Editing Edge effects

{{Short description|Ecological concept}}
{{Refimprove|date=November 2010}}
[[File:Edge Effect.jpg|thumb|250px|Edges arise where two or more habitat types come into contact as here in [[Pennsylvania]], United States.]]
[[File:Rosfordstreet.jpg|thumb|250px|And edge between an open parkland and a [[Coastal Swamp Oak Forest|riparian zone]] in [[Sydney]], Australia.]]
In [[ecology]], '''edge effects''' are changes in [[population ecology|population]] or [[community (ecology)|community]] structures that occur at the boundary of two or more [[habitat]]s.<ref>{{cite book|last=Levin|first=Simon A.|title=The Princeton Guide to Ecology|url=https://archive.org/details/princetonguideto00levi|url-access=limited|publisher=Princeton University Press|year=2009|page=[https://archive.org/details/princetonguideto00levi/page/n794 780]|isbn=9780691128399 }}</ref> Areas with small [[habitat fragmentation|habitat fragments]] exhibit especially pronounced edge effects that may extend throughout the range. As the edge effects increase, the boundary habitat allows for greater [[biodiversity]].

[[Urbanization]] is causing humans to continuously [[Habitat fragmentation|fragment]] landscapes and thus increase the edge effect.  This change in [[landscape ecology]] is proving to have consequences.<ref>{{Cite journal |last1=PORENSKY |first1=LAUREN M. |last2=YOUNG |first2=TRUMAN P. |date=2013-03-26 |title=Edge‐Effect Interactions in Fragmented and Patchy Landscapes |url=http://dx.doi.org/10.1111/cobi.12042 |journal=Conservation Biology |volume=27 |issue=3 |pages=509–519 |doi=10.1111/cobi.12042 |pmid=23531018 |s2cid=13546312 |issn=0888-8892 |access-date=2022-04-01 |archive-date=2023-07-31 |archive-url=https://web.archive.org/web/20230731180313/https://conbio.onlinelibrary.wiley.com/doi/10.1111/cobi.12042 |url-status=live |url-access=subscription }}</ref>  [[Generalist and specialist species|Generalist]] species, especially [[Invasive species|invasive]] ones, have been seen to benefit from this landscape change whilst specialist species are suffering.<ref>{{Cite journal |last=Holway |first=David A. |date=February 2005 |title=Edge effects of an invasive species across a natural ecological boundary |url=https://linkinghub.elsevier.com/retrieve/pii/S0006320704002423 |journal=Biological Conservation |language=en |volume=121 |issue=4 |pages=561–567 |doi=10.1016/j.biocon.2004.06.005 |access-date=2022-04-01 |archive-date=2022-01-20 |archive-url=https://web.archive.org/web/20220120171641/https://linkinghub.elsevier.com/retrieve/pii/S0006320704002423 |url-status=live |url-access=subscription }}</ref>  For example, the [[alpha diversity]] of edge-intolerant birds in [[Lacandon Jungle|Lacandona rainforest]], Mexico, is decreasing as edge effects increase.<ref>{{Cite journal |last1=Carrara |first1=Emilia |last2=Arroyo-Rodríguez |first2=Víctor |last3=Vega-Rivera |first3=Jorge H. |last4=Schondube |first4=Jorge E. |last5=de Freitas |first5=Sandra M. |last6=Fahrig |first6=Lenore |date=April 2015 |title=Impact of landscape composition and configuration on forest specialist and generalist bird species in the fragmented Lacandona rainforest, Mexico |url=https://linkinghub.elsevier.com/retrieve/pii/S000632071500035X |journal=Biological Conservation |language=en |volume=184 |pages=117–126 |doi=10.1016/j.biocon.2015.01.014 |access-date=2022-04-01 |archive-date=2022-06-19 |archive-url=https://web.archive.org/web/20220619215412/https://linkinghub.elsevier.com/retrieve/pii/S000632071500035X |url-status=live |url-access=subscription }}</ref> 

==Types==
* Inherent &ndash; Natural features stabilize the border location.
* Induced &ndash; Transient natural disturbances (e.g., fire or flood) or human related activities, subject borders to successional changes over time.
* Narrow &ndash; One habitat abruptly ends and another begins (e.g., an agricultural field.)
* Wide ([[ecotone]]) &ndash; A large distance separates the borders of two clearly and purely definable habitats based upon their physical conditions and vegetation, and in between there exists a large transition region.
* Convoluted &ndash; The border is non-linear.
* Perforated &ndash; The border has gaps that host other habitats.

