In the story of Hanukkah, a one-day supply of olive oil miraculously kept a menorah burning for eight days after a struggle for religious freedom in ancient Israel. So olive oil and the tree it comes from have a long history.

“It’s a very significant tree, the olive tree,” says Jaime Lillo of the International Olive Council, an industry group. He says olive trees survive in places where many other crops cannot.

“They can grow … with very little water and in very poor ground,” he says.

But even olive trees are feeling the strain of climate change. Prolonged drought and extreme heat can decrease yields. Heavy rain is also growing more common. That can cause pests and bacteria to thrive.

“We see more diseases affecting the plant,” Lillo says.

The resilient trees typically survive these extremes. But Lillo says these changes in the weather are now causing wide swings in crop yields in many countries.

For example, Italy is one of the top producers of olive oil. The country’s production has spiked and plunged repeatedly over the past decade, with yields some years dropping by more than 50%.

So even olive oil, an ancient religious symbol of hope and resilience, is not immune to climate change.

Reporting credit: Sarah Kennedy/ChavoBart Digital Media.