Singapore consists of 63 islands, including the main island, Pulau Ujong. There are two man-made connections to Johor, Malaysia: the Johor–Singapore Causeway in the north and the Tuas Second Link in the west. Jurong Island, Pulau Tekong, Pulau Ubin and Sentosa are the largest of Singapore's smaller islands. The highest natural point is Bukit Timah Hill at 163.63 m (537 ft).
Ongoing land reclamation projects have increased Singapore's land area from 581.5 km2 (224.5 sq mi) in the 1960s to 719.1 km2 (277.6 sq mi) in 2015, an increase of some 23% (130 km2). The country is projected to grow by another 100 km2 (40 sq mi) by 2030. Some projects involve merging smaller islands through land reclamation to form larger, more functional islands, as has been done with Jurong Island.
Nearly 10% of Singapore's land has been set aside for parks and nature reserves. The network of nature reserves, parks, park connectors, nature ways, tree-lined roads and other natural areas have enhanced the sense of green space in the city. This is a result of five decades of greening efforts, which began in 1963, when Prime Minister Lee Kuan Yew launched Singapore's first tree-planting campaign by planting a mempat tree (Cratoxylum formosum). The aim was to soften the harshness of urbanisation and improve the quality of life. This initiative continued into the 1970s and 1980s under the Parks and Recreation Department (PRD), renamed the National Parks Board (abbreviation: NParks) in July 1996.
Due to these efforts, Singapore was ranked fourth in the 2014 Environmental Performance Index, which measures the effectiveness of state policies for environmental sustainability.
Singapore's environment has changed drastically due to rapid urbanization and immense population density. In 1819, when a British trading post was first established on the island, Singapore was still nearly entirely covered in rainforests. During that time it still contained flora shared with the Malay Peninsula, but the biodiversity of the fauna was even then relatively low. Following the establishment of the trading post, rapid deforestation began due to crop cultivation. Deforestation of Singapore was largely completed by the 20th century. By some estimates, there has been a loss of 95% of the natural habitats of Singapore over the course of the past 183 years.
In modern times, over half of the naturally occurring fauna and flora in Singapore is present only in nature reserves, such as the Bukit Timah Nature Reserve and the Sungei Buloh Wetland Reserve, which comprise only 0.25% of Singapore's land area.
To combat these problems, the Singaporean government has made the Singapore Green Plan in 1992 and the new Singapore Green Plan in 2012 to continue it. The plan aims to keep tabs on the unstable populations of fauna and flora, to place new nature parks, and to connect existing parks. In addition, there are plans to set up a "National Biodiversity Reference Centre" (now known as the National Biodiversity Centre).
As of mid-2015, the estimated population of Singapore was 5,535,000 people, 3,375,000 (60.98%) of who were citizens, while the remaining 2,160,000 (39.02%) were permanent residents (527,700) or foreign students/foreign workers/dependants (1,632,300). According to the country's most recent census in 2010, nearly 23% of Singaporean residents (i.e. citizens and permanent residents) were foreign born (which means about 10% of Singapore citizens were foreign-born naturalised citizens); if non-residents were counted, nearly 43% of the total population were foreign born.
The same census also reports that about 74.1% of residents were of Chinese descent, 13.4% of Malay descent, 9.2% of Indian descent, and 3.3% of other (including Eurasian) descent. Prior to 2010, each person could register as a member of only one race, by default that of his or her father, therefore mixed-race persons were solely grouped under their father's race in government censuses. From 2010 onward, people may register using a multi-racial classification, in which they may choose one primary race and one secondary race, but no more than two.
90.3% of resident households (i.e. households headed by a Singapore citizen or permanent resident) own the homes they live in, and the average household size is 3.43 persons (which include dependants who are neither citizens nor permanent residents). However, due to scarcity of land, 80.4% of resident households live in subsidised, high-rise, public housing apartments known as "HDB flats" because of the government board (Housing and Development Board) responsible for public housing in the country. Also, 75.9% of resident households live in properties that are equal to, or larger than, a four-room (i.e. three bedrooms plus one living room) HDB flat or in private housing. Live-in foreign domestic workers are quite common in Singapore, with about 224,500 foreign domestic workers there, as of December 2013.
The median age of Singaporean residents is 39.3, and the total fertility rate is estimated to be 0.80 children per woman in 2014, the lowest in the world and well below the 2.1 needed to replace the population. To overcome this problem, the Singapore government has been encouraging foreigners to immigrate to Singapore for the past few decades. The large number of immigrants has kept Singapore's population from declining.