Leo, an orphaned Sumatran orangutan, is taken to the Sumatran Orangutan Conservation Programme rehabilitation centre. Leo will join other orangutans who have been reintroduced to the Pinus Jantho nature reserve. The SOCP has gradually formed a completely new wild population of species that have been threatened with extinction. (Photo by Sutanta Aditya/Barcroft Images)

Members of Pakistan's Christian minority attend a service ahead of Christmas in Lahore, Pakistan, 22 December 2021. Pakistan is a majority Sunni Muslim country and home to four million Christians out of a total population of around 200 million people. (Photo by Rahat Dar/EPA/EFE)

The rabbit population of San Juan Island, brought in to feed lighthouse keepers, got so big that in the 1930s foxes were introduced to kill them. Although they are red foxes, their coats can be orange, silver, black or multi-coloured. Picture date: September 2023. (Photo by Jun Zuo/Solent News)

Gers, traditional Mongolian tents, are seen on a hill in an area known as a ger district in Ulan Bator June 26, 2013. Approximately 60 percent of the population of Ulan Bator live in settlements known as ger districts and in many cases residents have limited access to basic services such as water and sanitation. According to a 2010 National Population Center census, every year between thirty and forty thousand people migrate from the countryside to the capital Ulan Bator. Ger districts in the city have been expanding rapidly in recent years. Mongolia is the world's least densely populated country, with 2.8 million people spread across an area around three times the size of France. (Photo by Carlos Barria/Reuters)

China has recently relaxed its one child policy that was used to control a burgeoning population. A couple has their wedding photo taken in an old quarter of Beijing on May 24, 2016. (Photo by Michael Robinson Chavez/The Washington Post)

Sri Lankan participants control their bulls during a traditional cart race to mark the Sri Lanka National New Year in Homagama near Colombo on April 23, 2017. The new year marked by both the majority Sinhalese and minority Tamil population fell on April 14. (Photo by Lakruwan Wanniarachchi/AFP Photo)

Children wearing cardboard lion dance masks walk along a street in Beijing on January 13, 2023. China has announced its first overall population decline in recent years amid an aging society and plunging birthrate. (Photo by Mark Schiefelbein/AP Photo)

Weddell seal numbers in 2025 have declined sharply on Signy Island, part of the South Orkney Islands in the Southern Ocean, where British Antarctic Survey researchers have tracked seal populations for nearly 50 years to understand the impact of melting sea ice. (Photo by Michael Dunn/The Times)