An ecosystem engineer is any species that creates, significantly modifies, maintains or destroys a habitat. These organisms can have a large impact on species richness and landscape-level heterogeneity of an area. [1] As a result, ecosystem engineers are important for maintaining the health and stability of the environment they are living in. Since all organisms impact the environment they live in one way or another, it has been proposed that the term "ecosystem engineers" be used only for keystone species whose behavior very strongly affects other organisms. [2]
Jones et al. [3] identified two different types of ecosystem engineers:
Allogenic engineers modify the biophysical environment by mechanically changing living or nonliving materials from one form to another. Beavers are the original model for ecosystem engineers; in the process of clearcutting and damming, beavers alter their ecosystem extensively. The addition of a dam will change both the distribution and the abundance of many organisms in the area. [2] Caterpillars are another example in that by creating shelters from leaves, they are also creating shelters for other organisms which may occupy them either simultaneously or subsequently. [4] An additional example may be that of woodpeckers or other birds who create holes in trees for them to nest in. Once these birds are through with them, the holes are used by other species of birds or mammals for housing. [2]
Autogenic engineers modify the environment by modifying themselves. Trees are an example of this; as they grow, their trunks and branches create habitats for other living things, which may include squirrels, birds or insects. In the tropics, lianas connect trees, which allow many animals to travel exclusively through the forest canopy. [5] [ better source needed ]
Being able to identify ecosystem engineers in an environment can be important when looking at the influence these individuals may have over other organisms living in the same environment – especially in terms of resource availability. [6] It's also vital to recognize that ecosystem engineers are not organisms that directly provide others with living or dead tissue. In other words, they are identified as engineers because of their ability to modify resources, not because of their trophic effect. [7] While the impact of ecosystem engineers can be as great as keystone species, they differ in their types of impact. Keystone species are typically essential because of their trophic effect, while ecosystem engineers are not.
As with keystone species, ecosystem engineers are not necessarily abundant. Species with greater density and large per capita effect have a more easily-noticeable effect, but less abundant species can still have a large impact. A prime example is the mud shrimp Filhollianassa filholi , an ecosystem engineer with a small population density, but were affects the temporal and spatial growth of macrofauna with its burrow structures. [8]
The presence of some ecosystem engineers has been linked to higher species richness at the landscape level. By modifying the habitat, organisms like the beaver create more habitat heterogeneity and so can support species not found elsewhere. [1] Thoughts may be that similar to other umbrella species by conserving an ecosystem engineer you may be able to protect the overall diversity of a landscape. [1] Beavers have also been shown to maintain habitats in such a way as to protect the rare Saint Francis' satyr butterfly and increase plant diversity. [9]
Biodiversity may also be affected by ecosystem engineer's ability to increase the complexity of processes within an ecosystem, potentially allowing greater species richness and diversity in the local environments. As an example, beavers have the capacity to modify riparian forest and expand wetland habitats, which results in an increase of the diversity of the habitats by allowing a greater number of species to inhabit the landscape. Coral-reef habitats, created by the ecosystem engineer coral species, hold some of the highest abundances of aquatic species in the world. [10]
There is controversy around the usage of the term "ecosystem engineer" to classify a species, as it can be perceived as a "buzzword" to the ecological science community. The use of the term "ecosystem engineering" might suggest that the species was intentionally and consciously modifying its environment. [11] Another argument postulates that the ubiquity of ecosystem engineers translates to all species being ecosystem engineers. [12] This would invite more ecological research to be done to delve into the classification of an ecosystem engineer. [7] The generality and the specifications of identifying an ecosystem engineer has been the root of the controversy, and now more research is being conducted to definitively classify and categorize species based on their impact as an ecosystem engineer. [7]
Ecosystem engineers do have their general types, allogenic and autogenic, but further research has suggested that all organisms can fall under specific cases. [7] It was proposed that there were six specific cases. [7] These cases were differentiated by the species' ability to transform their resources to different states, as well as their ability to combat abiotic forces. A state refers to the physical condition of a material and a change in state refers to a physical abiotic or biotic material change [7]
Case # | Autogenic or Allogenic | Rationale | Example |
---|---|---|---|
1 | Autogenic | Not considered ecosystem engineering | Any species that are not considered ecosystem engineers. |
2 | Allogenic | Transform resources into usable and/or more beneficial forms | Cows, after eating grass, produce cow pats with their dung and are used by other invertebrates as a food source and a shelter. |
3 | Autogenic | Organism transforms itself from one state to another and affects distribution and/or availability of resources and/or the traits of the physical environment. | Coral and forests grow, which induce developmental change in the environment surrounding them |
4 | Allogenic | Able to transform one material from one state to another | Beavers can take live trees and turn them into dead trees, then utilize those dead trees to build dams that are shelter for other animals and stabilize water flow in arid areas. |
5 | Autogenic | Modulate extreme abiotic forces, which then controls resource flow | Crustose coralline algae break waves and protect coral reefs from immense amounts of water force. |
6 | Allogenic | Species falls under one or more of these cases | Ribbed mussels secrete byssal threads that bind together to protect sediment and prevent erosion. |
Species are able to be transported across all parts of the world by humans or human-made vessels at boundless rates resulting in foreign ecosystem engineers changing the dynamics of species interactions and the possibility for engineering to occur in locations that would not have been accessible by engineers without the mediation by humans.
