close enough to the equator to prevent this consequence.

The researchers admit there are still many uncertainties, but argue that the only way to know for sure is to carry out the experiment - or, as Simran Vedvyas herself put it last month: "Stop talking, start planting."

 

Robert Matthews is visiting reader in science at Aston University, Birmingham, England