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 processes that slowly alter the layout of the physical environment[1] (suspected of being one of the major causes of speciation[1]),and human activity such as land conversion, which can alter the environment much faster and causes the extinction of many species.

Amazonie deforestation
Deforestation and increased road-building in the Amazon Rainforest are a significant concern because of increased human encroachment upon wild areas, increased resource-extraction and further threats to biodiversity.
Grasp africa
Fragmentation and destruction of Great Ape habitat in Central Africa, from the GLOBIO and GRASP projects. Areas shown in black and red delineate areas of severe and moderate habitat loss, respectively.


The term habitat fragmentation includes five discrete phenomena:

  • Reduction in the total area of the habitat
  • Decrease of the interior: edge ratio
  • Isolation of one habitat fragment from other areas of habitat
  • Breaking up of one patch of habitat into several smaller patches
  • Decrease in the average size of each patch of habitat

"fragmentation ... not only causes loss of the amount of habitat, but by creating small, isolated patches it also changes the properties of the remaining habitat" (van den Berg et al. 2001). Habitat fragmentation is the landscape level of the phenomenon, and patch level process. Thus meaning, it covers; the patch areas, edge effects, and patch shape complexity.[2]

In scientific literature, there is some debate whether the term "habitat fragmentation" applies in cases of habitat loss, or whether the term primarily applies to the phenomenon of habitat being cut into smaller pieces without significant reduction in habitat area. Scientists who use the stricter definition of "habitat fragmentation" per se[3] would refer to loss of habitat area as "habitat loss" and explicitly mention both terms if describing a situation where the habitat becomes less connected and there is less overall habitat.


Natural causes

Evidence of habitat destruction through natural processes such as volcanism, fire, and climate change is found in the fossil record.[1] For example, habitat fragmentation of tropical rainforests in Euramerica 300 million years ago led to a great loss of amphibian diversity, but simultaneously the drier climate spurred on a burst of diversity among reptiles.[1]

Human causes

Habitat fragmentation is frequently caused by humans when native plants is cleared for human activities such as agriculture, rural development, urbanization and the creation of hydroelectric reservoirs. Habitats which were once continuous become divided into separate fragments. After intensive clearing, the separate fragments tend to be very small islands isolated from each other by cropland, pasture, pavement, or even barren land. The latter is often the result of slash and burn farming in tropical forests. In the wheat belt of central western New South Wales, Australia, 90% of the native vegetation has been cleared and over 99% of the tall grass prairie of North America has been cleared, resulting in extreme habitat fragmentation.

Endogenous vs. exogenous

There are two types of processes that can lead to habitat fragmentation. There are exogenous processes and endogenous processes. Endogenous are process that develop as a part of a species biology so they typically include changes in biology, behavior and interactions within or between species. Endogenous threats can result in changes to breeding patterns or migration patterns and are often triggered by exogenous processes. Exogenous processes are independent of species biology and can include habitat degradation, habitat subdivision or habitat isolation. These processes can have a substantial impact on endogenous processes by fundamentally altering species behavior. Habitat subdivision or isolation can lead to changes in dispersal or movement of species including changes to seasonal migration. These changes can lead to decrease in a density of species, increased competition or even increased predation.[4]


Habitat Loss and Biodiversity

One of the major ways that habitat fragmentation affects biodiversity is by reducing the amount of suitable habitat available for organisms. Habitat fragmentation often involves both habitat destruction and the subdivision of previously continuous habitat.[5] Plants and other sessile organisms are disproportionately affected by some types of habitat fragmentation because they cannot respond quickly to the altered spatial configuration of the habitat.[6]

Habitat loss, which can occur through the process of habitat fragmentation, is considered to be the greatest threat to species.[7] But, the effect of the configuration of habitat patches within the landscape, independent of the effect of the amount of habitat within the landscape (referred to as fragmentation per se[3]), has been suggested to be small.[8] A review of empirical studies found that, of the 381 reported significant effect of habitat fragmentation per se on species occurrences, abundances or diversity in the scientific literature, 76% were positive whereas 24% were negative.[9] Despite these results, the scientific literature tends to emphasize negative effects more than positive effects.[10] Positive effects of habitat fragmentation per se imply that several small patches of habitat can have higher conservation value than a single large patch of equivalent size.[9] Land sharing strategies could therefore have more positive impacts on species than land sparing strategies.[9]

Indiana Dunes Habitat Fragmentation
Habitat fragmented by numerous roads near the Indiana Dunes National Lakeshore.

