Ecosystem engineer
An ecosystem engineer is any
Types
Jones et al.[3] identified two different types of ecosystem engineers:
Allogenic engineers
Allogenic engineers modify the
Autogenic engineers
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,
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.[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
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]
Controversy
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]
Classification
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. |
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.
Humans as ecosystem engineers
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
Examples
Terrestrial environments
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 –
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][19] Bark beetles are an ecosystem engineer of forest ecosystems and can affect fire spread and severity when attacking their host pine species.[20]
Not only animals are ecosystem engineers. Fungi are able to connect regions that are distant from one another and translocate nutrients between them.[21] Doing so they create nutritional niches for xylophagous invertebrates,[22][23] supply trees with nitrogen translocated from previously predated animals[24] or even form an "underground pipeline" that redistributes carbon between trees.[25] Thus fungi are engineers controlling nutrient cycles in ecosystems.
Marine environments
In marine environments,
Another example of ecosystem engineers in marine environments would be
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.[31] 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".
See also
References
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- ^ a b c Haemig, PD (2012). "Ecosystem Engineers: wildlife that create, modify and maintain habitats". ecology.info. Archived from the original on 6 May 2021.
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Bibliography
- Buse, J; Ranius, T; Assmann, T (2008). "An endangered longhorn beetle associated with old oaks and its possible role as an ecosystem engineer". Conservation Biology. 22 (2): 329–337. S2CID 24150325.
- Crawford, KM; Crutsinger, GM; Sander, NJ (2007). "Host-plant genotypic diversity mediates the distribution of an ecosystem engineer". Ecology. 88 (8): 2114–2120. S2CID 27037737.
- Commito, J. A.; Celano, E. A.; Celico, H. J.; Como, S.; Johnson, C. P. (2005). "Mussels matter: postlarval dispersal dynamics altered by a spatially complex ecosystem engineer". Journal of Experimental Marine Biology and Ecology. 316 (2): 133–147. .
- Wright, JP; Jones, CG (2006). "The concept of organisms as ecosystem engineers ten years on: progress, limitations, and challenges". BioScience. 56 (3): 203–209. .
External links
- A lecture by Moshe Shachak, the developer of the concept of ecosystem engineers (together with CG. Jones and JH. Lawton) during the 90's.