Sugarcane has cooling effect, Stanford researchers say

April 19, 2011 | Susanne Rust, California Watch

Rufino Uribe/Wikimedia Commons

Not all cropland is created equal.

And despite the bad press sugar has been receiving in the past few days, sugarcane may be one of the more climate friendly crops available.

At least at a local level.

Researchers at Stanford University and the University of Montana have found that converting cropland to sugarcane fields creates a cooling effect.

But they say this does not mean that razing forests for sugarcane is good.

What it means is that if you’re going to convert land already being used for agricultural purposes, sugarcane may be the way to go.

Scott Loarie, a postdoctoral student with Stanford’s Carnegie Institution, and colleagues decided to take a look at the local climate effects of biofuel agriculture on Brazil’s Cerrado – a wide expanse of tropical savannah and grassland in central Brazil.

Biofuels – fuels made from agricultural crops such as corn or sugar canes – emit less carbon to the atmosphere when burned than fossil fuels.

In particular, they wanted to see what the difference was between converting natural land into sugarcane fields and converting already existing agricultural land into sugarcane.

Most research into biofuel land expansion has looked at the carbon output and greenhouse gas-emission effects of converting land into biofuel crops. In general, converting land already in use for agriculture releases less carbon, and requires less energy, than converting natural forests or ecosystems.

Loarie’s research reinforces that assumption by showing there are significant local effects when pre-existing agricultural land is converted into sugarcane. The sugarcane actually seems to reduce local temperatures by nearly 2 degrees.

The team says that's because sugarcane reflects more of the sun's heat, instead of absorbing it. And the crop releases extra water vapor, which has a cooling effect on the local climate.

Loarie pointed out that converting the natural landscape to agriculture warmed the temperature by nearly 3 degrees. It’s the subsequent conversion to sugarcane that then cools it.

So, in the end, sugarcane land still produces a net warming effect over the natural system. It’s just that if you compare it to other crops – or convert the land from other crops – it’ll cool things off.

Loarie also said that what is good for the climate is not necessarily good for other environmental concerns, such as biodiversity. Rangeland, or cattle grazing land, supports a large number of different species.

“You go out (and) bird watch on ranch land in the Cerrado, and you’ll see a lot of birds,” he said. “Put in sugarcane, it becomes a biological desert.”