Height can create borders between patches as well.<ref>{{cite journal
 | last = Smith
 | first = T.M.
 | author2=Smith, R.L.
 | title = Elements of Ecology
 | pages = 391–411
 | year = 2009
 }}</ref>

==Biodiversity==
Environmental conditions enable certain species of plants and animals to colonize habitat [[Geographic range limit|borders]]. Plants that colonize forest edges tend to be [[shade tolerance|shade-intolerant]]. <ref>{{Cite journal |last=Wales |first=Bruce A. |date=1972 |title=Vegetation Analysis of North and South Edges in a Mature Oak-Hickory Forest |url=https://www.jstor.org/stable/1942167 |journal=Ecological Monographs |volume=42 |issue=4 |pages=451–471 |doi=10.2307/1942167 |jstor=1942167 |issn=0012-9615 |access-date=2023-02-14 |archive-date=2023-02-14 |archive-url=https://web.archive.org/web/20230214102333/https://www.jstor.org/stable/1942167 |url-status=live |url-access=subscription }}</ref> These plants also tend to be [[Desiccation tolerance|tolerant of dry conditions]], such as [[shrubs]] and [[vines]].  Animals that colonize tend to be those that require two or more habitats, such as white-tailed and [[mule deer]], [[elk]], [[cottontail rabbits]], blue jays, and [[American robin|robins]].{{cn|date=August 2022}} Some animals travel between habitats, while edge species are restricted to edges. Larger patches have increased native species biodiversity compared to smaller patches.<ref>{{Cite journal |last=Noss |first=Reed F. |date=1999-03-22 |title=Assessing and monitoring forest biodiversity: A suggested framework and indicators |url=https://www.sciencedirect.com/science/article/pii/S0378112798003946 |journal=Forest Ecology and Management |language=en |volume=115 |issue=2 |pages=135–146 |doi=10.1016/S0378-1127(98)00394-6 |s2cid=8683460 |issn=0378-1127|url-access=subscription }}</ref> The width of the patch also influences diversity: an edge patch must be more pronounced than just a stark border in order to develop gradients of edge effects. 

Animals traveling between communities can create travel lanes along borders, which in turn increases light reaching plants along the lanes and promotes [[primary production]]. As more light reaches the plants, greater numbers and sizes can thrive. Increased primary production can increase numbers of herbivorous insects, followed by nesting birds and so on up the [[trophic level]]s.

In the case of wide and/or overgrown borders, some species can become restricted to one side of the border despite having the ability to inhabit the other. Sometimes, the edge effects result in [[abiotic]] and biotic conditions which diminish natural variation and threaten the original ecosystem. Detrimental edge effects are also seen in physical and chemical conditions of border species. For instance, fertilizer from an agricultural field could invade a bordering forest and contaminate the habitat. The three factors affecting edges can be summarized:
* Abiotic effect—Changes in the environmental conditions that result from the proximity to a structurally dissimilar matrix
* Direct biological effects—Changes in [[species abundance]] and distribution caused directly by physical conditions near the edge
* Indirect biological effects which involve changes in species interactions such as [[predation]],<ref>{{cite journal |author1= Valentine, E.C. |author2= Apol, C.A. | author3= Proppe, D.S. | year=2019| title= Predation on artificial avian nests is higher in forests bordering small anthropogenic openings| journal=Ibis| volume=161| pages=  662–673| doi= 10.1111/ibi.12662| issue=3|s2cid= 91309233 }}</ref> [[brood parasitism]], competition, [[herbivory]], and biotic [[pollination]] and [[seed dispersal]]<ref>{{cite journal
  | last = Murcia
  | first = C.
  | title = Edge effects in fragmented forests:implications for conservation
  | journal = Tree
  | volume = 20
  | issue = 2
  | pages = 58–62
  | year = 1995
  | url = https://owa.stevenson.edu/owa/redir.aspx?C=f92c3d2bbd1746e4a1ff9899aeb03e1f&URL=http%3a%2f%2fresearch.eeescience.utoledo.edu%2flees%2fTeaching%2fEEES4760_05%2fMurcia95.pdf
  | doi = 10.1016/S0169-5347(00)88977-6
  | pmid = 21236953
  | access-date = 2011-12-06
  | archive-date = 2023-07-31
  | archive-url = https://web.archive.org/web/20230731180319/https://owa.stevenson.edu/owa/auth/logon.aspx?replaceCurrent=1&url=https%3a%2f%2fowa.stevenson.edu%2fowa%2fredir.aspx%3fURL%3dhttp%253a%252f%252fresearch.eeescience.utoledo.edu%252flees%252fTeaching%252fEEES4760_05%252fMurcia95.pdf%23C%3df92c3d2bbd1746e4a1ff9899aeb03e1f
  | url-status = live
  }}</ref>

