ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overl ...

, edge effects are changes in

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...

community A community is a social unit (a group of living things) with commonality such as place, norms, religion, values, customs, or identity. Communities may share a sense of place situated in a given geographical area (e.g. a country, village, t ...

structures that occur at the boundary of two or more

habitat In ecology, the term habitat summarises 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 ...

s. 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 Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') ...

Urbanization Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly th ...

is causing humans to continuously fragment landscapes and thus increase the edge effect. This change in

landscape ecology 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 organizatio ...

is proving to have consequences. Generalist species, especially invasive ones, have been seen to benefit from this landscape change whilst specialist species are suffering. For example, the

alpha diversity In ecology, alpha diversity (α-diversity) is the mean species diversity in a site at a local scale. The term was introduced by R. H. WhittakerWhittaker, R. H. (1960) Vegetation of the Siskiyou Mountains, Oregon and California. Ecological Monograp ...

of edge-intolerant birds in Lacandona rainforest, Mexico, is decreasing as edge effects increase.

Types

* 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 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 (the zone between a field and forest) or regional (the transition between forest and gras ...

) – 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 non-linear. * Perforated – The border has gaps that host other habitats. Height can create borders between patches as well.

Biodiversity

Environmental conditions enable certain species of plants and animals to colonize habitat

borders A border is a geographical boundary. Border, borders, The Border or The Borders may also refer to: Arts, entertainment and media Film and television * ''Border'' (1997 film), an Indian Hindi-language war film * ''Border'' (2018 Swedish film), ...

. Plants that colonize tend to be

shade-intolerant In ecology, shade tolerance is a plant's ability to tolerate low light levels. The term is also used in horticulture and landscaping, although in this context its use is sometimes imprecise, especially in labeling of plants for sale in commercial ...

and tolerant of dry conditions, such as

shrubs A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

and

vines A vine (Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth Habit (biology), habit of trailing or wikt:scandent, scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to ...

. Animals that colonize tend to be those that require two or more habitats, such as white-tailed and

mule deer The mule deer (''Odocoileus hemionus'') is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. Two subspecies of mule deer are grouped into the black-tailed deer. Unlike the related whi ...

, elk, cottontail rabbits, blue jays, and robins. Some animals travel between habitats, while edge species are restricted to edges. Larger patches include more individuals and therefore have increased biodiversity. 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 In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through ...

. 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 The trophic level of an organism is the position it occupies in a food web. A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it ...

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 In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them under ...

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 Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

brood parasitism Brood parasites are animals that rely on others to raise their young. The strategy appears among birds, insects and fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its ow ...

, competition,

herbivory A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

, and biotic

pollination Pollination is the transfer of pollen from an Stamen, anther of a plant to the stigma (botany), stigma of a plant, later enabling fertilisation and the production of seeds, most often by an animal or by Anemophily, wind. Pollinating agents can ...

and

seed dispersal In Spermatophyte plants, seed dispersal is the movement, spread or transport of seeds away from the parent plant. Plants have limited mobility and rely upon a variety of dispersal vectors to transport their seeds, including both abiotic vector ...

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 invasives/exotics * Higher severity and frequency of fires * Companion animals (pets) acting as predators and competitors * Trails *

Pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, th ...

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...

Loss Loss may refer to: Arts, entertainment, and media Music * ''Loss'' (Bass Communion album) (2006) * ''Loss'' (Mull Historical Society album) (2001) *"Loss", a song by God Is an Astronaut from their self-titled album (2008) * Losses "(Lil Tjay son ...

of foraging habitats *

Habitat 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 process ...

Deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...

and land use change

Examples

When edges divide any

natural Nature, in the broadest sense, is the physical world or universe. "Nature" can refer to the phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. Although humans ar ...

