Ecosystem resilience refers to the capacity of an ecosystem to resist, recover from, or adapt to disturbances while maintaining its essential structure, function, and ability to provide ecosystem services. It represents the ability of an ecosystem to absorb shocks, maintain its stability, and continue to provide benefits to both human and natural systems.
Ecosystem resilience is achieved through the intricate interconnections between organisms and the underlying mechanisms that sustain their interactions. Within an ecosystem, species rely on each other for resources, such as food, shelter, and pollination, creating complex networks of interdependence. These connections facilitate the flow of energy, matter, and information, enhancing the ecosystem’s capacity to withstand disturbances and recover from perturbations.
Academic researchers have endeavored to identify these interconnections and mechanisms. For example, Lundberg and Moberg (2003) studied the role of mobile link organisms in maintaining ecosystem resilience. The term ‘mobile link’ typically refers to an organism that moves between different habitats or ecosystems, connecting them and facilitating the exchange of energy, nutrients, or other ecological processes. Lundberg and Moberg (2003) classified mobile link organisms into three types: resource linkers, genetic linkers, and process linkers.
Resource linkers transport nutrients and energy from productive areas to less productive ones, playing a crucial role in shaping food web dynamics and enhancing overall stability (Lundberg and Moberg, 2003). Genetic linkers aid the movement of genetic material within ecosystems, promoting genetic diversity and enabling adaptation to environmental changes. Certain animals, such as seed dispersers or those involved in the spread of mycorrhizal fungi, contribute to the recolonization of ecosystems following severe disturbances, such as intense fires, thereby enhancing ecosystem resilience (Lundberg and Moberg, 2003, Wilcox and Murphy 1985). Process linkers, including sediment operators and soil modifiers, connect habitats and modify physical structures, thereby facilitating recolonization and improving habitat suitability in the aftermath of disturbances (Lundberg and Moberg, 2003).
Cheung et al. (2021) explores the role of ecosystem engineers in maintaining coral reef ecosystem resilience. Ecosystem engineers are organisms that create, maintain, and modify habitats by significantly altering the chemical and physical composition of substrates (Šobotník and Dahlsjö, 2017). One example of ecosystem engineers is herbivorous fishes, which primarily feed on plants and algae. These fishes play a crucial role in maintaining the balance between corals and algae on the reef by grazing on algae, preventing it from overgrowing and outcompeting corals for space and resources (Green and Bellwood, 2009). Additionally, herbivorous reef fishes contribute to bioerosion, which involves the erosion or removal of material from natural structures through biological activities. In coral reefs, bioerosion occurs through the physical and chemical breakdown of coral structures by various organisms, such as grazing fish, burrowing invertebrates, and boring organisms. These organisms remove or break down coral skeleton material, including dead or decaying coral, which helps reshape the reef over time. Larger herbivorous fish, like excavating parrotfishes, play a particularly important role in bioerosion. Bioerosion is essential for coral reef resilience as it eliminates accumulated dead coral that can impede reef growth and health. By keeping the reef clean and free of debris, herbivorous fishes create space for the colonization of benthic organisms.
Ecosystem resilience is supported by a range of mechanisms that help maintain ecosystem structures and functions while mitigating the impacts of disturbances. However, disturbances can have varying degrees of impact, and when they surpass a critical threshold, resilience can be compromised. This threshold represents a pivotal point at which significant and potentially irreversible changes occur in the ecosystem’s structure, function, or dynamics. Crossing this threshold triggers a regime shift, resulting in a fundamental change in the ecosystem’s behavior. Such shifts can lead to a loss of ecological integrity and a decline in the ecosystem’s capacity to provide essential services.
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References:
Cheung, P-Y, Nozawa, Y, Miki, T. (2021). Ecosystem engineering structures facilitate ecological resilience: A coral reef model. Ecological Research, 36: 673– 685.
Green, A.L., Bellwood, D.R., & (2009). Monitoring functional groups of herbivorous fishes as indicators of coral reef resilience—A practical guide for coral reef managers in the Asia Pacific region. IUCN working group on climate change and coral reefs. Gland, Switzerland: International Union for the Conservation of Nature. https://www.iucn.org/sites/default/files/import/downloads/resilience_herbivorous_monitoring.pdf
Lundberg, J., Moberg, F. (2003). Mobile Link Organisms and Ecosystem Functioning: Implications for Ecosystem Resilience and Management. Ecosystems 6, 0087–0098. https://doi.org/10.1007/s10021-002-0150-4
Šobotník, J., Cecilia A.L. Dahlsjö. Isoptera☆, Reference Module in Life Sciences, Elsevier, 2017, ISBN 9780128096338. https://doi.org/10.1016/B978-0-12-809633-8.02256-1
Wilcox BA, Murphy DD. (1985). Conservation strategy: the effects of fragmentation on extinction. The American Naturalist, 125 (6):879–887.
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