Climate Change Enhanced Wildfires: Will These Burned Forests Grow Back?

My friend (and fellow GTU PhD) Peter Hess wrote an excellent post today for the National Center for Science Education highlighting the strong links between climate change and wildfires. California has wildfires every summer, but this year’s Rim Fire has been particularly nasty, growing to be the fourth largest fire in state history, and consuming nearly a quarter of a million acres.

Peter explains that with climate change we should expect things to get worse:

Climate change is likely to exacerbate this situation by changing many of the variables influencing fire behavior. Some regions will no doubt experience prolonged droughts (e.g. Arizona, New Mexico, and Colorado), leading to pine and fir beetle infestations that will kill thousands of trees. This increased load of dead and downed fuel will amplify fire potential, and when a fire is started we may find that a changed climate has altered patterns of humidity, air temperature, and wind speed. Fires will burn hotter and more destructively, delaying or even preventing full recovery after an area has been burned.

That is all bad, but it is actually even worse. Hotter climates, lower humidity, increased drought, and increased extreme weather are all bad, but the lingering effects threaten to take on a life of their own.

Wildfires have no doubt existed since land plants first evolved. Plants burn, CO2 goes out, plants grow back, and the CO2 goes back in – a balance.  But the balance is now shifting slightly. Wildfires present a positive-feedback loop for warming: burning releases CO2, CO2 causes more warming, changing climate and causing more drought, due to changed climate forests do not re-grow, the CO2 released from burning is not reabsorbed from the atmosphere, and the cycle only gets worse. And earlier spring melt and later arrival of winter extends the fire season, leaving a larger vulnerable window for these events to occur.

In California, certain types of forests are only found at certain elevations. They depend on the altitude for adequate climactic conditions: enough cold, enough snow, enough humidity, enough water. With climate change these climactic conditions and therefore ideal altitude distributions are going to migrate higher – until the mountains run out (and/or the Sierra granite proves impossible to grow in).

A huge swath of Sierra forest has just gone up in smoke. What replaces it will likely not be the same type of forest as what just burned, in fact it might not be forest at all – it might be open woodlands, chaparral, or even desert. These lands will not absorbs CO2 like a forest would. In fact, these replacement ecosystems might be like nothing that we are familiar with – this has been called “the no-analog future,”  with ecosystems not analogous to ours at all.

The quip “prediction is very difficult, especially about the future” is attributed to Niels Bohr, and it ever remains true. But we can tell this much: the world is changing, and the changes are generally not for the better. Unless we want a future where human society is at serious risk for numerous major and disanalogous disasters we need to get the Earth’s CO2 budget significantly in the negative, and soon.


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