Editing Amazon rainforest (section)

==Geography==
===Location===
Nine countries share the Amazon basin—most of the rainforest, 58.4%, is contained within the borders of Brazil. The other eight countries are Peru with 12.8%, Bolivia with 7.7%, Colombia with 7.1%, Venezuela with 6.1%, Guyana with 3.1%, Suriname with 2.5%, French Guiana with 1.4% and Ecuador with 1%.<ref name="Segamazonia_Coca-Castro_201301">{{citation|title=Land use Status and Trends in Amazonia|publisher=Amazonia Security Agenda Project|date=January 2013|last1=Coca-Castro|last2=Reymondin|last3=Bellfield|last4=Hyman|first1=Alejandro|first2=Louis|first3=Helen|first4=Glenn|url=http://segamazonia.org/sites/default/files/press_releases/land_use_status_and_trends_in_amazonia.pdf |access-date=August 25, 2019|url-status=dead|archive-url=https://web.archive.org/web/20160319140931/http://segamazonia.org/sites/default/files/press_releases/land_use_status_and_trends_in_amazonia.pdf|archive-date=March 19, 2016}}</ref>

===Natural===
[[File:Walking tree.jpg|thumb|Amazon rainforest in Colombia]]
[[File:Amazon CIAT (2).jpg|thumb|Aerial view of the Amazon rainforest, near [[Manaus]]]]
The rainforest likely formed during the [[Eocene]] era<!-- , following the evolutionary appearance of [[angiosperm]] plants [nonsense - they evolved during the Cretaceous!] --> (from 56 million years to 33.9&nbsp;million years ago). It appeared following a global reduction of tropical temperatures when the [[Atlantic Ocean]] had widened sufficiently to provide a warm, moist climate to the Amazon basin. The rainforest has been in existence for at least 55 million years, and most of the region remained free of [[savanna]]-type [[biome]]s at least until the [[current ice age]] when the climate was drier and savanna more widespread.<ref name=morley>{{cite book
 | first=Robert J. | last=Morley | year=2000
 | title=Origin and Evolution of Tropical Rain Forests
 | publisher=Wiley | isbn=978-0-471-98326-2
}}</ref><ref name=ptors359>{{cite journal
 | last=Burnham | first=Robyn J.
 | author2=Johnson, Kirk R.
 | title=South American palaeobotany and the origins of neotropical rainforests
 | journal=Philosophical Transactions of the Royal Society
 | year=2004 | volume=359 | issue=1450
 | pmid=15519975
 | pmc=1693437
 | pages=1595–1610 | doi=10.1098/rstb.2004.1531}}</ref>

