User:Ktjylee/Ecosystem engineer

Importance

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. 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. 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.

Similar to keystone species, a species of ecosystem engineers does not necessarily always have high abundance. Although their effect is more easily identifiable and more often a species with greater density and large per capita effect, species with smaller abundance can still have great impact. A prime example being Callianassa filholi, an ecosystem engineer with a small population density, but were evaluated to affect the temporal and spatial growth of macrofauna with their burrow structures.

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. 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. 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.

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.

Controversy

However, there is controversy when using the term "ecosystem engineer" to classify a species because it can be perceived as a "buzz word" to the ecological science community. The use of the term "ecosystem engineering" suggested that the species were intentionally and consciously modifying their environment. There's also an argument to say that the ubiquity of ecosystem engineers translates to all species being ecosystem engineers. This would invite more ecological research to be done to delve into the classification of an ecosystem engineer. 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.

Classification

Ecosystem engineers do have their general types, allogenic and autogenic, but further research has suggested that all organisms can fall under specific cases. It was proposed that there were six specific cases. 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

The information in the following table is based off of the research of Jones et. al

Cases of Ecosystem Engineers

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.

Introduced species as ecosystem engineers

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.

The Gordon Dam in Tasmania

Humans as ecosystem engineers

Humans are thought to be one of the most dramatic ecosystem engineers. Niche construction has been prevalent since the earliest days of human activity. 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. Humans also do not fit under a specific case, and are able to mimic autogenic effects as well as implement their own allogenic effects. Air-conditioning is one prime example of the way humans mimic autogenic effects

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. 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.