Ohio officials seized about 40 percent fewer marijuana plants in 2012 as part of a national program to battle growing operations. Officials said the drop can be attributed to drought conditions decreasing production.

The anti-marijuana operation, in which Ohio Bureau of Criminal Investigation works with county sheriffs, seized about 30,000 marijuana plants this year, the Ohio Attorney General’s Office announced last week. That was a drop from 50,704 in 2011 in the U.S. Drug Enforcement Administration-led Domestic Cannabis Eradication/Suppression Program.

The decades-long program funds state agencies — including about $500,000 annually in recent years for Ohio — to search and seize or destroy marijuana growing operations. Officials say the effort is important because marijuana is the only “drug of abuse” grown inside the U.S.

States use much of that money to pay for helicopters that fly over residential areas or farmland looking for growing operations. Those operations are often cut into farmland without a farmer’s knowledge.

But this year, Ohio officials noticed more marijuana growing in residential areas, such as gardens. BCI employs trained spotters to look for signs of marijuana from helicopters, and agents on the ground find the operations and make arrests, if possible.

“I think people are seeing what’s happening in other states, with some attitudes and some legislation passed about legalization for medicinal purposes, and they think, ‘I’ll take my chances,’ ” said Scott Duff, a BCI special agent supervisor for Ohio’s marijuana eradication program.

Ohio ranked in the top five nationally in seizing outdoor growing operations each year from 2007 to 2011. National data for 2012 is not yet available, but in 2011 the DEA-led program eradicated 6.7 million plants and 10,547 outdoor growing operations.

The largest Ohio bust of 2012 came in Pike County. Officials seized about 1,200 plants on a site with suspected ties to a Mexican drug cartel, which has been a growing concern in Ohio. Such sites often include guards creating living areas near the growing operations with more sophisticated security and weapons.

“Selling and buying marijuana not only leads to more crimes in our communities, but it is also a gateway drug that could lead users to try drugs like heroin and cocaine,” Ohio Attorney General Mike DeWine said in a statement announcing 2012 results. “Drugs have destroyed too many lives, and we will do everything we can to prevent further tragedies.”

The noted increase of residential growing sites requires officials to use the same manpower to find fewer plants, Duff said. A residential grow site will commonly contain 10 to 14 plants, while many rural growing operations will include hundreds of plants.

While the decrease in seized plants could be viewed as officials finding fewer existing operations, Duff said the poor growing conditions this year played a bigger role in the statistics. He added that the smaller residential growing sites are a signal that producers are trying to avoid the state’s surveillance efforts.

Duff said the DEA’s marijuana eradication funding to Ohio has been consistent and that an individual year’s statistics don’t necessarily affect that funding level.

“We’ve been fortunate in Ohio, and we haven’t seen the (funding) decreases that some areas have,” Duff said. “I think the DEA recognizes the results we get.”