Coral Tree

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Chasing corals

With spectacularly bright red flowers branching off from a central stem, it is little wonder that the tree, which actually belongs to the legume family, was to become more commonly known as the coral tree. Fulfilling a life-long desire to visit East Africa, Schrieben finally arrived in what was then Tanganyika Territory, but is now Tanzania, in 1930. He wanted to visit the “lush primeval forests” and the “sun-drenched steppes” of the country, while collecting plants for the Botanical Museum Berlin-Dahlem.

Spending five years travelling the country, he amassed over 50,000 specimens for the Museum. Not long after describing the coral tree, Schrieben returned to Germany with his enormous collection just a few years before World War II broke out. It was during this conflict that much of Schriben’s herbarium was destroyed, including many of the specimens of E. schliebenii. Those that did survive in other collections were in poor condition.

 

The bad news

Over the next few decades, countless botanists explored the coastal regions of Tanzania and Kenya recording what they found as they went, and yet no-one could find the lost coral tree. The former superintendent of the University of Dar es Salaam’s herbarium, Leonard Mwasumbi, even managed to track down the original site from which Schlieben collected his samples. By retracing the German botanist’s footsteps around Lake Lutamba and across the Lindi plateaux, Mwasumbi learned some dismaying news.

Talking to the locals, he discovered that the original patch of forest which Schlieben sampled was no more. The likely location from which the coral tree came from had been torn down, replaced instead with a cashew nut tree plantation in the years following the Second World War. This was not only a blow for the now assumed extinct tree, but for much of the other flora of the region.

The Lindi plateaux is – like a lot of the coastal forests of East Africa – an area of particularly high plant endemism which means it contains many species of plants found nowhere else in the world. Recognised globally as an important region, plant diversity has been found to peak in this corner of Tanzania.

But for over 80 years, this rich community of plants has faced a barrage of threats. Only very recently have authorities and conservationists come to formally recognise this diversity, and yet still the clearance of forest and woodlands continues across the plateaux. Only around 100 square kilometres of woodland remains standing, and all evidence of the coral tree was wiped out. Eventually, in 1998, the International Union for the Conservation of Nature declared Erythrina schliebenii extinct after having been missing for 63 years.

 

The good news

In 2001, a group of Danish researchers set out to analyse and document the remaining extent of the coastal forests of southeastern Tanzania. Using satellite imagery, they looked through the pictures to see if they could identify any patches of forest that have managed to survive the decades of intensification from farmers and plantations. What they stumbled across was the largest contiguous block of coastal forest in Tanzania that had – until now – remained completely unknown to scientists.

The finding was backed up after the team, along with botanists from the University of Dar es Salaam, went out on multiple trips into the field to fully confirm and map these last vestiges of precious woodland. There, nestled within this patch of forest, they stumbled across an endemic species of tree that had not been seen for over six decades.

This was the first time since Schieben collected his specimens in the 1930s that new samples of the coral tree had ever been recorded. Considering that most of the original samples had been obliterated, this was a rare moment to restore what had been until then irreplaceable.

These specimens were compared with the fragments that had survived the war, and the scientists were able to confirm that the trees were indeed E. schliebenii, definitively proving that the coral tree was not extinct. Yet things were not to last.

 

Twists and turns

Just seven years later the patch of forest that contained the rediscovered coral tree found nowhere else on the planet, was destroyed after a Dutch company cleared the woodland to create a biofuel plantation. Once again, E. schliebenii was feared to have been pushed over the brink of extinction by the insatiable demand for yet more land.

It fell once more to the botanists at the University of Dar es Salaam, along with support provided by the World Wide Fund for Nature. Not giving up hope, in 2012 they mounted yet another expedition back to the region where the last specimens of the coral tree had been collected.

Growing on a rocky outcrop unsuitable for cultivation, they managed to find another small stand of the coral trees, along with another species of tree, Karomia gigas, which itself was thought to have gone extinct twice already. This allowed researchers for the first time to collect mature E. schliebenii seeds, meaning that the botanists could finally conclude that it was indeed a distinct species in its own right, and not the same as another type of coral tree which grows on the island of Madagascar as some had suggested.

The astonishing tale of the coral tree, believed by many to have gone extinct twice only to be rediscovered again and again, does not end there. Because after such a tumultuous existence at the hands of people, story comes full circle.

Recent tests on the natural compounds found within the root, bark, and leaves of the coral tree show that it does actually have a pharmacological effect. Analysis of the molecules have found that they may be able to fight not only the bacteria responsible for tuberculosis, but that they may even be able to target breast cancer. This highlights why even the most obscure species may harbour in them secrets that can help us live longer and better lives.

 

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