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Freeway passage to offer safe route for migrating butterflies

Although tensions often arise between environmentalists and developers, the Taiwan Area National Freeway Bureau has come up with a creative method to try to please both camps.

The bureau announced yesterday that it would create a 10m long ultraviolet-lit passage under an overpass of the Formosa Freeway (National Freeway No. 3), between kilometer marker 251.7 and 252.3, to accomodate the seasonal migration of milkweed butterflies (台灣紫斑蝶). The area in Yunlin County is also known as Linnei (林內) section.

A protection net 20m long and 2.5m tall will also be placed next to the northbound lanes of the highway to force the migrating butterflies to fly higher, which will prevent them from being run over.

The measures are scheduled to be completed tomorrow.

The bureau may also close the northbound lanes on the far right during peak days of migration, which is expected to occur from April 3 to April 5, when the nation observes Tomb-Sweeping Day. The bureau will observe the numbers of butterflies and close the lanes if necessary.

The construction will cost the bureau NT$1 million (US$31,250).

Lee Tai-ming (李泰明), the bureau's director-general, said that milkweed butterflies normally migrate from the south to the north of the country in the spring and their migration route usually crosses the freeway's Linnei section.

Lee said the Butterfly Conservation Society of Taiwan had found through field research last year that more than 1 million butterflies could cross the section every day during the Tomb-Sweeping Day holidays.

Research conducted by I-Shou University has indicated that traffic on the freeway threatens the existence of the unique, endemic subspecies.

Lee said that researchers had forecast that the migration this year could begin next Monday and last until April 6, with a majority of the butterflies moving across the freeway between 9am and 12pm.

"This is the first time the bureau has taken proactive measures to protect a rare species in Taiwan," he said.

Lin Tieshyong (林鐵雄), an associate professor in the university's civil engineering department, said the protection measures were "emergency measures," since the migration was set to begin very soon.

Lin said the conservation of milkweed butterflies was urgent. In 2005 more than 1 million per day could be observed during the migration, but the number dropped to 100,000 a day last year.
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