The foundation is holding its 26th Conservation Day – themed “Cherish the Hidden Treasures” – at Ocean Park. Its aims are to broaden public understanding of Hong Kong’s biodiversity and promote the connection people have to nature as well as their awareness of conservation.

The OPCFHK is focusing on six endangered species known to live or breed in Hong Kong: the green turtle, Chinese horseshoe crab, Indo-Pacific finless porpoise, Beale‘s eyed turtle, golden birdwing butterfly and Acropora coral. Visitors to the theme park will learn about the roles these creatures play in the ecosystem and the threats they face.

As well as educational games and exhibitions, scientists will be on hand to talk about their research into these species. Although conservation efforts are ongoing, with varying degrees of success, much more must be done if we are to sustain our diversity of wildlife while meeting the needs of a busy city.

Green turtle

International Union for Conservation of Nature (IUCN) Red List status: endangered

With a hard shell reaching more than a metre in length, and weighing up to 190kg as adults, the green is the world’s second largest turtle, and the only one known to have nested in Hong Kong. But their numbers have dwindled, adults having been killed for their meat and in fishing nets, while others die after mistakenly eating plastic. Turtle eggs have also long been considered a delicacy. The last regular Hong Kong nesting site – Sham Wan, in the south of Lamma Island – is protected from human disturbance, but no turtles have returned there since 2012.

Chinese horseshoe crab

IUCN Red List status: endangered

There are four species of horseshoe crabs, which are more closely related to spiders and scorpions than crabs. Chinese horseshoe crabs are found in southern China and the Sea of Japan and, like green turtles, adults live in coastal waters and breed on beaches and mudflats.

Overfishing – for food and for their blood, which is used by the biomedical industry – pollution and damage to their breeding grounds have reduced their numbers drastically. A programme at City University of Hong Kong, supported by the OPCFHK, aims to redress the balance, by breeding Chinese horseshoe crabs and releasing young specimens in suitable locations.

Indo-Pacific finless porpoise

IUCN Red List status: vulnerable

The Indo-Pacific finless porpoise is less “glamorous” than its local cousin, the Chinese white dolphin, growing to just 1.7m long and appearing like a big tyre bobbing briefly to the surface. Yet it is no less deserving of attention.

Surveys indicate there are around 200 finless porpoises in Hong Kong waters, mostly to the south of Lantau Island and near Po Toi, in the southeast. The number of stranded individuals has risen in recent years, for reasons that are not entirely clear; although it’s thought they are being affected by the reclamation of land for the Shek Kwu Chau incinerator, which is being built in an area that was formerly a haven for porpoises.

Acropora coral

With a branching form that resembles deer antlers, the Acropora is among the most attractive of corals. Its presence also helps indicate the richness of coral communities, which is crucial for commercially important fish.

Research has shown that the range of Acropora corals in Hong Kong has shrunk, from a wide spread of coastal sites to only a few eastern areas, today. Even in the east, they are becoming scarce. Reasons for their decline include harvesting for the lime-making industry, which peaked in the mid-1900s, fishing with explosives and pollution. Although some coral areas are protected within marine reserves, and there are ongoing restoration efforts, proper safeguarding of these sensitive corals would include the cleaning up of inshore waters.

Beale’s eyed turtle

IUCN Red List status: endangered

With a shell that reaches just 15cm long, the Beale’s eyed turtle is far smaller than its seagoing cousins. Named after a pair of eye-like spots on top of its head, it is a freshwater species that feeds on small fish and tadpoles, and is found in central and southern China. It is extremely rare in Hong Kong

While the hill forests and streams this turtle inhabits can be difficult to access, it is highly sought after by poachers, especially as its shell is used as an ingredient in traditional Chinese medicine. This, together with habitat loss, has led to the Beale’s eyed turtle being threatened with extinction.

Golden birdwing butterfly

With a wingspan of up to 16cm, the golden birdwing and its similar looking cousin, the common birdwing, are the largest butterflies in Hong Kong. Although not abundant, they might sometimes be seen gliding over trees on back wings that have eye-catching bright yellow patches at the rear, or fluttering over flowers as they feast on nectar.

The caterpillars of both birdwings feed on a climbing vine, the Indian birthwort, which is legally protected in Hong Kong. The vine contains a chemical that is carcinogenic to many creatures, but does not affect the caterpillars, which accumulate the toxin to protect themselves – and the butterflies they will become – from predators.