Saturday, March 27, 2010

forests are red

--climate happenings are at the data bank--

A startling piece of information in the data flow is on the partial collapse of western forest ecosystems. The great forest die-off, by Montana-based New York Times journo Jim Robbins, appeared first on 3-16 at Yale's Environment 360. This is what it says:
Across western North America, from Mexico to Alaska, forest die-off is occurring on an extraordinary scale, unprecedented in at least the last century-and-a-half, and perhaps much longer. All told, the Rocky Mountains in Canada and the United States have seen nearly 70,000 square miles [180,000 sqkm], an area the size of Washington State, die since 2000.
Basically all western conifers are threatened, especially mountain pines; Colorado sees also a die-off of aspen. commondreams posted the piece next; comments there (3-21) add more factoids and threaten to spawn an unwelcome gestalt: in British Columbia, conifers are dying faster than loggers can remove them / in Minnesota, ash are dying / in Indiana, elm and dogwood are dying / in Michigan maple and beech are dying / in Appalachia, hemlock and oak are dying / at the west coast, oak are dying.

The huge American injection of GHGs into the Earth System is a main factor driving global warming. Global warming to date has involved greater seasonal oscillations and rising temperatures, which, in the western half of North America, show themselves in warmer winters. Warmer winters let tree parasites such as bark beetles survive easier. Higher winter survival rates cause bigger parasite proliferation in spring and summer. Trees sicken in greater numbers, more intensely, and over larger areas. And die.

This is a causal cascade typical of the emerging realities. Americans drive Dodge Rams and Ford F-150, and oops! forests turn red. The way of Nature is a wave. As long as trees infested in summer have a chance to get clean in winter, they're ready for another round next year, and beetles and trees can coexist. But when trees infested in summer carry the burden over into winter, they weaken come spring and eventually get exhausted. The stress killing them off can also be understood as a symptom of exposure. Like fields and limits, exposure is a concept to explain the phenomena of climate change.

See also

C. Allen et al., "A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests," Forest Ecology and Management 259 (2010): 660-684

Meanwhile realclimate ran a thread on the Amazon dieback, with entries here and here. This is another seed of destruction. First one reads about Amazon dieback in pessimistic climate scenarios a la Lovelock--not his most recent book, The Vanishing Face of Gaia, 2009, but the previous volume, Gaia's Revenge (New York: Basic, 2006, p. 30)--and then the topic spreads, like into this 2010 thread.

Relevant papers are

A. Samanta et al., "Amazon forests did not green up during the 2005 drought," Geophysical Research Letters 37 (2010) L05401

which is a response to

S. Saleska et al., "Amazon forests green-up during 2005 drought," Science 318 (2007): 612

and which had already been qualified by

O. Phillips et al., "Drought sensitivity of the Amazon rain forest," Science 323 (2009): 1344-1347
Lovelock, 2006, 30, writes,
R.Betts ... has shown how the great tropical rainforests have to some extent overcome this limitation [of water evaporating faster in heat] by adapting to their warm environment so as to be able to recycle water. The ecosystem does it by sustaining the clouds and rain above the forest canopy, but this ability has limits. He and P.Cox suggest a 4 C rise in temperature would be enough to disable the Amazon forest and turn it into scrub and desert, and it would happen partly from the local consequences of a faster evaporation of rain but also from global changes in wind patterns in a 4 C warmer world.
Betts (Hadley Centre) has done various items on the topic, e.g.:

R. Betts et al., effects of large-scale Amazon forest degradation on climate and air quality
Phil. Trans.of the Royal Society B 327 (2008): 1873-1880

C. Jones, R. Betts, the impact of climate change on major habitats
Met Office PPT, The Linnean Society 27.11.08

A non-technical account of how climate change forces Amazon dieback is in S. Faris, Forecast (NY: Holt 2009), ch. 4 p.114-115

For North America, the upshot is simple: climate change warms winters, and the trees can't take it. For South America, the upshot is also simple: climate change reduces rainfall in the dry season, the trees don't like it, and eventually can't take it either. In the rainforest, it's the old giants that die of thirst first. As they keel over and crash down, they open gaps in the forest. The unbroken rainforest is fire-resistant. The forest with gaps is not. Less rain in the dry season signals what might be called the power-up, the amplitudinal growth of seasonal waves that comes with the change.

Sometimes only a dictionary helps.

The OED defines "poignant" as 1. sharp-pointed, piercing, 2. pungent, piquant, 3. moving, touching, 4. hurtful, 5. keen


Eighty-one months left.

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