The butterfly population at a reserve in Tai Po has shrunk by up to 60 per cent since 2009 when a massive housing development started nearby, a conservation group claims.
But the decline is just part of a larger problem at major butterfly habitats in Hong Kong that are under threat from development and excessive human disturbance, according to the Tai Po Environmental Association, which carries out regular inspections.
Only four of 10 major habitats - Yung Shue O, Luk Keng, Ho Sheung Heung, and Hoi Ha - are still largely intact, while six in Tuen Mun, Lantau and Tai Po face serious or mild degrees of degradation, the association says.
One of the six is the Fung Yuen site, which is of special scientific interest. The number of butterflies recorded there in June had fallen 40 per cent to 146, compared to 242 in 2009. The numbers seen in April and May were down 60 and 57 per cent compared with three years ago.
The association, which has run the government-sponsored butterfly reserve over a two-hectare private site in Fung Yuen since 2005, blames the decline on a housing development owned by Li Ka-shing's Cheung Kong.
The first phase involves eight blocks of 17 to 28 storeys being built just 50 metres from the boundary of Fung Yuen.