During the past 300 years or so, the concept of reasoning as a thinking process has been successfully combined with the concept of “science”. As science has married with logic, more people have learned that myth, folklore, and even intuition do not activate the same neurologic process for thinking in the brain. Through using Functional Magnetic Resonance Imaging (fMRI) techniques, we can now plot brain scans which illustrate different portions of our brains (or in some cases - different pathways), in use when applying various forms of thought. This will become important as this story continues.
In the early 1830’s, Darwin and Wallace explored all over the planet, frequently focusing on islands (e.g., Galapagos Islands, West Indies, Aegean Islands, etc.) to further their research on evolution. What they independently deduced caused an explosion of scientific reasoning. One of the concepts which both Darwin and Wallace investigated has now become what is called the theory of island biogeography. I’d like to introduce you to a book, currently recognized as a masterful culmination of that theory. However, if you are going to read this book, please entertain the following three questions and pass a “test” to see if you can answer all three questions with a resounding “Yes.”
Question #1: Do you consider yourself to be a “scientist?”
Question #2: Do the biological sciences and related research philosophies and methods appeal to you (perhaps even as a profession)?
Question #3: Are you familiar and even comfortable with moderately advanced mathematics? If you answered “Yes” to all three of the above questions, then I suggest that you read The Theory of Island Biogeography, written by Robert H. MacArthur (ecologist) and Edward O. Wilson (taxonomist and zoographer), in 1967, copyrighted by Princeton University Press, published by the Maple Press Company. A follow-up edition, The Theory of Island Biogeography Revisited (J. Losos and R. Ricklefs, editors) published in 2009 evaluates and demonstrates how the field has extended and confirmed--as well as challenged and modified--MacArthur and Wilson's original ideas.
Interesting stories illustrate the various research methods used to validate their theory. Perhaps you remember reading about the island of Krakatau in Indonesia. In 1883, the entire island exploded, and after 3 months of explosions, this island and two other nearby islands were buried with hot pumice and ash up to 60 meters in depth. All flora and fauna were killed. Repopulation commenced soon after, and that provided a primary research site to study repopulation, as well as for the justification (proof) of MacArthur and Wilson’s 20th century theories.
A portion of the developing theory in MacArthur’s and Wilson’s book is: “Island populations are fragmented and the boundaries of their subunits set by factors have little to do with innate biological properties.” Perhaps you already know and understand that theory. Let us make this a little more complicated. I used to define the word “island” as a piece of land (rock, soil, etc.) surrounded by water. The literal definition has expanded. Paraphrasing the American College Dictionary, “island” can now also mean a thing resembling an island especially in being isolated, detached, or surrounded completely by something else, radically different, in every way.
Let’s expand on this “island biogeography” theory, using the second definition. Back in 2012, I read a fascinating book titled The Spine of the Continent, by Mary Ellen Hannibal, Lyons Press, Guilford, CT. One of the purposes of this book was to examine mountain tops as a type of island. Many large mammals travel vast distances during their yearly cycles of living. This is true for bears, caribou, elk, buffalo, etc. When the types of habitat for these creatures are reduced in volume or size, or by increasing distances, it becomes difficult for many of these species to survive.
During this past century, those special places needed for survival by many species - including birds - have been reduced. Picture a topographic map of a particular mountain range on your computer screen, with elevations ranging from 3,000 feet at the lowest elevation up to 12,000 feet at the highest elevation. Using a mapping application, select all areas on your computer screen from the 3,000 foot level to the 9000 foot level, and turn all of the selected area to the color blue, eliminating all contour lines. I'll submit that you are now able to see the 9,000 to 12,000 foot elevations appearing as islands floating in an ocean. For the aforementioned mammals, the metaphorical water level is rising, creating islands difficult to reach, threatening their survival as a species. Why? How is the "water level" rising? We humans are responsible. Timber extraction is occurring at ever higher elevations. Homes are being built at higher elevations, further back in the hills. More farmland is being developed at higher elevations than ever before, with the lack of water being one of the reasons for the move. Aha: Mountain Islands!
While I was working in the cloud forests of Ecuador with Dr. Dusti Becker on an Earthwatch expedition, one component of the project was to collect data on a specific species of bird in an effort to determine the number of hectares required to maintain a healthy population of that species. From this, I realized that even a single consolidated unit of a specified ecological type could be accurately considered as an “island.”
When you travel in Arizona and New Mexico, and work with various natural resource agencies such as the Bureau of Land Management or various National Forests, as I have, a familiar term shows up: sky islands. What is meant by sky islands is that portions of mountainous areas, (far removed from each other perhaps by hundreds of miles), each become their own island. Frequently, each sky island may have species of birds, lizards, and even cacti not found in neighboring sky island mountains.
Choose any state in the East. Can you imagine what the forests in that state looked like in the year 1700? Now, picture the forest in the same place in that same state today. Would you suppose that the amount of forest acreage has been reduced? Can you picture the "islands" of forests that now exist there? Note Figure 1 on the next page as an example from Wisconsin. I observed another weird adaptation of this concept of island biogeography on a trip to the Shetland Islands, north of Scotland. Family tradition there would let you define the land you owned by constructing rock walls around the perimeter of your land. Once you died, your children were given the land, frequently in equal amounts per child. Guess what the children of the children did? They defined their property by building rock walls around their perimeters. And then the next generation, and the next generation continued to split the property. Eventually, each individual unit was so small that farming was no longer sustainable. They were inadvertently making their own islands, each becoming increasingly unsustainable.
Another theory of island biogeography to consider: We humans are creating too many, too small, too isolated islands. The result is as islands become too isolated, or too small, or overpopulated, frequently the plants and animals which depend on that island leave the island to never return again or become extinct. Almost universally, this is not good news. Why? Generally, diversity implies sustainability, and diversity is declining around the globe. By now you might be asking yourself why I have written this article. Here’s why. I believe how I traditionally thought about islands was not well thought out, nor completely accurate. So now I have learned something new, fascinating, and important by reading these books. Hence I can change my actions based on new knowledge. As people who care about land and species conservation, it behooves us to persistently have the courage and emotional stamina to evolve with what we once thought to be true, or learn what we didn’t know. There are things that we do which result in consequences that we don’t know, don’t think about, don’t recognize, or don’t understand. In my experience, both scientists and non-scientists struggle with unlearning, new learning, and even relearning. I suggest that we have to learn and understand - at a deeper level than ever before - that every single thing that we do has an impact on the world’s environment. Perhaps this is why the rigor and discipline of science needs to be upheld and challenged at the same time. I hope you learned something new about islands in this article and I hope you challenge this research as well. Thank you for taking the time to read about island biogeography.