Can Lebanon's cedars outlive climate change and a pesky insect?

Beirut, Lebanon - In the Lebanese highlands overlooking the Qadisha Valley, north of Beirut, a small but thick cluster of long-lived cedars, some up to 3,000 years old, cling to a rugged limestone slope, keeping alive the memory of an era long past.

A staple of the country's identity proudly featured in the national flag, its banknotes currency and the national anthem, these looming evergreen trees once blanketed most of Lebanon's upper reaches.

Now they can hardly be seen across the country. For centuries, Egyptians, Phoenicians and Sumerians chopped cedar trees for construction, shipbuilding and ceremonies, depleting the national forest stock. Ottoman Turks axed many of the surviving cedars for trade, while British troops used cedar wood to build railroads during wartime.

Only 17 square-kilometres, 0.4 percent of the estimated ancient cover, of cedars remain in Lebanon nowadays, hanging on in a few scattered redoubts. The tree is listed as vulnerable on the International Union for Conservation of Nature's red list of threatened species.

But while these coniferous trees outlasted empires and centuries of relentless exploitation, they might not survive the last on a string of threats to their existence: climate change.

Hotter and drier

In order to grow, cedars need humid, calcareous soil with a certain level of moisture. They also require cold temperatures, and a minimum amount of rain and snow to regenerate naturally.

As temperatures rise across the eastern Mediterranean country, cedars are retreating to higher altitudes in search of the distinct climatic conditions they need to thrive.

This migration is already evident in the Shouf Biosphere Reserve, home to a quarter of the remaining cedar population. But south of Beirut, where the reserve is located, mountains average no more than 1,800 metres, the upper limit of cedars' ecological comfort zone. "There isn't much higher the trees can go here," said Joe Rahmeh, an eco-tour guide at the reserve.

"Climate change has disrupted weather patterns in this region," said Nizar Hani, director general of the Shouf Biosphere Reserve. Here, temperatures increased by 0.7 degrees as compared with the annual average.

A few decades ago, rain or snow fell for more than 100 days in the year. Cool temperatures kept the snow on the ground for three to four months up in the mountains. Last winter, rainfall was less than half the average, and snowpack lasted only a month.

As weather patterns become more erratic, cedar saplings, which usually germinate in May, are finding the conditions to come up earlier and earlier. "This increases the risk of losing the new seedlings to cold snaps and pest outbreaks," said Hani.

The Lebanese government estimates that temperatures in the country will rise from around one degree Celsius on the two degrees Celsius in the mainland by 2040, while rainfall is projected to decrease by up 20 percent. Snow cover could decrease by 40 percent around the same time.

If warming continues as expected, experts predict that cedars may be able to grow in only three refugial areas in the northern tip of the country, where mountains are higher, by the end of this century.

Tiny insect, big damage

The combination of drier and hotter conditions has boosted the rise of a further threat for the cedars: the proliferation of the cedar web-spinning sawfly, or Cephalcia tannourinensis, a tiny green grub that feeds off the trees' young needles.

"The origin of the outbreak is directly tied to climate change," explained Nabil Nemer, a forest entomologist at Lebanon's Holy Spirit University of Kaslik who helped discover the insect after an epidemic killed swaths of the Tannourine Cedars Forest Nature Reserve, Lebanon's densest and largest cedar patch, in the late 1990s.

Normally, the adult sawflies emerge in spring, said Nemer, laying their eggs on the cedar trunks. As they spring out, the larvae eat cedar needles before burying themselves into the earth for up to four years and surface again as adult sawflies with wings.

But as snow melts earlier and the soil becomes less humid, larvae are emerging every year and in larger numbers, feeding on new shoots and preventing them from making novel needles.

"A repetitive attack of three years on the same branch or tree will lead to its death," said Nemer. The sawfly killed more than seven percent of the Tannourine forest's trees over the last two decades, and more than 70 percent are now affected, he said.

In the past, the pest was contained by sprinkling pesticides from above. But with the use of chemicals banned in protected areas - the reserve was established soon after the discovery of the sawfly - scientists are now resorting to native microorganisms that naturally kill the larvae to restrain the spreading.

The method, however, has its flaws. "We depend on the university laboratories to produce these control agents. But there's not enough funding, space and manpower to produce sufficient quantities to cover the whole cedar surfaces," said Nemer. "We started to have a new rise in the sawfly population three years ago."

A gleam of hope

As scientists fight to preserve the dwindling cedar population, conservationists are trying to understand if cedars can survive above their natural range. Meanwhile, the Beirut government is seeking to replenish the country's depleted forests.

Five years ago, the Ministry of Agriculture began a reforestation scheme to plant 40 million native trees, including some cedars, by 2030. But with a lingering sectarian power-sharing system making the government too weak to deliver even basic reforms, enforcement is weak. So far, less than three million were planted under the scheme.

Civil society organisations are trying to fill the gap. Jouzour Loubnan, a non-profit organisation, has managed to plant 300,000 new trees in a decade. Separately, the Lebanon Reforestation Initiative, a partnership between grassroots organisations and the US Agency for International Development, planted more than 600,000 trees since 2010.

In Arz al-Rab, a local body has planted more than 100,000 trees in a number of parcels around the Cedars of God forest, Lebanon's most iconic cedar stretch, since it was added to Unesco World Heritage list two decades ago.

But here, as elsewhere, there are hurdles. Most cedar patches are isolated and their ability to enlarge is limited. In the Bsharri District, where the Cedars of God forest lies, most of the utile land for afforestation has already been populated, said Charbel Tawk, head of the Friends of the Cedar Forest Committee.

In other regions, he added, plots of land where the cedars could naturally spread and connect are privately-owned, or entitled for other uses. Even when belonging to the public, municipalities are not always willing to allocate the land for afforestation, preferring tourism development.

Even so, Lebanese are bullish on the chances of the cedars to stand the test of climate change, seeing in the tree a powerful metaphor of the country's ability to survive the challenges of history.

"They fought against whatever threat you can imagine. And they kept reproducing and giving siblings that thrived," said Magda Bou Dagher, a plant geneticist who is also the president of the Jouzour Loubnan organisation.

"Despite how hard human made their live, they are still harbouring in their genes the potential to overcome environmental crisis," she said.

"We just have to give them this small push by reconnecting their populations and then stay aside and let them accomplish their fate."

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