By Robert Hazen, George Mason University
Many of today’s ecologists modify ecosystems one variable at a time to see how they’re affected. This simple strategy of altering one variable of a complex system at a time pervades modern biological research, from genetics to brain science. However, there’s an alternative approach to doing this kind of research, and that’s to model ecosystems by computer.
Global Circulation Models
At the largest scale, we have global climate models. These are based on what are called global circulation models, or GCMs; it’s a computer approach to understanding global climate.
This approach divides the Earth’s surface into uniform blocks, typically a few hundred miles on a side. Each of the vertical blocks is further subdivided into horizontal slabs; maybe a dozen or so horizontal slices, containing land and ocean, atmosphere, and so forth. These elaborate schemes include detailed information in every box on ocean currents, wind speed, humidity, distribution of mountains, cloud cover, vegetation; about atmospheric composition and temperature; about all different kinds of variables that we might associate with a chunk of atmosphere, or a chunk of land that interacts with the atmosphere.
The Sun’s energy then has to be fed into the system, and out of it again; there are ongoing exchanges of matter and energy between boxes, and those have to be governed by the laws of thermodynamics, the laws of motion, the conservation of atoms, and so forth. We have lots of mathematical parameters that represent these boxes, which represent chunks of the Earth’s atmosphere.
This is a transcript from the video series The Joy of Science. Watch it now, on Wondrium.
Advantages of GCM
In a typical experiment, the modeler sets up initial conditions and lets the model run through lots and lots of cycles, watching how the global climate changes.
These models have a great advantage, because we can run controlled experiments on the entire Earth. We can rearrange the position of continent, change ocean currents, and put mountain ranges in the way, or get rid of the mountain ranges, and see what happens. Each change in initial conditions yields a different global outcome.
We have models of ever-increasing sophistication now; we’re able to duplicate many of the details that we read in historic climate change, at this point. We can make plausible predictions about how key changes in atmospheric composition, or in land position, or in ocean currents, might change global climate.
Limitations of GCM
However, in spite of the success of some of these GCM approaches, no model is yet sufficiently complex to predict the Earth in detail. The boxes are just too large. For example, we need to have boxes only a few miles on the side, rather than 100 miles on a side. Instead of 12 vertical sections, we might have to have 100 vertical sections. Even so, we’d need to be able to get finer and finer resolution to understand how the Earth really works.
No matter how sophisticated these models become, there are always going to be uncertainties, because our models are only as good as our current understanding of the factors that are important in global climate.
Preservation of Ecosystems
All this leads to a philosophical question: Why should we care about the disappearance of other species? After all, humans don’t appear to be in any immediate danger of extinction. There are three compelling reasons that have been proposed for why we should preserve Earth’s biodiversity.
The first reason is that all species are interdependent on others; they’re all part of complex ecosystems. Loss of one species may adversely affect the whole system, with consequences that we just can’t predict. They may be completely unexpected, and they may be very tragic.
Damaged ecosystems, in turn, may affect rainfall and climate; they can affect soil nutrient development and erosion processes. We can change pollination rate, pest control, water quality—all of these factors may be dependent on the preservation of ecosystems as they now stand. As more species are threatened, the risk to humans of these adverse conditions increases.
Preserving Different Species
The second argument to preserve species focuses on our health and well-being. Humans have enjoyed untold benefits from all the new foods, the new drugs, the new chemicals that are discovered as part of living things.
Every living thing has its own unique set of genes, and therefore, its own unique set of proteins. Each of those proteins has the possibility of serving a useful function, as a chemical that we could apply to our own needs. There are surely countless natural substances, many of them of great economic value that remain to be discovered. Each lost species, therefore, represents a lost opportunity for improving our lot.
Finally, many people argue for species protection on ethical and on aesthetic grounds. There is a well-known quote by the eminent biologists Paul Ehrlich and E.O. Wilson. They state, “People have an absolute moral responsibility to protect what are our only known living companions in the universe. Human responsibility in this respect is deep, beyond measure. We cannot easily measure our loss, or our guilt, in causing a species to become extinct.”
Common Questions about Preserving Earth’s Biodiversity
In GCMs, there is detailed information in every box on ocean currents, wind speed, humidity, distribution of mountains, cloud cover, vegetation; about atmospheric composition and temperature; about all different kinds of variables that we might associate with a chunk of atmosphere, or a chunk of land that interacts with the atmosphere.
A great advantage of global circulation models is that we can run controlled experiments on the entire Earth. We can rearrange the position of continents; we can change ocean currents; we can put mountain ranges in the way, or get rid of the mountain ranges, and see what happens. Each change in initial conditions yields a different global outcome.
One of the reasons to preserve species is to focus on our health and our well-being. Every living thing has its own unique set of genes, and therefore, its own unique set of proteins. Each of those proteins has the possibility of serving a useful function, as a chemical that we could apply to our own needs. There are surely countless natural substances, many of them of great economic value that remain to be discovered. Each lost species, therefore, represents a lost opportunity for improving our lot.