Area is the primary determinant of the number of species in a fragment[11] and the relative contributions of demographic and genetic processes to the risk of global population extinction depend on habitat configuration, stochastic environmental variation and species features.[12] Minor fluctuations in climate, resources, or other factors that would be unremarkable and quickly corrected in large populations can be catastrophic in small, isolated populations. Thus fragmentation of habitat is an important cause of species extinction.[11] Population dynamics of subdivided populations tend to vary asynchronously. In an unfragmented landscape a declining population can be "rescued" by immigration from a nearby expanding population. In fragmented landscapes, the distance between fragments may prevent this from happening. Additionally, unoccupied fragments of habitat that are separated from a source of immigrants by some barrier are less likely to be repopulated than adjoining fragments. Even small species such as the Columbia spotted frog are reliant on the rescue effect. Studies showed 25% of juveniles travel a distance over 200m compared to 4% of adults. Of these, 95% remain in their new locale, demonstrating that this journey is necessary for survival.[13]

Additionally, habitat fragmentation leads to edge effects. Microclimatic changes in light, temperature and wind can alter the ecology around the fragment, and in the interior and exterior portions of the fragment. Fires become more likely in the area as humidity drops and temperature and wind levels rise. Exotic and pest species may establish themselves easily in such disturbed environments, and the proximity of domestic animals often upsets the natural ecology. Also, habitat along the edge of a fragment has a different climate and favours different species from the interior habitat. Small fragments are therefore unfavourable for species which require interior habitat. The percentage preservation of contiguous habitats is closely related to both genetic and species biodiversity preservation. Generally a 10% remnant contiguous habitat will result in a 50% biodiversity loss.[14]

Informed Conservation

Habitat fragmentation is often a cause of species becoming threatened or endangered. The existence of viable habitat is critical to the survival of any species, and in many cases the fragmentation of any remaining habitat can lead to difficult decisions for conservation biologists. Given a limited amount of resources available for conservation is it preferable to protect the existing isolated patches of habitat or to buy back land to get the largest possible continuous piece of land. In rare cases a conservation reliant species may gain some measure of disease protection by being distributed in isolated habitats. This ongoing debate is often referred to as SLOSS (Single Large or Several Small).

One solution to the problem of habitat fragmentation is to link the fragments by preserving or planting corridors of native vegetation. In some cases, a bridge or underpass may be enough to join two fragments.[15] This has the potential to mitigate the problem of isolation but not the loss of interior habitat.

Another mitigation measure is the enlargement of small remnants in order to increase the amount of interior habitat. This may be impractical since developed land is often more expensive and could require significant time and effort to restore.

The best solution is generally dependent on the particular species or ecosystem that is being considered. More mobile species, like most birds, do not need connected habitat while some smaller animals, like rodents, may be more exposed to predation in open land. These questions generally fall under the headings of metapopulations island biogeography.

Genetic Risks

As the remaining habitat patches are smaller, they tend to support smaller populations of fewer species.[16] Small populations are at an increased risk of a variety of genetic consequences that influence their long-term survival.[17] Remnant populations often contain only a subset of the genetic diversity found in the previously continuous habitat. Processes that act upon underlying genetic diversity such as adaptation have a smaller pool of fitness-maintaining alleles to survive in the face of environmental change.

