Editing Beaver (section)

===Environmental effects===
{{main article|Environmental impacts of beavers}}
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{{Multiple image
| header = Beaver dam enlargement
| total_width = 440
| image1 = Beaver dam - geograph.org.uk - 1452003.jpg
| caption1 = September 2009
| image2 = Beaver dam - four months on - geograph.org.uk - 1623430.jpg
| caption2 = December 2009
| footer = Images of a beaver dam over a four-month period. Dams block rivers and create ponds.
| altfooter = Beaver dams being built to block a stream
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The beaver works as an [[ecosystem engineer]] and [[keystone species]], as its activities can have a great impact on the landscape and [[biodiversity]] of an area. Aside from humans, few other extant animals appear to do more to shape their environment.<ref name=Rosell/> When building dams, beavers alter the paths of streams and rivers, allowing for the creation of extensive [[wetland]] habitats.<ref>{{cite journal |author1=Burchsted, D. |author2=Daniels, M. |author3=Thorson, R. |author4=Vokoun, J. |year=2010 |title=The river discontinuum: applying beaver modifications to baseline conditions for restoration of forested headwaters |journal=[[BioScience]] |volume=60 |issue=11 |pages=908–922 |doi=10.1525/bio.2010.60.11.7 |s2cid=10070184 |url=http://opencommons.uconn.edu/cgi/viewcontent.cgi?article=1000&context=geosci |access-date=September 18, 2020 |archive-date=August 5, 2020 |archive-url=https://web.archive.org/web/20200805173711/https://opencommons.uconn.edu/cgi/viewcontent.cgi?article=1000&context=geosci |url-status=live }}</ref> In one study, beavers were associated with large increases in open-water areas. When beavers returned to an area, 160% more open water was available during droughts than in previous years, when they were absent.<ref>{{cite journal|last1=Hood|first1=Glynnis A.|last2=Bayley|first2=Suzanne E.|year=2008|title=Beaver (''Castor canadensis'') mitigate the effects of climate on the area of open water in boreal wetlands in western Canada|journal=Biological Conservation|volume=141 |issue=2|pages=556–567 |doi=10.1016/j.biocon.2007.12.003|bibcode=2008BCons.141..556H |s2cid=84584842 }}</ref> Beaver dams also lead to higher [[water table]]s in mineral soil environments and in wetlands such as [[Fen|peatlands]]. In peatlands particularly, their dams stabilize the constantly changing water levels, leading to greater [[Carbon sequestration|carbon storage]].<ref>{{Cite journal|last1=Karran|first1=Daniel J.|last2=Westbrook|first2=Cherie J.|last3=Bedard-Haughn|first3=Angela|date=2018|title=Beaver-mediated water table dynamics in a Rocky Mountain fen|journal=Ecohydrology|language=en|volume=11|issue=2|pages=e1923|doi=10.1002/eco.1923|bibcode=2018Ecohy..11E1923K |s2cid=133775598|issn=1936-0592}}</ref>

Beaver ponds, and the wetlands that succeed them, remove sediments and pollutants from waterways, and can stop the loss of important soils.<ref>{{cite journal |title=Beaver pond biogeochemical effects in the Maryland Coastal Plain |journal=Biogeochemistry |year=2000 |pages=217–239 |jstor=1469618 |last1=Correll|first1=David L.  |last2= Jordan|first2=Thomas E. |last3= Weller|first3=Donald E. |volume=49 |issue=3 |doi=10.1023/a:1006330501887|s2cid=9393979 }}</ref><ref>{{cite journal|last1=Puttock|first1=A.|last2=Graham|first2=H. A.|last3=Carless|first3=D.|last4=Brazier|first4=R. E.|year=2018|title=Sediment and Nutrient Storage in a Beaver Engineered Wetland|journal=[[Earth Surface Processes and Landforms]]|volume=43|issue=11|pages=2358–2370|doi=10.1002/esp.4398|pmid=30333676|pmc=6175133|bibcode=2018ESPL...43.2358P|doi-access=free}}</ref> These ponds can increase the [[Productivity (ecology)|productivity]] of freshwater ecosystems by accumulating [[nitrogen]] in sediments.<ref name=Rosell/> Beaver activity can affect the temperature of the water; in northern latitudes, ice thaws earlier in the warmer beaver-dammed waters.<ref name=ice>{{cite journal |title=Beavers (''Castor canadensis'') facilitate early access by Canada geese (''Branta canadensis'') to nesting habitat and areas of open water in Canada's boreal wetlands |journal=Mammalian Biology |year=2013 |volume=78 |pages=73–77 |author=Bromley, Chantal K. |author2= Hood, Glynnis A. |issue=1 |doi=10.1016/j.mambio.2012.02.009|bibcode=2013MamBi..78...73B }}</ref> Beavers may contribute to [[climate change]]. In Arctic areas, the floods they create can cause [[permafrost]] to thaw, [[Arctic methane emissions|releasing methane into the atmosphere]].<ref>{{cite journal|last1=Jones|first1=B. M.