One of the striking things I noticed this summer in New Jersey, during brief intense heatwaves coupled with drought, was the increasing number of dead trees in the forests around here, as well as trees that were in the process of dying. When I wrote my diary on nitrogen and trees that I linked above, I was unfamiliar with the mechanism by which trees die in drought (and heat) conditions, but now, regrettably, I am far more familiar with the process.
Although the types of trees that were being killed by these climate related events included many hardwood species, it would seem, in terms of destruction that pines suffered the worst, just as they did in the two recent hurricanes here.
You cannot pass very many houses in my neighborhood that don't feature a huge pile of destroyed pine in front of them.
If you check around in the scientific (or even Pop google based) literature, you can quickly learn that pine forests are the forests that are most dramatically connected with destruction owing to climate change. Often the mechanism involves drought and heat alone, but more often a subsidiary effect related to the weakening of tree resistance to parasites because of drought and heat is involved. For instance, in Western North America, vast stretches of lodgepole pine are being destroyed by pine beetles, and one of the reasons involves the fact that winters that kill off the beetles are observed with decreasing frequency. Science: Climate Change Sends Beetles Into Overdrive.
There's no mystery here.
And then there's the matter of fires...
And then there's mistletoe...
Some excerpts from the paper cited above:
Forest decline has been detected worldwide being linked to multiple interacting factors including biotic agents and drought induced stress (Allen et al. 2010). Following the Manion (1991) decline model, drought-stressed trees may be negatively affected or even finally be killed off by secondary biotic agents such as mistletoes, insects and pathogenic fungi (McDowell et al. 2011). Interactions among decline drivers may be complex because climate change may also alter tree–organism relationships in drought-prone ecosystems with important implications for tree growth and survival (Ayres and Lombardero 2000).For instance, warming-induced drought stress may make host trees more vulnerable to the negative effects of hemiparasitic plants such as mistletoes. However, few detailed data exist on how mistletoe infestation and drought affect tree growth through time...
The authors opine that one can discern the effects of drought, along with parasite infestation, by examining the growth patterns (wood production) of the trees that died as a result of these processes, this as a surrogate for direct determination of their carbon budgets.
Mistletoes are perennial and aerial hemiparasitic plants of trees and take from their hosts water, photosynthates and mineral nutrients, thus increasing the drought stress and compromising the carbon balance of the host tree, particularly in areas with pronounced water deficit (Glatzel and Geils 2009). The main hosts of European pine mistletoe (Viscum album ssp.austriacum L.) are Scots pines (Pinus sylvestris L.) (Zuber2004). Previous studies indicate that pine mistletoe can adversely affect long-term tree growth and vigour in drought prone areas (Dobbertin et al. 2005). For instance, in dry inner valleys of the Swiss Alps, Scots pines infested by mistletoe showed mortality rates to be more than twice that of noninfested trees, and most defoliated trees were among the most vulnerable individuals to stress imposed by mistletoe on its host tree (Dobbertin and Rigling 2006). Rigling et al. (2010) suggested that pine mistletoe increases the risk of drought induced mortality of its host making trees more susceptible to drought stress when growing in a xeric environment due to the enhanced needle loss. Such mistletoe-related defoliation of tree crowns was also suggested as a decline driver of trees affected by dwarf mistletoes in Northern American forests (Geils and Hawksworth 2002).
How about a kiss?
