Morse, N. B., P. A. Pellissier, E. N. Cianciola, R. L. Brereton, M. M. Sullivan, N. K. Shonka, T. B. Wheeler, and W. H. McDowell. 2014. Novel ecosystems in the Anthropocene: a revision of the novel ecosystem concept for pragmatic applications. Ecology and Society 19(2): 12.
The term “novel ecosystem” generally refers to ecosystems altered by human activity. It has become a common term used by ecologists since its first use in 1997, however, it is not always well-defined. Morse and colleagues proposed an encompassing definition: “A novel ecosystem is a unique assemblage of biota and environmental conditions that is the direct result of intentional or unintentional alteration by humans, i.e., human agency, sufficient to cross an ecological threshold that facilitates a new ecosystem trajectory and inhibits its return to a previous trajectory regardless of additional human intervention.” The definition goes on to further clarify that a novel ecosystem must be self-sustaining, and a defining characteristic is a change in species composition relative to the composition before crossing a critical threshold. There are a couple of concepts to be unpacked from this definition. First, human alteration of the ecosystem in this definition only includes direct human impact, meaning the cause of the impact is in the same geographic area as the ecosystem (e.g., land-use change). This excludes indirect human impacts, such as acid rain or seasonal variations from climate change. Second, a threshold in this definition is a point in an ecosystem’s trajectory where a change is next to impossible to reverse (e.g., the establishment of an invasive species). Using this narrowed definition of novel ecosystems makes it easier to distinguish between degraded ecosystems from human impact and ecosystems that have changed but are still stable after human impact.
Take Home Points:
- The definition here includes four criteria to be considered a novel ecosystem - direct human impact, the crossing of an ecological threshold, a unique species composition that differs from the pre-threshold composition, and self-sustainability.
- Not all human-influenced ecosystems should be considered degraded, as most ecosystems in today’s world are human-influenced, but many still function productively.
- Managers should focus on converting degraded ecosystems into novel ecosystems that thrive alongside human interaction rather than converting them back to their original, natural state.
- Novel ecosystem function should be measured through the ecosystem services they provide rather than comparing the function to a pre-threshold standard.
- Long-term monitoring of ecosystems should be implemented because it helps to identify ecological thresholds.