Gene Flow and Inbreeding

Gene flow occurs when individuals of the same species exchange genetic information through reproduction. Populations can maintain genetic diversity through migration. When a habitat becomes fragmented and reduced in area, gene flow and migration is typically reduced. Fewer individuals will migrate into the remaining fragments, and small disconnected populations that may have once been part of a single large population will become reproductively isolated. Scientific evidence that gene flow is reduced due to fragmentation depends on the study species. While trees that have long-range pollination and dispersal mechanisms may not experience reduced gene flow following fragmentation,[18] most species are at risk of reduced gene flow following habitat fragmentation.[6]

Reduced gene flow, and reproductive isolation can result in inbreeding between related individuals. Inbreeding does not always result in negative fitness consequences, but when inbreeding is associated with fitness reduction it is called inbreeding depression. Inbreeding becomes of increasing concern as the level of homozygosity increases, facilitating the expression of deleterious alleles that reduce the fitness. Habitat fragmentation can lead to inbreeding depression for many species due to reduced gene flow.[19][20] Inbreeding depression is associated with conservation risks, like local extinction.

Genetic Drift

Small populations are more susceptible to genetic drift. Genetic drift is random changes to the genetic make up of populations and always leads to reductions in genetic diversity. The smaller the population is, the more likely genetic drift will be a driving force of evolution rather than natural selection. Because genetic drift is a random process, it does not allow species to become more adapted to their environment. Habitat fragmentation is associated with increases to genetic drift in small populations which can have negative consequences for the genetic diversity of the populations.[19]


In order for populations to evolve in response to natural selection, they must be large enough that natural selection is a stronger evolutionary force than genetic drift. Recent studies on the impacts of habitat fragmentation on adaptation in some plant species have suggested that organisms in fragmented landscapes may be able to adapt to fragmentation.[21][22] However, there are also many cases where fragmentation reduces adaptation capacity because of small population size.[23]

Examples of Impacted Species

Some species that have experienced genetic consequences due to habitat fragmentation are listed below:

Macquarie perch
Macquarie perch
  • Macquaria australasica [24][25]
  • Fagus sylvatica [26]
  • Rhinella ornata [27]
  • Ochotona princeps[28]
  • Uta stansburiana[29]
  • Plestiodon skiltonianus[29]
  • Sceloporus occidentalis[29]
  • Chamaea fasciata[29]

Effect on Animal Behaviours

Although the way habitat fragmentation affects the genetics and extinction rates of species has been heavily studied, fragmentation has also been shown to affect species' behaviours and cultures as well. This is important because social interactions have the ability to determine and have an effect on a species' fitness and survival. Habitat fragmentation alters the resources available and the structure of habitats, as a result alters the behaviours of species and the dynamics between differing species. Behaviours affected can be within a species such as reproduction, mating, foraging, species dispersal, communication and movement patterns or can be behaviours between species such as predator prey relationships.[30]

Predation Behaviours

Habitat fragmentation due to anthropogenic activities has been shown to greatly affect the predator-prey dynamics of many species by altering the amount of species and the members of those species.[30] This affects the natural predator-prey relationships between animals in a given community [30] and forces them to alter their behaviours and interactions, therefore resetting the so called "behavioral space race".[31] The way in which fragmentation changes and re-shapes these interactions can occur in many different forms. Most prey species have patches of land that are refuge from their predators, allowing them the safety to reproduce and raise their young. Human introduced structures such as roads and pipelines alter these areas by facilitating predator activity in these refuges, increasing predator-prey overlap.[31] The opposite could also occur in the favour of prey, increasing prey refuge and subsequently decreasing predation rates. Fragmentation may also increase predator abundance or predator efficiency and therefore increase predation rates in this manner.[31] Several other factors can also increase or decrease the extent to which the shifting predator-prey dynamics affect certain species, including how diverse a predators diet is and how flexible habitat requirements are for predators and prey.[30] Depending on which species are affected and these other factors, fragmentation and its resulting effects on predator-prey dynamics may contribute to a species extinction.[30] In response to these new environmental pressures, new adaptive behaviours may be developed. Prey species may adapt to increased risk of predation with strategies such as altering mating tactics or changing behaviours and activities related to food and foraging.[30]

