Trees that help keep soils fertile could slow or stop deforestation in Brazil’s “arc of destruction”.

A project using inga trees hopes to show smallholders that they can earn a decent living from the land. Inga trees, known as ice-cream bean trees, fix nitrogen into the soil, boosting productivity levels.

Scientists hope the scheme will convince smallholders not to sell their land to large agri-businesses and remain farmers in the Amazon.

“It’s very much a kind of ‘miracle tree’ or a super tree because some of the species can do some amazing things,” said Toby Pennington, professor of tropical plant diversity and biogeography at the University of Exeter, UK. They can grow really fast on very, very poor soils, even soils where a rainforest has been cut down and have become very degraded.”

The trees (there are more than 300 species) are in the legume family and that means they can fix atmospheric nitrogen into the soil. “But even amongst legumes, they have pretty fantastic growth rates…more than that, these species have fruits that are edible and often have local markets right across Latin America.” The trees can also be coppiced, providing wood fuel, and the leaves are a good source of forage for cattle.

As the tree was common and found throughout the Amazon Basin it was deemed to be a miracle tree or super tree by projects trying to stem the relentless deforestation in the region.

Prof Pennington said properties like nitrogen fixation and lots of leaf fall, which produces mulch, means that you can grow crops underneath them with low input of fertiliser and herbicides.

“If you had a cup of coffee this morning that came from Latin America, the odds are that it was growing underneath one of these inga trees.”

Prof Pennington, who has been studying inga trees for more than two decades, has been working alongside a project that promotes the benefits of the trees to smallholders in southern Brazil’s frontier of deforestation – an area known as the “arc of destruction”.

Dr Saulo de Souza from the Institute of Green Gold [Instituto Ouro Verde] said that the trees helped local communities by helping to restore the fertility and viability of the land that had become degraded.

These systems are more resilient to severe drought and diseases, which have been the main cause of pasture degradation in the region,” he explained.

“Communities will benefit from increased food security and income provided by the agricultural species planted, as well as from increased land productivity and premium prices paid for agro-ecological dairy products.”

Another important factor of the projects, Dr de Souza said, was the ability to reduce social marginalisation.

“It is of great importance to offer new opportunities and green technologies to help smallholders. Family farming also plays a critical role for global food production. In Brazil, they are responsible for 70% of domestic food consumption.”

By showing that the land could be harvested sustainably and profitably, the land owners were less inclined to sell out to industrial cattle and soy producers, Dr de Souza said. This would allow local communities to thrive and slow the relentless mark of deforestation in the region.

However, the current political situation in the country is making it hard for researchers and NGOs, such as the Instituto Ouro Verde, to operate and continue their work.

In August, Germany and Norway announced they would suspend money going to the Amazon Fund, a multi-million dollar global effort to tackle deforestation in the region.

Politicians from the two European nations said the Brazilian government, headed by President Jair Bolsonaro, was backing policies that favoured deforestation and was actively pursuing ways to hamper pro-rainforest projects.