To save the planet, give cows better pasture

The other day, in Puerto Rico, I stumbled across one small piece of an agricultural revolution. It didn't look all that revolutionary — just an abandoned sugar plantation where workers are clearing away a mass of grass, bushes and trees in order to create better pasture for cattle.

Mike McCloskey, the dairy magnate who's behind this particular venture, says that the tropical grasses that he's removing are terrible food for cattle; they're full of cellulose and lignin, and not very nutritious. "The problem with tropical pastures, in the past, is that they're very low in their digestibility," he says.

McCloskey should know. He grew up in Puerto Rico, worked as a veterinarian with dairy farmers in Mexico and California, then got into dairy farming himself and became one of the biggest milk producers in the United States.

He's planning to grow varieties of grass called Mulato and Cayman on this pasture. The grasses grow quickly, they're far more nutritious and cattle love them.

And, by the way, they are a key to fighting global warming.

"I'm kind of obsessed with this topic" of better pasture for cattle in the tropics, admits Tim Searchinger, a researcher at Princeton University and senior fellow at the World Resources Institute. "It's the single most decisive factor for whether we'll be able to feed the world with an acceptable level of greenhouse gas emissions."

Cattle are a huge source of greenhouse gas emissions. According to widely accepted calculations, global livestock production accounts for about 15 percent of all human-caused greenhouse gas emissions. This includes the impact of clearing forests to make way for pastures.

But there's an enormous disparity in emissions from cattle in different parts of the world. Basically, the more slowly cattle grow, or the less milk they give, the greater their greenhouse gas emissions per pound of beef or milk. And in many parts of the world, cattle grow very slowly, because they're grazing on sparse and poorly maintained pastures. The impact is astounding. Producing a pound of beef in East Africa probably causes a hundred times more global warming than the same product from a feedlot in the United States. The good news, Searchinger says, is that "there are enormous opportunities to improve efficiency" at a very modest cost.

Chief among those opportunities: faster-growing, more nutritious grasses like the ones that McCloskey wants to establish in Puerto Rico. Those grasses are part of a botanical family known by the scientific name Brachiaria that came originally from eastern Africa. Researchers at the International Center for Tropical Agriculture (CIAT), based in Colombia, identified specific varieties that are best for cattle grazing. They're helping to distribute them across the tropics. Commercial seed companies are selling the new seeds in Brazil, Mexico and Kenya.

According to Michael Peters, who leads CIAT's research on tropical grazing, pastures made up of these grasses can support three times more cattle, compared to typical tropical pastures today. The animals also gain weight twice as quickly. It translates into a six-fold increase in production per acre, and a dramatic cut in greenhouse emissions.

"It sounds too good to be true, but we are completely confident about it," Peters says. There are limitations: Farmers need to manage cattle on these pastures to avoid over-grazing, and add a bit of fertilizer every few years. Also, these grasses need plentiful rainfall — at least 35 inches a year, and a rainy season at least six months long.

But compared to their impact, the new grasses really don't cost much. "In rice, you need to invest a lot of money to achieve significant reduction" of greenhouse gas emissions, says Jacobo Arango, a researcher at CIAT. "The same in other crops. Livestock is the sector where you can get more reduction for less money."

Adding other plants to the mix of pasture vegetation would make it even better, Peters admits. Legumes like beans or clover would enrich the soil. Trees would provide shade.

Such pastures do exist in the tropics, and visiting them is "practically a religious experience," says Searchinger. But Peters says that CIAT's efforts to promote them haven't been very successful. Maintaining them takes too much work. Farmers have been more enthusiastic about all-grass pastures. According to Peters, Brazilian farmers have planted the new grasses on more than 200 million acres of grazing land.

Arango says that in some places, improving pastures requires farmers to adopt new attitudes toward grazing. "Maybe people don't think of pasture in the tropics as a crop, or something that they need to invest in," he says. Instead, many farmers think of pasture as something natural "that just grows there, and you put your animals there, and you don't have to do anything more."

In Puerto Rico, McCloskey isn't really building these pastures as a way to increase production; instead, it's a way to lower costs. Right now, he says, Puerto Rico's dairy farmers don't graze their dairy cattle outside at all, because their Holstein cows, which were bred in temperate climates to produce lots of milk, don't tolerate tropical heat and insect pests. But keeping cows indoors in the tropics, keeping them cool and bringing in feed from farms far away, involves "tremendous costs," McCloskey says.

He thinks these new pastures are one part of the solution. The other part is a new genetic strain of dairy cows that scientists in Brazil created. It's the result of mating a Holstein and a "Brahma-type" breed known as Gyr. Each of the new hybrid animals will be created by in-vitro fertilization. "We'll get good productivity and great tropical resistance to heat and parasites and ticks and all the things that have been difficult" for dairy cattle in the tropics, McCloskey says.

McCloskey doesn't expect to set up a large-scale dairy in Puerto Rico himself. His project is supposed to show that cattle grazing can work. He's planning to raise heifers on the pasture and sell them to Puerto Rico's existing dairy farmers, along with beef cattle.

If it works, he says, the impact could be enormous. "We believe that the right breed, and the right pastures, can really revolutionize how milk can be produced in the tropics," he says. "Not only in Puerto Rico! We're looking at this as a possibility for great changes all through the tropics." Copyright 2019 NPR. To see more, visit https://www.npr.org.