VISTA HERMOSA, Colombia – White Brahman cattle munched grass under a mango tree as Bernardo Velasco stretched out his right hand, pointing to a section of green pasture on his farm.

"This all used to be coca," he said, referring to the plant used to make cocaine, which he and other farmers here once grew in abundance.

Today Velasco, 50, and most of his neighbors have traded in their coca for other crops, growing cacao (for making chocolate), corn and plantains in an ambitious plan to stabilize parts of Colombia long controlled by rebel fighters, paramilitary groups and drug traffickers.

The effort has suddenly gained new urgency, given the government’s decision last month to halt a longstanding U.S.-backed campaign to kill coca crops with aerial spraying. Now, Colombia will have to rely more heavily on approaches like this one.

But despite early advances, the effort here has fallen far short of expectations, raising questions about whether the government can transform other troubled parts of the country.

"We’re going on eight years since they eradicated coca here, eight years," said Gilberto Olaya, 54, a dairy farmer and a member of the municipal council here in Vista Hermosa. "And you don’t see clear policies where the government says, ‘OK, we’re going to come to you with the things you need to get by, to earn a decent wage that you can survive on, like you could with coca.’"

The farmers here are the earliest beneficiaries of a showcase project financed with hundreds of millions of dollars in U.S. aid.

The goal was to use the Colombian army and the police to drive out the guerrillas, destroy coca and then bring in the civilian authorities to help local farmers grow legal crops in a place where the government had no more than a token presence for decades.

But years after the program started, many residents say that they are still waiting for electricity and paved roads, and that rebel fighters still lord over them, frustrating the farmers and others whose confidence it was meant to win over.

"We need much more commitment, more decisiveness from the government," Olaya said. "Things have stagnated."

The success, or failure, of such efforts are especially important given the government’s negotiations with the country’s largest guerrilla group, the Revolutionary Armed Forces of Colombia, or FARC.

If the talks lead to a peace agreement, the government’s ambitious goal of integrating former guerrilla strongholds into the national fabric will depend greatly on the experiences here.

Heightening concerns, a large stream of U.S. aid backing the program is coming to an end, at the same time that the Colombian government’s funding for the effort has declined.

Begun in 2007, the consolidation program, as the effort is known, focused on a rural area in central Colombia known as La Macarena. It includes this farming town, where the Colombian plains meet the foothills of the Andes.

Started by President Juan Manuel Santos when he served as defense minister under his predecessor, Alvaro Uribe, the project made immediate strides.

The FARC was pushed back, government teams ripped up vast plantings of coca, and farmers planted cacao and other substitute crops. The region became a showcase. U.S. congressmen, business executives, diplomats, foreign correspondents and many others were brought in to get a glimpse of the future of Colombia.

The project set out to bring rural residents under the governmental umbrella for the first time and create the conditions for them to succeed. That meant improving roads needed to bring crops to market, giving titles to farmland, granting agricultural loans, bringing electricity to isolated hamlets, and setting up government services like courts, schools and health clinics.

But critics say that after Santos was elected president in 2010, the government’s interest seemed to wane.

Alvaro Balcazar, the original director of the program, who left in 2012, said that it suffered from the start from bureaucratic inertia and that other government agencies were slow to get involved. After some initial success in La Macarena, the program was expanded to include other areas of the country, but he said it ultimately lost focus.

"The promise was that the government was going to establish a presence in the regions, and that promise has not been met," Balcazar said.

The area around Vista Hermosa shows notable achievements and stunning shortfalls.

This was once one of the country’s most productive coca-growing areas. It was also part of a zone that was ceded to the FARC, which uses drug trafficking to finance its activities, during an earlier round of peace negotiations from 1999 to 2002.

Today, fields once bright with the pale green of coca plants are now filled with the dark green of cacao bushes planted with U.S. assistance.

A paved road connects Vista Hermosa to nearby cities. There is a government health clinic and a branch of the government-run agricultural bank. With the help of a privately owned dairy company and U.S. financing, dairy farmers now send their milk to collection centers where it is stored in refrigerated tanks. As a result, dairy production has soared.

But much remains to be done. Among the government’s top priorities was giving farmers title to their land. Having a title is vital because it allows farmers to use land as collateral for loans.

But it took until last month, after years of waiting, for the first 16 farm families to receive titles to their land. Officials said they hoped that a few dozen more could get titles by the end of the year.

Outside town, unpaved roads leading to smaller farming communities are in ruinous condition. Rivers must be crossed without bridges, and a heavy rain can make roads impassable.

Several hamlets remain without electricity, though some recently had new posts put in as part of a project to bring them electricity later this year.

And while residents said that the region was much less violent, the FARC and other armed groups remain a menacing presence. Farmers said they had to pay protection money to the FARC of about 22 cents for every 10 gallons of milk they sell.

Drivers said that at gas stations they pay an additional 12 cents for every 10 gallons of gas, half of which goes to the FARC and the other half to a paramilitary group.

An employee of one local company told of going with his boss to pay about $1,200 in protection money to a FARC commander. They were even given a receipt.

Many people here said that much of the momentum that remains comes from American aid.

Velasco, the cacao farmer, has a drying rack for his cacao beans built last year with U.S. help.

Olaya, the councilman, showed off a milk collection center built with U.S. financing in his hamlet, Santo Domingo, down 23 miles of rutted road that can take two hours to drive, in good weather. A final batch of U.S. aid money will be used to upgrade the road this summer.

Overall, the U.S. Agency for International Development has spent $266 million on the Macarena project and other consolidation projects around the country since 2007. The aid ends this year, although Peter Natiello, the director in Colombia for the U.S. agency, said that it was developing a new round of projects.

German Chamorro, the director of Colombia’s effort in these areas, said that his office’s budget had been cut this year as well, by about 5 percent, to about $65 million. Money from other government agencies has also dropped and was about 21 percent less last year than in 2012, he said.

Now, with the end of spraying to kill coca – a decision based on concerns that the herbicide used could cause cancer – the unit may need a lot more money. It carries out all manual eradication of coca in the country, sending groups of workers to pull up coca crops by hand.

Efilia Ariza, 47, and her husband, Lucas Moica, 44, were among those who last month finally got title to their land, a 61-acre parcel they call Paradise Farm. They hope it will help them get a loan to plant cacao and avocados. In their front yard was a freshly dug hole for a new electricity post.

"The government never got here until now," Ariza said. "They’ve been promising us the land title and electricity for years."

The couple have several cows that give them about nine gallons of milk a day, which they set out in a metal container by the dirt road that passes in front of their house.

Normally, the dairy company sends a truck each day to collect milk from local farms. But the pickup had just resumed after a week’s interruption, caused when the dairy company refused to continue making protection payments to the FARC.

Workers on the milk truck, which stopped at Ariza’s farm, said they had resumed the pickups despite the threat that the FARC might try to stop them or burn their truck.

"These guys show up when you least expect them," said the driver, Jorge Lspez, 43.

The search for solutions comes at a critical time, with data showing that coca cultivation jumped sharply across Colombia last year. A five-minute drive outside one of the hamlets near Vista Hermosa, hidden among fields of corn and yucca, was a two-acre patch of coca plants.

"It’s easier to grow coca than corn because with corn you’ve got nowhere to sell it," said the farmer of the plot, bemoaning the poor state of local roads that makes it extremely costly for farmers to get their crops to market.

With coca, the buyers come to him.

"That’s why farmers plant coca," he said, "because there’s no help from the government."

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