{{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 riparian zone in Sydney, Australia.]]
== Definition == In ecology, '''edge effects''' are changes in population or community structures that occur at the boundary of two or more habitats.<ref>{{cite book|last=Levin|first=Simon A.|title=The Princeton Guide to Ecology|url=https://research.ebsco.com/c/qakpnb/search/details/wjk67kod6f?request-context=plink&db=nlebk&db=nlabk|url-access=limited|publisher=Princeton University Press|year=2009|page=[https://archive.org/details/princetonguideto00levi/page/n794 780]|isbn=978-0-691-12839-9 }}</ref> These effects transpire since environmental conditions near habitat boundaries differ from those in the interior areas.<ref name=":0">{{Cite journal |last1=Ries |first1=Leslie |last2=Sisk |first2=Thomas D. |date=2004 |title=A Predictive Model of Edge Effects |journal=Ecology |volume=85 |issue=11 |pages=2917–2926 |doi=10.1890/03-8021 |jstor=3450531 |bibcode=2004Ecol...85.2917R |issn=0012-9658}}</ref> Habitat boundaries experience conditions like increased wind exposure, light, and temperature fluctuations. Areas with small habitat fragments exhibit especially pronounced edge effects that may extend throughout the range.<ref name=":1">{{Cite journal |last=Murcia |first=Carolina |date=February 1995 |title=Edge effects in fragmented forests: implications for conservation |url=https://linkinghub.elsevier.com/retrieve/pii/S0169534700889776 |journal=Trends in Ecology & Evolution |language=en |volume=10 |issue=2 |pages=58–62 |doi=10.1016/S0169-5347(00)88977-6 |pmid=21236953 |bibcode=1995TEcoE..10...58M |url-access=subscription }}</ref> As the edge effects increase, the boundary habitat can support higher levels of biodiversity than adjacent ecosystems with increased habitat fragmentation because they serve as transitional zones for overlapping environmental conditions.<ref name=":2">{{Cite journal |last1=Willmer |first1=Julian Nicholas G. |last2=Püttker |first2=Thomas |last3=Prevedello |first3=Jayme Augusto |date=2022-08-01 |title=Global impacts of edge effects on species richness |url=https://www.sciencedirect.com/science/article/pii/S0006320722002075 |journal=Biological Conservation |volume=272 |article-number=109654 |doi=10.1016/j.biocon.2022.109654 |bibcode=2022BCons.27209654W |issn=0006-3207|url-access=subscription }}</ref> In this way species from each of these two separate ecosystems are able to co-exist in the same general area along with species which have developed adaptations specific to the edge environment.
==Biodiversity== Environmental conditions enable certain species of plants and animals to colonize habitat borders. Plants that colonize forest edges tend to be 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 |journal=Ecological Monographs |volume=42 |issue=4 |pages=451–471 |doi=10.2307/1942167 |jstor=1942167 |bibcode=1972EcoM...42..451W |issn=0012-9615 }}</ref> These plants also tend to be 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 robins.<ref>{{Cite web |date=2017-04-01 |title=Edge and Other Wildlife Concepts - Oklahoma State University |url=https://extension.okstate.edu/fact-sheets/edge-and-other-wildlife-concepts.html |access-date=2026-03-09 |website=extension.okstate.edu |language=en}}</ref> Some animals travel between habitats, while edge species (generalists) are restricted to edges.<ref>{{Cite journal |last=Nams |first=Vilis O. |date=2011 |title=Emergent properties of patch shapes affect edge permeability to animals |journal=PLOS ONE |volume=6 |issue=7 |article-number=e21886 |doi=10.1371/journal.pone.0021886 |doi-access=free |issn=1932-6203 |pmc=3128623 |pmid=21747965 |bibcode=2011PLoSO...621886N }}</ref> 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 |bibcode=1999ForEM.115..135N |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 levels.