Some technical stuff, for technical people, much maligned as they are:
The study site is a Scots pine (Pinus sylvestris L.) forest located in Teruel, Eastern Spain (40°22′26″N, 0°40′14″ W, 1585 ma.s.l.), i.e., near the southern distribution limit of the species (Figure 1). The mean density and basal area of the site are600 trees ha−1 and 19.4 m2 ha−1, respectively. The site is located on an almost flat slope (0–5°). The climate in the study area is Mediterranean with continental influence. The mean annual temperature is 9.4 °C and the annual precipitation is670 mm (see Table S1 and Figure S1 available as Supplementary Data at Tree Physiology Online).Climate data To obtain a robust regional climatic series, local data from four meteorological stations located from 10 up to 30 km from the study site were combined into a regional mean for the period1954–2008 (see Table S1 available as Supplementary Data at Tree Physiology Online). To estimate the missing data for each station, and to combine them, we used the MET program from the Dendrochronology Program Library (Holmes 1994). For each station, monthly variables (mean temperature and total precipitation) were transformed into normalized standard deviations to give each station the same weight in calculating the average monthly values for each year. We calculated a regional cumulative water deficit using a modified Thornthwaite water-budget procedure based on the mean temperature and total precipitation monthly data (Willmott et al. 1985). Soil water balance was modelled by estimating soil water withdrawal, recharge and surplus using the AET calculator program developed by D.G. Gavin (http://geography.uoregon.edu/...). The soil water balance is modelled on a daily time step by estimating actual evapotranspiration (AE), recharge and surplus…
This study was in Europe, but is applicable around the world.
There's a whole bunch of blah...blah...blah...technical stuff in this paper, the chemistry of wood, biophysics...blah...blah...blah...it's a fine paper, but I suspect that nobody cares.
I'll cut to the chase, from the concluding remarks:
To conclude, mistletoe infestation increased defoliation and induced growth decline in host trees. The decline in radial growth was exacerbated by drought stress. Further, this growth decline was particularly noticeable in the stem apex. The studied forest is located near the southernmost distribution limit of Scots pine, i.e., probably close to the xeric climatic limit of the species. If drought frequency and severity increase in the study area during this century due to rising temperatures, which is the most likely climatic scenario (IPCC2007), increasing water deficit in spring may aggravate the negative impacts of expanding mistletoe infestation causing growth decline and enhancing defoliation. Nevertheless, the role assigned to mistletoe as an opportunistic stressor (a ‘contributing factor’ sensu Manion 1991) negatively affecting growth of trees already weakened by drought (‘inciting factor' sensu Manion 1991) should be adequately and critically evaluated. Long-term mistletoe effects on tree growth and performance in drought-prone forests may be cumulative, i.e., acting when mistletoe has invaded most of the tree crown and after successive severe droughts. Our study suggests that mistletoe may act as a ‘predisposing factor’ sensu Manion (1991) by predisposing trees to drought effects on tree vigour (increased defoliation and reduced radial growth), so they enter a decline process in which other pathogens, e.g., bark beetles, could ultimately cause death of the tree.
The bold is mine.
The brief attention paid here to climate change after Hurricane Sandy, like the brief attention paid after Hurricane Katrina, has now passed into history. Neither New Orleans nor New York were permanently inundated with seawater but they will be.
The crisis de jour is, I recognize, concerned with the horrible murder of children in their schools this week.
Here is what I think will be done about gun control in this country: Nothing. It will be forgotten until the next time, when it will get brief attention, attention that will in turn, be forgotten.
Even worse for children than this particular burst of horror, will be what I predict will be done about climate change: Nothing.
The mentality associated with climate change here, and almost everywhere else in the world, as far as I can tell, is best expressed by a diary here that was just a sign post in my ever widening disillusionment with any kind of seriousness ever arising with respect to the climate and environment: I'll be 104 in 2050, and I want to live in a world powered by renewable energy.
"I want! I want!"
Tell it to Santa Claus. (Santa Claus was invented by the way, by a previous generation that did live - albeit often short and brutal lives - in a world that was powered by so called "renewable energy," one consequence being, um, the destruction of forests.)
"But I want! I want!"
"I want! I want!" This is the clarion call of the baby boom generation that wasted their lives talking endlessly about dumping the onus for their irresponsibility and indifference and distractability on future generations.
Children who are between the ages of five and ten, the children the age of the children for whom we grieve today will not have the tools to survive what is coming, never mind provide much for cranky Centenarian who will still be screaming "I want! I want!."
They want. They want. They want.
Somehow I think that in this country a real discussion of "want" is impossible.
May you get everything you want for Christmas, Kwanza, Hanukkah, whatever...
I apologize in advance for this cynical Christmas diary.