In dry areas in the Horn of Africa, there are frankincense trees that thrive in the extreme aridity.
These trees are harvested for the frankincense resin that they produce. It is used to make perfumes and incense, and can only be obtained from the wild trees.
For many years, frankincense trees have faced challenges that could threaten their very survival. Now a new analysis provides hope that this downward spiral could be prevented.
To get frankincense out of the tree, it first needs to be cut. This causes it to "bleed" and release resin. If a tree is cut over and over again, it can be severely damaged, as these cuts can harm the tree's growth and reproduction rate. Currently, there is no universal regulation on how resin is harvested in order to protect the trees.
This cutting is only one of the issues facing frankincense trees.
In this area, about 30% of household income is attributed to frankincense
The forests are also used for grazing cattle, and farmers burn the grass at the end of the season to help stimulate growth for the next season, says Pieter Zuidema of Wageningen University in the Netherlands. "This might increase mortality rates and prevents the seedlings growing up into trees. So we see this lack of regeneration across the many sites, both in Ethiopia and also Eritrea and Sudan."
The third major issue is deforestation, which is occurring at alarming rates. In fact, dry forests are believed to be more threatened by deforestation and degradation than wet, tropical forests. "More attention is going to wet tropical forests, so dry ones are getting hammered harder," says Zuidema.
A new study proposes that one frankincense-producing species, Boswellia neglecta is particularly well suited to overcome some of the threats it faces. The species is abundant in the dryland forests of Ethiopia, which cover about 48% of Ethiopia's entire land area.
The tree is economically important: in this area, about 30% of household income is attributed to frankincense, second only to livestock production.
The species is also found in Kenya, Somalia, Tanzania and Uganda.
The key reason for B. neglecta's resilienceis how well-adapted it is to its dry habitat, according to a paper published in November 2016 in the journal Forest Ecology and Management.
If a tree is cut over and over again, it can be severely damaged
Researchers assessed how well the species grows in extremely dry areas of Ethiopia, where there is only 300-800ml of rainfall per year on average.
Despite this lack of water, the tree thrives. It does much better than another African frankincense-producing tree, Boswellia papyrifera, many of which die.
Thescientists found that the B. neglecta trees were also relatively young, just 16-28 years old. That suggests the species only colonised parts of south-east Ethiopia recently.
One factor in the tree's success is that it is good at trapping moisture to avoid damage from drought. That means it responds easily to a changing climate, says lead author Mulugeta Mokria of the World Agroforestry Centre in Nairobi, Kenya.
The restoration potential of B. neglecta has not yet been tested
Mokria and his colleagues also found that B. neglecta trees form two growth rings per year, and that they coincided with the area's two wet seasons. This suggests the tree can respond quickly when moisture becomes available.
"These characteristics gives it the potential to restore degraded drylands of Ethiopia and eastern Africa," says Mokria. "This species can also be used in restoration schemes where climate is similar."
B. neglecta could therefore "fill the gap we are going to lose from B. papyrifera," he says, in both the local and international markets.
This could in turn help stimulate the local economy, increase frankincense production and improve the lives of local people who depend on the forest for their livelihoods.
Growing more of these trees could have another less obvious benefit. It could increase rainfall in the Congo Basin, as studies have suggested that rainfall there is a direct consequence of moisture evaporating from vegetation in east Africa.
This species provides a glimmer of hope for bringing back some of Africa's rapidly-shrinking forests
However, Zuidema – who was not involved with the latest work – urges a note of caution. The restoration potential of B. neglecta has not yet been tested.
"It seems that the conclusion is maybe a little bit too optimistic, because whether it really has the potential for restoration doesn't only depend on what extent these species [are] adapted to drought and climatic conditions, but also on how easy is it to raise those trees in nurseries, and get seeds to germinate," he says.
Mokria agrees that restoration will not be an easy task, noting that Ethiopia is a poor country and projects like this rarely provide a rapid return on investments. "We have to look at the return long-term and convert the benefits into financial terms," he says.
Regardless, with the climate changing so rapidly, this species provides a glimmer of hope for bringing back some of Africa's rapidly-shrinking forests.
Melissa Hogenboom is BBC Earth's feature writer. She is @melissasuzanneh on Twitter.
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