Editing Deforestation (section)

==== Changes to the water cycle ====
The [[water cycle]] is also affected by deforestation. Trees extract [[groundwater]] through their roots and release it into the atmosphere. When part of a forest is removed, the trees no longer transpire this water, resulting in a much [[dry climate|drier climate]]. Deforestation reduces the content of water in the soil and groundwater as well as atmospheric moisture. The dry soil leads to lower water intake for the trees to extract.<ref>{{cite web|url=http://www.wrm.org.uy/deforestation/UNreport.html|title=Underlying Causes of Deforestation|work=UN Secretary-General’s Report|url-status=dead|archive-url=https://web.archive.org/web/20010411092448/http://wrm.org.uy/deforestation/UNreport.html|archive-date=11 April 2001}}</ref> Deforestation reduces soil cohesion, so that [[Soil erosion|erosion]], flooding and [[landslide]]s ensue.<ref>{{cite web|url=https://people.uwec.edu/jolhm/eh2/rogge/index.htm|author=Rogge, Daniel|work=University of Wisconsin-Eau Claire|title=Deforestation and Landslides in Southwestern Washington}}</ref><ref>[http://news.bbc.co.uk/1/hi/world/asia-pacific/413717.stm China's floods: Is deforestation to blame?] BBC News. 6 August 1999.</ref>

Shrinking [[forest cover]] lessens the landscape's capacity to intercept, retain and [[Transpiration|transpire]] precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. Forests return most of the water that falls as precipitation to the atmosphere by transpiration. In contrast, when an area is deforested, almost all precipitation is lost as run-off.<ref>Raven, P. H. and Berg, L. R. (2006) ''Environment'', 5th ed, John Wiley & Sons. p. 406. {{ISBN|0471704385}}.</ref> That quicker transport of surface water can translate into [[flash flood]]ing and more localized floods than would occur with the forest cover. Deforestation also contributes to decreased [[evapotranspiration]], which lessens atmospheric moisture which in some cases affects precipitation levels downwind from the deforested area, as water is not recycled to downwind forests, but is lost in runoff and returns directly to the oceans. According to one study, in deforested north and northwest China, the average annual precipitation decreased by one third between the 1950s and the 1980s.<ref>{{Cite book|title = The Economic Costs of China's Environmental Degradation: Project on Environmental Scarcities, State Capacity, and Civil Violence, a Joint Project of the University of Toronto and the American Academy of Arts and Sciences|chapter-url = http://www.library.utoronto.ca/pcs/state/chinaeco/forest.htm|archive-url = https://web.archive.org/web/20091230071928/http://www.library.utoronto.ca/pcs/state/chinaeco/forest.htm|url-status = dead|archive-date = 30 December 2009|publisher = Committee on Internat. Security Studies, American Acad. of Arts and Sciences|date = 1 January 1998|first = Wang|last = Hongchang|chapter = Deforestation and Desiccation in China A Preliminary Study|editor-last = Schwartz|editor-first = Jonathan Matthew}}</ref>

[[File:Madagascar highland plateau.jpg|thumb|Deforestation of the [[Central Highlands (Madagascar)|Highland Plateau]] in Madagascar has led to extensive [[siltation]] and unstable flows of western rivers.]]
Trees, and plants in general, affect the [[water cycle]] significantly:<ref name="Mishra-2010" />
* their canopies intercept a proportion of [[precipitation (meteorology)|precipitation]], which is then evaporated back to the atmosphere ([[Interception (water)|canopy interception]]);
* their litter, stems and trunks slow down [[surface runoff]];
* their roots create [[macropore]]s – large conduits – in the soil that increase [[infiltration (hydrology)|infiltration]] of water;
* they contribute to terrestrial evaporation and reduce [[Water content|soil moisture]] via [[transpiration]];
* their [[plant litter|litter]] and other organic residue change soil properties that affect the capacity of soil to store water.
* their leaves control the [[humidity]] of the atmosphere by [[transpiration|transpiring]]. 99% of the water absorbed by the roots moves up to the leaves and is transpired.<ref>[http://www.ag.ndsu.edu/pubs/ageng/irrigate/eb66w.htm "Soil, Water and Plant Characteristics Important to Irrigation".] {{Webarchive|url=https://web.archive.org/web/20121125074838/http://www.ag.ndsu.edu/pubs/ageng/irrigate/eb66w.htm |date=25 November 2012 }} North Dakota State University.</ref>
As a result, the presence or absence of trees can change the quantity of water on the surface, in the soil or groundwater, or in the atmosphere. This in turn changes erosion rates and the availability of water for either ecosystem functions or human services. Deforestation on lowland plains moves cloud formation and rainfall to higher elevations.<ref>{{cite journal|last1=Ray|first1=Deepak K.|last2=Nair|first2=Udaysankar S.|last3=Lawton|first3=Robert O.|last4=Welch|first4=Ronald M.|last5=Pielke|first5=Roger A.|title=Impact of land use on Costa Rican tropical montane cloud forests: Sensitivity of orographic cloud formation to deforestation in the plains|journal=Journal of Geophysical Research|date=2006|volume=111|issue=D2|pages=D02108|doi=10.1029/2005JD006096|bibcode=2006JGRD..111.2108R|doi-access=free}}</ref>

The forest may have little impact on flooding in the case of large rainfall events, which overwhelm the storage capacity of forest soil if the soils are at or close to saturation.

[[Tropical rainforest]]s produce about 30% of Earth's [[fresh water]].<ref name="The Times">{{Cite news|date=8 October 2006|title=How can you save the rain forest. 8 October 2006. Frank Field|work=The Times|location=London|url=http://www.timesonline.co.uk/tol/news/article664544.ece|archive-url=https://web.archive.org/web/20080517091952/http://www.timesonline.co.uk/tol/news/article664544.ece|url-status=dead|archive-date=17 May 2008|access-date=1 April 2010}}</ref>

Deforestation disrupts normal weather patterns creating hotter and drier weather thus increasing drought, desertification, crop failures, melting of the polar ice caps, [[coastal flooding]] and displacement of major vegetation regimes.<ref>{{Cite news|title=Deforestation as a major threat|url=https://www.daily-sun.com/printversion/details/465873/Deforestation-as-a-major-threat|access-date=2022-02-26|work=Daily Sun|type=Opinion|language=en}}</ref>