In the boreal woodland caribous of British Columbia the effects of fragmentation are clearly demonstrated. The species refuge area is peatland bog which has been interrupted by linear features such as roads and pipelines.[32] These features have allowed their natural predators, the wolf and the black bear to more efficiently travel over landscapes and between patches of land.[32] Since their predators can more easily access the caribous' refuge, the females of the species attempt to avoid the area, affecting their reproductive behaviours and offspring produced.[32]

Communication Behaviours

Fragmentation affecting the communication behaviours of birds has been well studied in Dupont's Lark. The Larks primarily reside in regions of Spain and are a small passerine bird which use songs as a means of cultural transmission between members of the species.[32] The Larks have two distinct vocalizations, the song and the territorial call. The territorial call is used by males to defend and signal territory from other male Larks and is shared between neighbouring territories when males respond to a rivals song.[33] Occasionally it is used as a threat signal to signify an impending attack on territory.[34] A large song repertoire can enhance a males ability to survive and reproduce as he has a greater ability to defend his territory from other males, and a larger number of males in the species means a larger variety of songs being transmitted.[33] Fragmentation of the Dupont's Lark territory from agriculture, forestry and urbanization appears to have a large effect on their communication structures.[34] Males only perceive territories of a certain distance to be rivals and so isolation of territory from others due to fragmentation leads to a decrease in territorial calls as the males no longer have any reason to use it or have any songs to match.[34]

Forest fragmentation

Forest fragmentation is a form of habitat fragmentation where forests are reduced (either naturally or man-made) to relatively small, isolated patches of forest known as forest fragments or forest remnants.[1] The intervening matrix that separates the remaining woodland patches can be natural open areas, farmland, or developed areas. Following the principles of island biogeography, remnant woodlands act like islands of forest in a sea of pastures, fields, subdivisions, shopping malls, etc. These fragments will then begin to undergo the process of ecosystem decay.

Forest fragmentation also includes less subtle forms of discontinuities such as utility right-of-ways (ROWs). Utility ROWs are of ecological interest because they have become pervasive in many forest communities, spanning areas as large as 5 million acres in the United States.[35] Utility ROWs include electricity transmission ROWs, gas pipeline and telecommunication ROWs. Electricity transmission ROWs are created to prevent vegetation interference with transmission lines. Some studies have shown that electricity transmission ROWs harbor more plant species than adjoining forest areas,[36] due to alterations in the microclimate in and around the corridor. Discontinuities in forest areas associated with utility right-of-ways can serve as biodiversity havens for native bees [35] and grassland species,[37] as the right-of-ways are preserved in an early successional stage.


Forest fragmentation is one of the greatest threats to biodiversity in forests, especially in the tropics.[38] The problem of habitat destruction that caused the fragmentation in the first place is compounded by:

  • the inability of individual forest fragments to support viable populations, especially of large vertebrates
  • the local extinction of species that do not have at least one fragment capable of supporting a viable population
  • edge effects that alter the conditions of the outer areas of the fragment, greatly reducing the amount of true forest interior habitat.[39]

The effect of fragmentation on the flora and fauna of a forest patch depends on a) the size of the patch, and b) its degree of isolation. Isolation depends on the distance to the nearest similar patch, and the contrast with the surrounding areas. For example, if a cleared area is reforested or allowed to regenerate, the increasing structural diversity of the vegetation will lessen the isolation of the forest fragments. However, when formerly forested lands are converted permanently to pastures, agricultural fields, or human-inhabited developed areas, the remaining forest fragments, and the biota within them, are often highly isolated.

Forest patches that are smaller or more isolated will lose species faster than those that are larger or less isolated. A large number of small forest "islands" typically cannot support the same biodiversity that a single contiguous forest would hold, even if their combined area is much greater than the single forest. However, forest islands in rural landscapes greatly increase their biodiversity.[40]

Approaches to understanding habitat fragmentation

Two approaches that are typically used to understand habitat fragmentation and its ecological impacts.