Following the [[Cretaceous–Paleogene extinction event]], the extinction of the [[dinosaur]]s and the wetter climate may have allowed the tropical rainforest to spread out across the continent. From 66 to 34 [[mya (unit)|Mya]], the rainforest extended as far south as [[45th parallel south|45°]]. Climate fluctuations during the last 34 million years have allowed savanna regions to expand into the tropics. During the [[Oligocene]], for example, the rainforest spanned a relatively narrow band. It expanded again during the [[Middle Miocene]], then retracted to a mostly inland formation at the [[Last glacial period|last glacial maximum]].<ref>{{cite journal
 |last        = Maslin
 |first       = Mark
 |author2     = Malhi, Yadvinder
 |author3     = Phillips, Oliver
 |author4     = Cowling, Sharon
 |title       = New views on an old forest: assessing the longevity, resilience and future of the Amazon rainforest
 |journal     = Transactions of the Institute of British Geographers
 |year        = 2005
 |volume      = 30
 |issue       = 4
 |pages       = 477–499
 |url         = http://earth.leeds.ac.uk/ebi/publications/Maslin_2005.pdf
 |access-date  = September 25, 2008
|doi         = 10.1111/j.1475-5661.2005.00181.x
 |bibcode = 2005TrIBG..30..477M
 |archive-url  = https://web.archive.org/web/20081001191320/http://earth.leeds.ac.uk/ebi/publications/Maslin_2005.pdf
 |archive-date = October 1, 2008
|url-status     = dead
 |df          = mdy-all
}}</ref> However, the rainforest still managed to thrive during these [[glacial periods]], allowing for the survival and evolution of a broad diversity of species.<ref name=yadvinder>{{cite book
 | first=Yadvinder | last=Malhi
 | author2=Phillips, Oliver | year=2005
 | title=Tropical Forests & Global Atmospheric Change
 | publisher=Oxford University Press
 | isbn=978-0-19-856706-6}}</ref>
[[File:Campo12Foto 2.JPG|thumb|Aerial view of the Amazon rainforest]]
During the [[mid-Eocene]], it is believed that the [[drainage basin]] of the Amazon was split along the middle of the continent by the [[Purus Arch]]. Water on the eastern side flowed toward the [[Atlantic]], while to the west water flowed toward the Pacific across the [[Amazonas Basin]]. As the [[Andes]] Mountains rose, however, a large basin was created that enclosed a lake; now known as the [[Solimões River|Solimões Basin]]. Within the last 5–10&nbsp;million years, this accumulating water broke through the Purus Arch, joining the easterly flow toward the Atlantic.<ref>{{cite journal
 | last=Costa | first=João Batista Sena
 | author2=Bemerguy, Ruth Léa|author3= Hasui, Yociteru|author4= Borges, Maurício da Silva
 | title=Tectonics and paleogeography along the Amazon river
 | journal=Journal of South American Earth Sciences
 | year=2001 | volume=14 | issue=4 | pages=335–347
 | doi=10.1016/S0895-9811(01)00025-6
 | bibcode = 2001JSAES..14..335C}}</ref><ref>{{cite journal | last1=Milani | first1=Edison José | last2=Zalán | first2=Pedro Victor | title=An outline of the geology and petroleum systems of the Paleozoic interior basins of South America | journal=[[Episodes (journal)|Episodes]] | year=1999 | volume=22 | issue=3 | pages=199–205 | df=mdy-all | doi=10.18814/epiiugs/1999/v22i3/007 | doi-access=free }}</ref>
[[File:Amazon CIAT (4).jpg|thumb|Aerial view of the Amazon rainforest near [[Manaus]]]]
There is evidence that there have been significant changes in the Amazon rainforest [[vegetation]] over the last 21,000 years through the [[last glacial maximum]] (LGM) and subsequent deglaciation. Analyses of sediment deposits from Amazon basin paleolakes and the Amazon Fan indicate that rainfall in the basin during the LGM was lower than for the present, and this was almost certainly associated with reduced moist tropical vegetation cover in the basin.<ref name="Colinvaux1">{{Cite journal | doi=10.1002/1099-1417(200005)15:4<347::AID-JQS537>3.0.CO;2-A| title=Palaeoecology and climate of the Amazon basin during the last glacial cycle| journal=Journal of Quaternary Science| volume=15| issue=4| pages=347–356| year=2000| last1=Colinvaux| first1=Paul A.| last2=Oliveira| first2=Paulo E. De| bibcode=2000JQS....15..347C}}</ref> In present day, the Amazon receives approximately 9 feet of rainfall annually. There is a debate, however, over how extensive this reduction was. Some scientists argue that the rainforest was reduced to small, isolated [[refugium (population biology)|refugia]] separated by open forest and grassland;<ref name="VanDerHammen">{{Cite journal | doi=10.1016/S0277-3791(99)00024-4|bibcode = 2000QSRv...19..725V|title = Neogene and Quaternary history of vegetation, climate, and plant diversity in Amazonia| journal=Quaternary Science Reviews| volume=19| issue=8| page=725|last1 = Van Der Hammen|first1 = Thomas| last2=Hooghiemstra| first2=Henry| year=2000| citeseerx=10.1.1.536.519}}</ref> other scientists argue that the rainforest remained largely intact but extended less far to the north, south, and east than is seen today.<ref name="Colinvaux2">{{cite journal
 | last=Colinvaux | first=P.A.
 | author2=De Oliveira, P.E.|author3= Bush, M.B.
 | title=Amazonian and neotropical plant communities on glacial time-scales: The failure of the aridity and refuge hypotheses
 | journal=Quaternary Science Reviews
 | date=January 2000 | volume=19 | issue=1–5
 | pages=141–169 | doi=10.1016/S0277-3791(99)00059-1 |bibcode = 2000QSRv...19..141C}}</ref> This debate has proved difficult to resolve because the practical limitations of working in the rainforest mean that data sampling is biased away from the center of the Amazon basin, and both explanations are reasonably well supported by the available data.

