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Theenvironment of Hong Kong features a subtropical climate with temperate conditions for about half of the year as well as a monsoon season. Despite being very densely populated, Hong Kong has a high level of biodiversity. Some threats to the environment includeclimate change,rising sea levels, pollution, and land development.
Hong Kong has asubtropical climate with temperate conditions for about six months of the year. The monsoon season lasts from April to September with July to September being the most likely months for tropical cyclones to occur. During the hot, humid summers, the average daily maximum temperatures range from 26°C at night to 31°C during the day, with late May to mid-September seeing the highest temperatures. Hong Kong receives between 1,400 to 3,000 millimetres of rain per year and 80% of that occurs from May to September. Of these, June and August are the wettest months, with rain falling on almost four out of seven days. The winters are dry and temperate. December and January, are the driest months, with an average of only one rainy day per week.[1]
The total land area of Hong Kong is 1,108 square kilometres, but about 75% of this land is open countryside and about 40% is designated as country parks.[2]
Hong Kong is home to many species despite being one of the most densely populated areas in the world. In a 2025 report, theWorld Wide Fund for Nature (WWF) Hong Kong counted 584 bird species, 272 butterfly species, 134 dragonfly species, 71 reptile species, 70 freshwater fish species, 24 amphibian species, 24 freshwater crustacean species, and 18 species of medium to large non-volant (flightless) land mammals.[3] In addition to the 8 groups assessed in the WWF report, Hong Kong has 25 species of bats, 20 species of marine mammals, 120 species ofintertidal invertebrates, about 350 species ofangiosperms andgymnosperms,[4] and 11 species of small non-volant land mammals.[5]
In 2020, the BBC reported that the population of the critically endangeredpink dolphin (Sousa chinensis), also called the Chinese white dolphin, had dropped by 60% around the area of construction for a bridge between Hong Kong and Macau.[6][7]
Numbers of the endangeredblack-faced spoonbill (Platalea minor) wintering inMai Po Marshes rose from roughly 35 in the late 1980s to 152 after 10 years. About 400 were spotted near the end of 2000.[8] Despite an increase in the worldwide black-faced spoonbill population from 2024 to 2025, the local population decreased from 375 to 328.[9]
Horseshoe crab species found in Hong Kong waters includeTachypleus tridentatus andCarcinoscorpius rotundicauda, in addition to some reported sightings ofTachypleus gigas.[10]
Hong Kong has 733 kilometres of coastline[11] with atidal range of about 1.4 metres.[12] Coastal habitats are broadly categorized as soft or rocky shores, with rocky shores being more exposed to tidal and temperature changes and soft shores being more sheltered.[13]
The distribution of species situated inrocky shores must be tolerant of conditions when the shore is covered with seawater at high tide and when the shore is directly exposed at low tide. Mobile species adapt to these varying conditions by successfully exploiting microhabitats such as cracks and crevices, orpools of water that remain during low tide. However,sessile organisms thatfilter-feed, like barnacles and oysters, may die in large numbers during the heat of summer, then recolonize during cooler months.[14]
Rocky shores can be categorized according to how exposed they are.Tai Tam andTolo Harbour are two areas that have sheltered rocky shores, while exposed rocky shores can be found atBig Wave Bay andShek O. Areas likeStanley andMiddle Bay are semi-exposed.[14]
Soft shores occur in sheltered areas with low wave disturbance. This allows for the deposition of finer sediment than on rocky shores. The amount of sediment varies and can result in different types of habitat such asmudflats, sandy beaches, andmangrove forests.[15]
Mangrove forests are habitats in tropical and subtropicalintertidal zones, occurring on soft shores that receive tidal flushing from nearby fresh water sources. The Pearl River is one such fresh water source and it promotes mangrove growth in theDeep Bay area. Of the eight species of mangrove local to Hong Kong,Kandelia obovata is the most common.[16]
Some mangrove stands that have been designated asSites of Special Scientific Interest (SSSI):[17]
