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Biodiversity: An Exploration

These pages are being generated as part of a senior seminar course directed by Neal Williams at Bryn Mawr College during fall semester, 2007 Among the topics to be considered are

  1. What is biodiversity?
  2. What's happening to biodiversity?
  3. Why is it happening?
  4. Why does it matter?
  5. What should/can be done about it?

While deceptively easy to ask, these prove to be sophisticated questions lacking simple answers. Links to weekly readings and discussion summaries will be provided here. Each will include a public on-line forum where visitors are encouraged to leave their own reactions, extensions, and further questions. General thoughts about the course are welcome in the on-line forum below. Postings will be reviewed to prevent spam and so may be delayed in appearing.

Week 1 - Starting thoughts - see forum at the end of this page

Week 2 - The End of the Wild and Tends in the State of Nature

Week 3 - Getting the Measure of Biodiversity

Week 4 - Ways of Measuring Biodiversity and their Significance

Week 5 - Conserving Biodiversity: Climate Change and the Significance of Genetic Diversity at Species Range Boundaries

Week 6 - Biodiversity Hotspots and Conservation

Week 7 - Biodiversity and Ecosystem Function

Week 8 - Biodiversity and Stability

Week 9 - Extinction Debt and Extinction Cascades

Week 10 - Biodiversity and Multiple Trophic Levels

Week 12 - Community Interactions and Stability 



Paul Grobstein's picture

some reflections on our biodiversity conversation so far

A few things that seem to me worth more discussion/consideration, maybe needing additional obervations:

How dependent is the story of "loss" on the definition of diversity? Quantitatively and qualitatively? Most attention is being paid to mega fauna/flora. Would the story be different if we paid more attention to the complete spectrum of living organisms, particularly microbes?

"Biodiversity" (however defined) involves a balance of loss and gain, but existing observations focus on loss. Would the story be different if more attention were paid to documenting gain?

How significant is the "human" perspective, ie concern about how things look to humans and what humans value/think is important? Would the story be different if we thought about things in the absence of humans? indifferent to human concerns? A new book, perhaps relevant: The World Without Us, by Alan Weisman.

rkumazaw's picture


I am a senior majoring in biology and minoring in psychology.

1. What is biodiversity?

Biodiversity is variation in living organisms that can be observed from a vast array of organizational scales from within species to within ecosystems. While variations within a species would be on a genetic level, variation within an ecosystem would not only be in terms of the number of various species but also the species richness. What is also an important aspect of diversity in a community is the functional diversity. Taking all of these into account, what should be focused when discussing biodiversity and its definition in ecosystems is the community composition.

2. What is happening to biodiversity?

Biodiversity is always changing and while these changes can be for the better in some areas, biodiversity is most likely declining on both a regional and global scale in recent years. Although we cannot deny the fact that some species, like weedy species, are flourishing, the quantity of species is decreasing as many face extinction in the near future, if they have not already.

3. Why is it happening?

Some of the main causes of this decline in biodiversity are habitat loss, overexploitation, pollution, and climate change, all of which are largely due to anthropogenic activities. Habitat loss is one of the biggest concerns because specialized organisms cannot survive in different niches due to their specialized nature, although these traits were what once allowed them to thrive. Moreover, the increased rate of habitat loss does not allow for organisms to find other niches. Overexploitation is, without a doubt, a direct cause of declining biodiversity as it is proved my many examples. Although data on the effects of climate change may not be as studied as habitat loss and overexploitation, it is likely to have caused negative changes in biodiveristy, although some may argue that it allows for new niches.

4. Why does it matter?

Other than the fact that it is a fundamental moral issue, we should be concerned with declining biodiversity because communities are established and maintained by the interactions between the species making up that community. Therefore, the loss of any one species has the potential to disrupt the balance that has been maintained by these interactions. Any one organism could be the primary food source for another and the extinction of this prey can lead the to the extinction of the predetor. The effect of the extinction of these two organisms may not stop there. If they are all connected, one incident can have a large effect.

We should also be concerned about the loss of biodiversity for our own sakes. Loss of biodiveristy means loss of resources for us as well. If we have reached the end of our only resource's reservoir, where do we turn to? We should maintain biodiverisity to ensure alternative resources in case what we use now runs out.