Introduced species, which may be invasive species, are often ecosystem engineers. Kudzu, a leguminous plant introduced to the southeast U.S., changes the distribution and number of animal and bird species in the areas it invades. It also crowds out native plant species. The zebra mussel is an ecosystem engineer in North America. By providing refuge from predators, it encourages the growth of freshwater invertebrates through increasing microhabitats. Light penetration into infected lakes also improves the ecosystem, resulting in an increase in algae. In contrast to the benefits some ecosystem engineers can cause, invasive species often have the reverse effect.
Humans are thought to be the most dramatic ecosystem engineers. Niche construction has been prevalent since the earliest days of human activity. [13] Through urban development, agricultural practices, logging, damming and mining, humans have changed the way they interact with the environment. This interaction is more studied in the field of human ecology. Considered both as an allogenic and autogenic engineers, humans do not necessarily fit into either category of ecosystem engineers. [7] Humans are able to mimic autogenic effects as well as implement their own allogenic effects. [7] Air-conditioning is one prime example of the way humans mimic autogenic effects [7]
Due to the complexity of many communities and ecosystems, restoration projects are often difficult. Ecosystem engineers have been proposed as a means to restore a given area to its previous state. While ideally these would all be natural agents, with today's level of development some form of human intervention may be necessary as well. In addition to being able to assist in restoration ecology, ecosystem engineers may be a helpful agent in invasive species management. [14] New fields are developing which focus on restoring those ecosystems which have been disrupted or destroyed by human activities as well as developing ecosystems that are sustainable with both human and ecological values. [15]
Besides the previously mentioned beaver acting as an ecosystem engineer, other terrestrial animals do the same. This may be through feeding habits, migration patterns or other behaviors that result in more permanent changes.
Research has suggested primates as ecosystem engineers as a result of their feeding strategies – frugivory and folivory – making them act as seed dispersers. [6] As a whole primates are very abundant and feed on a large quantity of fruit that is then distributed around their territory. Elephants have also been designated ecosystem engineers as they cause very large changes to their environment whether it be through feeding, digging or migratory behavior. [16]
Prairie dogs are another terrestrial form of allogenic ecosystem engineers due to the fact that the species has the ability to perform substantial modifications by burrowing and turning soil. They are able to influence soils and vegetation of the landscape while providing underground corridors for arthropods, avians, other small mammals, and reptiles. This has a positive effect on species richness and diversity of their habitats which results in the prairie dogs being labelled as keystone species. [17]
Arthropods can also be ecosystem engineers, such as spiders, ants, and many types of larvae that create shelters out of leaves, as well as gall-inducing insects that change the shapes of plants. [18] Bark beetles are an ecosystem engineer of forest ecosystems and can affect fire spread and severity when attacking their host pine species. [19]
Not only animals are ecosystem engineers. Fungi are able to connect regions that are distant from one another and translocate nutrients between them. [20] Doing so they create nutritional niches for xylophagous invertebrates, [21] [22] supply trees with nitrogen translocated from previously predated animals [23] or even form an "underground pipeline" that redistributes carbon between trees. [24] Thus fungi are engineers controlling nutrient cycles in ecosystems.
