Non-random species loss and ecosystem productivity in grassland communities

Extinction and the Ecosystem

The ability of a species to survive the extinction of another depends on its ability to adapt. Omnivores fair better than those with a limited range of food. When a single food source disappears from the environment, it can more easily find another suitable food source. More highly specialized members of the ecosystem will not be able to substitute food as those that can eat a variety of food. The extinction of a single food species will quickly follow the elimination of their major food source. This research will support the thesis that non-random species loss will have a more devastating effect on the community and than random species loss.

Research Methods and Extinction

Non-random species loss is the result of human managerial practices and other humanly controllable events. At this time, research into species loss depends on computer simulation as the basis for its theory. This has the advantage of allowing researchers to manipulate variables to precise standards (Drake, p. 1). However, it can be argued that this type of study does not represent real world scenarios. This is one of the difficulties of research in the extinction of any plant or animal species. The only real-world studies that can be performed are those where an actual extinction is taking place. However, in this research scenario, the researcher does not have the ability to manipulate variables, as in the computer simulation (Drake, p. 1). This creates a dilemma in the study of species within ecosystems.

In a computer simulation, Schlapper, Pfister, and Schmid, (p. 13) examined the potential effects of non-random species loss on grassland productivity. In this study, the researches set up an environment with 15 species. They exposed this population to 2-years of high-intensity management that resulted in the extinction phase of many species. After the extinction phase, they exposed the plot to 2 years of low intensity management, which comprised the restoration phase. This allowed the recolonization of neighboring plots under different management schemes.

Some unexpected results came from this experiment. For instance, during the extinction phase, species in a monoculture environment had lower extinction probabilities than those in a mixed community (Schlapper, Pfister, and Schmid, (p. 13). One of the more significant findings of this research is that species that were more productive during the extinction phase were different than those that predominated during the restoration phase. Inconsistency between in recolonization from neighboring communities was also observed (Schlapper, Pfister, and Schmid, p. 13).

This research was supported by stochastic models of population growth and decline. In populations that are randomly fluctuating a lack of empirical evidence makes it difficult to predict population rises and declines (Drake, p. 1).To examine how the repopulation process occurs means an examination of those that are responsible for spreading the seeds. It is important for humans to understand these dynamics, as the disruption of these processes can have an impact on society (Sekerciosglu, Daily, and Ehrlich, p. 18043). Birds play an important role in the repopulation of plants. Birds provide a service to the plant community by spreading seeds from one place to another (Sekerciosglu, Daily, and Ehrlich, p. 18043). Declines in bird populations can lead to a decline in plant species as a result.

Conclusions

There are many reasons why a species may become extinct. Overharvesting of species is often blamed as the single reason for species extinction. However, it is unlikely that overharvesting alone is responsible for species extinction, as the costs of finding the last of a species is high (Courchamp, et al., p. 1). However, there is also a connection between the rarity of a species and its desirability as a fashion object. As a species becomes rarer, it will become more desirable as a fashion statement. As the species becomes more valuable, it might outweigh the costs of hunting the last of a species. This is referred to as the Allee effect (Courchamp, et al., p. 1). In this way, a species might go extinct as they become more rare and pricey on the open market.

In order to understand the extent and severity of the current crisis that we are facing regarding the rapid decline in bird species, we must look to past extinction events. Geochemical analysis is often used in conjunction with paleontological data in order to examine past extinctions more closely (Martin, 2007). Fossil evidence analyzed in this manner demonstrates that increasing oxygen levels increases the number of species as well. As oxygen levels decrease, the number of species in the fossil record decreases as well (Martin, 2007).

One of the key problems with observations such as this is the establishment of causality. Just as we have difficulty assigning causality between the extinction of one species as the direct result of the extinction of another, we cannot determine the cause of the decrease in oxygen between these layers. There also might be confounding variables such as the effects of the substrate on the retention of fossil oxygen.

The example of the effects of declining bird populations was used for this examination of the interdependence of species and the effects of the extinction of a certain species due to declining bird populations in recent times. The extinction of birds will have a devastating effect on other species, largely through the destruction of plants upon which they feed. The loss of scavengers could harm human populations by reducing the chance of disease spread. The loss of scavengers also has the effect of reducing soil nutrients that promote new plant growth.

We discovered that a loss of fish is connected to a loss of fish eating birds. This brings up the question of whether the loss of marine fish is responsible, at least in part, for the loss of fish eating birds. Demonstrating causality between the loss of one species and its effects is difficult. This is largely due to the researcher's inability to isolate the variables the cause the extinction.

Much of the research on the causes and effects of extinction focuses on the extinction of one particular species or another. It often fails to consider the entirety of the environmental impact. Many times these relationships are obscure, but they are important if one is to understand the full impact of our actions as human beings on the ecosystems of which we are a part. This study demonstrated that much more emphasis needs to be placed on studying the interrelationships and complexities of the ecosystem.