Canadian Greenhouse Emissions Thrown Off By Bugs

Simon Donner has  a couple of posts on Canadian Green House Gas emissions and the government's spin on them.  In the first, he notes that:

GHG emissions grew by only 2 Mt CO2e (that includes CO2 plus other GHGs converted to "units" of CO2) despite the fact that the economy was rebounding from the recession. This was viewed by some, including the Environment Minister, as good climate news, because it suggests that  the economy is decoupling from greenhouse gas emissions.

While casting a skeptical eye on the alleged decoupling--after all, our current federal government's economic strategy relies on Canadians returning to their roots as resource extractors (hewers of wood and bearers of bitumen)--he notes in the second post that, in any case, this apparent progress has been undermined by other circumstances:

...if you include land cover, land use change and forestry, GHG emissions grew by 86 Mt from 2009 to 2010 [rather than the reported 2 Mt]. 

Why such a large change? According to the Canadian government model, forests went from a net sink of 17 Mt in 2009 to a net source of 72 Mt in 2010 (see Table 7-1 in NIR). If you break the GHG balance of forests up by region, the driver of this change was the "Montane Cordillera", or #14 on the map to the left. These forests of western BC were a net source of 100 Mt. The only other net sources regions in 2010 were the "Boreal Shield West" (#9 at 22 Mt), the "Pacific Maritime" (#15 at 5.7 Mt) and the "Taiga Shield East" (#4 at 1.7 Mt).

He's got a nice chart showing these regions:

So what's up with the forests of western B.C., which have gone from a carbon sink to a carbon source?  The answer comes from the government's National Inventory Report itself:

The upward trend in dead organic matter (DOM) decay since the year 2000 reflects the long-term, growing effect of past disturbances, especially insect epidemics that have left substantial quantities of decaying DOM. Over the last decade, insect epidemics have affected a total of over 56 Mha3 of managed forests, with 72% being located in the Montane Cordillera reporting zone and corresponding to the epidemics of Mountain Pine Beetle. In contrast, much of the interannual variability of the GHG budget of managed forests hinges on the occurrence and severity of fires.

This result is something that has been predicted for awhile, and will presumably get worse now that the beetle has jumped the Rocky Mountains and been found able to tolerate Alberta's cold winters.  And, as an interesting side note, last year's Alberta wildfires, which shut down enough tar-sands production to lop a few tenths off our national GDP, can at least be partially attributed to beetle infested trees, which burn to a savage intensity