5. What should/can be done about it?

We need to gather more information, more data, in order to make people more aware of criticality of the situation we are in now. Perhaps then, people will start caring more and become more active in trying to decrease the rate of declining biodiversity.

maggie_simon's picture

Week 1: Biodiversity

I am a senior at Haverford College.  I am majoring in biology, with a minor in physics.

1.      What is biodiversity?

Biodiversity is a way to describe the make-up of an area with respect to groups of organisms: it describes the abundance of a group of organisms (grouped by some similar characteristic; here I will be using species as my scale for measuring biodiversity) and the relative distribution of the members of the group within an area.

 2.      What's happening to biodiversity?

As organisms interact with each other and their surroundings, population sizes and distributions will change.  These fluctuations mean that biodiversity is an ever changing phenomenon.  While I believe that these changes have always occurred, I suspect that the rate at which these changes take place has accelerated during the past century or two in such a way that biodiversity is decreasing in general on a global scale.

 3.      Why is it happening?

During the past century or so there have been many industrial, agricultural, and technological achievements whose effects in the natural world are not entirely known.  These human influences are changing the environment in rapid ways (as compared to geological and evolutionary time scales).  Thus, organisms must adapt or evolve to these changes, or become extinct.  Because the anthropogenic changes are taking place faster than most species can evolve or adapt, I think that rates of extinction are increasing.  Since here I am viewing biodiversity as a measurement of species abundance and distribution, biodiversity is decreasing as a result of these extinctions in the sense that the numbers of different species (the richness) in certain areas (such as in cities, for example), i.e., the way in which they are distributed (the evenness), is decreasing. 

 4.      Why does it matter?

From an environmental point of view, a decrease in biodiversity could lead to huge changes in the biomes of the earth.  A larger variety of organisms means more of a balance in an area because if a sudden change takes place there is more of a chance that some of the species in the area will be able to deal with the change.  This is important because almost all species of organisms on earth depend on their interactions with species.  From an anthropocentric point of view, humans have adapted to live in the world as it has been for thousands of years.  Significant changes in biodiversity can completely change that world in drastic ways.  It is possible that humans would not be able to adapt to such changes and our lifestyles would completely change.  A less drastic and more realistic way in which human lifestyles would be affected is through global warming which may lead to a decrease in biodiversity, but could also be aided by a decrease in biodiversity in so much as plant populations are concerned.  Also in answering this question, the intrinsic value of biodiversity on earth should be considered.

 5.      What should/can be done about it?

Research is needed to determine what can be done about it.  Since the problem stems from humans, policy may need to be implemented in order to curb human influences on the environment and biodiversity.  This means information should be gathered and presented to the public.


Paul Grobstein's picture

Biodiversity-starting thoughts

I'm a professor of biology at Bryn Mawr College, with a background in neurobiology.

1. Biodiversity is a measure of the variation among living organisms at any given place and time. How best to make such a measure depends on the use to which one wants to put it.

2. By most ways of measuring, biodiversity has in recent times been declining, at least in many locations for particular subsets of living organisms.

3. Human impact seems to be playing a role in the reduction of biodiversity. Other factors are probably involved as well.

4. Biodiversity is a significant element in the ability of living systems to adapt and further explore the potentials of life.

Ashley Himelfarb's picture

Week 1 Post

I am a senior biology major at Bryn Mawr College. My main area of interest is ecology.

Biodiversity is the variation in forms of life at a given spatial and temporal scale. The biodiversity could be measured at the level of species, communities, and ecosystems, up to a global scale and over many time periods. It is used to evaluate the health of they system. It is important to create an experiment with the appropriate spatial and temporal scales for the hypothesis being tested. Biodiversity also has several components. Species diversity for example, is calculated using measurements of both species richness (number of species) and species evenness (how many of each species).

Globally biodiversity is decreasing. This could be a reflection of decreasing health in the global environment. Life forms have existed on earth for several million years. During this time the global biodiversity has certainly fluctuated. We must use the data on extinction rates and other measures of biodiversity to decide for ourselves if this decline is part of that background fluctuation or truly an anomaly.

If the interpretation of the data suggests an anomalous decrease in biodiversity, why should we care? We care because we too are a species on this earth that is subject to extinction. In a less extreme case humans are connected to other life forms, whether it is through ecosystem services or a love of nature. Humans have the power to alter the environment both locally and globally. This manipulation often has a goal in mind, whether it is through development, flood prevention, habitat protection. We can better predict the outcomes of these manipulations if given information about the health and makeup of ecosystems.

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