Trees of the world: The Brazil nut's uncertain future

THE Brazil nut tree (Bertholletia excelsa) grows wild in stands in the Amazon River basin. It will often tower over its neighbours, reaching heights of 50 metres, with its crown spreading over 30 metres across. It may live for 500 years or more. The stem or trunk is straight and commonly without branches for well over half the tree’s height, topped out with a large, emergent crown of long branches above the surrounding canopy of other lesser trees.

This species is particularly associated with the state of Pará, in northeastern Brazil – neighbouring what were the Guyanas, in old money – and is sometimes dubbed the Pará nut. 

It is one of the tallest and longest-lived trees in the Amazon rainforest and is sometimes spared during forest clearance for its valuable crop of nuts and is the last tree standing when everything else is felled.

WANT MORE LIKE THIS? 

• Why the walnut tree may be one of the world's most underappreciated
• What do a national icon and burning at the stake have in common? The ceibo tree
• It has outlived empires. But what does the future hold for Lebanon's cedar?

The flowers are born in panicles of cream-coloured petals. Large insects are the main pollinators. The fruit takes about 14 months to mature once fertilised and the resulting final body is quite sizeable (10–15 cm) and reminiscent of coconuts, with a thick, woody shell dangling on strings and weighing up to 2 kg. Each encases a number of the individual crescent- or moon-shaped nuts we see on sale here. 

The sphere or ball has a hard, woody shell 8–12 mm thick, which contains eight to 24 wedge-shaped seeds 4–5 cm long (the ‘Brazil nuts’) packed like the segments of an orange, but not limited to one whorl of segments. Up to three whorls can be stacked on top of each other, with the narrow ends of the segments of the middle whorl nestling into the upper and lower ones.

The capsule contains a small hole at one end, which enables rodents like the agouti to gnaw it open. They then eat some of the seeds inside while burying others for later use; some of these are able to germinate into new Brazil nut trees. Most of the seeds are ‘planted’ by the agoutis in caches, and the young saplings may have to wait years, in a state of dormancy, for an adjacent tree to fall creating a gap in the closed canopy and sunlight to reach it, when they start growing again. 

What’s an agouti, you may well ask? These are essential players in the regeneration of these nut-bearing trees. Agoutis are local jungle rodents that look a little like overgrown guinea pigs. They will eat some nuts when they fall but also stash others which in turn will germinate once conditions are right. 

AS A FOOD

Brazil nuts are perfect as a healthy snack. They are also a tasty addition to sweet and savoury dishes and a key ingredient in nut roasts.

They are a great source of healthy fats, protein, fibre, and micronutrients and antioxidants, such as selenium. Benefits from consuming this food range from helping boost heart health, improving brain function, managing blood sugar, and more. And a big sales plus is that they are organically grown out in the forest. 

Like most things that are good for you, too much can prove harmful. Brazil nuts are one such case, so don’t go too mad on them. 

They’re exceptionally high in selenium, a mineral with potent antioxidant properties that may be great for the thyroid, brain, and heart health. Yet taking in too much selenium can lead to toxicity. Brazil nuts also have higher than normal traces of barium and radium. To avoid the risk of eating too much of these elements, nutritionists advocate limiting your daily intake to one to three medium-sized Brazils. So go easy on the nuts.

LOOKALIKES

In the literature of the timber trade you may stumble across reference to Pau brasil or Caesalpinia echinata – but don’t get confused. This native tree from the legume family is endemic to the Atlantic Forest coast of Brazil, a little further south. It is a timber tree commonly known as Pernambuco wood or brazilwood and just happens to be the national tree of Brazil.

This plant has a dense, orange-red heartwood used for musical instruments. 

These coastal forests it originates from have been reduced in some areas to as little as five per cent of their original spread although some last-minute steps are currently being taken to help revert the trend. 

Ripening nut globes. (Image: libin jose)

The Brazilian nut-bearing tree should not be confused either with Couroupita guianensis, also known by a variety of common names including ‘the cannonball tree’. It is deciduous and native to the tropical forests of Central and South America, and it is cultivated in many other tropical places throughout the world for its fragrant flowers and showy, strange, large globular, brownish grey fruit. 

OTHER USES

If, when and where available, the timber or lumber from Brazil nut trees (not to be confused with Brazilwood) is of excellent quality, having diverse uses from flooring, to carpentry to heavy construction. Logging this tree is prohibited by law in all three producing countries (Brazil, Bolivia, and Peru). 

Brazil nut oil is used as a lubricant in clocks and in the manufacturing of paint and cosmetics, such as soap and perfume. Because of its hardness, the nutshell is often pulverised and used as an abrasive to polish materials such as metals and ceramics. The charcoal from the nut shells may be pressed into service to purify water. 

HARVESTING AND PRODUCTION

The nuts are most often gathered out in the forest by migrant workers known as castañeros (in Spanish) or castanheiros (in Portuguese). 

Overharvesting of this long-lived tree can impair regeneration of this tree in the wild if not enough nuts are left behind on the forest floor to germinate naturally. 

In 2020, global production of Brazil nuts (in shells) was around 70,000 tonnes, most of which derive from wild harvests in tropical forests, especially the Amazon regions of Brazil and Bolivia which produced 92 per cent of the world total – about half each. But all is not well ...

AN UNCERTAIN FUTURE

As an alternative or addition to wild collected nuts, Brazil nuts have been harvested from trial plantations in a handful of other tropical rainforest nations but production is poor, with a long lead-in period before harvest and is currently not economically viable. And why bother if they grow wild for free in the tropical Amazon rainforest – and are organic.

But times change. Brazil nuts are one of the most commercially traded ones in the world market.

Yet in recent times, these nuts have been in short supply and savvy UK shoppers will have spotted how prices have doubled in some instances. Production has plummeted by perhaps 50 per cent. How come? 

Bertholletia excelsa is very sensitive to even slight changes in temperature or rainfall. It evolved cossetted in a pretty stable overall environment in the rainforest. But things are changing and not for the best as far as the tree is concerned. To understand what is causing the shortage, it is important to look at the roles of climate change, deforestation, human consumption, and the economic implications. 

Chestnuts from Pará, also known as Brazil nuts. (Image: Getty Images)

The effects of climate change have been particularly damaging to bulk Brazil nut production.

Warmer temperatures and erratic rainfall have meant the trees produce fewer nuts, while the possible spread of pests and diseases has further reduced yields. Deforestation has had a major impact as well. The reduction of the Amazon rainforest tracts in Bolivia and Brazil led to a decrease in mature Brazil nut-producing trees. This has had devastating consequences for the industry and those whose livelihoods revolve around it. 

Watch this space as climate change begins to bite on yields of Brazilian nut trees and prices in the shops.