Dead Plants

Acorns A-Plenty

One David Maddox of the Nature Conservancy in Arlington, Virginia, in a report to the AP [6/29/92], assumed a 5° C warming by 2100 and concluded that 21% of all US plant life would be destroyed and that 50% of all rare plant species would croak. Death by too rapid global warming means the "envelope" for the species is no longer available. There is no word if the temperature in question is average temperature, minimum temperature or maximum temperature. Mark Schwartz, of the Illinois Natural History Survey says the work of Maddox is a good starting point to identify vulnerable species, but to "say they are goners" is going a bit far. He notes beech trees are as happy in Florida and Georgia as they were at the end of the last ice age.

This reporter views the problem differently. CED readers are aware that all the warming thus far (cause unknown) is nocturnal warming with daily maximum temperatures unchanged over the period of record. It is not at all clear that daily maximum temperatures are in any way set by greenhouse gasses. Sunlight with latitude, time of day and time of year variations, evapotranspiration rates and cloud cover seem to explain variation in daily temperature maxima. Greenhouse gases retard nighttime cooling. Without them our nighttime temperatures would average around 255 K (-18°C). Most studies of vegetation response to global warming use average temperatures. They kick it up and see who doesn't make it. The literature on vegetation control by average temperatures is scarce and literature on physiological control scarcer-yet. Low temperature control, photoperiod, water sufficiency, growing season length and growing degree-days all seem important. Temperature maxima are important in setting the vapor pressure deficits and evapotranspiration losses but the evidence that maximum temperatures are set by greenhouse gases is lacking.

As reported in this blog, we are in a plateau phase in the contemporary history (16 years and counting). So says the NewYirk. We don’t know what the still-stand in average temporatures fortells for our plants on “death row”. Don’t count your acorns before they germinate.


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