Edge effects

Last updated

In ecology, edge effects are changes in population or community structures that occur at the boundary of two or more habitats. [1] Areas with small 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.

Contents

Urbanization is causing humans to continuously fragment landscapes and thus increase the edge effect. This change in landscape ecology is proving to have consequences. [2] Generalist species, especially invasive ones, have been seen to benefit from this landscape change whilst specialist species are suffering. [3] For example, the alpha diversity of edge-intolerant birds in Lacandona rainforest, Mexico, is decreasing as edge effects increase. [4]

Edges arise where two or more habitat types come into contact as here in Pennsylvania, United States. Edge Effect.jpg
Edges arise where two or more habitat types come into contact as here in Pennsylvania, United States.

Types

Height can create borders between patches as well. [5]

Biodiversity

Environmental conditions enable certain species of plants and animals to colonize habitat borders. Plants that colonize forest edges tend to be shade-intolerant. [6] 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.[ citation needed ] Some animals travel between habitats, while edge species are restricted to edges. Larger patches have increased native species biodiversity compared to smaller patches. [7] 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. 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:

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:

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.'. 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.

Amazon rainforest

One study estimated that the amount of Amazon Basin area modified by edge effects exceeded the area that had been cleared. [10] "In studies of Amazon forest fragments, micro-climate effects were evident up to 100m (330ft.) into the forest interior." [11] 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. [11]

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. [12] Another example of a species benefiting from the proliferation of forest edge is poison ivy. [13]

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 that thrive where there is more light and vegetation that is close to the ground. Deer and elk benefit particularly[ citation needed ] 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 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 assays 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 ]

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.[ citation needed ]

See also

Related Research Articles

<span class="mw-page-title-main">Landscape ecology</span> Science of relationships between ecological processes in the environment and particular ecosystems

Landscape ecology is the science of studying and improving relationships between ecological processes in the environment and particular ecosystems. This is done within a variety of landscape scales, development spatial patterns, and organizational levels of research and policy. Concisely, landscape ecology can be described as the science of "landscape diversity" as the synergetic result of biodiversity and geodiversity.

This glossary of ecology is a list of definitions of terms and concepts in ecology and related fields. For more specific definitions from other glossaries related to ecology, see Glossary of biology, Glossary of evolutionary biology, and Glossary of environmental science.

<span class="mw-page-title-main">Habitat conservation</span> Management practice for protecting types of environments

Habitat conservation is a management practice that seeks to conserve, protect and restore habitats and prevent species extinction, fragmentation or reduction in range. It is a priority of many groups that cannot be easily characterized in terms of any one ideology.

<span class="mw-page-title-main">Ecotone</span> Transition area between two biological communities

An ecotone is a transition area between two biological communities, where two communities meet and integrate. It may be narrow or wide, and it may be local or regional. An ecotone may appear on the ground as a gradual blending of the two communities across a broad area, or it may manifest itself as a sharp boundary line.

<span class="mw-page-title-main">Habitat fragmentation</span> Discontinuities in an organisms environment causing population fragmentation.

Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological processes that slowly alter the layout of the physical environment, and human activity such as land conversion, which can alter the environment much faster and causes the extinction of many species. More specifically, habitat fragmentation is a process by which large and contiguous habitats get divided into smaller, isolated patches of habitats.

<span class="mw-page-title-main">Habitat</span> Type of environment in which an organism lives

In ecology, habitat refers to the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical manifestation of its ecological niche. Thus "habitat" is a species-specific term, fundamentally different from concepts such as environment or vegetation assemblages, for which the term "habitat-type" is more appropriate.

<span class="mw-page-title-main">Habitat destruction</span> Process by which a natural habitat becomes incapable of supporting its native species

Habitat destruction is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby reducing biodiversity and species abundance. Habitat destruction is the leading cause of biodiversity loss. Fragmentation and loss of habitat have become one of the most important topics of research in ecology as they are major threats to the survival of endangered species.

<span class="mw-page-title-main">Biological Dynamics of Forest Fragments Project</span>

The Biological Dynamics of Forest Fragments Project is a large-scale ecological experiment looking at the effects of habitat fragmentation on tropical rainforest. The experiment which was established in 1979 is located near Manaus in the Brazilian Amazon rainforest. The project is jointly managed by the Amazon Biodiversity Center and the Brazilian Institute for Research in the Amazon (INPA).

<span class="mw-page-title-main">Fire ecology</span> Study of fire in ecosystems

Fire ecology is a scientific discipline concerned with natural processes involving fire in an ecosystem and the ecological effects, the interactions between fire and the abiotic and biotic components of an ecosystem, and the role as an ecosystem process. Many ecosystems, particularly prairie, savanna, chaparral and coniferous forests, have evolved with fire as an essential contributor to habitat vitality and renewal. Many plant species in fire-affected environments use fire to germinate, establish, or to reproduce. Wildfire suppression not only endangers these species, but also the animals that depend upon them.