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 Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when ...

and

wind Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ...

penetrate to a much greater extent, drying out the interior of the

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

close to the edge and encouraging growth of opportunistic

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

there. Air temperature,

vapor pressure deficit Vapour-pressure deficit, or VPD, is the difference (deficit) between the amount of moisture in the air and how much moisture the air can hold when it is saturated. Once air becomes saturated, water will condense out to form clouds, dew or films o ...

soil moisture Soil moisture is the water content of the soil. It can be expressed in terms of volume or weight. Soil moisture measurement can be based on ''in situ'' probes (e.g., capacitance probes, neutron probes) or remote sensing methods. Water that enter ...

, light intensity and levels of

photosynthetically active radiation Photosynthetically active radiation (PAR) designates the spectral range (wave band) of solar radiation from 400 to 700 nanometers that photosynthetic organisms are able to use in the process of photosynthesis. This spectral region corresponds more o ...

(PAR) all change at edges.

Amazon rainforest

One study estimated that the amount of

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Boli ...

area modified by edge effects exceeded the area that had been cleared. "In studies of Amazon forest fragments, micro-climate effects were evident up to 100m (330ft.) into the forest interior." 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 In forestry and ecology, understory (American English), or understorey (Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the forest canopy without penetrating it to any great extent, but abo ...

growth. Increased understory

biomass Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bio ...

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 An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...

. The overall effect of these fragment processes is that all forest fragments tend to lose native

depending on fragment size and shape, isolation from other forest areas, and the forest matrix.

North America

The amount of

forest edge A woodland edge or forest edge is the transition zone (ecotone) from an area of woodland or forest to fields or other open spaces. Certain species of plants and animals are adapted to the forest edge, and these species are often more familiar to hu ...

is orders of magnitude greater now in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

than when the Europeans first began settling

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

. Some species have benefited from this fact, for example, the

brown-headed cowbird The brown-headed cowbird (''Molothrus ater'') is a small, obligate brood parasitic icterid native to temperate and subtropical North America. It is a permanent resident in the southern parts of its range; northern birds migrate to the southern ...

, which is a

brood parasite Brood parasites are animals that rely on others to raise their young. The strategy appears among birds, insects and fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were it ...

that lays its eggs in the

nest A nest is a structure built for certain animals to hold eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of organic materi ...

s of

songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...

s nesting in forest near the forest boundary. Another example of a species benefiting from the proliferation of forest edge is poison ivy. Conversely,

Dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threa ...

eat

mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...

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 Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...

es,

huckleberries Huckleberry is a name used in North America for several plants in the family Ericaceae, in two closely related genera: ''Vaccinium'' and ''Gaylussacia''. The huckleberry is the state fruit of Idaho. Nomenclature The name 'huckleberry' is a Nort ...

, flowering currants and

trees such as the

Douglas-fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Oregon pine, and Columbian pine. There are three va ...

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 Kudzu (; also called Japanese arrowroot or Chinese arrowroot) is a group of climbing, coiling, and trailing deciduous perennial vines native to much of East Asia, Southeast Asia, and some Pacific islands, but invasive in many parts of the wor ...

Japanese honeysuckle ''Lonicera japonica'', known as Japanese honeysuckle and golden-and-silver honeysuckle, is a species of honeysuckle native to eastern Asia. It is often grown as an ornamental plant, but has become an invasive species in a number of countries. Jap ...

and

multiflora rose ''Rosa multiflora'' — (syn. ''Rosa polyantha'') is a species of rose known commonly as multiflora rose, baby rose, Japanese rose, many-flowered rose, seven-sisters rose, Eijitsu rose and rambler rose. It is native to eastern Asia, in China, J ...

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 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 Succession is the act or process of following in order or sequence. Governance and politics *Order of succession, in politics, the ascension to power by one ruler, official, or monarch after the death, resignation, or removal from office of ...

, 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 (

) 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 An assay is an investigative (analytic) procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of a ...

s refer to artifacts in data that are caused by the position of the wells on a screening plate rather than a biological effect. 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.

References

External links

Reducing Edge Effects in biological assays
{{DEFAULTSORT:Edge Effect Landscape ecology Ecological succession Habitats Ecology terminology Biology terminology Environmental terminology Habitat Systems ecology