Tuesday, May 17, 2016

Alberta forest fire update: the monster is not dead yet..

 abbreviations employed:

CO2 - a greenhouse gas, contributing to global warming
GHG - greenhouse gas
GW - global warming  

              Never count a good fire down. With tinder dry conifer forest, high winds and little rain, Alberta's fire season got off the blocks early and strong this year. The Fort McMurray fire, covered in a previous article, is still technically "out of control" (the best one can do is steer it away from population centers and critical infrastructure).


           Steered by shifting winds, the fire has turned and once again threatens the city of Fort McMurray. Crews carrying our repair of essential infrastructure in the city are now being forced to leave due to poor air quality.            Two weeks ago oil sands work camps north of the city received fire refugees. Now the camps themselves are threatened and under "mandatory evacuation order" meaning that some fire refugees are being forced to evacuate for the second time in two weeks. 

                           climate crisis: when the 1st world meets the 3rd world?

            Oil sands extraction plants which recently recalled their work forces and restarted operations have been forced to reclose operations and re-evacuate their employees. Meanwhile, one work camp housing 665 employees has been destroyed and two others are under mandatory evacuation orders. Suncor corporation claims that it has sufficient fire fighting capacity to protect its extraction and processing facilities. Only time will tell..


            The following report commissioned by the United States Forest Services indicates quite clearly what the future warmer climate will mean in economic terms:

"Over the last few decades, however, wild land fire suppression costs have increased as fire seasons have grown longer and the frequency, size, and severity of wildland
fires has increased."


             Quantitatively, what do these findings indicate in concrete, practical terms?

             Well, to begin with, the average fire season in the USA has grown by an incredible 78 days since 1970. If you do the math that works out to a whopping two and a half week increase in the average US state's fire season per decade! The climate is not (rapidly) changing, you say? 

             Twice as much forest area burns today than did three decades ago. Translate: acreage burnt increases by 33% of the 1985 fire losses each decade for the last three decades. And the annual losses may double again by midcentury..

             Twenty years ago, the US Forest Services spent just a sixth of its annual budget on fire suppression. Today, fire suppression counts for a full 50% of the annual budget, a tripling of costs (on a percentage basis). Accordingly, other services have had to be cut back (for we live in a time of anti-government neoconservative "Free Market" Ideology). Forest Services staff not engaged in fire suppression have been cut by 39%. These figures are telling and their magitudes indicate that these long term shifts in forest fire behavior are probably not due to "natural cycles and fluctuations".

             To be fair, it should by noted that aging Baby Boomers are retiring to wooded areas. These new developments usually lack "fire wall" cleared spaces - so as not to compromise the scenic beauty so appreciated by well-heeled Boomer pensioners and semi-retired professionals. In addition, ignorance of the positive ecological functions provided by periodic burns, has created disastrous fire suppression campaigns which have actually created fire prone fuel stocked forest floors. 


             Thus, badly conceived, anti-ecological forest management and stupid municipal zoning practices have contributed to the increased incidence and cost of fires. But they cannot account for all the increase. For example, the incredible lengthening of the fire season by two and a half weeks per decade in the US requires understanding in terms of global warming (GW) and decreased annual percipitation. Example: the recent Alberta and US west coast droughts (California and environs). The next time you are at a cocktail party or BBQ and some idiotic GW "sceptic" says he would actually like winter a few degrees warmer, let him know about the results of the US Forest Services report..

             From several perspectives, boreal (northern) forests fires are very troubling. Many of these forest "sequester" incredible amounts of carbon because the north is cold much of the year. Cold suppresses microbial decomposition of organic matter: this is why we freeze food to stop it going bad. In the case of boreal conifer forests organic carbon can accumulate as dry forest floor "duff".

            You can click on the above image for higher resolution. This duff is composed mostly of fine dead - and dry! - twigs and small branches. Obviously super-flammable.

            In conifer forests, the forest litter can also be composed of pine needles and cones. Again, highly flammable..

            Depending upon the amount of annual decomposition permitted by the local climate, duff can accumulate to produce a thick carpet. In some northern ecosystems, this process produces a deep humid carpet (peat), which is highly acidic (thus hindering decomposition: pickles are acidic, right..). GW dries out peat bogs making their rich carbon content available for burning.

            In subarctic climates, forest litter can accumulate over a layer of permafrost, permanently frozen soil left over from the last ice age. The duff or peat act as an insulator protecting the permafrost from melting. As long as the permafrost remains frozen its rich carbon content will not be attacked by bacteria and fungi. 

           Global warming liberates this naturally sequestred carbon in several ways.

           Direct warming will cause more southerly permafrost to thaw and decompose as a result of microbial digestion. This liberates GHGs like CO2 and methane which then "amplify" the initial warming. Thus, due to liberated GHGs an initial 1 C rise in temperature may be magnified, say, into a 1.4 C rise (see footnote 1).

                However, duff and peat dried by GW, provide lots of carbon for forest fires.

                Very interesting fires too: they can smolder (sometimes unsuspected) for years underground, actually providing enough internal heat to withstand subartic winter temps (-30 C and below) - such are the insulating properties of duff and dried peat.  

               Now, a burning duff or peat layer has two effects (at least!). First, as the organic layer disappears, it exposes underlying "fossil" permafrost (left over from last ice age), to warmer modern atmospheric conditions. The permafrost thaws and begins to rapidly decompose, liberating GHGs and further warming the earth. Secondly, burning duff or peat directly heats and dries the permafrost. In some cases the dessicated, thawed permafrost becomes immediately available as a fuel for a northern peat fire. Such fires can liberate incredible amounts of GHGs (CO2, methane), amplifying GW.

              In the above figure, "mineral soil" indicates a frozen, lifeless permafrost layer containing massive amounts of sequestered organic carbon. The burning peat or duff layer thaws and dries the underlying permafrost making its stored carbon available as fire fuel or as food for microbial digestion (source of GHG).

               In contrast, the deforestation of tropical rain forests, while immoral, criminal and suicidal, does not liberate as much GHG as burning northern forests, peat bogs and tundra (nordic ecosystem beyond the tree line). Tropical soils, due to constant rapid decomposition of organic matter, are actually carbon impoverished.

                Burning the northern forests, peat bogs and tundra is potentially much more dangerous and impactful than burning equatorial rain forests. Northern burning could trigger rapid, possibly uncontrolled, positive feedbacks, amplifying ongoing global temperature rises. And the northern forests and peat bogs are starting to burn to a degree and in ways formely unknown (to find climate analogs you have to go back to previous geological epochs when the earth was decidedly warmer than it is now).  



1- Some hardcore ("Death Metal") Doomers argue that an apocalypic runaway positive feedback might be established in which GW causes massive release of GHG sequestered in the earth and in offshore seabeds. The earth, they say, could end up as a superheated, lifeless greenhouse planet like Venus. There is, in fact, some paleontological, paleoclimatic evidence to support the existence of rapid GW involving such feedback mechanisms. The Permian extinction, 250 million years ago, is one case in point. However, even that Mother of Great Extinctions, did not push the earth into a terminal Venus-like greenhouse state. In fact, given all the past excursions of climate, temperature and GHG content of the atmosphere, if the earth were prone to catastrophic runaway GHG warming, it probably would have happened already and I wouldn't be here to write about it or you to read about it!) 


No comments:

Post a Comment

Note: Only a member of this blog may post a comment.