<span class="mw-page-title-main">Disturbance (ecology)</span> Temporary change in environmental conditions that causes a pronounced change in an ecosystem

In ecology, a disturbance is a temporary change in environmental conditions that causes a pronounced change in an ecosystem. Disturbances often act quickly and with great effect, to alter the physical structure or arrangement of biotic and abiotic elements. A disturbance can also occur over a long period of time and can impact the biodiversity within an ecosystem.

<span class="mw-page-title-main">Railroad ecology</span>

Railroad ecology or railway ecology is a term used to refer to the study of the ecological community growing along railroad or railway tracks and the effects of railroads on natural ecosystems. Such ecosystems have been studied primarily in Europe. Similar conditions and effects appear also by roads used by vehicles. Railroads along with roads, canals, and power lines are examples of linear infrastructure intrusions.

<span class="mw-page-title-main">Cross-boundary subsidy</span>

Cross-boundary subsidies are caused by organisms or materials that cross or traverse habitat patch boundaries, subsidizing the resident populations. The transferred organisms and materials may provide additional predators, prey, or nutrients to resident species, which can affect community and food web structure. Cross-boundary subsidies of materials and organisms occur in landscapes composed of different habitat patch types, and so depend on characteristics of those patches and on the boundaries in between them. Human alteration of the landscape, primarily through fragmentation, has the potential to alter important cross-boundary subsidies to increasingly isolated habitat patches. Understanding how processes that occur outside of habitat patches can affect populations within them may be important to habitat management.

<span class="mw-page-title-main">Wildlife corridor</span> Connecting wild territories for animals

A wildlife corridor, habitat corridor, or green corridor is an area of habitat connecting wildlife populations separated by human activities or structures. This allows an exchange of individuals between populations, which may help prevent the negative effects of inbreeding and reduced genetic diversity that often occur within isolated populations. Corridors may also help facilitate the re-establishment of populations that have been reduced or eliminated due to random events. This may potentially moderate some of the worst effects of habitat fragmentation, wherein urbanization can split up habitat areas, causing animals to lose both their natural habitat and the ability to move between regions to access resources. Habitat fragmentation due to human development is an ever-increasing threat to biodiversity, and habitat corridors serve to manage its effects.

Patch dynamics is an ecological perspective that the structure, function, and dynamics of ecological systems can be understood through studying their interactive patches. Patch dynamics, as a term, may also refer to the spatiotemporal changes within and among patches that make up a landscape. Patch dynamics is ubiquitous in terrestrial and aquatic systems across organizational levels and spatial scales. From a patch dynamics perspective, populations, communities, ecosystems, and landscapes may all be studied effectively as mosaics of patches that differ in size, shape, composition, history, and boundary characteristics.

<span class="mw-page-title-main">Browsing (herbivory)</span> Type of herbivory

Browsing is a type of herbivory in which a herbivore feeds on leaves, soft shoots, or fruits of high-growing, generally woody plants such as shrubs. This is contrasted with grazing, usually associated with animals feeding on grass or other lower vegetations. Alternatively, grazers are animals eating mainly grass, and browsers are animals eating mainly non-grasses, which include both woody and herbaceous dicots. In either case, an example of this dichotomy are goats and sheep.

<span class="mw-page-title-main">Defaunation</span> Loss or extinctions of animals in the forests

Defaunation is the global, local, or functional extinction of animal populations or species from ecological communities. The growth of the human population, combined with advances in harvesting technologies, has led to more intense and efficient exploitation of the environment. This has resulted in the depletion of large vertebrates from ecological communities, creating what has been termed "empty forest". Defaunation differs from extinction; it includes both the disappearance of species and declines in abundance. Defaunation effects were first implied at the Symposium of Plant-Animal Interactions at the University of Campinas, Brazil in 1988 in the context of Neotropical forests. Since then, the term has gained broader usage in conservation biology as a global phenomenon.

<span class="mw-page-title-main">Riparian-zone restoration</span> Ecological restoration of river banks and floodplains

Riparian-zone restoration is the ecological restoration of riparian-zonehabitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies. A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth; the habitats of plant and animal communities along the margins and river banks are called riparian vegetation, characterized by aquatic plants and animals that favor them. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grassland, woodland, wetland or sub-surface features such as water tables. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone.

The effects of climate change in Saskatchewan are now being observed in parts of the province. There is evidence of reduction of biomass in Saskatchewan's boreal forests that is linked by researchers to drought-related water stress stemming from global warming, most likely caused by greenhouse gas emissions. While studies, as early as 1988 have shown that climate change will affect agriculture, whether the effects can be mitigated through adaptations of cultivars, or crops, is less clear. Resiliency of ecosystems may decline with large changes in temperature. The provincial government has responded to the threat of climate change by introducing a plan to reduce carbon emissions, "The Saskatchewan Energy and Climate Change Plan", in June 2007.