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.<ref>{{Cite journal |last1=Piessens |first1=Katrien |last2=Honnay |first2=Olivier |last3=Devlaeminck |first3=Rebecca |last4=Hermy |first4=Martin |date=2006-06-01 |title=Biotic and abiotic edge effects in highly fragmented heathlands adjacent to cropland and forest |url=https://www.sciencedirect.com/science/article/pii/S0167880905005463 |journal=Agriculture, Ecosystems & Environment |volume=114 |issue=2 |pages=335–342 |doi=10.1016/j.agee.2005.11.016 |bibcode=2006AgEE..114..335P |issn=0167-8809|url-access=subscription }}</ref> Abiotic effects refer to changes in non-living environmental conditions at edges while biotic effects refer to changes in living organisms along with their interactions. An example of abiotic edge effects is increased temperature and wind, while an example of biotic edge effects is increased predation and competition. 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.<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 |bibcode=2005BCons.121..561H |url-access=subscription }}</ref> 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 | bibcode = 1995TEcoE..10...58M | 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> Edge effects will have an effect on the ways that animals behave and how ecosystems are stable over time. The edge environment could be suitable for some species, but other species could suffer from increased predation risk and competition.<ref name=":0" /> This leads to a shift in species composition, with the most competitive species (generalists) becoming more common than those that require a specific niche (specialists).<ref name=":2" /> Additionally, edge habitats are affected by increased environmental variability which will add additional pressures to the biodiversity of the area.<ref name=":1" /> Urbanization and agriculture practices increase the amount of habitat edges created through fragmentation.<ref name=":3" /> Therefore, areas with many edges may lose diversity and have their ecological processes disrupted. Thus, understanding the mechanisms behind this is important for developing conservation strategy to help limit the negative aspects of edge effects and preserve natural habitats.
==Types== Edge effect variability is influenced by many factors including environmental conditions, human activities, and the composition of ecosystems. The extent to which edge effects affect species interactions and resource distribution varies as a result. Ecologists have thus defined various types of edge effects to describe differing features of habitat edges or transition zones.<ref>{{Cite journal |last1=Parkins |first1=Kate |last2=York |first2=Alan |last3=Di Stefano |first3=Julian |date=June 2018 |title=Edge effects in fire-prone landscapes: Ecological importance and implications for fauna |journal=Ecology and Evolution |volume=8 |issue=11 |pages=5937–5948 |doi=10.1002/ece3.4076 |issn=2045-7758 |pmc=6010856 |pmid=29938104 |bibcode=2018EcoEv...8.5937P }}</ref> * Inherent – Natural features stabilize the border location. * Induced – Transient natural disturbances (e.g., fire or flood) or human related activities, subject borders to successional changes over time. * Narrow – One habitat abruptly ends and another begins (e.g., an agricultural field.) * Wide (ecotone) – 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 – The border is irregular, or non-linear in shape. * Perforated – 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=Thomas Michael | title = Elements of Ecology | pages = | year = 2015 |journal=Elements of Ecology|volume=9th edition|url=https://colostate.primo.exlibrisgroup.com/permalink/01COLSU_INST/1e7gacf/alma991031478534003361}}</ref>
== Urbanization == Urbanization is causing humans to continuously fragment landscapes, thus intensifying edge effects. These changes in landscape ecology is proving to have significant ecological consequences.<ref name=":3">{{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 |journal=Conservation Biology |volume=27 |issue=3 |pages=509–519 |doi=10.1111/cobi.12042 |pmid=23531018 |bibcode=2013ConBi..27..509P |s2cid=13546312 |issn=0888-8892 }}</ref> Generalist species, especially 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 |bibcode=2005BCons.121..561H |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 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 |bibcode=2015BCons.184..117C |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>
== Effects on succession == Edge effects also apply to succession, influencing how vegetation spreads over time.<ref>{{Cite journal |last1=Yang |first1=Xifu |last2=Zhao |first2=Kunming |last3=Zhang |first3=Zhibin |date=2025-12-01 |title=Environmental gradients drive context-dependent seed fate: Synergistic roles of forest succession, edge effects, and masting in shaping rodent dispersal dynamics |url=https://www.sciencedirect.com/science/article/pii/S0006320725005154 |journal=Biological Conservation |volume=312 |article-number=111478 |doi=10.1016/j.biocon.2025.111478 |bibcode=2025BCons.31211478Y |issn=0006-3207|url-access=subscription }}</ref> 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).