Species-oriented approach

The species-oriented approach focuses specifically on individual species and how they each respond to their environment and habitat changes with in it. This approach can be limited because it does only focus on individual species and does not allow for a broad view of the impacts of habitat fragmentation across species.[41]

Pattern-oriented approach

The pattern-oriented approach is based on land cover and its patterning in correlation with species occurrences. One model of study for landscape patterning is the patch-matrix-corridor model developed by Richard Forman The pattern-oriented approach focuses on land cover defined by human means and activities. This model has stemmed from island biogeography and tries to infer causal relationships between the defined landscapes and the occurrence of species or groups of species within them. The approach has limitations in its collective assumptions across species or landscapes which may not account for variations amongst them.[42]

Variegation Model

The other model is the variegation model. Variegated landscapes retain much of their natural vegetation but are intermixed with gradients of modified habitat [43] This model of habitat fragmentation typically applies to landscapes that are modified by agriculture. In contrast to the fragmentation model that is denoted by isolated patches of habitat surrounded by unsuitable landscape environments, the variegation model applies to landscapes modified by agriculture where small patches of habitat remain near the remnant original habitat. In between these patches are a matrix of grassland that are often modified versions of the original habitat. These areas do not present as much of a barrier to native species.[44]

See also


  • Lindenmayer D.B & Fischer J (2013) Habitat Fragmentation and Landscape Change: An Ecological and Conservation Synthesis (Island Press)


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External links

Agile gibbon

The agile gibbon (Hylobates agilis), also known as the black-handed gibbon, is an Old World primate in the gibbon family. It is found in Indonesia on the island of Sumatra, Malaysia, and southern Thailand. The species is listed as endangered on the IUCN Red List due to habitat destruction and the pet trade.

Alabama waterdog

The Alabama waterdog (Necturus alabamensis) is a medium-sized perennibranch salamander inhabiting rivers and streams of Alabama. It is listed as endangered by the IUCN and the United States Fish and Wildlife Service.

Andean mountain cat

The Andean mountain cat (Leopardus jacobita) is a small wild cat native to the high Andes that has been classified as Endangered by IUCN because fewer than 2,500 individuals are thought to exist in the wild.It was first described by Emilio Cornalia who named it in honour of Jacobita Mantegazza. It is one of only two cat species for which no subspecies has been described.

Angonoka tortoise

The angonoka tortoise (Astrochelys yniphora) is a critically endangered species of tortoise endemic to Madagascar. It is also known as the angonoka, ploughshare tortoise, Madagascar tortoise, or Madagascar angulated tortoise.

Chalkhill blue

The chalkhill blue (Polyommatus coridon) is a butterfly in the family Lycaenidae.

Common box turtle

The common box turtle (Terrapene carolina) is a species of box turtle with six existing subspecies. It is found throughout the Eastern United States and Mexico. The box turtle has a distinctive hinged lowered shell (the box) that allows it to completely enclose itself. Its upper jaw is long and curved.

The turtle is primarily terrestrial and eats a wide variety of plants and animals. The females lay their eggs in the summer. Turtles in the northern part of their range hibernate over the winter.

Common box turtle numbers are declining because of habitat loss, roadkill, and capture for the pet trade. The species is classified as Vulnerable to threats to its survival by the IUCN Red List. Three U.S. states name subspecies of the common box turtle as their official reptile.

Disjunct distribution

In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a species range.

Ecoregion conservation status

Conservation status of the Global 200 ecoregions is used to classify ecoregions into one of three broad categories: "critical/endangered",

"vulnerable", or "relatively stable/relatively intact".

The conservation status of terrestrial ecoregions is noted : CE for critical or endangered, V for vulnerable, and RS for relatively stable or intact.

Ecoregions vary in their biological particularities, as well as in their conservation status. This latter represents an estimation of the current and future ability of the ecoregion to sustain ecological viability and to react to environmental changes.