|last2=Tape|first2=K. D.|last3=Clark |first3=J. A.|last4=Nitze|first4=I. |last5=Grosse|first5=G.|last6=Disbrow|first6=J. |year=2020 |title=Increase in beaver dams controls surface water and thermokarst dynamics in an Arctic tundra region, Baldwin Peninsula, northwestern Alaska |journal=[[Environmental Research Letters]] |volume=15|issue=7 |page=075005|doi=10.1088/1748-9326/ab80f1|bibcode=2020ERL....15g5005J|doi-access=free}}</ref><ref>{{cite web|author=Hunt, Kate|date=June 30, 2020|title=Beavers are gnawing away at the Arctic permafrost, and that's bad for the planet|work=CNN|access-date=March 11, 2021|url=https://www.cnn.com/2020/06/29/americas/beavers-arctic-scn-climate-change-trnd/index.html|archive-date=June 2, 2023|archive-url=https://web.archive.org/web/20230602042218/https://www.cnn.com/2020/06/29/americas/beavers-arctic-scn-climate-change-trnd/index.html|url-status=live}}</ref>

As wetlands are formed and [[riparian]] habitats are enlarged, aquatic plants colonize the newly available watery habitat.<ref name=Rosell/> One study in the [[Adirondacks]] found that beaver engineering lead to an increase of more than 33 percent in [[herbaceous plant]] diversity along the water's edge.<ref>{{cite journal |author1=Wright, J. P. |author2=Jones, C. G. |author3=Flecker, A. S. | year=2002 | title=An ecosystem engineer, the beaver, increases species richness at the landscape scale | journal=[[Oecologia]] | volume=132 | issue=1 | pages=96–101 | doi=10.1007/s00442-002-0929-1 |pmid=28547281 | url=http://www.caryinstitute.org/sites/default/files/public/reprints/Wright_et_al_2002_An_ecosystem_Oecologia_132_96-101.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.caryinstitute.org/sites/default/files/public/reprints/Wright_et_al_2002_An_ecosystem_Oecologia_132_96-101.pdf |archive-date=2022-10-09 |url-status=live|bibcode=2002Oecol.132...96W |s2cid=5940275 }}</ref> Another study in semiarid [[eastern Oregon]] found that the width of riparian vegetation on stream banks increased several-fold as beaver dams watered previously dry terraces adjacent to the stream.<ref>{{cite journal |doi=10.1002/esp.1553 |title=Geomorphic changes upstream of beaver dams in Bridge Creek, an incised stream channel in the interior Columbia River basin, eastern Oregon |author1=Pollock, Michael M. |author2=Beechie, Timothy J. |author3=Jordan, Chris E.  |name-list-style=amp |journal=[[Earth Surface Processes and Landforms]] |volume=32 |issue=8 |pages=1174–1185 |year=2007 |bibcode=2007ESPL...32.1174P |s2cid=129844314 |doi-access=free }}</ref> Riparian ecosystems in arid areas appear to sustain more plant life when beaver dams are present.<ref>{{cite journal|last1=Fairfax|first1=E.|last2=Small|first2=E. E.|year=2018|title=Using remote sensing to assess the impact of beaver damming on riparian evapotranspiration in an arid landscape|journal= Ecohydrology|volume=11|issue=7|page=e1993|doi=10.1002/eco.1993|bibcode=2018Ecohy..11E1993F |s2cid=134994160}}</ref> Beaver ponds act as a refuge for riverbank plants during [[wildfires]], and provide them with enough moisture to resist such fires.<ref name=wildfire>{{cite journal|last1=Fairfax|first1=E|last2=Whittle|first2=A.|year=2020|title=Smokey the Beaver: beaver-dammed riparian corridors stay green during wildfire throughout the western United States|journal=[[Ecological Applications]]|volume=30|issue=8|page=e02225|doi=10.1002/eap.2225|pmid=32881199|doi-access=free|bibcode=2020EcoAp..30E2225F}}</ref> [[Beaver eradication in Tierra del Fuego|Introduced beavers at Tierra del Fuego]] have been responsible for destroying the indigenous forest. Unlike trees in North America, many trees in South America cannot grow back after being cut down.<ref name=nature>{{Cite journal | last1=Choi | first1=C. | title=Tierra del Fuego: The beavers must die | doi=10.1038/453968a | journal=[[Nature (journal)|Nature]] | volume=453 | issue=7198 | page=968 | year=2008 | pmid=18563116| doi-access=free }}</ref><ref>{{cite web|author=Gilliland, H. C.|date=June 25, 2019|title=Invasive beavers are destroying Tierra del Fuego|website=[[National Geographic]]|url=https://www.nationalgeographic.com/animals/2019/07/beaver-overpopulation-tierra-del-fuego/|archive-url=https://web.archive.org/web/20190725134742/https://www.nationalgeographic.com/animals/2019/07/beaver-overpopulation-tierra-del-fuego/|url-status=dead|archive-date=July 25, 2019|access-date=December 20, 2020}}</ref>
[[File:Sockeye salmon jumping over beaver dam Lake Aleknagik, AK Kristina Ramstad 1997.jpg|thumb|left|upright|[[Salmon]] (''[[Oncorhynchus nerka]]'') jumping a beaver dam.]]
