ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...

, edge effects are changes in

population Population is a set of humans or other organisms in a given region or area. Governments conduct a census to quantify the resident population size within a given jurisdiction. The term is also applied to non-human animals, microorganisms, and pl ...

community A community is a social unit (a group of people) with a shared socially-significant characteristic, such as place, set of norms, culture, religion, values, customs, or identity. Communities may share a sense of place situated in a given g ...

structures that occur at the boundary of two or more

habitat In ecology, habitat refers to the array of resources, 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 ...

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 is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

Urbanization Urbanization (or urbanisation in British English) is the population shift from Rural area, 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. ...

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 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) – 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. Plants that colonize forest edges tend to be shade-intolerant. These plants also tend to be tolerant of dry conditions, such as

shrubs A shrub or 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 by their multiple ...

and vines. 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 whit ...

, elk, cottontail rabbits, blue jays, and robins. Some animals travel between habitats, while edge species are restricted to edges. Larger patches have increased native species biodiversity compared to smaller patches. 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. Within 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 ...

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 Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

, brood parasitism, competition,

herbivory A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

, and biotic

pollination Pollination is the transfer of pollen from an anther of a plant to the stigma (botany), stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or bu ...

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 vectors, ...

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 harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

* Loss 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 proces ...

Deforestation Deforestation or forest clearance is the removal and destruction 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. Ab ...

and land use change

Examples

When edges divide any

natural Nature is an inherent character or constitution, particularly of the ecosphere or the universe as a whole. In this general sense nature refers to the laws, elements and phenomena of the physical world, including life. Although humans are part ...

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 the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...

and

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

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

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

close to the edge and encouraging growth of opportunistic

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

there. Air temperature, vapor pressure deficit,

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 enters ...

, 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 ...

(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 tributary, 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 ...

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 (English in the Commonwealth of Nations, Commonwealth English), also known as underbrush or undergrowth, includes plant life growing beneath the Canopy (biology), forest ca ...

growth. Increased understory

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

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 is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...

. 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 is orders of magnitude greater now in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

than when the Europeans first began settling

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. Some species have benefited from this fact, for example, the brown-headed cowbird, which is a

brood parasite Brood may refer to: Nature * Brood, a collective term for offspring * Brooding, the incubation of bird eggs by their parents * Bee brood, the young of a beehive * Individual broods of North American periodical cicadas: ** Brood X, the largest ...

that lays its eggs in the

nest A nest is a structure built for certain animals to hold Egg (biology), 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 ...

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 5,00 ...

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

poison ivy Poison ivy is a type of allergenic plant in the genus '' Toxicodendron'' native to Asia and North America. Formerly considered a single species, '' Toxicodendron radicans'', poison ivies are now generally treated as a complex of three separate s ...

. Conversely,

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

eat

mosquito Mosquitoes, the Culicidae, are a Family (biology), family of small Diptera, flies consisting of 3,600 species. The word ''mosquito'' (formed by ''Musca (fly), mosca'' and diminutive ''-ito'') is Spanish and Portuguese for ''little fly''. Mos ...

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 ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and spe ...

es, huckleberries, flowering currants and shade-intolerant trees such as the

Douglas-fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is the tallest tree in the Pinaceae family. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Or ...

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. It is invasive species, invasive in ...

, 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 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 ( 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. The edge effect in

scanning electron microscopy A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that ...

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 Environmental terminology Habitat Systems ecology