Seeing the wood for the trees

A new campaign is under way to save Brazil’s endangered pernambuco tree, the wood most favoured by bow makers. The goal is clear, but the devil is in the detail

Read all the breaking news in the string world online www.thestrad.com

Planting a pernambuco seedling

COURTESY TREES OF MUSIC

The chances of an endangered species becoming the focus of a conservation effort are boosted if the species in question is of use to some sector of the human population. Paradoxically for the environmentally conscious, this produces situations where those fighting most for a particular species belong to an industry that has contributed to its demise. This is true of Brazil’s pernambuco tree, whose endangered status has resulted partly from the expansion of the bow trade, and whose future depends on efforts of bow makers to help replace those trees. As a 2019 article in Strategies and Tools for a Sustainable Rural Rio de Janeiro put it, ‘Current conservation and plantation efforts are mainly enforced and financed by bow makers, violin makers and musicians, who might be the most affected stakeholders.’

It is now illegal to take a pernambuco tree from a native forest, which means that, after current stocks disappear, future supplies must come from plantations. The first attempt at a pernambuco plantation was made by the Fundação Nacional do Pau-Brasil in 1972. Since then, organisations such as the bow maker-led International Pernambuco Conservation Initiative have been responsible for planting hundreds of thousands of seedlings. A new project, launched in March, is fronted by the Classical Community for Trees of Music, a handful of high-profile musicians fundraising for the Regenerative Agroforestry Impact Network (RAIN). RAIN will work alongside the Instituto Verde Brasil (IVB, founded by bow maker Marco Raposo) to produce 50,000 seedlings, to be distributed to farmers for nurturing, with assistance from scientists and local government organisations in the state of Espírito Santo.

The basic idea is to grow more than enough trees to ensure species survival, before selectively harvesting a small number to supply the bow trade. In a 2007 document, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) estimated that the annual worldwide demand for pernambuco is 200 cubic metres. The CITES document does not include an estimate for how much wood can, on average, be extracted from a single tree. One ballpark figure is that a single tree might provide about one cubic metre of wood. Even if the true average turned out to be far lower, it seems that the needs of the trade can be safely met if only a fraction of the seedlings reach maturity. Government benefits incentivise farmers to nurture these young plants, which is important because some estimate it takes at least 30 years to produce good bow wood. As Marco Raposo explains:

‘Trees from natural forests tend to be of higher quality than plantation ones’ 

‘The farmers get the seedlings for free, but they’ve got to assure the government that they will grow them correctly because otherwise they won’t get the benefits the government has promised them.’

Selection is vital because not all pernambuco can produce a high-quality bow, and it is essential to a sustainable trade that only suitable trees are felled. The pernambuco species (whose botanical name is Paubrasilia echinata) divides into three ‘morphotypes’ (arruda, café and laranja), with each morphotype thought to produce differences in wood quality. This is also influenced by the conditions in which the tree grows. A 2020 study found that the wood from five historic French bows had most in common with samples of the arruda morphotype, taken from the northern states of Paraíba and Rio Grande do Norte. However, more research is needed before such conditions can be created on a plantation. As noted by RAIN’s director Danny Diskin: ‘The trees which, in the past, have been taken out of natural forests tend to be of higher quality than plantation ones. It’s not as easy to get high-quality pernambuco from plantations as it is from the natural environment.’

Not only must forestry techniques be refined, but so must methods of testing wood quality, as selective harvesting will only be effective if the quality can be accurately estimated prior to harvesting. For this to be possible, it must first be known precisely what properties are needed to produce a high-quality bow. Some researchers have looked for correlations between certain chemical features of the wood (such as its percentage of ‘extractives’) and its physical suitability for bow making. Arguably more conclusively, efforts have also been made to understand how physical properties such as density and stiffness affect quality. For instance, a 2009 study in the German Holzforschung journal highlighted density and stiffness as particularly useful indicators of quality, and worked out an average density (1,119kg/m³) and stiffness (25.2 GPa) from a sample of excellent sticks. Non-destructive wood-testing technologies are also improving. For instance, while a 2011 experiment, reported in the Journal of Near Infrared Spectroscopy, examined pernambuco samples in a lab, and noted that ‘testing pernambuco wood properties in the field using a portable NIR spectrometer may be possible’. Provided they are cost-effective, such investigations could greatly enhance the evaluation process for plantation trees.

Until then, some argue that the priority should be on planting. As Raposo puts it, ‘If we don’t know exactly what to plant, let’s plant. Let’s put seedlings in the ground and eventually there will come a time when we will have a better understanding of what to do.’ The 50,000 new seedlings will bring the IVB’s total to 420,521. Their goal is one million.