Cows are no strangers to methane. As a cow goes about its daily life, browsing through pasture or chewing the cud in the shade of a tree, it will typically emit 70-120kg (150-260lb) methane a year. This methane is a potent greenhouse gas, trapping heat in the atmosphere many times more efficiently than CO2 does.
To reduce these climate-warming emissions, switching to a plant-based diet has been found to be an effective solution, and reducing consumption of beef in particular as it is a high-carbon meat. But the human appetite for beef has nonetheless been growing steadily for decades: today around 72 million tonnes of beef are produced a year. That's about 12.5 times the weight of the Pyramid of Giza.
One country with a big incentive to make its beef more sustainable is Brazil, the world's largest exporter of beef, providing almost 20% of the world's exports. Researchers at the state-owned Brazilian Agricultural Research Corporation (Embrapa) have been searching for a way to counteract the emissions from the country's massive cattle herd – culminating in 2020 with a certified brand of Carbon Neutral Beef.
Forest loss for cattle farming in the Amazon releases about 6% of the world's greenhouse gases
Rather than simply paying for offsets to make up for emissions (an approach that can be fraught with difficulties), Embrapa has aimed to make the process of cattle-rearing carbon neutral within the farm, in an approach it hopes could make the country's carbon-intensive beef industry more sustainable.
When cattle graze alongside eucalyptus trees, there are benefits for the cows' nutrition and wellbeing, as well as potential carbon savings (Credit: Getty Images)
Brazil's incentive to clean up its beef industry is not just about carbon emissions. The country is also where a third of the world's tropical deforestation for commercial use happens. One of the main commercial uses of that deforested land is farming cattle. Worldwide, 2.11 million hectares of forest is lost each year to graze cows. Forest loss for cattle farming releases about 6% of the world's greenhouse gases, including the long-lived greenhouse gas CO2, as well as the methane from the cows and more methane emitted from soils. Meanwhile, the forest loss culls biodiversity and increases the risk of new diseases jumping to humans.
The animals spend less time in the pasture before slaughter, giving them less time to emit methane
Embrapa's Carbon Neutral Beef involves planting eucalyptus trees in the same area where cattle graze, turning a featureless grassland into one dotted with trees. Around 250-350 trees per hectare is thought to be the optimal number to keep Brazilian farms financially viable, producing 25 cubic metres of wood per hectare per year, according to studies by the Embrapa researchers. That sequesters up to five tonnes of carbon – the equivalent of emissions from about 12 adult cattle.
In all, these trees occupy around 10% to 15% of the area, planted every 2m in rows between 14-22m (46-72ft) apart.
This can also make a farm more productive, says Roberto Giolo de Almeida, who leads the Embrapa team. In traditional Brazilian cattle farming, there is typically around one animal grazing per hectare of land. When the land is planted with trees, the quality of the pasture actually improves.
When the pasture is shadowed by the trees, the grass in its shade gets less sunlight. The grass reacts by investing more in photosynthesis, making more of the organelle where photosynthesis takes place: chloroplasts. These are the organelles that contain chlorophyll – the molecule that gives green plants their colour. A plant enriched in chloroplasts has higher nitrogen content, needed to make protein, and so it becomes more nutritious for the cows.
The trees grown on cattle pasture can be sold for uses such as construction or furniture, meaning the carbon stored in them stays locked out of the air (Credit: Getty Images)
Giolo de Almeida's team found that tree-dotted pastures can support up to twice as many cattle because of the improved pasture. And the cows fatten up faster too – as well as better nutrition, they have the added benefit that the trees offer some shade to escape the intense heat of the day. Typically, a cow raised among tree-dotted pasture will reach 250kg (550lb) of meat in two years. This is around 30% better productivity than expected in traditional systems, he says. This means the animals spend less time in the pasture before slaughter, giving them less time to emit methane.
