How does rising atmospheric CO2 affect marine organisms?

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The Specter of Species Extinction
Will Global Warming Decimate Earth's Biosphere?

X. Discussion of the Results of Parmesan and Yohe's Additional Studies


Of the twelve studies analyzed by Parmesan and Yohe, above and beyond those analyzed by Root et al., two appear to directly refute the CO2-induced global warming extinction hypothesis (PY.2, PY.9).  The first of these studies describes opportunistic upslope migrations of plants that do not displace higher-elevation species and therefore end up increasing mountain species richness.  The second study describes both latitudinal and elevational distributions of a butterfly species that is not precluded from living across a range of temperatures comparable to those found hundreds of kilometers south of the United States' border with Mexico to those found hundreds of kilometers north of the United States' border with Canada.

Three studies describe opportunistic extensions of cold-limited range boundaries in response to regional warming (PY.5, PY.7, PY.8).  The first deals with foxes in North America and Eurasia, the second with shrubs in Alaska, and the third with vascular plants in Antarctica.  All of the range extensions appear to have benefited the species in question and none appears to have threatened any other species with extinction, although one species of fox forced another species of fox to move further north as it encroached upon its territory.  As earth's climate alternately warms and cools in natural cycles, however, this shifting of the foxes' competition-determined boundary is but a part of the natural scheme of things; and as it has been considerably warmer over much of the current interglacial than it is now - by 2 to 6°C, in fact (Taira, 1975; Porter and Orombelli, 1985; Huntley and Prentice, 1988; Korotky et al., 1988) - the simple existence of both species today is living proof that even the most cold-adapted of them can "take the heat" of a major climate warming.

Four studies document shifts of species' ranges in response to changes in climate (PY.1, PY.3, PY.4, PY.6).  The first deals with populations of Adelie and chinstrap penguins in Antarctica that follow the climatic conditions to which they are each best suited, alternately replacing one another in different locations as the climate either warms or cools.  The second deals with macroinvertebrates in a rocky intertidal community just off the California coast, where warming between 1931-33 and 1993-96 led to the replacement of many "northern" species by "southern" species.  The third deals with certain crustaceans in the eastern North Atlantic Ocean and European shelf seas, some of which shifted north in parts of the region that warmed between 1960 and 1999 and some of which shifted south in parts of the region that cooled over the same time period.  The fourth deals with near-shore reef fishes in the Southern California Bight, where dominance shifted from cold-affinity species to warm-affinity species after a 1°C increase in temperature centered on 1976-77.  In all four cases, there were no indications that any species suffered as a result of the temperature-induced range shifts; they merely appeared to move from one location to another.

The final three studies reviewed by Parmesan and Yohe are a mixed bag of oddities.  Although the globe is known to have warmed substantially over the past century, a study of exposed tree-line sites in Canada (PY.10) could find "no conclusive evidence of a positive vegetation response."  In another study (PY.11), it was determined that pine trees on islands of the Lower Florida Keys died as a result of "the salinization of ground- and soil-water that occurs as sea level rises."  With respect to the CO2-induced global warming extinction hypothesis, therefore, which says rising temperatures will force species to migrate faster than they are capable of doing, these investigations have little relevance.  Finally, the study of Johnson (PY.12) describes species of birds extending their ranges in every direction imaginable in the western United States and concludes that climatic warming is not the primary cause of the range expansions, making one wonder how this and many of the other studies cited by Parmesan and Yohe could possibly be used to support irrational fears of impending species extinctions driven by CO2-induced global warming.