The pillar mandarin orange sector on South Korea's Jeju island is facing mounting challenges as climate change disrupts traditional cultivation practices, with prolonged tropical nights and rising temperatures delaying harvests and impacting fruit quality, according to latest industry reports.

"Mandarins develop their yellow color when nighttime temperatures fall below 20 C," said Hyun Jong-ho, manager at the Namwon Agricultural Product Center, one of Jeju's busiest distribution centers.

"This year's prolonged heat has reduced the quantity of harvest-ready mandarins," Hyun said.

Hyun explained that extreme conditions are increasingly causing delays in ripening and disruptions to harvest timelines, with the challenges prompting the island to adapt its agricultural practices.

According to the Korea Meteorological Administration, tropical nights lasted 63 days from July to September — nearly double the previous year — while heatwave days, when temperatures exceed 33 C, totaled 21.4 during the same period.

Jeju's deep-rooted affection for mandarin oranges reflects their importance to the island's identity and economy.

As of 2023, the oranges accounted for 55.8 percent of Jeju's total agricultural revenue, generating 1.32 trillion won ($941 million) that year, with 35.7 percent of Jeju's arable land devoted to citrus farming, according to the Korea Rural Economic Institute.

The significance of mandarin oranges is part of the 2024 Jeju citrus expo, which is celebrating its 12th year. The event features exhibitions, business consultations, and forums addressing climate resilience and varietal development.

Mandarin oranges are also a symbol of Jeju's agricultural history as the fruit trees on the island bloom during the harvest season.

The cultivation of the fruits has been a part of Jeju's agriculture for generations. They are the pride of the island's residents and are usually considered as gifts, especially during festive seasons, due to the meanings of health and wealth attached to them.

Ko Byung-gi, chairman of the organizing committee of the 2024 Jeju citrus expo, highlighted the industry event's dual role in advancing the oranges and fostering global collaboration.

"Mandarins are more than just a crop — they're a symbol of Jeju's heritage and resilience," Ko said.

Taking action

To address the latest challenges, Jeju authorities revised regulations in October to allow the sale of green mandarin oranges if they meet strict sweetness standards.

The adjustment, along with modified size and quality criteria, is expected to slightly boost harvested volume.

But local officials acknowledged the growing challenges posed by erratic weather patterns, including decreased fruit size and delayed coloring.

Meanwhile, subtropical crops are emerging as a potential alternative as Jeju's climate grows warmer.

The Agricultural Research Institute for Climate Change Adaptation, under the Rural Development Administration, has introduced 58 subtropical crops and identified 17 promising varieties, including mangoes, passion fruit and dragon fruit.

"To address the declining cultivation areas for traditional crops, we need to develop new varieties and expand subtropical farming techniques," said Han Hyun-hee, a researcher at the institute.

Transitioning to subtropical fruits is still considered a challenge because their cultivation requires costly greenhouses and a shift from traditional mandarin orange farming methods.

"Farmers remain hesitant to switch to subtropical crops due to higher initial investments and unfamiliar farming practices," Han added.

The Korea Herald, South Korea