In marine environments, filter feeders and plankton are ecosystem engineers because they alter turbidity and light penetration, controlling the depth at which photosynthesis can occur. [25] This in turn limits the primary productivity of benthic and pelagic habitats [26] and influences consumption patterns between trophic groups. [27]
Another example of ecosystem engineers in marine environments would be scleractinian corals as they create the framework for the habitat most coral-reef organisms depend on. [28] Some ecosystem engineers such as coral have help maintaining their environment. Parrotfish often help maintain coral reefs as they feed on macroalgae that competes with the coral. [29] As this relationship is mutually beneficial, a positive feedback cycle is formed between the two organisms, making them both responsible for creating and maintaining coral reef ecosystems. [29]
Whales are also being increasingly recognised for their role as ecosystem engineers despite the loss of up to 90% of their numbers during the commercial whaling era. [30] Whales defecate at the surface and release nutrients that boost the growth of phytoplankton. As whales migrate across the oceans, and move up and down the water column, they help to spread these nutrients in a process that is known as the "Whale Pump".
Ecology is the natural science of the relationships among living organisms and their environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere levels. Ecology overlaps with the closely related sciences of biogeography, evolutionary biology, genetics, ethology, and natural history.
A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Some keystone species, such as the wolf and lion, are also apex predators.
Urban ecology is the scientific study of the relation of living organisms with each other and their surroundings in an urban environment. An urban environment refers to environments dominated by high-density residential and commercial buildings, paved surfaces, and other urban-related factors that create a unique landscape. The goal of urban ecology is to achieve a balance between human culture and the natural environment.
Ecological succession is the process of change in the species that make up an ecological community over time.
Ecosystem diversity deals with the variations in ecosystems within a geographical location and its overall impact on human existence and the environment.
Niche construction is the ecological process by which an organism alters its own local environment. These alterations can be a physical change to the organism’s environment, or it can encompass the active movement of an organism from one habitat to another where it then experiences different environmental pressures. Examples of niche construction include the building of nests and burrows by animals, the creation of shade, the influencing of wind speed, and alternations to nutrient cycling by plants. Although these modifications are often directly beneficial to the constructor, they are not necessarily always. For example, when organisms dump detritus, they can degrade their own local environments. Within some biological evolutionary frameworks, niche construction can actively beget processes pertaining to ecological inheritance whereby the organism in question “constructs” new or unique ecologic, and perhaps even sociologic environmental realities characterized by specific selective pressures.
Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. Species richness is sometimes considered synonymous with species diversity, but the formal metric species diversity takes into account both species richness and species evenness. Species richness has proven to be a positive representation to show how species interaction in ecosystems can lead to the productivity and growth of biodiversity.
Habitat destruction occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved to elsewhere or are dead, leading to a decrease in biodiversity and species numbers. Habitat destruction is in fact the leading cause of biodiversity loss and species extinction worldwide.
Reconciliation ecology is the branch of ecology which studies ways to encourage biodiversity in the human-dominated ecosystems of the anthropocene era. Michael Rosenzweig first articulated the concept in his book Win-Win Ecology, based on the theory that there is not enough area for all of earth's biodiversity to be saved within designated nature preserves. Therefore, humans should increase biodiversity in human-dominated landscapes. By managing for biodiversity in ways that do not decrease human utility of the system, it is a "win-win" situation for both human use and native biodiversity. The science is based in the ecological foundation of human land-use trends and species-area relationships. It has many benefits beyond protection of biodiversity, and there are numerous examples of it around the globe. Aspects of reconciliation ecology can already be found in management legislation, but there are challenges in both public acceptance and ecological success of reconciliation attempts.
The intermediate disturbance hypothesis (IDH) suggests that local species diversity is maximized when ecological disturbance is neither too rare nor too frequent. At low levels of disturbance, more competitive organisms will push subordinate species to extinction and dominate the ecosystem. At high levels of disturbance, due to frequent forest fires or human impacts like deforestation, all species are at risk of going extinct. According to IDH theory, at intermediate levels of disturbance, diversity is thus maximized because species that thrive at both early and late successional stages can coexist. IDH is a nonequilibrium model used to describe the relationship between disturbance and species diversity. IDH is based on the following premises: First, ecological disturbances have major effects on species richness within the area of disturbance. Second, interspecific competition results in one species driving a competitor to extinction and becoming dominant in the ecosystem. Third, moderate ecological scale disturbances prevent interspecific competition.
In ecology, a community is a group or association of populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, biological community, ecological community, or life assemblage. The term community has a variety of uses. In its simplest form it refers to groups of organisms in a specific place or time, for example, "the fish community of Lake Ontario before industrialization".
Any action or influence that species have on each other is considered a biological interaction. These interactions between species can be considered in several ways. One such way is to depict interactions in the form of a network, which identifies the members and the patterns that connect them. Species interactions are considered primarily in terms of trophic interactions, which depict which species feed on others.
