A recent study presents the possibility of “carbon farming” as a less risky alternative to other carbon capture and storage technologies. It suggests that a significant percentage of atmospheric CO2 could potentially be removed by planting millions of acres of a shrub known as the Barbados nut（麻疯树）, in dry, coastal areas. But other experts doubted whether the Barbados nut would be able to grow well in sandy desert soils and absorb the quantity of carbon their models predict.
The researchers behind the study say Barbados nut plantations（种植园）could help to reduce the local effects of global warming in desert areas, causing a decrease in average temperature and an increase in rainfall. If a large enough portion of the Earth were blanketed with carbon farms, these local effects could become global, capturing between 17 and 25 metric tons of CO2 per hectare each year over a 20-year period.
Carbon farms would not compete with food production if they were concentrated in dry coastal areas. In their analysis, oceanside desalination（海水淡化）plants provide a low-emission irrigation method. The study states that the Barbados nut is uniquely suited to growing in regions unsuitable for other crops .The plant, which produces a non-edible seed that can be used to create biodiesel（生物柴油）, is comfortable growing at temperatures exceeding 100 degrees Fahrenheit. It can also stand up to high levels of pollution in the soil, making waste water another potential source for irrigation.
The cost of carbon farming is comparable to the costs associated with other carbon capture and storage technologies, the study claims. Wulfmeyer stressed that carbon farming could have “fantastic value for the local people” if international carbon markets pick up, promoting rural development and opening up the possibility of additional agriculture as the soil quality improves around the plantation.
In an email, Van Noordwijk, a chief science advisor, questioned the growth rate and the atmospheric carbon capture rate assumed by the study's authors, calling the estimated carbon price of the plantations a “considerable underestimate”. “We are talking about a plant with a shrubby growth habit and a long track record of misleading farmers with production potentials that are not being realized,” he said, and “Even with abundant water, the nutrient storage in sandy desert soil is low. He added, “The estimated carbon price of this option already indicates that there are far better opportunities for reducing ongoing emissions from peatland（泥炭地）use and deforestation.”
