Hello this is the description for the essay I wrote: As a class, you have gathered data on extinction in mammals. This data includes information on the number of countries this animal can be found in, body size, and reproduction rate (# of offspring per female per year).
Using this data set, your task is to write a ~1000 word report on the following topic:
Patterns that explain species vulnerability to extinction
Please critique the living hell out of this
You cannot see the graphs that were included in the essay
Ignore the citation errors
ESSAY:
Introduction
Currently, there is no definitive answer for what determines how at risk a species is for extinction; however there are observable traits within a species population and environment that can be used to come to a conclusion. Species currently classified under the IUCN’s conservation status are ranked in terms of their risk of extinction. Currently, body mass, environmental range, and reproductive rate are some of the best predictors used to determine the likelihood of extinction.
Background
In 1980, the International Union for Conservation of Nature Red List of Threatened Species was increasingly used to gauge the risk faced by species for conservation and policy practises. The system grouped species in terms of their risk for extinction in the following order: critically endangered, endangered, vulnerable, near threatened and least concern. This system is widely used because it is applicable to all species that inhabit diversified environments.
Theory
Populations become threatened with the possibility of extinction when the mortality rate is higher than the reproductive rate of the specie population. The vulnerability of any given species is determined by its population density and size, trophic level, life history, geographical range, environmental circumstances, external and internal threats, genetic variability, habitat requirements, and reproductive rate. The interaction of these traits makes up approximately 50% of the factors that can influence species vulnerability, while the rest is from anthropogenic factors. (Quantification of Extinction Risk: IUCN’s System for Classifying Threatened Species).
Analysis
The data revealed that animals that were above 140 kilograms had a relatively low reproductive rate. On average these animals had a reproductive rate 0.57. While the average weight of these species was 1705.9 kilograms. Of the 18 species that were above 140 kg, 3 were critically endangered, 5 were endangered, 5 were vulnerable, and 5 were least threatened. The low reproductive rate of these species leads to smaller populations. This is not necessarily the cause of their vulnerability, but rather a factor that makes the more susceptible to endangerment. All of the critically endangered, endangered, and 4 of the vulnerable species are located in Asian or African regions where poaching, human activities, and habitat loss are the most likely causes of these species acquiring a conservation status of vulnerable or more severe (Diamond 1984).
In contrast, the 24 species that were categorized under least concern had an average weight of 88.14 kilograms. But it is important to note that the species of least concern contain the giraffe, the American black bear, and the brown bear, all of which have an average weight of 1240, 170, and 370 kilograms, respectively. If these mammals were excluded from the least concern species group, the average weight for the group of least concern decreases to 15.97 kg and the average reproduction rate increases to 4. Species of least concern were also found on average in 12 countries. This implies that the majority of the species have appropriate population dispersal and are not as threatened by the loss of habitat.
Figure 1 illustrates the reproductive rates of the different categorizations of species conservation groups. It can be observed that the vulnerable specie group has a significantly lower reproductive rate than the other groups. This is a result of only 9 species being classified and documented within this group. However, after the critically endangered species group, each successive group has a slightly higher average reproductive rate per year. This data may show a possible correlation with conservation status and reproductive rate per year.
Figure 2 below displays the average amount of locations species within each conservation group are found. With the exception of the vulnerable species group, a positive trend can be seen in the average amount of locations species within each group are found. Again, the vulnerable group only contained 9 species which affected the presentation of data, whereas the least concerned group contained 25. Had both groups possess the same amount of species; the data would have been presented in a more positive linear fashion. The overall structure of the graph indicates a possible correlation between a species conservation status and the amount of locations they are found in.
Discussion
The majority of the endangered species within the data spread sheet have a high body mass and low reproductive rate. These features results in many of these species having small populations and makes them susceptible to demographic stochasticity. This is where random variation in birth and death rates lead to extinction or endangerment, even when the average population growth is positive. (Richter-Dyn & Goel 1972; Goodman 1987). However, these animals face this natural phenomenon along with the negative effects of human expansion and resource consumption, as well as a changing climate and environment. A study done by Marcel Cardillo et al. found that the impacts of intrinsic and environmental factors sharply increase for animals with a threshold body mass above3 kilograms. (CITATION)
Take for example the mountain gorilla and south china tiger. They are found in few locations because their habitats have been fragmented by anthropogenic activities. Also, the polar bear faces increased extinction risk due to reduction in sea ice coverage, thereby limiting its environmental range and the potential to find mates to produce offspring. These factors have a more profound impact on large mammals because their low population densities, requirement for large environmental ranges, slow life histories, and a low productive rate. (J. X. He, Ecology 82. 784 (2001). The low reproductive rates and population sizes of these species make it more difficult for population recovery after declines are caused by human activities and natural occurrences.
17 of the species classified under the least concern risk live in habitats that experience annual seasonal changes. These changes in climate and environmental conditions activate process called “clumping” or population aggregation. This can cause an increase in competition for nutrients and space but it also increases the potential of mating. Aggregation can also increase cooperativeness among individuals within a species and decrease the mortality rate during adverse conditions. (Odum and Barrett, 2006) This phenomenon combined with adequate reproduction rates is a likely factor that contributes to the resilience of least concern species to extinction drivers.
Conclusion
A species vulnerability to extinction often correlates with its body mass, habitat requirements, and the amount of offspring born each year. From the data gathered, there is a clear indication that species that have low reproduction rates and large environmental range requirements are more prone to extinction. While it can be difficult to exactly determine how vulnerable a species is, the alarming data on endangered species indicate a urgent need for a better understanding of the complex interactions between extinction drivers and implementation of conservation policy.