A marine habitat is a habitat that supports marine life. Marine life depends in some way on the saltwater that is in the sea. A habitat is an ecological or environmental area inhabited by one or more living species. The marine environment supports many kinds of these habitats.
Ecological inheritance occurs when an organism's offspring inhabit a modified environment that a previous generation created. Therefore, the selective pressures created from the modifications must remain for the next generation in order for it to be deemed ecological inheritance. It was first described in Odling-Smee (1988) and Odling-Smee et al. (1996) as a consequence of niche construction. Standard evolutionary theory focuses on the influence that natural selection and genetic inheritance has on biological evolution, when individuals that survive and reproduce also transmit genes to their offspring. If offspring do not live in a modified environment created by their parents, then niche construction activities of parents do not affect the selective pressures of their offspring. However, when niche construction affects multiple generations, ecological inheritance acts an inheritance system different than genetic inheritance which is also termed "legacy effects".
Soundscape ecology is the study of the acoustic relationships between living organisms, human and other, and their environment, whether the organisms are marine or terrestrial. First appearing in the Handbook for Acoustic Ecology edited by Barry Truax, in 1978, the term has occasionally been used, sometimes interchangeably, with the term acoustic ecology. Soundscape ecologists also study the relationships between the three basic sources of sound that comprise the soundscape: those generated by organisms are referred to as the biophony; those from non-biological natural categories are classified as the geophony, and those produced by humans, the anthropophony.
A mesophotic coral reef or mesophotic coral ecosystem (MCE), originally from the Latin word meso (meaning middle) and photic (meaning light), is characterized by the presence of both light-dependent coral and algae, and organisms that can be found in water with low light penetration. Mesophotic coral ecosystems occur at depths beyond those typically associated with coral reefs as the mesophotic ranges from brightly lit to some areas where light does not reach. Mesophotic coral ecosystem (MCEs) is a new, widely-adopted term used to refer to mesophotic coral reefs, as opposed to other similar terms like "deep coral reef communities" and "twilight zone", since those terms sometimes are confused due to their unclear, interchangeable nature. Many species of fish and corals are endemic to the MCEs making these ecosystems a crucial component in maintaining global diversity. Recently, there has been increased focus on the MCEs as these reefs are a crucial part of the coral reef systems serving as a potential refuge area for shallow coral reef taxa such as coral and sponges. Advances in recent technologies such as remotely operated underwater vehicles (ROVs) and autonomous underwater vehicles (AUVs) have enabled humans to conduct further research on these ecosystems and monitor these marine environments.
A habitat cascade is a common type of a facilitation cascade. where “indirect positive effects on focal organisms are mediated by successive formation or modification of biogenic habitat”.
An ecosystem, short for ecological system, is defined as a collection of interacting organisms within a biophysical environment. Ecosystems are never static, and are continually subject to both stabilizing and destabilizing processes. Stabilizing processes allow ecosystems to adequately respond to destabilizing changes, or perturbations, in ecological conditions, or to recover from degradation induced by them: yet, if destabilizing processes become strong enough or fast enough to cross a critical threshold within that ecosystem, often described as an ecological 'tipping point', then an ecosystem collapse. occurs.
A marine coastal ecosystem is a marine ecosystem which occurs where the land meets the ocean. Worldwide there is about 620,000 kilometres (390,000 mi) of coastline. Coastal habitats extend to the margins of the continental shelves, occupying about 7 percent of the ocean surface area. Marine coastal ecosystems include many very different types of marine habitats, each with their own characteristics and species composition. They are characterized by high levels of biodiversity and productivity.
A facilitation cascade is a sequence of ecological interactions that occur when a species benefits a second species that in turn has a positive effect on a third species. These facilitative interactions can take the form of amelioration of environmental stress and/or provision of refuge from predation. Autogenic ecosystem engineering species, structural species, habitat-forming species, and foundation species are associated with the most commonly recognized examples of facilitation cascades, sometimes referred to as a habitat cascades. Facilitation generally is a much broader concept that includes all forms of positive interactions including pollination, seed dispersal, and co-evolved commensalism and mutualistic relationships, such as between cnidarian hosts and Symbiodinium in corals, and between algae and fungi in lichens. As such, facilitation cascades are widespread through all of the earth's major biomes with consistently positive effects on the abundance and biodiversity of associated organisms.