Logo of Phnom Penh Post newspaper Phnom Penh Post - Greenhouse gas level from rice paddies may be twice as high as originally thought

Greenhouse gas level from rice paddies may be twice as high as originally thought

Greenhouse gas level from rice paddies may be twice as high as originally thought

The way some irrigated rice paddies are managed worldwide, with cycles of flooding followed by dry periods, may lead to twice the planet-warming greenhouse gas pollution as previously thought, researchers said Monday.

Since rice is a major staple for at least half the world’s seven billion people, the way it is managed has significant effects on the Earth’s warming climate, said the report in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal.

For the study, researchers at the non-profit Environmental Defense Fund took a closer look at emissions of nitrous oxide, a long-lasting atmospheric pollutant that is more potent than methane or carbon dioxide.

N2O rises when rice fields are allowed to dry before being wetted again.

This process, called intermittent flooding, happens when water falls below the soil level several times per year.

It is encouraged by some agricultural organisations affiliated with the United Nations Food and Agriculture Organization as a way of saving water and reducing methane, another major greenhouse gas emitted by rice paddies. It remains unclear how many farmers do it.

“When the soils are frequently wetted and dried, they repeatedly become ideal environments for microbes that produce nitrous oxide,” explained lead author Kritee Kritee, senior scientist at the EDF.

“Methane on the other hand is produced by microbes that require soils to be submerged in water,” she told AFP in an email.

It is widely assumed that “almost all irrigated farms in the world are continuously flooded and it is a fact that continuously flooded farms do not produce significant amounts of nitrous oxide,” she added.

But it is not true that all farms are continuously flooded.

That’s why Kritee says the “full climate impact of rice farming has been significantly underestimated.”

200 coal plants

Currently, the amount of unaccounted-for N2O global emissions from rice may be as high as the annual climate pollution from about 200 coal power plants, according to the authors.

In India alone, where the study took place across five intermittently flooded rice fields, nitrous oxide emissions “could be 30-45 times higher than reported under continuous flooding,” researchers estimated.

Overall, they calculated that nitrous oxide per hectare (2.5 acres) was three times higher than ever reported by research on intermittently flooded farms before.

“When this new information is extrapolated across the world and embedded into estimates of methane emissions, the net climate impact from both methane and nitrous oxide could be two times higher than previous estimates,” Kritee said.

Experts say a better way would be for all irrigated rice farmers to shallowly flood their fields, meaning the water level stays within five to seven centimeters of the soil level.

“This flooding regime produces the least amount of methane and nitrous oxide,” Kritee said.

As of now, N2O from rice-growing simply isn’t being tracked on a broad scale, and is left out of greenhouse gas inventories reported to the United Nations by major rice-producing countries including China and India.

But as water becomes scarcer around the globe, many rice farmers may look to wet and dry cycles as a solution, not knowing the danger they are posing to the planet.

MOST VIEWED

  • Phnom Penh unveils rules for post-lockdown transition

    The Phnom Penh Municipal Administration issued a set of detailed guidelines for the seven days to May 12 after the capital emerges from lockdown at the onset of May 6. In the 14-page document signed by municipal governor Khuong Sreng released on the evening of May 5, the

  • SBI LY HOUR Bank Launches Cross Border Money Transfer Service between Cambodia and Vietnam on RippleNet, utilizing DLT

    SBI LY HOUR Bank Plc and Hanoi-based Tien Phong Commercial Joint Stock Bank (TPBank) on Friday launched the first Cambodia-Vietnam money transfer service in real currency via RippleNet, provided by SBI Ripple Asia Co Ltd to provide safe, fast and convenient services. SBI LY HOUR

  • Gov’t issues guidelines as lockdown nears end

    The government has issued a five-page set of instructions to be enforced when the three-week lockdown of Phnom Penh and adjacent Takmao town in Kandal province ends on May 6. According to an announcement signed by Prime Minister Hun Sen on May 4, the instructions cover a

  • Cambodia ready to exit LDC status

    Cambodia is well-prepared to minimise economic risks when it graduates from its Least Developed Countries status, according to a senior official at the Ministry of Commerce on May 7. Four LDCs – Cambodia, Laos, Bangladesh and Nepal – met at a virtual workshop last week to explore potential

  • Nine US franchises eye Cambodia debut

    Nine famous US franchising companies are looking for business opportunities and expansion into Cambodia to build a footstep for a strong foundation in Southeast Asia. The US embassy in Phnom Penh, in partnership with the US Foreign Commercial Service and with support from the American

  • Lost in translation: ‘Starvation’ in capital’s designated red zones

    “DACH bay” is a Khmer slang meaning a “loss of income”, that could also be literally translated to «deprived of rice”, which alludes to starvation. However, civil society organisation (CSO) officials have independently confirmed the government’s prior assertions that there are no cases of