Wetenschap - 9 februari 2012

Whiff of death

Help, the frankincense tree is dying out! This, basically, was the message sent out just before Christmas by Professor Frans Bongers (Forest Ecology and Forest Management). And his SOS signal was no exaggeration, as Wageningen research shows.


Foto: .

The media responded en masse. ‘I was on the phone almost continuously for a week.' The BBC alone reported the alarming threat to the Frankincense tree in six different programmes (including the World News). So the strategy worked. As expected, actually, Bongers recalls with satisfaction. Exactly the same thing happened a few years ago with a press release on the frankincense tree. It seems the combination of Christmas and frankincense is one journalists find irresistible. ‘All because it's about frankincense', says Bongers. ‘Frankincense is a fantastic product that gives everyone a good feeling. Frankincense is something that matters to hundreds of millions of people. One of the reasons is its symbolic function in religion. And not just in Christian circles, mind you. Muslims and Buddhists burn incense as well.'

Scab tissue
Frankincense is resin from trees of the Boswellia family. The species in Ethiopia for which Bongers has sounded the alarm, is the Boswellia papyrifera. This tree accounts for more than 80 percent of the country's export of gum and resin. Resin is really a sort of scab tissue, Bongers explains. ‘Harvesting is done by making little cuts in the tree's bark. The white fluid that is then emitted dries in the air; more or less the way a scab forms on a wound on your skin.' The comparison holds water: the resin has the same protective function as a scab does on a wound. Two weeks later, the resin is scraped off the tree and the process can begin all over again. The harvesting takes place in the dry season that lasts nine months. The heat makes it hard work, says Bongers.
Incense is a product of tropical dry forests. According to Bongers, they come in for much less attention than tropical wet forests. ‘And yet they cover a gigantic area. Northern Ethiopian forests largely consist of frankincense trees. In other dry forests, Acacia gum is harvested, and elsewhere there is myrrh.' The Boswellia family includes 19 species. The best quality incense traditionally came from the Arabian peninsula, from Oman and Yemen, or from a country known in the old sources as Puntland. ‘This is probably what is now northern Somalia, but no one knows for sure. We are talking here about Biblical frankincense or Boswellia sacra. But production in Oman and Yemen is on its last legs. The trees have been felled and there is no regeneration going on. At the moment, Ethiopia is the biggest producer in this region. Production is spread over the entire northern region of the country. That is where we find the populations of Boswellia papyrifa which we are studying.'
Sacred smoke
The word frankincense is derived from words for ‘sacred smoke'. Frans Bongers divulges that he served as an acolyte in church himself in his younger days. But that is not the reason for his interest in the Boswellia family. This dates back to the mid-nineteen nineties when an Eritrean student knocked on his door, asking him to supervise a PhD research on frankincense trees in Eritrea. A visit to Ethiopia in 2003 led two years later to a long-term research programme on the fortunes of the frankincense tree in Ethiopia. The ensuing studies have produced four whole PhD theses on frankincense in the last six months. Hence the SOS sent out in December. The frankincense tree is under threat. The trees are dying out at a rate of seven percent per year in the populations studied. The question is why. Bongers suspects that the long-horn beetle (Idactus spinipennis) plays a role. ‘This insect has become more and more common in recent years, according to the locals. But of course, the question is: are there more insects because more trees are dying or are more trees dying because there are more insects? Which is the cause and which is the effect? We don't know.'
Deaths are not such a problem if regeneration goes on. But this is not happening. Bongers: ‘There are no saplings left. In the whole of northern Ethiopia I could only find one place where regeneration was going on. Saplings no longer get the chance to grow up into adult trees.' The reasons for this are known: overgrazing, deforestation for agriculture, and burning. Then there is the fact that the frankincense trees are tapped more and more intensively to boost production. All that tapping weakens the trees, as PhD researcher Tefera Mengistu Woldie demonstrated. He researched the influence of tapping on the frankincense tree's carbon balance. After all, tapping means a loss for the tree. Carbon that is tapped is no longer available for growth, for reserve formation in leaves and roots, or for flowering and seed production. His conclusion is clear: Intensive harvesting leads to fewer vital trees and hence to more deaths.
Halved over 17 years
The decline of the frankincense tree is reflected in hard figures. Bongers: ‘From our model studies you can see that only 10 percent of the current population will be left in 50 years' time. Frankincense production in those forests has been halved in 17 years. So something must be done to save the frankincense tree.' Bongers has already put forward several proposals. In the first instance, the way the harvesting is organized needs to be changed. It is currently too focused on the short term. ‘So concessions should no longer be granted for one of two years of harvesting, but for much longer periods. Then farmers and cooperatives will be forced to think more long-term.'
Secondly, frankincense trees should be better protected against felling and fires. ‘That demands rigorous control, and I can't see that happening for the time being, although it is badly needed', says Bongers, thinking aloud. One alternative is to establish plantations, but that would require some major investments. And frankincense trees grow slowly. Woldie argues for strict guidelines for both the number of taps per tree and the harvesting rate. Sustainable production, says Woldie, needs to be based on the tree's carbon balance. ‘And of course we must also analyse the role played by the long-horn beetle in the deaths and see what we can do about that', adds Bongers. He does not see the Boswellia research as finished, by a long way. But he is not short of willing helpers. His alarm has had an impact. ‘This month I received several applications from Ethiopians wanting to come and do a PhD on it here.'

In money terms
Ethiopia is the world's leading exporter of frankincense. Both production and export have expanded massively in recent decades. At the end of the 20th century, about 1,700 tons of frankincense were being exported annually. Ten years later, this amount has almost quadrupled to 4,700 tons. About 80 percent of the frankincense currently gets shipped abroad, the bulk of it to China, where it is used in medicines. The price of frankincense depends on the quality. Top quality frankincense fetches 5,000 dollars per ton, while the poorest quality goes for 2,000 dollars or even less. So the kilo price is anywhere between 2 and 5 dollars, giving it only marginal economic value. Bongers estimates the value of Ethiopia's total exports of frankincense at less than 12 million dollars.