Ecosystem: “A biological community of interacting organisms and their physical environment.” - https://en.oxforddictionaries.com/definition/ecosystem
Per many ecologists, ecosystems are either in a stable state or shifting from one stable state to another – otherwise known as “catastrophic change”. Although ecosystems are never completely stable, the idea is that they achieve a dynamic equilibrium by absorbing and accommodating change. But once some threshold of change is reached, we get catastrophe.
Are those the only choices we get: stability or catastrophe? Does such a categorical approach represent how ecosystems actually work?
Not according to an increasing number of bioscientists. For instance, Brian Huntley and Thompson Webb argue that biological communities are bested viewed as temporary assemblages of flora and fauna that have come together by chance and opportunity, in continuous flux as species migrate in and out and evolve in response to changing conditions. Long before humans entered the scene, dynamic disequilibrium ruled the biosphere.
When the parts of a system are constantly changing, at what point do you say that the system is no longer itself? That may be easy to answer when the system is a living organism, which is either alive or dead. But ecosystems aren’t single organisms, so the either/or approach doesn’t really apply. The concept of ecosystem needs to be freed from the shackles of its founding metaphor – that of a living organism – for us to better understand and manage ecological processes and change, without the bias inherent in presenting catastrophe as the sole alternative to stability.
References:
Huntley, B. and Webb, T. Migration: Species' Response to Climatic Variations Caused by Changes in the Earth's Orbit Journal of Biogeography Vol. 16, No. 1 (Jan., 1989), pp. 5-19. DOI: 10.2307/2845307
Kricher, John (2009) The Balance of Nature: Ecology's Enduring Myth Princeton University Press, Princeton, NJ; ISBN: 9780691138985
Mascaro J, Hughes RF, Schnitzer SA (2011) Novel forests maintain ecosystem processes after the decline of native tree species. Ecological Monographs 82(2): 221-228. http://dx.doi.org/10.1890/11-1014.1
Scheffer, M., Carpenter, S., Foley, J.A., Folke, C. & Walker, B. Catastrophic shifts in ecosystems Nature 413, 591-596 (11 October 2001) | doi:10.1038/35098000
Truitt AM, Granek EF, Duveneck MJ, Goldsmith KA, Jordan MP, and Yazzie KC What is Novel About Novel Ecosystems: Managing Change in an Ever-Changing World. Environmental Management (2015) 55: 1217. doi:10.1007/s00267-015-0465-5 http://link.springer.com/article/10.1007/s00267-015-0465-5