When the trees are mature, they are cut to be sold, and new saplings replace them. Richard Eckard, professor of sustainable agriculture at the University of Melbourne, who is familiar with Embrapa's project but not involved in it, sees many advantages in using eucalyptus, a commercial fast-growing tree native to Australia.
"If you harvest those trees and put them into construction timber, if you build houses or furniture, at least two-thirds of the carbon remains out of the atmosphere indefinitely or for the next hundreds of years," says Eckard.
So far, Embrapa has not carried out studies on the use of native trees to sink carbon, which typically take longer to grow. However, one project called Native Carbon Stamp is beginning to investigate whether native trees could one day be used in a similar scheme. And in southern Brazil, one ongoing experiment aims to introduce Araucaria angustifolia (Brazilian pine), an endangered native symbol of the region, to livestock pasture integrated with croplands.
These systems to combine livestock and tree-planting do not have just one "recipe", says the agronomist Claudete Reisdorfer Lang, professor at Federal University of Parana, in Brazil, who leads the Brazilian pine experiment. "[It] depends on the different components – crops, trees, animals, among others," she says, as well as the ways the different parts of the system are integrated in the field.
And combining cattle and tree-planting may not be an approach that works everywhere, notes Eckard – each area has its own climate and soil, and needs its own solution. Despite this, Giolo de Almeida estimates that around 10% of all pastures in Brazil already have a degree of integration between forest, crops and livestock, though only a small fraction of these are close to carbon neutral.
Lang says she has seen rapidly growing interest in integrating livestock, trees and crops in the past 10 years. This could partly be because there are other incentives for farmers beyond the environmental benefits – Julie Ryschawy, assistant professor at the French National Institute for Agronomy, says that this approach to farming means there's less need to buy goods such as food for animals or chemical fertilisers. "[Farmers] would both diversify the crop rotation and limit chemical inputs on the crop and grasslands," says Ryschawy, which could help biodiversity, limit livestock disease and store carbon.
Eucalyptus seedlings grow rapidly and reach maturity quickly, making them an attractive option for farmers (Credit: Getty Images)
The meat industries in many regions have set targets for low or carbon-neutral livestock, including Australia, another of the world's main beef exporters. "We are seeing an inevitable push towards low emissions livestock production," Eckard says. "We have no options, we have to do this."
However, there are barriers to the expansion of tree and livestock-integrated systems like the kind used by Embrapa, including resistance from farmers. "Many of them specialised in monocultures, which are profitable in a short-term, but unsustainable in the long-term," says Lang.
There are also upfront costs to consider and the livestock sector can be reluctant to take financial risks, says Edegar de Oliveira Rosa, director of conservation and restoration of ecosystems at WWF-Brazil. "It is necessary to face a huge challenge, the challenge of scale, since Brazil has one of the biggest herds of the world, around 200 million animals."
Rosa believes that regenerative agriculture could help improve a large swathe of Brazil's former forests. "Currently livestock is the activity which most occupies recently deforested land," says Rosa. "Deforestation and subsequent fires to clear the land are the main source of greenhouse gases emission in Brazil."
While better use of deforested land could help lower beef's emissions, the challenge looming over cattle farming in Brazil is stopping deforestation in the first place. "In the end it all comes back to government policy," says Eckard. He points to Australia's attempt to halt its historic problem with deforestation for cattle rearing through public policy. "The only reason the Australian government achieved its Kyoto protocols targets was because they legislated against deforestation in Queensland. It requires leadership from government," Eckard says.
While switching to a plant-based diet may remain a powerful solution to limit the environmental impact of cattle farming, in some parts of the world livestock provide essential nutrition, says Eckhard. "Livestock are so integral to a lot of developing countries in allowing them to have food security," he says.
In a region blighted by deforestation, it might seem like a small consolation to regrow just a hundred or so trees per hectare on the land now used for cattle pasture. But, for a global industry that is still steadily growing, Embrapa's project at least shows one way that the climate-warming emissions from those cattle can be curbed.
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