At about the same time world farmers were harvesting the one billionth acre of biotech crops, a British research firm was releasing a study showing that since their introduction in 1996, genetically modified varieties have meant an extra $27.5 billion in farm income.

And the report, offering the first quantifiable global look at the impact of biotech crop production, noted significant environmental benefits: a 6 percent reduction in the volume of pesticide use, reduced fuel use as a result of more minimum tillage, and a decline in greenhouse gas emissions from agriculture.

Although nobody knows the specific location of the one billionth harvested acre of biotech crops, the milestone event occurred Sunday, Oct. 2, somewhere in the Northern Hemisphere, according to Truth About Trade and Technology (TATT), an organization that tracks biotech crop acres planted and harvested around the world.

“Ten years of use and a billion acres harvested around the world have clearly shown the economic benefits of biotech crops,” said Ross Korves, economist and policy analyst for TATT. “Documented analyses of producer experiences in both developed and developing countries indicate increased economic return and environmental benefits as a direct result of biotech crop production.”

More than 8.25 million farmers in 18 countries around the world have adopted biotech crops, according to the British study, “GM crops: The global socio-economic impact — the first nine years, 1996-2004.”

The $27.5 billion increase in global farm income came from a combination of enhanced productivity and efficiency gains, and is equivalent, the researchers say, to adding 3 percent to 4 percent to the value of global production of the four main biotech crops.

Herbicide-resistant soybeans racked up the greatest gains, with more than $17 billion in increased income, while biotech cotton added another $6.5 billion over the nine-year period.

Growers in the United States and Argentina reaped the greatest gains, about $10.7 billion and $10.1 billion respectively, while cotton farmers in China had a $4 billion increase.

In addition to “greatly enhancing the way farmers produce food, feed, and fiber,” widespread adoption of biotech crops has also brought environmental benefits, said Graham Brookes, director of PG Economics, and one of the authors of the study.

These include a significant reduction in greenhouse gas emissions from agriculture, resulting from 475 million gallons less fuel used by farm equipment, and additional soil carbon sequestration due to reduced plowing or improved conservation tillage.

“This is the equivalent of eliminating more than 22 billion pounds of carbon dioxide from the atmosphere, or removing 5 million cars from the road for one year,” he said. “As the world is increasingly focused on the need to reduce greenhouse gas emissions, it is clear that biotech crops are already making an important positive contribution toward achieving that goal.”

The volume of pesticide spraying has been reduced globally by 6 percent since 1996, the researchers say — the equivalent of 380 million pounds, or 1,514 railcars of pesticide active ingredient. The largest environmental gains from changes in pesticide application have been from biotech soybeans, 19 percent, and cotton, 17 percent.