What Is The Paradox Of Enrichment?

By Antonia Čirjak on May 30 2020 in Did You Know

Predator and its prey.
Predator and its prey.
  • The paradox of enrichment happens when the food available to animal prey in nature starts to increase, which leads to the population of the predators to be destabilized.
  • When it was first coined, the paradox was used in an ironic way, since by increasing the number of animals in an ecosystem, we can actually cause the opposite effect.
  • One of the exceptions to the paradox is inedible prey, which could absorb nutrients and thereby work in a way that would stabilize the cyclical functioning of nature.

The paradox of enrichment is an incredibly niche term used in population ecology. This term deals with a specific occurrence that is known to happen in nature from time to time. The paradox of enrichment happens when the food available to animal prey in nature starts to increase, which leads to the population of the predators to be destabilized. It is easier to explain with an example. 

Let’s say that the number of rabbits in nature starts to grow because the food available to them increases, and their numbers suddenly become unbounded. This might make the population of an animal species that feeds on rabbits to grow much larger as well. It can become harder to sustain these numbers once it happens. This can lead to a crash in the population numbers of the predators. Sometimes it even leads to the extinction of the species. This is why it is called a paradox. An entire species can become endangered if they start having too much food available.

The Origins Of The Paradox

This term was coined by Michael Rosenzweig, a professor in ecology, in 1971. He researched six different models of predator and prey relations in nature. He picked the examples where the increase in available food for the prey caused the predator numbers to reach unsustainable heights.

The way the word paradox is used when explaining this phenomenon varies and can be contradicting. When it was first coined, the paradox was used in an ironic way, since by increasing the number of animals in an ecosystem, we can actually cause the opposite effect. We can create an imbalance in nature, so to say. However, in recent times, this term has been used to describe the difference between two modes of interaction between predator and prey. Those two modes are the real interaction that occurs in nature, and the modeled interaction used for research.

Michael Rosenzweig, a professor in ecology, in 1971. He researched six different models of predator and prey relations in nature.
Michael Rosenzweig, a professor in ecology, in 1971, researched six different models of predator and prey relations in nature.

In his research, Rosenzweig tried simulating a prey population using equation models. He was using enrichment to increase the carrying capacity of the prey, which then also caused the population of the prey to destabilize as well. Rosenzweig continued exploring this phenomenon in other papers and discussions that followed. 

The Exceptions To The Paradox

There were also other studies that followed that showed how this paradox doesn’t work in all circumstances. Other scientists proposed several exceptions to the paradox. One of the exceptions is inedible prey, which could absorb nutrients and thereby work in a way that would stabilize the cyclical functioning of nature. Of course, inedible prey would only appear if there are multiple prey species available. Another exception would be an invulnerable prey, meaning prey that can run away and hide from its predator.

Some other circumstances where the paradox might not function include unpalatable prey which doesn’t fulfill the needs of the predator from a nutritional perspective and a heterogeneous environment. The paradox of enrichment only functions if the environment is homogenous, which creates the cyclic patterns where it appears. However, if the environment is heterogeneous, these patterns might not happen, which means the paradox would not appear either. Since it is a relatively new term, it still needs to be explored more thoroughly, but it could help us better understand nature, and how to stop certain species from becoming endangered.

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