Implications of climate change for ecological restorations

The Intergovernmental Panel on Climate Change (IPCC) is a committee of hundreds of scientists from all over the world that has been reporting since 1990 to the United Nations its consensus predictions of the future of climate change.  They made their latest report recently and these are their primary findings:

• They report with 95% certainty that current climate change is being caused by the activities of humans, particularly burning fossil fuels.
• They predict that sea level could rise as much as 3 feet by the end of this century if current levels of greenhouse gas emissions continue.
• During the same timeframe and in the same conditions, the temperature is expected to rise between 2.7 to 8.1 degrees Fahrenheit.
• If carbon dioxide emissions double by the end of the century, as the current trajectory predicts, the IPCC says current climate trends will be irreversible.

The Earth’s constantly changing climate

The public is preoccupied with the current round of climate change as well as predictions of its trajectory and consequences partly because it may be within our power to stop the trend by reducing greenhouse gas emissions.  But we should not lose sight of the fact that the 4.5 billion year history of the Earth is a history of a constantly changing climate which humans did not influence.  Conventional wisdom is that current climate change is unique in that it is a more rapid change than past changes, making adjustment to the change more difficult for the Earth’s inhabitants.  In fact, many historical changes in the climate occurred even more rapidly when they were precipitated by cataclysmic events such as the impact of huge asteroids or volcanic eruptions.

Our readers may wonder where we are headed with this train of thought.  We hasten to preview our point lest our readers think our goal is to dismiss the seriousness of the current round of climate change.  Our intention in this article is to invite our readers to consider the absurdity of the concept of “native plant and animal species” in the context of the dynamism of nature, climate changes being one of the many factors in producing that dynamism.  We will use the last ice age as an example to illustrate this point, drawing from an excellent book on that subject:  After the Ice Age.  (1)

The Last Glacial Age

In the past billion years, there have been many glacial periods, popularly called ice ages.  It’s worthwhile to consider their cause to understand that they are as likely to occur in the future as they did in the past.  They are thought to be a consequence of the constantly shifting tectonic plates that change ocean currents as well as cycles in the rotation of the Earth and its orbit around the sun.  The former pattern is unpredictable, even random, and the latter is a more predictable sequence.  There are intervening variables that make this an oversimplification of the causes, but this is a sufficient explanation to make the main point: 

“At no time has there been a return to ‘things as they were.’  It is true that there must have been times when average temperatures were similar to those of the present.  Thus, before the beginning and after the end of the warmer-than-now hypsithermal interval [the warmest time interval between glacial periods], the average annual temperature must, for a while, have been much the same as now.  But in other respects, conditions would have been radically different, as there were still extensive ice sheets that would have cooled their immediate neighborhoods, and sea level was still about twenty-to twenty-five meters lower than at present” (1)

In other words, the changes in the Earth are always moving forward.  To suggest that a past period represents some ideal to be reified, is to treat nature as a still life painting rather than the motion picture it is.  Particularly at a time of rapidly changing climate, attempting to replicate a landscape that existed 250 years ago on the West Coast and 500 years ago on the East Coast is a fool’s errand (the pre-European landscape is selected by native plant advocates to define “native”).  The naturalized landscape that exists presently is surely better adapted to current conditions than whatever landscape existed hundreds of years ago.  As Matt Chew (Arizona State University) says, “belonging” is when the organism is capable of persisting. (2) The Natural Areas Program in San Francisco has demonstrated in the past 15 years that the plants that existed here 250 years ago are not capable of persisting here without intensive gardening.  Therefore, using Matt Chew’s definition, we might say they no longer “belong.”

The last ice age on the North American continent

The most recent ice age in North America was at its height 20,000 years ago and a tiny fraction of those glaciers persist in the Arctic today.  The climate oscillated many times in the past 20,000 years, but the over-all pattern was a gradual melting.  As the glaciers receded, they left a barren landscape, scraped of all vegetation and sculpted by the enormous weight of the ice and the eroding action of the rocks carried within the ice.  The ice was so heavy that it actually weighed down the land, lowering its elevation relative to the ocean.  As the ice melted, the land returned to its previous elevations when relieved of the weight of the ice.

As the ice melted, the land was slowly vegetated by seeds blowing onto the bare land, germinating, and growing.  The strength and direction of the wind was therefore an important factor in the process.  Which seeds blow in depends upon what plants are close by and the mobility of the seeds which varies by species.  Which seeds germinate depends upon the soil conditions where they land as well as the resource requirements of the seed species.  Local climate conditions will also determine which seeds survive:  the temperature, the hours of light, the amount of moisture and precipitation, etc. 

Add to this complexity of variables, the interaction of the plants as they grow, some hindering the growth of their neighbors by shading them, for example.  In other words, there are many different factors at play as the bare land is vegetated and those factors vary enormously from one place to another.  The outcome is random, largely unpredictable, and outside the control of human witnesses to the process. 

The initial vegetation of the bare ground as the ice melts is only the beginning of the story.  The rocky surface lacks nutrients initially.  Nitrogen-fixing plants are needed to begin the process of building soil from which subsequent species of plants will benefit.  Bacteria and fungi slowly populate the soil, contributing to its fertility for later plant arrivals.   Animals participate in the process by distributing seeds as well as selectively eating vegetation.

This is a severely truncated version of a far more complex story none of which humans could control.  We hope we have not exhausted your patience, but have given sufficient background to help you understand the most important point as explained by After the Ice Age:

 “There is a wealth of evidence, however, showing that climatic change is never ending.  Even if major climatic ‘steps’ are comparatively quick, it is almost certain that the climate in the intervals between steps undergoes continual lesser changes.  In the light of present knowledge, therefore, [Margaret] Davis’s view, that disequilibrium in ecological communities is much commoner than equilibrium, is the more acceptable.  It should lead, in time, to a much needed change in popular thought.  The notion espoused by so many nonprofessional ecologists—that the living world is ‘marvelously’ and ‘delicately’ attuned to its environment—is not so much a scientifically reasonable theory as a mystically satisfying dogma.  Its abandonment might lead to a useful fresh start in environmental politics.” (3)

We conclude with a nota bene:  this remarkable book was published in 1991!!!   Isn’t it long past time for the public to be aware of scientific information that has been available for over 20 years?  When will we abandon the mystical fiction that there is some ideal landscape that may or may not have existed hundreds of years ago that we must attempt to re-create?  Even if we thought such an effort would be of some benefit, what makes us think that it is physically possible, given the changes that have occurred in our environment?

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(1)    E.C. Pielou, After the Ice Age:  The Return of Life to Glaciated North America, University of Chicago Press, 1991

(2)    Matthew Chew, “Anekeitaxonomy:  Botany, Place and Belonging,” chapter in Invasive & Introduced Plants and Animals:  Human Perspectives, Attitudes, and Approaches to Management, editors Ian D. Rotherham and Robert A Lambert, Earthscan, 2011

(3)    Margaret Davis is “one of North America’s leading palynologists,” who studied the development of eastern forests after glaciers melted.