==Human effects==
Human activity creates edges through development and agriculture. Often, the changes are detrimental to both the size of the habitat and to species. Examples of human impacts include:
* Introduction of [[invasive species|invasives]]/exotics
* Higher severity and frequency of fires
* Companion animals (pets) acting as predators and competitors
* Trails
* [[Pollution]], [[erosion]]
* [[habitat loss|Loss]] of foraging habitats
* [[Habitat fragmentation]]
* [[Deforestation]]  and land use change 

==Examples==
When edges divide any [[nature|natural]] ecosystem and the area outside the boundary is a disturbed or unnatural system, the natural ecosystem can be seriously affected for some distance in from the edge. In 1971, Odum wrote, 'The tendency for increased variety and diversity at community junctions is known as the ''edge effect''... It is common knowledge that the density of songbirds is greater on estates, campuses and similar settings...as compared with tracts of uniform forest.'. In a forest where the adjacent land has been cut, creating an open/forest boundary, [[sunlight]] and [[wind]] penetrate to a much greater extent, drying out the interior of the [[forest]] close to the edge and encouraging growth of opportunistic [[species]] there.  Air temperature, [[vapor pressure deficit]], [[water content|soil moisture]], light intensity and levels of [[photosynthetically active radiation]] (PAR) all change at edges.

===Amazon rainforest===
One study estimated that the amount of [[Amazon Basin]] area modified by edge effects exceeded the area that had been cleared.<ref>{{cite journal
  | last = Skole
  | first = D. L.
  |author2=C. Tucker
  | title = Tropical deforestation and habitat loss fragmentation in the Amazon: satellite data from 1978-1988
  | journal = [[Science (journal)|Science]]
  | volume = 260
  | issue =5116
  | pages = 1905–1910
  | year = 1994
  | doi =10.1126/science.260.5116.1905
  | pmid = 17836720  | hdl = 10535/3304
 | s2cid = 12853752
 | hdl-access = free
  }}</ref> "In studies of Amazon forest fragments, micro-climate effects were evident up to 100m (330ft.) into the forest interior."<ref name = "Corlett2011">{{cite book|last=Corlett|first=Richard, T|title=Tropical Rain Forests an Ecological and Biogeographical Comparison|year=2011|publisher=Wiley-Blackwell|location=John Wiley & Sons Ltd, The atrium, Southern Fate, Chichester, West Sussex, PO19 8SQ|isbn=978-1-4443-3254-4|pages=266–267|edition=Second|author2=Richard B. Primack}}</ref> The smaller the fragment, the more susceptible it is to fires spreading from nearby cultivated fields. Forest fires are more common close to edges due to  increased light availability that leads to increased desiccation and increased [[understory]] growth. Increased understory [[biomass]] provides fuel that allows pasture fires to spread into the forests. Increased fire frequency since the 1990s is among the edge effects that are slowly transforming Amazonian forests. The changes in temperature, humidity and light levels promote invasion of non-forest species, including [[invasive species]]. The overall effect of these fragment processes is that all forest fragments tend to lose native [[biodiversity]] depending on fragment size and shape, isolation from other forest areas, and the forest matrix.<ref name = "Corlett2011"/>

