Tag Archives: drought

Higher climate temperatures mean more and faster tree deaths

Higher average temperatures acres of pine trees dead due to pine beetles mean much more frequent droughts and trees dying faster in droughts because of the temperatures. That plus pine beetles, according to research from 2009. Forestry is Georgia’s second largest industry in terms of employment and wages and salaries, more than $28 billion a year according to the Georgia Forestry Commission, plus an estimated $36 billion a year in ecosystem services such as water filtration, carbon storage, wildlife habitat, and aesthetics, not to mention hunting and fishing. Climate change matters to Georgia’s forests and to Georgia.

The paper appeared 13 April 2009 in the Proceedings of the National Academy of the Sciences, Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought, by Henry D. Adams, Maite Guardiola-Claramonte, Greg A. Barron-Gafford, Juan Camilo Villegas, David D. Breshears, Chris B. Zou, Peter A. Troch, and Travis E. Huxman, 106(17) 7063-7066, doi: 10.1073/pnas.0901438106.

Fig. 1. Water relations progression and death dates.

All drought trees in the warmer treatment died before any of the drought trees in the ambient treatment (on average 18.0 vs. 25.1 weeks, P <0.01; Fig. 1A).

They say warmer trees dying faster in drought wasn’t due to a difference in amount of water. Instead, they infer the warmer trees couldn’t breathe.

Combined, our results provide experimental evidence that piñon pines attempted to avoid drought-induced mortality by regulating stomata and foregoing further photosynthesis but subsequently succumbed to drought due to carbon starvation, not sudden hydraulic failure. Importantly, we isolate the effect of temperature from other climate variables and biotic agents Fig. 3. Drought frequency and die-off projections. and show that the effect of warmer temperature in conjunction with drought can be substantial.

Our results imply that future warmer temperatures will not only increase background rates of tree mortality (13, 16), but also result in more frequent widespread vegetation die-off events (3, 35) through an exacerbation of metabolic stress associated with drought. With warmer temperatures, droughts of shorter duration—which occur more frequently—would be sufficient to cause widespread die-off.

How much more frequently? They calculated an estimate for that, too: five times more frequently. Of course, that’s for the specific kinds of forests they were studying, and the exact number may vary, but the general trend is clear: higher temperatures mean more frequent droughts, like drought in south Georgia the year-long drought we just experienced in south Georgia.

pine beetle tube

This projection is conservative because it is based on the historical drought record and therefore does not include changes in drought frequency, which is predicted to increase concurrently with warming (2, 37—39). In addition, populations of tree pests, such as bark beetles, which are often the proximal cause of mortality in this species and others, are also expected to increase with future warming (7, 9, 38).

Bark beetles, such as the ones that bored into this 19 inch slash pine and spread from there to twenty others I had to cut down to prevent further spread of the pine beetles. What happens when pine beetles spread is what you see in the first picture in this post: acres and acres of dead red pine trees. slash pine killed by pine beetles Monoculture slash pine plantations may show this effect most clearly, but look around here, and you’ll see red dead loblolly and longleaf pines, too.

The article is saying that if the beetles don’t get the trees weakened by droughts that will be much more frequent, the trees will die more quickly of suffocation, because the temperature is higher. Higher temperatures is something that should concern every Georgian in our state where forestry is the second largest industry and our forests protect our wildlife and the air that we breathe and the water that we drink.

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Largest U.S. declared drought disaster ever

It's not just us. More than half the country is in drought, and almost one third is in a federal disaster area for drought: the biggest ever declared.

Dashiell Bennett wrote for Atlantic Wire today, U.S. Declares the Largest Natural Disaster Area Ever Due to Drought

The blistering summer and ongoing drought conditions have the prompted the U.S. Agriculture Department to declare a federal disaster area in more than 1,000 counties covering 26 states. That's almost one-third of all the counties in the United States, making it the largest distaster declaration ever made by the USDA.

The declaration covers almost every state in the southern half of the continental U.S., from South Carolina in the East to California in the West. It's also includes Colorado and Wyoming (which have been hit by devatasting wildfires) and Illinois, Indiana, Kansas and Nebraska in the Midwest. However, it does not include Iowa, which is the largest grain and corn producer in the U.S. This map show the counties affected:

Look, there we are, right in the center of the red area in the southeast!

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Protracted extreme drought: U.S. Drought Monitor, 2012-05-08

Acording to U.S. Drought Monitor, drought throughout south Georgia and surrounding areas is either extreme or exceptional, and has been for months.

Here you can see detail for Georgia:

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Groundwater levels: red

In case anybody thinks the recent rains have done away with the drought in Georgia, take a look at this USGS map of groundwater levels today:

USGS Active Groundwater Network map 18 April 2012
Legend for USGS Active Groundwater Network map 18 April 2012

South Georgia, all red and orange. Here’s more detail.

It’s also worth remembering that while our Floridan Aquifer does recharge somewhat, that much of its water has been there since the last ice age. So if we keep mining water at a rapid rate, the aquifer will keep falling.

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