Tuesday, October 23, 2007

Ecological causes and effects of SoCal fires: Initial thoughts

There are numerous wildfires currently blackening southern California. The short term response has to be to the fire itself. Save the people, save the pets, save the homes and the businesses. But what should be the response when the fires are out? Ruibiuld everything exactly as is was? That is the most likely outcome. After a disaster, people want to rebuild, regardless of how likely it is that disaster will happen again. But how likely is it these fires will return? What ecological factors played into this disaster, what ecological effects can be expected and what lessons should we draw from all of this?

I feel it is important to raise these issues before everyones attention moves on and we fail to learn from previous mistakes. I'll appreciate your input and comments.

With no further ado:

Ecological Causes:

1. Obviously the big'un is the Santa Ana Wind, the hot dry wind that blow-dries out of the Great Basin and over southern California every year. The topography and climate of coastal southern California, combined with the Santa Anas make for fires pretty much every year. It is being reported that the Santa Ana's are stronger and more persistent than usual this year. It is not yet known, so far as I know, if the Santa Ana's are expected to be stronger every year now that the Great Basin's climate is turning much hotter and drier.

2. California has had an unusually dry year this year. Unusual meaning "in comparison to the last 150 years." This year may turn out to be unusually wet as compared to the next 150 years, because, as mentioned, the climate of the southwest is drying.

3. A lot of these areas have many times the natural fuel-load. The last 150 years are important, because that is how long we have been suppressing fires in southern California. This unusually wet period allowed for a lot of biomass to build up, and not burn off, because we would not let it burn.

The natural time between fires in most of these areas is a few decades. Fires would pass through, burn off much of the fuels without destroying the local ecology because in most cases, the previous fire was recent enough to keep this fire from getting too hot. By putting out every fire we could for so long, we allowed the fuel load to build up to the point that the fires now get incredibly hot and spread incredibly fast. Some of the areas currently burning have burned recently, but the mean time since the last fire is much higher than what is natural.

4. We tend to build our settlements and structures without regard to the fact that we are building in a fire maintained ecology, and another fire will come. By failing to take that into account, we make things that much harder for firefighters and those who need to evacuate. It is like building in a floodplain and expecting your house to not get washed away every once in a while.

5. The climate is changing and the southwest is becoming more of a desert. When wet areas dry out, the vegetation eventually burns off.

Ecological Effects:

1. California is a world center of biodiversity, and quite a few of our species are found nowhere else. Many of the native plants and animals are already endangered by habitat loss, invasive species, pollution and climate change. Most of our natural areas are fragmented by human edifices. The native populations could deal with the comparatively mild natural wildfires of the past. Smaller, more fragmented and already declining native species with small ranges may well have trouble keeping a foothold in areas burning as hot and wide as the current fires.

I have a colleague who studies a species of native mouse found primarily in San Diego County. This year he could find almost none of his mice because their habitat is turning to desert. He did find them in a few places. In the last two days some of those places have gone up in smoke.

2. Fuel loads in the areas currently burning will be reduced, which is both good and bad. Good in that future fires will have less fuel. Bad in that all that fuel load was sequestered carbon, which is now in the atmosphere, and because the drier southwest won't have as much vegetation, that carbon is not going to be taken back out by the same land. My guess is, without having seen any numbers, that total carbon output from these fires will actually be quite minuscule on a global scale, and we are better off without all that tinder lying around.

3. If the rains in SoCal do get started in a month or two, we can expect some serious erosion from all the areas that have been stripped of their vegetation.

Lessons, not just for SoCal, but for the country:

1. Don't just let fuel build up until it explodes. Areas like this need to have some plan for how to get rid of fuel. My personal preference is controlled burns at times of year when the fire is easier to keep in hand. We can't keep pretending we can keep fire based ecologies from burning forever.

2. Notice that climate change is a serious problem now. Stop making the problem worse.

3. Take fire risk into consideration when deciding where and when to build. Developers should be legally responsible for planning their developments such that they are not putting residents and firefighters at risk. Planners should disallow building in areas that cannot be defended from fires.

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