<ref>{{Cite journal |last1=Smith |first1=T. |last2=Bookhagen |first2=B. |date=January 2021 |title=Climatic and Biotic Controls on Topographic Asymmetry at the Global Scale |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JF005692 |journal=Journal of Geophysical Research: Earth Surface |language=en |volume=126 |issue=1 |article-number=e2020JF005692 |doi=10.1029/2020JF005692 |bibcode=2021JGRF..12605692S |issn=2169-9003}}</ref> Other factors such as light intensity, soil composition and duration of growing periods can affect the composition and structure of vegetation leading to area with larger edge effect.<ref>{{Cite journal |last=Inger |first=Maren Elisabeth |title=Journal of Arid environments |url=https://www.sciencedirect.com/science/article/pii/S0140196315001378 |access-date=March 24, 2026 |website=sciencedirect.com |doi=10.1016/j.jaridenv.2015.06.004 |hdl=1956/10889 |hdl-access=free }}</ref>
==Human effects== Human activity such as road construction, logging, and urban development create edges by fragmenting habitats.<ref>{{Cite journal |last=Fahrig |first=Lenore |date=2003-11-01 |title=Effects of Habitat Fragmentation on Biodiversity |url=https://www.annualreviews.org/content/journals/10.1146/annurev.ecolsys.34.011802.132419 |journal=Annual Review of Ecology, Evolution, and Systematics |language=en |volume=34 |issue= |pages=487–515 |doi=10.1146/annurev.ecolsys.34.011802.132419 |issn=1543-592X|url-access=subscription }}</ref> Often, the changes are detrimental to both the size of the habitat and to species. Examples of human impacts include: * Introduction of invasives/exotics * Agriculture * Higher severity and frequency of fires * Companion animals (pets) acting as predators and competitors * Trails * Pollution, erosion * Loss of foraging habitats * Habitat fragmentation * Deforestation and land use
==Examples== When edges divide any 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'.<ref>{{Cite book |last=Odum |first=Eugene P. |title=Fundamentals of ecology |date=1971 |publisher=Saunders |isbn=978-0-7216-6941-0 |edition=3d |location=Philadelphia}}</ref> 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, soil moisture, light intensity and levels of photosynthetically active radiation (PAR) all change at edges.<ref>{{Cite journal |last=Harris |first=Larry D. |date=1988 |title=Edge Effects and Conservation of Biotic Diversity |journal=Conservation Biology |volume=2 |issue=4 |pages=330–332 |doi=10.1111/j.1523-1739.1988.tb00196.x |jstor=2386291 |bibcode=1988ConBi...2..330H |issn=0888-8892}}</ref>
===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 | 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 Europeans 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 eggs in the nests of songbirds 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 |journal=Landscape Ecology |language=en |volume=22 |issue=2 |pages=273–284 |doi=10.1007/s10980-006-9022-1 |bibcode=2007LaEco..22..273H |s2cid=2775157 |issn=1572-9761 }}</ref> Another example of a species benefiting from the proliferation of forest edge is 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-access=subscription}}</ref>
Conversely, Dragonflies eat mosquitoes, 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. Grasses, huckleberries, flowering currants and 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 exotics 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 lighter and vegetation that is close to the ground. Deer and elk <ref>{{Cite web |date=2025-08-24 |title=What Do Deer and Elk Eat? A Comparison of Their Diets |url=https://biologyinsights.com/what-do-deer-and-elk-eat-a-comparison-of-their-diets/ |access-date=2026-03-12 |website=Biology Insights |language=en-US}}</ref>benefit particularly as their principal diet is that of grass and shrubs which are found only on the edges of forested areas.
==Alternative definitions of edge effect == 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 assays refer to artifacts in data that are caused by the position of the wells on a screening plate rather than a biological effect<ref>{{Cite web |last=Neeley |first=Cindy |date=2016-09-27 |title=Defeating The Edge Effect to Drive Drug Discovery |url=https://www.thermofisher.com/blog/cellculture/defeating-edge-effect-to-drive-discovery/ |access-date=2026-03-12 |website=Advancing Cell Culture |language=en-US}}</ref>
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 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.<ref>{{Cite journal |last1=El Gomati |first1=M. M. |last2=Prutton |first2=M. |last3=Lamb |first3=B. |last4=Tuppen |first4=C. G. |date=March 1988 |title=Edge effects and image contrast in scanning Auger microscopy: A theory/experiment comparison |url=https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/sia.740110506 |journal=Surface and Interface Analysis |language=en |volume=11 |issue=5 |pages=251–265 |doi=10.1002/sia.740110506 |issn=0142-2421|url-access=subscription }}</ref>
==See also== *Ecotone *Habitat fragmentation *Landscape ecology *Ruderal species *Spatial ecology *Woodland edge *Deforestation
==References== {{reflist}}
==External links== {{Clear}} {{modelling ecosystems|expanded=other}}
{{DEFAULTSORT:Edge Effect}} Category:Landscape ecology Category:Ecological succession Category:Habitats Category:Ecology terminology Category:Environmental terminology Category:Habitat Category:Systems ecology