Beaver activity impacts [[Community (ecology)|communities]] of [[aquatic invertebrate]]s. Damming typically leads to an increase of [[lentic ecosystem|slow or motionless water]] species, like [[dragonflies]], [[oligochaetes]], [[snails]], and [[mussels]]. This is to the detriment of [[Lotic ecosystems|rapid water]] species like [[black flies]], [[stoneflies]], and [[Hydropsychidae|net-spinning caddisflies]].<ref name="Rosell" /><ref>{{cite journal|last1=McDowell|first1=D. M.|last2=Naiman|first2=R. J.|year=1986|journal=Oecologia|title=Structure and function of a benthic invertebrate stream community as influenced by beaver (''Castor canadensis'')|volume=68|issue=4|pages=481–489|doi=10.1007/BF00378759|jstor=4217870|pmid=28311700|bibcode=1986Oecol..68..481M|s2cid=24369386}}</ref><ref>{{cite journal|author=Harthun, M.|year=1999|title=The influence of the European beaver (''Castor fiber albicus'') on the biodiversity (Odonata, Mollusca, Trichoptera, Ephemeroptera, Diptera) of brooks in Hesse (Germany)|journal=Limnologica|volume=29|issue=4|pages=449–464|doi=10.1016/S0075-9511(99)80052-8|doi-access=free}}</ref> Beaver floodings create more dead trees, providing more habitat for terrestrial invertebrates like ''[[Drosophila]]'' flies and [[bark beetles]], which live and breed in dead wood.<ref name="Rosell" /><ref>{{cite journal|author=Spieth, H. T.|year=1979|title=The virilis group of ''Drosophila'' and the beaver ''Castor''|journal=The American Naturalist|volume=114|issue=2|pages=312–316|doi=10.1086/283479|jstor=2460228|s2cid=83673603}}</ref><ref>{{cite journal|author=Saarenmaa, H.|year=1978|title=The occurrence of bark beetles (Col. Scolytidae) in a dead spruce stand flooded by beavers (''Castor canadensis'' Kuhl)|journal=Silva Fennica|pages=201–216|doi=10.14214/sf.a14857|doi-access=free|hdl=10138/14857|hdl-access=free}}</ref> The presence of beavers can increase wild [[salmon]] and [[trout]] populations, and the average size of these fishes. These species use beaver habitats for spawning, overwintering, feeding, and as havens from changes in water flow. The positive effects of beaver dams on fish appear to outweigh the negative effects, such as blocking of migration.<ref>{{cite journal |author1=Kemp, P. S. |author2=Worthington, T. A. |author3=Langford, T. E. L. |author4=Tree, A. R. J. |author5=Gaywood, M. J. | year=2012 | title=Qualitative and quantitative effects of reintroduced beavers on stream fish | journal=Fish and Fisheries | volume=13 | issue=2 |pages=158–181 | doi=10.1111/j.1467-2979.2011.00421.x|bibcode=2012AqFF...13..158K }}</ref> Beaver ponds have been shown to be beneficial to [[frog]] populations by protecting areas for larvae to mature in warm water.<ref>{{cite journal|last1=Stevens|first1=C. E.|last2=Paszkowsk|first2=C. A.|last3=Foote|first3=A. L.|year=2007|title=Beaver (''Castor canadensis'') as a surrogate species for conserving anuran amphibians on boreal streams in Alberta, Canada|journal=[[Biological Conservation (journal)|Biological Conservation]]|volume=134|issue=1|pages=1–13|doi=10.1016/j.biocon.2006.07.017|bibcode=2007BCons.134....1S |url=https://www.beaverinstitute.org/wp-content/uploads/2017/08/beaver-Castor-canadensis-as-a-surrogate-species-for-amphibian-conservation-2.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.beaverinstitute.org/wp-content/uploads/2017/08/beaver-Castor-canadensis-as-a-surrogate-species-for-amphibian-conservation-2.pdf |archive-date=2022-10-09 |url-status=live}}</ref> The stable waters of beaver ponds also provide ideal habitat for freshwater [[turtles]].<ref>{{cite journal|last1=Russel|first1=K. R.|last2=Moorman|first2=C. E.|last3=Edwards|first3=J. K.|last4=Guynn|first4=D. C.|year=1999|title=Amphibian and reptile communities associated with beaver (''Castor canadenis'') ponds and unimpounded streams in the Piedmont of South Carolina|journal=Journal of Freshwater Ecology|volume=14|issue=2|pages=149–158|doi=10.1080/02705060.1999.9663666|doi-access=free|bibcode=1999JFEco..14..149R }}</ref>

