21st century

===Population and urbanization===
The [[world population]] was about 6.1 billion at the start of the 21st century and reached 8 billion by November 2022. It is [[Projections of population growth|estimated to reach]] nearly 8.6 billion by 2030,<ref>{{cite news|url=https://economictimes.indiatimes.com/news/politics-and-nation/by-2030-world-will-have-8-6bn-people-1-5bn-of-them-in-india/articleshow/59279842.cms|title=By 2030, world will have 8.6bn people, 1.5bn of them in India|date=23 June 2017|newspaper=The Economic Times|access-date=12 January 2019|archive-date=3 December 2020|archive-url=https://web.archive.org/web/20201203115326/https://economictimes.indiatimes.com/news/politics-and-nation/by-2030-world-will-have-8-6bn-people-1-5bn-of-them-in-india/articleshow/59279842.cms|url-status=live}}</ref> and 9.8 billion by 2050. According to the [[United Nations]] World Urbanization prospects, a 60% projection of the world's human population is to live in [[megacity|megacities]] and [[megalopolis]]es by 2030, 70% by 2050, and 90% by 2080. It is expected by 2040, the investing of more than 5 times the current global [[gross domestic product]] is expected to be in urban infrastructure.<ref>{{cite web |url=https://esa.un.org/unpd/wup/publications/files/wup2014-highlights.pdf |title=World Population Prospects |access-date=13 October 2018 |archive-url = https://web.archive.org/web/20170202002014/https://esa.un.org/unpd/wup/Publications/Files/WUP2014-Highlights.pdf |archive-date=2 February 2017 |url-status=live }}</ref>

[[Life expectancy]] has increased as [[child mortality]] continues to decline. A baby born in 2019, for example, will, on average (globally), live to 73 years—27 years longer than the global average of someone born in 1950.<ref>{{Cite web |date=9 May 2023 |title=GHE: Life expectancy and healthy life expectancy |url=https://www.who.int/data/gho/data/themes/mortality-and-global-health-estimates/ghe-life-expectancy-and-healthy-life-expectancy |url-status=live |archive-url=https://web.archive.org/web/20230322174132/https://www.who.int/data/gho/data/themes/mortality-and-global-health-estimates/ghe-life-expectancy-and-healthy-life-expectancy |archive-date=22 March 2023 |access-date=9 May 2023 |website=www.who.int |language=en}}</ref> Ten million [[Britons]] (16% of the [[United Kingdom]] population) will, on average, live to 100 or older.<ref>{{cite web|url=https://uk.news.yahoo.com/10-million-brits-alive-today-will-live-see-100th-birthday-150028500.html|title=10 million Brits alive today will live to see their 100th birthday|website=uk.news.yahoo.com|date=12 March 2018 |access-date=12 January 2019|archive-date=19 September 2020|archive-url=https://web.archive.org/web/20200919072737/https://uk.news.yahoo.com/10-million-brits-alive-today-will-live-see-100th-birthday-150028500.html|url-status=live}}</ref>

[[Climate change]] remains a serious concern; UN Chief [[António Guterres]], for instance, has described it as an "[[Global catastrophic risk|existential threat]]" to humanity.<ref>{{cite web|url=https://news.un.org/en/story/2018/05/1009782|title=Climate change: An 'existential threat' to humanity, UN chief warns global summit|date=15 May 2018|website=UN News|access-date=12 January 2019|archive-date=23 December 2020|archive-url=https://web.archive.org/web/20201223154410/https://news.un.org/en/story/2018/05/1009782|url-status=live}}</ref> Furthermore, the [[Holocene extinction]] event, the sixth most significant extinction event in the Earth's history, continues with the widespread degradation of highly [[Biodiversity hotspot|biodiverse habitats]] as a by-product of human activity.<ref>{{cite journal |last1=Ceballos |first1=Gerardo |last2=Ehrlich |first2=Paul R. |title=The misunderstood sixth mass extinction |journal=[[Science (journal)|Science]] |date=8 June 2018 |volume=360 |issue=6393 |pages=1080–1081 |doi=10.1126/science.aau0191 |pmid=29880679 |bibcode=2018Sci...360.1080C |s2cid=46984172 |oclc=7673137938}}</ref>

[[File:Isolierte-Völker.png|thumb|A map of [[Uncontacted peoples|uncontacted tribes]], around the start of the 21st century]]