Damaged by hurricanes, burnt by fires, devoured by predatory starfish… How do ecosystems cope?

From time to time, ecosystems are hit by storms, fires or other types of disturbance. Resilience is the ability of an ecosystem to resist or recover from these events. Resilience preserves ecosystem diversity, productivity and sustainability. Disturbance has more impact on ecosystems that have lost diversity.

Relience and disturbance

Disturbance varies in scale from cataclysmic to minor, but every disturbance upsets the smooth functioning of an ecosystem to some degree. Disturbance is a natural part of the ecosystem, and can promote diversity (under the right conditions). However, too much disturbance decreases productivity and diversity.

Resilience is the ability of an ecosystem to resist or recover from disturbance. A healthy, diverse ecosystem usually recovers quickly, because they have more options for dealing with different types of disturbance. Diversity is also important because usually many organisms are needed to repair ecosystem damage.

Human activity, disturbance and resilience

Our actions can create unique types of disturbance, like pollution or overfishing, or magnify natural disturbance. This adds to the level of disturbance an ecosystem must deal with. Healthy ecosystems can often cope with this extra disturbance, but too much lowers diversity and resilience.

Resilience loss can feed back on itself, because disturbance has a greater effect on ecosystems that have already lost resilience. It is easier to lose diversity, productivity and (even more) resilience from ecosystems with decreased resilience. An ecosystem can decay and become unsustainable if resilience is lost.

How do you prevent resilience loss?

A healthy and resilient ecosystem needs:

• A source of young
  Young organisms from a seed source provide the basis for recovery. They invade a damaged area and begin to repair ecosystem damage.
  
• Time to recover
  It takes time to repair ecosystem damage, and if a series of disturbances hit an ecosystem, it takes longer and longer to recover after each one. The health of the ecosystem erodes if recovery time is longer than the time between each disturbance.
  
• A complete set of species
  Diverse ecosystems are more resilient in the face of disturbance. A complete set of species provides more options for recovery.

One of the best strategies for preserving resilience is to set aside and protect areas from human caused disturbance. Marine protected areas and national parks are good examples of this tactic.

Conclusion

Diversity and resilience are interconnected. Resilience needs ecosystem diversity to resist or recover from disturbance, and resilience protects against diversity loss. Together they influence ecosystem productivity and sustainability. Preserving diversity preserves resilience. Preserving resilience preserves diversity.

References

Elmqvist, T. et al. (2003). Response diversity, ecosystem change, and resilience. Frontiers in Ecology and the Environment 1(9): 488–494.

Gunderson, L. H. (2000). Ecological resilience—in theory and application. Annual Review of Ecology and Systematics 31:425–39.

Hofmann, G E. & Gaines, S. D. (2008). New tools to meet new challenges: emerging technologies for managing marine ecosystems for resilience. Bioscience 58(1): 43-52.

Levin, S. A. & Lubchenco, J. (2008). Resilience, robustness, and marine ecosystem-based management. Bioscience 58(1): 27-42.

Moral, R. & Walker, L.R. (2007). Environmental disaster, natural recovery and human responses. Cambridge University Press: Cambridge.

Palumbi, S.R., McLeod, K. L., Grünbaum, D. (2008). Ecosystems in action: lessons from marine ecology about recovery, resistance, and reversibility. Bioscience 58(1): 33-42.

The Resilience Alliance. Resilience. The Resilience Alliance. Retrieved 2 June 2008 from http://www.resalliance.org/576.php