Freshwater habitats can be classified by their rate of water flow.Lentic bodies of water are slow moving and can include lakes, wetlands, and agricultural fields.Lotic bodies of water are those that are fast moving like rivers and streams.[18] Another factor that differentiates fresh water habitats is the amount of available oxygen. These factors influence animals' various adaptive responses. They may have to attach themselves to surfaces in fast moving bodies of water like rivers[19] or have a mechanism for obtaining maximum oxygen supply in bodies of water where this resource is scarce.[20]
Hong Kong has more than 200 streams and rivers, most of them short and without names. Some are natural and some, especially those in urban areas, have been altered and lined with concrete. These concrete lined rivers are called urban rivers or nullahs.[21]
Some of the major rivers of Hong Kong:[21]
In 1989, the Hong Kong government realised that Hong Kong was in danger of becoming a vast, densely populated city. Due to the growth of the economy, the impacts of pollution were increasingly becoming evident in the environment.[citation needed]
Previously, Victoria Harbour suffered from pollution to such a degree that, despite a government plan to clean the harbour, environmentalists in 1995 worried that it was beyond repair.[22] Since 2015 the water quality of the harbour has improved due to the full implementation of the Harbour Area Treatment Scheme (HATS) which began in 1994.[23]
Oyster farms have been impacted by a mixture of pollution and competition from cheaper oyster cultivation across the border in China.[citation needed]
Air pollution is another problem. Factories, construction, and diesel vehicles have led to increased levels ofparticulate matter andnitrogen dioxide. Air pollution affects flora, fauna, and human health. Cases ofasthma and bronchial infections have risen in recent years, and poor air quality is a factor.[citation needed]
According to aBaptist University study, daily average minimum temperatures have increased by 0.02 degrees (Celsius) annually between 1965 and 2003, due to theurban heat island effect, which traps heat during the daytime and releases it at night. Average daily maximum temperatures have fallen by 0.014 degrees each year, as air pollution blocks solar radiation. Resulting increased nighttime ambient temperatures incite families to use domestic air-conditioning, which further compounds the problem.[24]
Research has shown that the ambient air-temperature in urban areas can be some 5 °C higher than non built-up areas. TheHong Kong Polytechnic University commissionedNASA to take a high-resolutionthermal image of urban Hong Kong by satellite at 22:40 on 4 August 2007, which showed at least a four-degree difference between the coolest areas and the "urban heat islands". The variations are attributable to greater absorbency of man-made materials, and building density that restrict air-flow. The affected area had expanded intoHung Hom since January, when the first image was taken.[25]
There has been increasing concern since 2006 over thewall effect caused by uniform high-rise buildings that block most air circulation. Due to the population density of Hong Kong and theeconomies of scale of mass developments, most newtower block developments are mass-constructed in groups of 10 to 100, ranging from 30 to 70 stories high. Developers ofhousing estates are often financially motivated to maximize view at the expense of air circulation. Huge wall-like estates along the waterfront .[26]
In-fill developments are typically constructed by smaller developers with less capital. These will be smaller in scale, and less prone to the wall effect.
Environmental group Green Sense expressed concern that their survey on 155 housing estates found 104 have a 'wall-like' design. It cited estates inTai Kok Tsui andTseung Kwan O as the "best examples".[26] In May 2007, citing concern over developments inWest Kowloon, and nearTai Wai andYuen Long railway stations, some legislators called for a law to stop developers from constructing tall buildings that adversely affect airflow in densely populated areas, but the bid failed.[27] In 2007, residents of Tai Kok Tsui, increasingly aware of the problem, have been lobbying against the further proliferation of such high-rises in their area that threaten the last air corridor.[25]
With increasing affluence of the mainland, some mainland Chinese people become able to afford luxury flora and fauna likePodocarpus macrophyllus (Cantonese:羅漢松;Jyutping: lo4 hon3 cung4 ) andCuora trifasciata (Cantonese:金錢龜; Jyutping: gam1 cin2 gwai1). Some of these species are in danger of extinction due to increased hunting.
Most of the introduced species do little harm to the ecology of Hong Kong.However, some species are invasive and cause massive damage to the ecology and/or economy of Hong Kong.[28]
Examples are the pinewood nematode from North America and pine-needle scale insect from Taiwan, which together virtually eliminated the nativePinus massoniana in the 1970s and 1980s.[29]