Beavers help [[waterfowl]] by creating increased areas of water. The widening of the [[riparian zone]] associated with beaver dams has been shown to increase the abundance and diversity of birds favoring the water's edge, an impact that may be especially important in [[semi-arid climate]]s.<ref>{{cite journal |title=Influence of Beaver Dam Density on Riparian Areas and Riparian Birds in Shrubsteepe of Wyoming |journal=[[Western North American Naturalist]] |year=2008 |volume=68 |issue=3 |pages=365–373 |author1=Cooke, Hilary A. |author2=Zack, Steve |doi=10.3398/1527-0904(2008)68[365:IOBDDO]2.0.CO;2 |s2cid=62833818 |url=https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2138&context=wnan |access-date=September 18, 2020 |archive-date=September 22, 2020 |archive-url=https://web.archive.org/web/20200922141102/https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2138&context=wnan |url-status=live }}</ref> Fish-eating birds use beaver ponds for foraging, and in some areas, certain species appear more frequently at sites where beavers were active than at sites with no beaver activity.<ref name=Rosell>{{cite journal |title=Ecological impact of beavers ''Castor fiber'' and ''Castor canadensis'' and their ability to modify ecosystems |author=Rosell F|author2= Bozser O|author3= Collen P|author4= Parker H |journal=[[Mammal Review]] |year=2005 |pages=248–276 |url=https://www.researchgate.net/publication/37687178|doi=10.1111/j.1365-2907.2005.00067.x |volume=35 |issue=3–4 |hdl=11250/2438080|hdl-access=free }}</ref><ref name=birds>{{cite journal |title=Bird species richness within beaver ponds in south-central New York |author=Grover, A. M. |author2= Baldassarre, G. A. |year=1995 |journal=Wetlands |pages=108–118|doi=10.1007/BF03160664 |volume=15 |issue=2|bibcode=1995Wetl...15..108G |s2cid=13053029 }}</ref><ref>{{cite journal|last1=Nummbi|first1=P.|last2=Holopainen|first2=S.|year=2014|title=Whole-community facilitation by beaver: ecosystem engineer increases waterbird diversity|journal=[[Aquatic Conservation: Marine and Freshwater Ecosystems]]|volume=24|issue=5|pages=623–633|doi=10.1002/aqc.2437|bibcode=2014ACMFE..24..623N }}</ref> In a study of [[Wyoming]] streams and rivers, watercourses with beavers had 75 times as many [[ducks]] as those without.<ref>{{cite journal |title=The Importance of Beavers to Waterfowl and Wetlands Habitats in Wyoming |author=McKinstry, M. C.|author2= Caffrey, P. |author3= Anderson, S. H. |journal=[[Journal of the American Water Resources Association]] |year=2001|doi=10.1111/j.1752-1688.2001.tb03660.x |volume=37 |issue=6 |pages=1571–1577|bibcode=2001JAWRA..37.1571M|s2cid=128410215}}</ref> As trees are drowned by rising beaver impoundments, they become an ideal habitat for [[woodpeckers]], which carve cavities that may be later used by other bird species.<ref name=Rosell/><ref name=birds/> Beaver-caused ice thawing in northern latitudes allows [[Canada geese]] to nest earlier.<ref name=ice/>

Other semi-aquatic mammals, such as [[European water vole|water voles]], [[muskrats]], [[minks]], and [[otters]], will shelter in beaver lodges.<ref name=Rosell/> Beaver modifications to streams in Poland create habitats favorable to [[bat]] species that forage at the water surface and "prefer moderate vegetation clutter".<ref>{{cite journal|last1=Ciechanowski|first1=M.|last2=Kubic|first2=W.|last3=Rynkiewicz|first3=A.|last4=Zwolicki|first4=A.|year=2011|title=Reintroduction of beavers ''Castor fiber'' may improve habitat quality for vespertilionid bats foraging in small river valleys|journal=European Journal of Wildlife Research|volume=57|issue=4|pages=737–747|doi=10.1007/s10344-010-0481-y|doi-access=free}}</ref> Large herbivores, such as some [[deer]] species, benefit from beaver activity as they can access vegetation from fallen trees and ponds.<ref name=Rosell/>