Editing Soil erosion (section)

===Deforestation===
[[File:BURNED CLEAR-CUT AREA OF OLYMPIC NATIONAL TIMBERLAND WASHINGTON. NEAR OLYMPIC NATIONAL PARK - NARA - 555088.tif|thumb|In this [[clearcut]], almost all of the vegetation has been stripped from the surface of steep slopes, in an area with very heavy rains. Severe erosion occurs in cases such as this, causing stream [[sedimentation]] and the loss of nutrient-rich [[topsoil]].]]

In an undisturbed [[forest]], the mineral soil is protected by a layer of ''[[leaf litter]]'' and an ''[[humus]]'' that cover the forest floor. These two layers form a protective mat over the soil that absorbs the impact of rain drops. They are [[porosity|porous]] and highly [[Permeability (Earth sciences)|permeable]] to rainfall, and allow rainwater to slow [[percolate]] into the soil below, instead of flowing over the surface as [[surface runoff|runoff]].<ref name="Sands-2005-pp74-75">{{cite book|author=Sands, Roger|chapter=The environmental value of forests|title=Forestry in a Global Context|publisher=CABI|year=2005|isbn=978-0-85199-089-7|pages=74–75|chapter-url=https://books.google.com/books?id=UO1DAI60IQEC&pg=PA74}}</ref> The roots of the trees and plants<ref>The [[Mycelium|mycelia]] of forest [[Fungus|fungi]] also play a major role in binding soil particles together.</ref> hold together soil particles, preventing them from being washed away.<ref name="Sands-2005-pp74-75" /> The vegetative cover acts to reduce the velocity of the raindrops that strike the foliage and stems before hitting the ground, reducing their [[kinetic energy]].<ref name="Goudie-2000-p188" /> However it is the forest floor, more than the canopy, that prevents surface erosion. The [[terminal velocity]] of rain drops is reached in about {{convert|8|m|ft|abbr=off}}. Because forest canopies are usually higher than this, rain drops can often regain terminal velocity even after striking the canopy. However, the [[intact forest landscape|intact forest]] floor, with its layers of leaf litter and organic matter, is still able to absorb the impact of the rainfall.<ref name="Goudie-2000-p188">{{Cite book|author=Goudie, Andrew|chapter=The human impact on the soil|title=The Human Impact on the Natural Environment|publisher=MIT Press|year=2000|isbn=978-0-262-57138-8|page=[https://archive.org/details/humanimpactonn00goud/page/188 188]|chapter-url=https://books.google.com/books?id=r8l-DMj3XTgC&pg=PA188|url=https://archive.org/details/humanimpactonn00goud/page/188}}</ref><ref>{{cite journal|author=Stuart, Gordon W.|author2=Edwards, Pamela J.|name-list-style=amp|title=Concepts about forests and water|journal=Northern Journal of Applied Forestry|volume=23|issue=1|pages=11–19|year=2006|url=http://treesearch.fs.fed.us/pubs/14744|doi=10.1093/njaf/23.1.11|doi-access=free|access-date=2015-10-05|archive-date=2017-07-01|archive-url=https://web.archive.org/web/20170701142057/https://www.treesearch.fs.fed.us/pubs/14744|url-status=dead}}</ref>

[[Deforestation]] causes increased erosion rates due to exposure of [[mineral]] [[soil]] by removing the humus and litter layers from the soil surface, removing the vegetative cover that binds soil together, and causing heavy [[soil compaction]] from logging equipment. Once trees have been removed by fire or logging, infiltration rates become high and erosion low to the degree the forest floor remains intact. Severe fires can lead to significant further erosion if followed by heavy rainfall.<ref>{{Cite book|author=Goudie, Andrew|chapter=The human impact on the soil|title=The Human Impact on the Natural Environment|publisher=MIT Press|year=2000|isbn=978-0-262-57138-8|pages=[https://archive.org/details/humanimpactonn00goud/page/196 196–197]|chapter-url=https://books.google.com/books?id=r8l-DMj3XTgC&pg=PA196|url=https://archive.org/details/humanimpactonn00goud/page/196}}</ref>

Globally one of the largest contributors to erosive soil loss in the year 2006 is the [[slash and burn]] treatment of [[tropical]] [[forest]]s. In a number of regions of the earth, entire sectors of a country have been rendered unproductive. For example, on the [[Madagascar]] high central [[plateau]], comprising approximately ten percent of that country's land area, virtually the entire landscape is sterile of [[vegetation]], with gully erosive furrows typically in excess of {{convert|50|m|ft}} deep and {{convert|1|km|mi|abbr=off|1}} wide. [[Shifting cultivation]] is a farming system which sometimes incorporates the [[slash and burn]] method in some regions of the world. This degrades the soil and causes the soil to become less and less fertile.<ref>{{Cite thesis|title=Shifting cultivation in the upland secondary forests of the Philippines: biodiversity and carbon stock assessment, and ecosystem services trade-offs in land-use decisions|publisher=University of Queensland Library|first=Sharif Ahmed|last=Mukul|year=2016 |doi=10.14264/uql.2016.222}}</ref>