Conservation status was based on landscape (or equivalent for freshwater and marine ecoregions), such as total habitat loss, habitat fragmentation, degree of degradation, degree of protection needed, degree of urgency for conservation needs, and types of conservation practiced or required.

The Global 200 ecoregions list can mostly help conservation at regional scale (local deforestation, destruction of swamps habitats, degradation of soils...). However, certain phenomena (such as bird or cetaceans migration) obviously depend on more complicated parameters not used in defining the current database (such as atmospheric currents, dynamic pelagic ecosystem...). These would require further gathering of information, and require coordination of efforts between several ecoregions. However, Global 200 ecoregions can help these efforts by identifying habitat sites and resting sites for migratory animals. It may also help identify the origin of invasive species, and offer leverage for slowing down or stopping the intrusion and settling of the latter.

Extinction threshold

Extinction threshold is a term used in conservation biology to explain the point at which a species, population or metapopulation, experiences an abrupt change in density or number because of an important parameter, such as habitat loss. It is at this critical value below which a species, population, or metapopulation, will go extinct, though this may take a long time for species just below the critical value, a phenomenon known as extinction debt.Extinction thresholds are important to conservation biologists when studying a species in a population or metapopulation context because the colonization rate must be larger than the extinction rate, otherwise the entire entity will go extinct once it reaches the threshold.Extinction thresholds are realized under a number of circumstances and the point in modeling them is to define the conditions that lead a population to extinction. Modeling extinction thresholds can explain the relationship between extinction threshold and habitat loss and habitat fragmentation.

Florida panther

The Florida panther is a North American cougar P. c. couguar population. In South Florida, it lives in pinelands, hardwood hammocks, and mixed swamp forests.

Males can weigh up to 160 lb (73 kg) and live within a range that includes the Big Cypress National Preserve, Everglades National Park, the Florida Panther National Wildlife Refuge, Picayune Strand State Forest, rural communities of Collier County, Florida including Golden Gate Estates, Hendry County, Florida, Lee County, Florida, Miami-Dade County, Florida, and Monroe County, Florida. This population, the only unequivocal cougar representative in the eastern United States, currently occupies 5% of its historic range. In the 1970s, an estimated 20 Florida panthers remained in the wild, but their numbers had increased to an estimated 230 by 2017.In 1982, the Florida panther was chosen as the Florida state animal.It was formerly classified as a distinct puma subspecies (Puma concolor coryi).

Golden mantella

The golden mantella (Mantella aurantiaca) is a small, terrestrial frog endemic to Madagascar. It has an extremely restricted distribution in three distinct areas centered on the town of Moramanga - Beparasy and Ambohibary Communes, Torotorofotsy Wetland northwest of Andasibe, and in the area of Ambakoana. Mantella aurantiaca is one of Madagascar's most threatened amphibian species due to its limited distribution in an area under tremendous anthropogenic pressure. It may also be threatened by over-collection for the pet trade.

Gray-shanked douc

The grey-shanked douc langur (Pygathrix cinerea) is a douc species native to the Vietnamese provinces of Quảng Nam, Quảng Ngãi, Bình Định, Kon Tum, and Gia Lai. The total population is estimated at 550 to 700 individuals. In 2016, Dr Benjamin Rawson, Country Director of Fauna & Flora International - Vietnam Programme, announced a discovery of an additional population of more than 500 individuals found in Central Vietnam, bringing the total population up to approximately 1000 individuals.

Ground pangolin

The ground pangolin (Smutsia temminckii), also known as Temminck's pangolin or Cape pangolin, is one of four species of pangolins which can be found in Africa, and the only one in southern and eastern Africa. The animal was named for the Dutch zoologist Coenraad Jacob Temminck. As a group, pangolins are among the most critically endangered animals in the world.


