An annual survey on butterflies has found three new species are now finding a home in Hong Kong – but this isn't necessarily such a good thing, an environmental group said on Thursday.

Green Power said that in the past year, it spotted 128 of Hong Kong's more than 260 butterfly species in two hotspots, Shing Mun Country Park and Tai Po Kau Nature Reserve.

Among them were the Lesser Gull, Silver Royal and Fluffy Tit which are new to the city, the group said.

But it added that all three are tropical butterfly species and their arrival here will be down to global warming – indicating trouble for the local ecosystem.

Green Power also noted that local Swallowtail butterflies are appearing earlier in the year due to warmer weather, saying this means fewer will be around to help pollinate plants during the flowering period.

The chances of successful pollination and fruiting will decrease and this could ultimately impact birds and mammals that feed on the plants' fruits, said Green Power's Helen Yau.

The group said measures must be implemented promptly to address climate change in order to avoid further damage to the ecosystem.