<span class="mw-page-title-main">Linear infrastructure intrusions</span>

Linear infrastructure intrusions into natural ecosystems are man-made linear infrastructure such as roads and highways, electric power lines, railway lines, canals, pipelines, firebreaks, and fences. These intrusions cause linear opening through the habitat or breakage in landscape connectivity due to infrastructure creation and maintenance, which is known to have multiple ecological effects in terrestrial and aquatic ecosystems. These effects include habitat loss and fragmentation, spread of invasive alien species, desiccation, windthrow, fires, animal injury and mortality, changes in animal behaviour, pollution, microclimate and vegetation changes, loss of ecosystem services, increased pressures from development, tourism, hunting, garbage disposal, and associated human disturbances. These intrusions, considered crucial infrastructure for economic sectors such as transportation, power, and irrigation, may also have negative social impacts on indigenous and rural people through exposure to novel social and market pressures, loss of land and displacement, and iniquitous distribution of costs and benefits from infrastructure projects. The study of the ecological effects of linear infrastructure intrusions has spawning sub-fields of research such as road ecology and railroad ecology.

In biology, overabundant species refers to an excessive number of individuals and occurs when the normal population density has been exceeded. Increase in animal populations is influenced by a variety of factors, some of which include habitat destruction or augmentation by human activity, the introduction of invasive species and the reintroduction of threatened species to protected reserves.

References

  1. Levin, Simon A. (2009). The Princeton Guide to Ecology . Princeton University Press. p.  780. ISBN   9780691128399.
  2. PORENSKY, LAUREN M.; YOUNG, TRUMAN P. (2013-03-26). "Edge‐Effect Interactions in Fragmented and Patchy Landscapes". Conservation Biology. 27 (3): 509–519. doi:10.1111/cobi.12042. ISSN   0888-8892. PMID   23531018. S2CID   13546312. Archived from the original on 2023-07-31. Retrieved 2022-04-01.
  3. Holway, David A. (February 2005). "Edge effects of an invasive species across a natural ecological boundary". Biological Conservation. 121 (4): 561–567. doi:10.1016/j.biocon.2004.06.005. Archived from the original on 2022-01-20. Retrieved 2022-04-01.
  4. Carrara, Emilia; Arroyo-Rodríguez, Víctor; Vega-Rivera, Jorge H.; Schondube, Jorge E.; de Freitas, Sandra M.; Fahrig, Lenore (April 2015). "Impact of landscape composition and configuration on forest specialist and generalist bird species in the fragmented Lacandona rainforest, Mexico". Biological Conservation. 184: 117–126. doi:10.1016/j.biocon.2015.01.014. Archived from the original on 2022-06-19. Retrieved 2022-04-01.
  5. Smith, T.M.; Smith, R.L. (2009). "Elements of Ecology": 391–411.{{cite journal}}: Cite journal requires |journal= (help)
  6. Wales, Bruce A. (1972). "Vegetation Analysis of North and South Edges in a Mature Oak-Hickory Forest". Ecological Monographs. 42 (4): 451–471. doi:10.2307/1942167. ISSN   0012-9615. JSTOR   1942167. Archived from the original on 2023-02-14. Retrieved 2023-02-14.
  7. Noss, Reed F. (1999-03-22). "Assessing and monitoring forest biodiversity: A suggested framework and indicators". Forest Ecology and Management. 115 (2): 135–146. doi:10.1016/S0378-1127(98)00394-6. ISSN   0378-1127. S2CID   8683460.
  8. Valentine, E.C.; Apol, C.A.; Proppe, D.S. (2019). "Predation on artificial avian nests is higher in forests bordering small anthropogenic openings". Ibis. 161 (3): 662–673. doi:10.1111/ibi.12662. S2CID   91309233.
  9. Murcia, C. (1995). "Edge effects in fragmented forests:implications for conservation" (PDF). Tree. 20 (2): 58–62. doi:10.1016/S0169-5347(00)88977-6. PMID   21236953. Archived from the original on 2023-07-31. Retrieved 2011-12-06.
  10. Skole, D. L.; C. Tucker (1994). "Tropical deforestation and habitat loss fragmentation in the Amazon: satellite data from 1978-1988". Science . 260 (5116): 1905–1910. doi:10.1126/science.260.5116.1905. hdl: 10535/3304 . PMID   17836720. S2CID   12853752.
  11. 1 2 Corlett, Richard, T; Richard B. Primack (2011). Tropical Rain Forests an Ecological and Biogeographical Comparison (Second ed.). John Wiley & Sons Ltd, The atrium, Southern Fate, Chichester, West Sussex, PO19 8SQ: Wiley-Blackwell. pp. 266–267. ISBN   978-1-4443-3254-4.{{cite book}}: CS1 maint: location (link) CS1 maint: multiple names: authors list (link)
  12. Howell, Christine A.; Dijak, William D.; Thompson, Frank R. (2007-02-01). "Landscape context and selection for forest edge by breeding Brown-headed Cowbirds". Landscape Ecology. 22 (2): 273–284. doi:10.1007/s10980-006-9022-1. ISSN   1572-9761. S2CID   2775157. Archived from the original on 2023-07-31. Retrieved 2023-02-14.
  13. Fraver, Shawn (1994). "Vegetation Responses along Edge-to-Interior Gradients in the Mixed Hardwood Forests of the Roanoke River Basin, North Carolina". Conservation Biology. 8 (3): 822–832. doi:10.1046/j.1523-1739.1994.08030822.x. ISSN   1523-1739. Archived from the original on 2021-01-31. Retrieved 2021-01-27.