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.