====Sahara Desert dust windblown to the Amazon====
More than 56% of the dust fertilizing the Amazon rainforest comes from the [[Bodélé depression]] in Northern Chad in the [[Sahara]] desert. The dust contains [[phosphorus]], important for plant growth. The yearly Sahara dust replaces the equivalent amount of phosphorus washed away yearly in Amazon soil from rains and floods.<ref>{{cite journal|doi=10.1002/2015GL063040 | volume=42 | issue=6 | title=The fertilizing role of African dust in the Amazon rainforest: A first multiyear assessment based on data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations | year=2015 | journal=Geophysical Research Letters | pages=1984–1991 | last1 = Yu | first1 = Hongbin| bibcode=2015GeoRL..42.1984Y | doi-access=free }}</ref>

NASA's [[CALIPSO]] satellite has measured the amount of dust transported by wind from the Sahara to the Amazon: an average of 182 million tons of dust are windblown out of the Sahara each year (some dust falls into the Atlantic), 15% of which of falls over the Amazon basin (22&nbsp;million tons of it consisting of phosphorus).<ref>{{cite web|url=http://www.nasa.gov/content/goddard/nasa-satellite-reveals-how-much-saharan-dust-feeds-amazon-s-plants|title=Saharan Dust Feeds Amazon's Plants|first=Rob|last=Garner|date=February 24, 2015|website=NASA|access-date=June 20, 2019|archive-date=June 23, 2019|archive-url=https://web.archive.org/web/20190623142203/https://www.nasa.gov/content/goddard/nasa-satellite-reveals-how-much-saharan-dust-feeds-amazon-s-plants/|url-status=live}}</ref>

CALIPSO uses a laser range finder to scan the Earth's atmosphere for the vertical distribution of dust and other aerosols. and regularly tracks the Sahara-Amazon dust plume. CALIPSO has measured variations in the dust amounts transported – an 86 percent drop between the highest amount of dust transported in 2007 and the lowest in 2011. This is possibly caused by rainfall variations in the [[Sahel]], a strip of semi-arid land on the southern border of the Sahara.<ref>{{cite web|url=https://science.nasa.gov/science-news/science-at-nasa/2015/29apr_amazondust/|title=Desert Dust Feeds Amazon Forests – NASA Science|work=nasa.gov|access-date=July 12, 2017|archive-date=May 14, 2017|archive-url=https://web.archive.org/web/20170514192932/https://science.nasa.gov/science-news/science-at-nasa/2015/29apr_amazondust|url-status=live}}</ref>

Amazon phosphorus also comes as smoke due to biomass burning in Africa.<ref>{{cite journal|last1=Barkley|first1=Anne E.|last2=Prospero|first2=Joseph M.|last3=Mahowald|first3=Natalie|author-link3=Natalie Mahowald|last4=Hamilton|first4=Douglas S.|last5=Popendorf|first5=Kimberly J.|last6=Oehlert|first6=Amanda M.|last7=Pourmand|first7=Ali|last8=Gatineau|first8=Alexandre|last9=Panechou-Pulcherie|first9=Kathy|last10=Blackwelder|first10=Patricia|last11=Gaston|first11=Cassandra J.|date=August 13, 2019|title=African biomass burning is a substantial source of phosphorus deposition to the Amazon, Tropical Atlantic Ocean, and Southern Ocean|url=|journal=Proceedings of the National Academy of Sciences|volume=116|issue=33|pages=16216–16221|bibcode=2019PNAS..11616216B|doi=10.1073/pnas.1906091116|pmc=6697889|pmid=31358622|doi-access=free}}</ref><ref>{{cite web |title=Smoke from Africa fertilizes the Amazon and tropical ocean regions with soluble phosphorous [''sic'']|url=https://phys.org/news/2019-08-africa-fertilizes-amazon-tropical-ocean.html |website=phys.org |language=en-us |access-date=August 14, 2019 |archive-date=August 14, 2019 |archive-url=https://web.archive.org/web/20190814181214/https://phys.org/news/2019-08-africa-fertilizes-amazon-tropical-ocean.html |url-status=live }}</ref>