How does rising atmospheric CO2 affect marine organisms?

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Thinking Outside the Climate Envelope
Volume 14, Number 1: 5 January 2011

In an overview of a symposium entitled "Molecules to Migration: Pressures of Life" -- which was held in Africa on the Maasai Mara National Reserve of Kenya -- Fuller et al. (2010) write that the theoretical approach most commonly used to predict future species distributions in a CO2-enriched and warmer world (i.e. the "climate envelope" approach) assumes that "animals and plants can persist only in areas with an environment similar to the one they currently inhabit." However, they say that this approach "typically ignores the potential physiological capacity of animals to respond to climate change," and they go on to explain how "behavioral, autonomic, and morphological modifications such as nocturnal activity, selective brain cooling, and body color may potentially serve as buffers to the consequences of climate change."

The six scientists begin by noting that all organisms "have the capacity to adapt to changing environmental conditions both by phenotypic plasticity within a life span and by microevolution over a few life spans." In the latter instance, they note "there is evidence that microevolution -- that is, heritable shifts in allele frequencies in a population (without speciation) -- has occurred in response to climate warming," citing Bradshaw and Holzapfel (2006, 2008). And in the first case, they say that phenotypic plasticity "is likely to represent the first response of individual organisms," and they report that "adaptive changes in phenotype induced by climate change have been documented, for example, in the morphology and phenology of birds (Charmantier et al., 2008) and mammals (Reale et al., 2003; Linnen et al., 2009; Maloney et al., 2009; Ozgul et al., 2009)."

So what are some examples?

Fuller et al. first cite the work of Pincebourde et al. (2009), who "showed that intertidal sea stars can behaviorally regulate their thermal inertia by increasing their rate of water uptake during high tide on hot days," which is "a response that affords protection against extreme aerial temperatures during subsequent low tides." Next, they note that "exposure of humans to hot conditions on successive days induces an increase in sweat capacity (Nielsen et al., 1993)." And they say that "other adaptations also ensue, including plasma volume expansion and decreased electrolyte content of sweat," such that "a typical unacclimatized male, who can produce about 600 ml of sweat per hour, can double that output with heat acclimatization (Henane and Valatx, 1973)," which "phenotypic adaptation (in this case, heat acclimatization) can alter physiological tolerance (the risk of heat illness)."

The Australian, South African and U.S. scientists also cite several studies -- Zervanos and Hadley (1973), Belovsky and Jordan (1978), Grenot (1992), Hayes and Krausman (1993), Berger et al. (1999), Dussault et al. (2004), Maloney et al. (2005) and Hetem et al. (2010) -- of large herbivores that "increase nocturnal activity in the face of high diurnal heat loads." And they say that "another adaptation that may enhance plasticity in response to aridity that is available to oryx and other artiodactyls, as well as members of the cat family (Mitchell et al., 1987), is selective brain cooling," whereby cooling the hypothalamus and the temperature sensors that drive evaporative heat loss "inhibits evaporative heat loss and conserves body water (Kuhnen, 1997; Fuller et al., 2007)," which result "is likely to be particularly valuable to animals under concurrent heat stress and dehydration." Last of all, they suggest that maintaining genetic diversity for a trait like fur or feather color that adapts various organisms to different thermal environments "may provide important plasticity for future climate change," citing Millien et al. (2006) and adding that "there is already evidence that, over the past 30 years as the climate has warmed, the proportion of dark-colored to light-colored Soay sheep has decreased on islands in the outer Hebrides," citing Maloney et al. (2009).

Clearly, much of earth's animal life is well endowed with inherent abilities to cope, either consciously or unconsciously, with climate changes over a period of a few generations, a single generation, or even in real time, which capacity is something totally foreign to the lifeless "climate envelope" approach that has typically been used by climate alarmists to project species migrations -- or extinctions -- in a potentially future warmer world.

Sherwood, Keith and Craig Idso

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