The Holarctic is the name for the biogeographic realm that encompasses the majority of habitats found throughout the northern continents of the world, combining Wallace's Palearctic zoogeographical region, consisting of North Africa and all of Eurasia (with the exception of the southern Arabian Peninsula, Southeast Asia, and the Indian subcontinent), and the Nearctic zoogeographical region, consisting of North America, north of Mexico. These regions are further subdivided into a variety of ecoregions. Many ecosystems, and the animal and plant communities that depend on them, are found across multiple continents in large portions of this realm. The continuity of these ecosystems results from the shared glacial history of the realm. The floristic Boreal Kingdom corresponds to the Holarctic realm.

Population fragmentation

Population fragmentation is a form of population segregation. It is often caused by habitat fragmentation.

Prehensile-tailed hutia

The prehensile-tailed hutia (Mysateles prehensilis) is a species of rodent in the family Capromyidae endemic to Cuba. It is an arboreal foliovore, found in both primary and secondary forest. Its karyotype has 2n = 34 and FN = 54-56.The species is listed as Near threatened on the IUCN Red List. Although locally common in some areas, it is in decline and is threatened by deforestation and habitat fragmentation.

Road ecology

Road ecology is the study of the ecological effects (both positive and negative) of roads and highways (public roads). These effects may include local effects, such as on noise, water pollution, habitat destruction/disturbance and local air quality; and wider effects such as habitat fragmentation, ecosystem degradation, and climate change from vehicle emissions.

The design, construction and management of roads, parking and other related facilities as well as the design and regulation of vehicles can change their effect. Roads are known to cause significant damage to forests, prairies, streams and wetlands. Besides the direct habitat loss due to the road itself, and the roadkill of animal species, roads alter water-flow patterns, increase noise, water, and air pollution, create disturbance that alters the species composition of nearby vegetation thereby reducing habitat for local native animals, and act as barriers to animal movements. Roads are a form of linear infrastructure intrusion that has some effects similar to infrastructure such as railroads, power lines, and canals, particularly in tropical forests.Road ecology is practiced as a field of inquiry by a variety of ecologists, biologists, hydrologists, engineers, and other scientists. There are several global centers for the study of road ecology: 1) The Road Ecology Center at the University of California, Davis, which was the first of its kind in the world; 2) the Centro Brasileiro de Estudos em Ecologia de Estradas at the Federal University of Lavras, Brazil; 3) The Center for Transportation and the Environment, North Carolina State University; and 4) the Road Ecology Program at the Western Transportation Institute, Montana State University. There are also several important global conferences for road ecology research: 1) Infra-Eco Network Europe (IENE), which is international, but focused primarily on Europe; 2) International Conference on Ecology and Transportation (ICOET), which is also global in scope, but primarily focused on the US; 3) Australasian Network for Ecology & Transportation (ANET), which focuses on the Australasian (sub)continent; and 4) a potential Southern African road ecology conference, being considered by the Endangered Wildlife Trust.

Wildlife corridor

A wildlife corridor, habitat corridor, or green corridor is an area of habitat connecting wildlife populations separated by human activities or structures (such as roads, development, or logging). This allows an exchange of individuals between populations, which may help prevent the negative effects of inbreeding and reduced genetic diversity (via genetic drift) 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 (such as fires or disease).

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 use all of the resources they need to survive. Habitat fragmentation due to human development is an ever-increasing threat to biodiversity, and habitat corridors are a possible mitigation.

Wildlife crossing

Wildlife crossings are structures that allow animals to cross human-made barriers safely. Wildlife crossings may include: underpass tunnels, viaducts, and overpasses (mainly for large or herd-type animals); amphibian tunnels; fish ladders; Canopy bridge (especially for monkeys and squirrels), tunnels and culverts (for small mammals such as otters, hedgehogs, and badgers); green roofs (for butterflies and birds).Wildlife crossings are a practice in habitat conservation, allowing connections or reconnections between habitats, combating habitat fragmentation. They also assist in avoiding collisions between vehicles and animals, which in addition to killing or injuring wildlife may cause injury to humans and property damage.

Similar structures can be used for domesticated animals, such as cattle creeps.

Food webs
Example webs
Ecology: Modelling ecosystems: Other components

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