The discovery of a tropical butterfly on North Lantau last month is a sign that ecological zones are shifting as a result of global warming, according to the Environmental Association.

The butterfly, Deudorix smilis, was spotted at Sha Lo Wan on October 28 – the first sighting of this species in Hong Kong.

“It is normally found in areas deep within tropical ­regions like India and Indonesia,” Environmental Association chief secretary, Dr Yau Wing-kwong, wrote in a letter to the South China Morning Post.

But it is not a one-off.

Another tropical butterfly, the Prosotas nora, was first seen in Hong Kong in November 2015 and has now made the city a permanent home, Yau said, noting that it is now enjoying “a baby boom.”

He pointed out that climate studies have shown that for every ­degree of global warming, the isotherm, or line of average temperature, will move by more than 160km.

This discovery sends a strong signal, indicating that global warming is moving ecological species northwards, as isotherms … simultaneously move north.

Although much climate change evidence is derived from complex mathematical models and data, it is beginning to affect the ecological world on a much wider, quicker and bigger scale than ever before. This is a clear, strong message and warning that we all act together to combat global warming and climate change, before it is too late and irreversible.

The Environment Association is a privately-funded conservation promotion and education foundation.

Photo (top): Wikimedia