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DEAR SIR

Climate change, habitat destruction, biotic impoverishment, selective culling of large oceanic fisheries, nuclear catastrophes (e.g., the Fukushima reactors in Japan), melting glaciers, changing oceans from mildly alkaline to mildly acidic, sea level rise, and endocrine disruptors all affect the natural evolutionary processes of life on planet Earth. Other factors affecting evolution include stochastic events such as earthquakes and tsunamis, for which humankind is frequently ill-prepared to respond. Until the late 20th century and into the 21st century, humans labored under the false pretense that their actions alone controlled the course of nature and that water and land resources were theirs for the taking. Humankind has mistakenly taken for granted that the present biospheric life support system, in which Homo sapiens has evolved and flourished, has and will always be present.

The universal laws of biology, chemistry, and physics are, and always have been, in control. The 5 major periods of biological extinction that have occurred on this planet, each followed by a reconfigured biosphere, are reminders that time can be fleeting. The 5 major, global, biotic turnovers were all caused by physical events that lay outside the normal climatic and other physical disturbances which species, and entire ecosystems, experience and survive. The first, second, and third extinctions have been attributed to climate change with 25%, 19%, and 54% of taxonomic families lost, respectively. The fourth extinction involved 23% taxonomic families lost with no exact cause known. The fifth extinction was possibly caused by Earth's collision with another celestial body or a volcanic event, with 17% of taxonomic families lost (Eldredge 2001). The sixth great biological extinction appears to be underway (Larsen 2004). Species loss due to climate change and other factors resulting from humankind's reckless and selfish behavior is proceeding at a rapid pace. How long before Earth changes into an increasingly hostile, unstable, uninhabitable planet? All complex systems have tipping points that can only be identified in retrospect. Some changes that occur are irreversible and, thus, are major factors in evolution. Early warning systems could possibly be developed, but they are not available now; consequently, prudent precautionary measures to avoid tipping points are justified.

Complex, multivariate systems, such as the biosphere, contain a large number of interactive components and feedback loops that can dramatically and rapidly alter Earth's climate and change its biota (Cairns 2010). For example, billions of tons of carbon are stored as frozen hydrated methane on the ocean floor or as carbon dioxide and methane in frozen tundra soils. Global warming can release enough carbon from the ocean to induce rapid climate change. Because the residence time of carbon dioxide in the atmosphere may be as much as 1000 years (Solomon et al. 2009), the release of ocean-stored carbon into the atmosphere is increasingly probable for a very long time (ScienceDaily 2005).

The oceans represent approximately 70% of the biosphere and land represents approximately 30%; both are already in serious danger. Humankind cannot afford any devastating changes in either of these interactive systems; however, both are in an ecological crisis that could worsen if “business as usual” continues. The 2 °C increase in global mean surface temperature now represents the threshold between “dangerous” and “extremely dangerous” climate change (Anderson and Bows 2011), and anthropogenic greenhouse gas emissions are still increasing (ScienceDaily 2010).

The planet's oceans have changed from mildly alkaline to mildly acidic because of increased carbon dioxide. Because carbon dioxide is more soluble in water at lower temperatures, the concentrations are highest in the polar regions. Research suggests “…that 10% of the Arctic Ocean will be corrosively acidic by 2018; 50% by 2050; and 100% by 2100” (McKie 2009). This prediction is significant to shellfish and copepods, which are important sources of food for marine life (Lewis 2011).

The effects of small temperature increases on terrestrial organisms are already evident—increased growing season, spread of disease, eruption of disease carrying species, changes in rainfall patterns, and much more (Poulin 2006). Global agricultural productivity is down and exponential human population growth continues. How many of the present nearly 7 billion humans would make adequate hunters and gatherers if the present agricultural system is badly damaged by climate change?

Several evolutionary scientists speculate that the species most fit to survive these turbulent conditions will probably be small, short-lived, highly fertile organisms with superb dispersal abilities, high exponential population growth, and able to expand into a variety of habitats and to use a wide variety of resources (Rees 2010). They may or may not be regarded as food for Homo sapiens. Almost certainly, they will compete with humans for available resources. If the past great extinctions are a useful guide, a new biosphere will eventually emerge and will be composed mostly of new, different species. Nurturing the present biosphere may help retain some of the conditions still favorable to the human species and will require that human practices are more congruent with universal laws. Nurturing will be facilitated by continual, in-depth scientific research on these laws.

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John Cairns Jr jcairns@vt.edu*, * Virginia Polytechnic Institute and State University, Department of Biological Sciences, 1016 Derring Hall, Blacksburg, Virginia 24061, USA