===North America===
The amount of [[forest edge]] is orders of magnitude greater now in the [[United States]] than when the [[European ethnic groups|European]]s first began settling [[North America]]. Some species have benefited from this fact, for example, the [[brown-headed cowbird]], which is a [[brood parasite]] that lays its [[egg (biology)|eggs]] in the [[bird nest|nest]]s of [[songbird]]s nesting in forest near the forest boundary.<ref>{{Cite journal |last1=Howell |first1=Christine A. |last2=Dijak |first2=William D. |last3=Thompson |first3=Frank R. |date=2007-02-01 |title=Landscape context and selection for forest edge by breeding Brown-headed Cowbirds |url=https://doi.org/10.1007/s10980-006-9022-1 |journal=Landscape Ecology |language=en |volume=22 |issue=2 |pages=273–284 |doi=10.1007/s10980-006-9022-1 |s2cid=2775157 |issn=1572-9761 |access-date=2023-02-14 |archive-date=2023-07-31 |archive-url=https://web.archive.org/web/20230731180239/https://link.springer.com/article/10.1007/s10980-006-9022-1 |url-status=live |url-access=subscription }}</ref> Another example of a species benefiting from the proliferation of forest edge is [[Poison ivy (plant)|poison ivy]]. <ref>{{Cite journal|last=Fraver|first=Shawn|date=1994|title=Vegetation Responses along Edge-to-Interior Gradients in the Mixed Hardwood Forests of the Roanoke River Basin, North Carolina|url=https://conbio.onlinelibrary.wiley.com/doi/abs/10.1046/j.1523-1739.1994.08030822.x|journal=Conservation Biology|language=en|volume=8|issue=3|pages=822–832|doi=10.1046/j.1523-1739.1994.08030822.x|issn=1523-1739|access-date=2021-01-27|archive-date=2021-01-31|archive-url=https://web.archive.org/web/20210131222233/https://conbio.onlinelibrary.wiley.com/doi/abs/10.1046/j.1523-1739.1994.08030822.x|url-status=dead|url-access=subscription}}</ref>

Conversely, [[Dragonfly|Dragonflies]] eat [[mosquito]]es, but have more trouble than mosquitoes surviving around the edges of human habitation.  Thus, trails and hiking areas near human settlements often have more mosquitoes than do deep forest habitats.  [[Grass]]es, [[huckleberry|huckleberries]], [[Ribes sanguineum|flowering currant]]s and [[shade-tolerant and -intolerant species|shade-intolerant]] trees such as the [[Douglas-fir]] all thrive in edge habitats.

In the case of developed lands juxtaposed to wild lands, problems with [[invasive exotic]]s often result. Species such as [[kudzu]], [[Japanese honeysuckle]] and [[multiflora rose]] have damaged natural ecosystems. Beneficially, the open spots and edges provide places for species<!-- which? native or invasive, ruderal/pioneer? --> that thrive where there is more light and vegetation that is close to the ground. Deer and elk benefit particularly{{Citation needed|date=November 2009}} as their principal diet is that of grass and shrubs which are found only on the edges of forested areas.

==Effects on succession==
Edge effects also apply to [[ecological succession|succession]], when vegetation spreads rather than losing to competitors. Different species are suited either to the edges or to central sections of the habitat, resulting in a varied distribution. Edges also vary with orientation: edges on the north or south receive less or more sun than the opposite side (depending on hemisphere and convex or concave relief), producing varying vegetation patterns.

==Other usage==
The phenomenon of increased variety of plants as well as animals at the community junction ([[ecotone]]) is also called the edge effect and is essentially due to a locally broader range of suitable environmental conditions or ecological niches.

Edge effects in [[biological assay]]s refer to artifacts in data that are caused by the position of the wells on a screening plate rather than a biological effect.{{citation needed|date=September 2013}}

The edge effect in [[scanning electron microscopy]] is the phenomenon in which the number of secondary and/or backscattered electrons that escape the sample and reach the detector is higher at an edge than at a surface. The interaction volume spreads far below the surface, but secondary electrons can only escape when close to the surface (generally about 10&nbsp;nm, although this depends on the material).  However, when the electron beam impacts an area close to the edge, electrons that are generated below an impact point that is close to an edge but that is far below the surface may be able to escape through the vertical surface instead.{{citation needed|date=September 2013}}

==See also==
*[[Ecotone]]
*[[Habitat fragmentation]]
*[[Landscape ecology]]
*[[Ruderal species]]
*[[Spatial ecology]]
*[[Woodland edge]]

==References==
{{reflist}}

==External links==
*[http://www.advancedmicroplates.com/images/stories/pdf2.pdf Reducing Edge Effects in biological assays]{{Dead link|date=March 2022 |bot=InternetArchiveBot |fix-attempted=yes }}
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{{DEFAULTSORT:Edge Effect}}
[[Category:Landscape ecology]]
[[Category:Ecological succession]]
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