The explosive nature of the vegetation currently burning in the California wildfires is a direct result of high temperature and a prolonged period with no rain. Vegetation, or fuel as it is often referred to in fire science, contains water. Water has a high specific heat, which is the amount of energy required to raise an amount water by one degree Celsius. In the case of water it is 4.186 joules of energy per gram of water. To get vegetation to burn you need enough heat to boil off the water in the vegetation first. It takes 540 kcal to boil a kilogram of water. This is precisely why if you try and start a campfire with wet wood, you are going to be cold.
In the shrub or chaparral ecosystems that are currently burning in southern California, fuel moisture after the winter rainy season is over 100%. That means that for every kilogram of shrub there is a kilogram or more of water. This year, Chamise, a common shrub in southern California, peaked at 120% fuel moisture and is currently at 60% fuel moisture. This means half as much energy is required to get the shrubs to burn now as was required back in early June.
When you are trying to light a campfire, the best thing to do is to get your head down near the base and blow. This increases the amount of air and oxygen moving past the flame. A little flicker, some well place blowing, and viola, you’ve got a nice campfire. Now add Santa Ana winds to already dry fuel and an ignition source and the result is explosive fire conditions. As vegetation burns and generates heat, it pre-heats the vegetation in front of it, causing the water to boil off before the flame reaches the vegetation. This preconditions the vegetation to burn, similar to seasoning your fire wood.
How climate change makes it worse
Climate change is causing higher temperatures, both during the day and at night. When the atmosphere is warmer, it can hold more water. This causes ecosystems to dry out as water in the ecosystem evaporates and plants release more water as they photosynthesize. As a result, higher temperatures alone are enough to dry out vegetation. Next we add the longer dry season in California. The length of time between when the winter rains in one year stop and the rains the next year start has been increasing with ongoing climate change. These two factors, higher temperatures and a longer dry season, increase the length of time each year that these ecosystems are available to burn. The longer it has been since the last rain event, the drier the vegetation. This prolong dry period and drier vegetation during the Santa Ana wind period causes explosive fire growth during high wind events.
Assuming you’ve thought long and hard about why you want and advanced degree in ecology and what specific sub-discipline you’ve decided to pursue, below I provide some advice on how best to approach the grad school application process.
Do not just apply to a program without first contacting potential advisors. Every year I get 1-3 students that do this and list me as their potential advisor. If I’m taking students that year, I’ve already encouraged 2-3 students to apply and will not look at your application. You may think that is harsh, but here is why I do what I do: I don’t want students to spend the time and money required to apply to our program unless I think they will be a good fit in my lab and that I think I will be a good advisor for them.
Here is what you should do. Reach out to people whose work interests you 2-4 months before the application deadline. Hopefully you’ve identified these people based on their publications. Make sure that you check their website for materials that they request of potential applicants and provide them with your initial email. I ask for a CV, a one-page description of research interests, and unofficial transcripts. I’m not looking for a ground-breaking question that you want to pursue. I’m trying to evaluate if you’ve thought through what you want to research and if you can present it in a coherent manner.
Assuming you get some interest from the potential advisor, then you need to plan for your first interaction with them beyond email. I schedule a video call with potential students so that we can each learn more about how the other operates. You need to be prepared for questions relevant to the work we do in my lab. I often ask potential students which of my papers they found most interesting and why? Your answer will help me understand why you’re interested in the work we do and what specifically about forest ecology gets you excited.
After having interviewed several students, I’ll recommend that 2-3 formally apply to our program. Sometime following your application, it is important to schedule a visit. Many programs/advisors will support your travel to visit, but even if they don’t, this is a worthy investment. This is your opportunity to get a sense of the department and the program. Most importantly, this is your opportunity to meet with your potential advisor and lab. I schedule time for potential students to meet with my current lab without me present. You need to ask current students how your potential advisor operates, what kind of support they provide, and what their expectations are. This is your opportunity to gather data about how well you think the potential advisor’s approach will work for you. You should also feel free to contact students who have graduated from the lab. They have a complete picture of the process. To make this process effective, you need the self-awareness to know what you require to be successful. Make sure you give this some thought well in advance of this process.
Remember, this process is a two-way street. The potential advisor is interviewing you, but you also need to be interviewing them.
With fires raging in multiple western states and in Canada, there is this assumption that there is a single cause for these large, hot wildfires that, in some cases, are creating their own weather. There is a tendency by different media outlets and political figures to say it’s climate change, or fire suppression has created a fuels problem, or if people just didn’t build houses in the forest there wouldn’t be a problem. The basic fact of the matter is this:
Now, I’ll unpack these three things.
Climate change influences wildfire in several ways. When vegetation is wet, it takes way more energy to get it to burn because essentially all of the water has to boil off before the vegetation will burn. This is why you don’t use wet wood to make a camp fire. As the air temperature goes up due to climate change, snow in the mountains melts out earlier in the year and increases the length of the fire season. Once the snow is gone, higher temperatures continue to make vegetation more flammable by drying it out. High air temperature means the more water is evaporating from the soil and dead vegetation and that live plants are using more water (transpiration) to photosynthesize. Human-caused climate change is responsible for approximately half of the fuel drying in the western US. So now we’ve got high temperatures making vegetation available to burn for a longer part of the year and making it more flammable by drying it out. But wait, there’s more…
The other climate change effect is that nighttime temperatures are remaining high. This is important for fire behavior and firefighting. When the temperature drops at night and the relative humidity increases, fire behavior tends to calm down. This is typically when much progress is made by wildland firefighters in containing the fire. With high nighttime temperatures, we are now seeing fires spread faster at night.
There are some forests that used to burn every few years to decades before we started putting fires out. This has increased fuels in these forest types and in some cases harvesting smaller trees to reduce the chance that fire burns through the forest canopy will reduce the chance of a large, hot fire. However, we also have to return more frequent fires to these forest types. If all we do is cut down smaller trees, we’re putting a band-aid on the situation because fuels will just build back up.
There are other forest types, like lodgepole pine forests, that are supposed to burn infrequently and when they do, they burn hot. The 1988 Yellowstone fires are a classic example. When these forests burn every 100-300 years, that is natural. Fire suppression has not drastically altered these forests and thinning to reduce the chance of a large, hot wildfire is not appropriate.
Human behavior creates three main problems when it comes to wildfire. The first is that humans cause many wildfires. We have increased the number of ignitions and because of the timing of the ignitions, increased the length of the fire season. The second problem that we’ve created is that we like to build houses in flammable environments and don’t take responsibility for managing the risks around our properties by building with non-flammable material and maintaining a fuel buffer around our homes and communities. This map shows where the wildland urban interface is located in the continental US. We like to live in beautiful places and that puts us at risk. The third problem is that we don’t want to have a bunch of smoke in the air from fires. Now, that’s like buying a house next to a freeway and getting pissed off when you hear traffic noise. Estimates of area burned in California before the 1800s suggest most of the state is quite flammable. If 6,900 square miles were burning each year, California was probably a pretty smokey place. For comparison, there are roughly 1015 square miles burning in California today (8/13/2018) and the smoke analysis looks like this:
The basic facts of the matter is that we are facing a challenge that we have created through human-caused climate change, fire suppression, and not thinking through our actions. Any solution that we develop will require addressing all three of these factors if it is going to be successful.