Species Area Curves

Introduction

One of the most intractable problems facing humanity today involves balancing human needs with those of ecosystems. Neither extreme is palatable; we would not want to live in a world in which all natural ecosystems had been replaced by human altered landscapes, and we would not be willing to give up all the amenities of our civilized world for a completely “natural” world. In addition, it is already too late to turn down the latter path; there are simply too many humans already to be supported by unaltered ecosystems. We have no choice but to alter some land to optimize its production of human food. The question becomes: How much land are we willing to their constituent species, are unique and deserve the same protection we give to species. How many ecosystems are we willing to preserve? An emerging viewpoint in the conservation community is that it makes more sense to concentrate on preserving whole ecosystems rather than individual species. preserve in its natural state? Some would argue that ecosystems themselves, not just

From a practical standpoint, whether it be ecosystems or species, land (and water) is the limiting resource, and it is reasonable to ask how much land will it take to preserve an ecosystem or a species. Biologists are beginning to grapple with this problem in several ways. One of the most dramatic is an ongoing project in the Brazilian rainforest. Headed by Thomas Lovejoy, the Biological Dynamics of Forest Fragments Project (abbreviated here as the FFP), has been gathering data for over 20 years

(Wilson, XXXXXXXXXXThis project was made possible by a Brazilian law that requires those that clear land to leave at least 1/2 uncut (Cousteau, XXXXXXXXXXIn 1963, Robert H. MacArthur and Edward O. Wilson presented a theory that addressed a topic that had been on the minds of biologists for many years. It was no secret that the larger a land mass, the more species the land mass would have. MacArthur and Wilson XXXXXXXXXXput this relationship into a mathematical perspective by developing the species-area curve (their theory, based on comparison of islands, also addressed a number of other relationships such as the effect of distance from the mainland on the number of species present on an island). The theory of island biogeography, as it is known, has withstood the test of time, and is an important tool

used by ecologists today in determining the size of an ecosystem needed to sustain an ecosystem.

The species area curve is expressed mathematically as this model:

S = c Az

Where:

S = number of species c = constant (= y-intercept)

A = area z = constant

As a general rule of thumb, it takes a tenfold increase in the size of a habitat to produce a doubling of the number of species. This rule of thumb does not hold in all cases, and, in fact, may not hold in our exercise today. Central to the application of this theory in many applications today is the realization that many ecosystems effectively behave in the same way an island does. For instance, to many organisms a pond is an island of water surrounded by an ocean of inhospitable land. Likewise, a remnant of tropical rain forest, perhaps on a hilltop, is an island of trees surrounded by grassland in which many arboreal species cannot survive. Yellowstone National Park, as well as many other parks, are also islands of relatively undisturbed ecosystems often surrounded by highly altered ecosystems. Modern ecologists, when planning nature preserves, are often challenged to create preserves

which will protect as many of the native species as possible. The species-area curve gives the ecologists a tool to predict how many species can survive in a given area. These values can then be used in the decision-making process.

The decision-making process might go as follows. A government might want to preserve some rainforest while developing the area around it. The area under consideration for development is 1,000,000 hectares (1 hectare = 100 meters x 100 meters =10,000 square meters = 2.471 acres). Ecologists could derive a species-area curve and be able to say "If you set aside 10,000 hectares you will preserve 50% of the species, but if you preserve 1,000 hectares you will preserve only 25% of the species." Other interesting questions arise. It is not just the total area preserved but the physical arrangement of that area that is important (Wilson XXXXXXXXXXFor instance, a park of 100,000 contiguous (adjacent, touching) hectares would normally contain more species than 10 separate parks of 10,000 hectares each, even though the total area is still 100,000 hectares. Note that this would not hold true if the ten separate areas were chosen to include widely different habitats or ecosystems as compared to a single large area dominated by one type of ecosystem.

In general, as the area increases, the number of species should also increase. In other words, as the larger the contiguous area, the higher the species diversity. This small experiment will allow you to investigate this hypothesis.

Methods

1. Find a meter stick or some measuring tool equal to a meter stick in length.

2. Go to an area of forest and/or woody, plant dominated land. Mark of a 1 m by 1 m plot of land. This is roughly 3.5 by 3.5 ft.

3. Write down the number of different species in the plot. Give each species a name of your choosing. You may want to take a picture of each species. (This indicates the species richness). Count the number of individuals of each species (This indicates relative abundance) and record this data.

4. Extend your original plot to 4 m by 4 m and repeat the process above. This is roughly 13 by 13 feet.

5. Extend your plot to 12 m by 12 m and repeat the process above. This is roughly 39 feet by 39 feet.

6. Construct a graph with plot size on the x axis and number of plant species on the y axis. It would be best to construct this graph using the log of the plot size and the log of plant species.

Write up

Briefly explain species diversity, species richness, and relative abundance. Briefly explain how fragmentation is thought to affect biodiversity/species diversity. Explain the role of the species area cure to ecologist. Generate a hypothesis that relates plot size to species diversity. Cite your sources.

Include your constructed graph in your report.

Indicate whether your hypothesis was supported or refuted by your data.

Methods and Material
s:

1 paragraph or so

A brief explanation of methods

Written in passive voice and past tense

Explains in enough detail to duplicate the experiment but does not contain unnecessary detail

Results:

Also written in passive voice and past tense

1 paragraph or so which details your exact findings in each of the three plots. This paragraph will likely be relatively short.

Do not analyze the data here-just report the results. Data analysis will occur in the discussion section.

A table which has your data visually represented. Tables are titled at the top. ex. Table 1: The Effects of Increasing Plot Size on Species Diversity.

A graph with
plot size on the x axis and
number of species on the y axis. T
itle the graph (below the graph
Example of Title:
Figure 1: The Effects of Plot Size on Species Diversity

Refer to both the table and the graph at the end of your paragraph by putting (Table 1, Figure 1) at the end.

Discussion Guidelines

As with the rest of the paper, the discussion should be written in passive voice and past tense.

The discussion section should include:

- A brief summary of the results (not numerical data, just a statement about which plots appeared to be more diverse/less diverse etc.)

-State whether the results supported the hypothesis or not? Why or why not?

-Implications-Based on these results, what could be implied about the effect of plot size on species diversity? What could be implied in regards to preservation efforts for contiguous areas of land?

-Flaws in the experiment

-Future studies

Final Paper Components Order

1. Title Page (in APA format w/ a running head)

Page Break

2. Abstract ( a brief 1 paragraph summary of the whole paper written in 10 point font and single-spaced)

3. Introduction (This was in the first rough draft submitted)

4. Methods and Materials ((This was part of the second rough draft submission)

5. Results (This was part of the second rough draft submission and should have included one paragraph, a table, and a graph).

6. Conclusions/Discussion (See Discussion guidelines in the ecology project folder for instructions).

Page Break

7. References (in APA)

Page Break

8. Appendix (pictures documenting the location used or the plants collected when doing the study).