PERSPECTIVE ON THE ENVIRONMENT : Fire Dangers are Knowable, So Make Them Known : Periodic canyon blazes are natural. The degree of risk should be disclosed to home buyers during purchase.

We learned about the Santa Barbara Painted Cave fire from BBC television news in London. A few phone calls later, friends told us that our house lay in the path of the fire if the winds shifted and continued to blow, and we took the next plane home.

Helpless for 10 hours at 30,000 feet, I had plenty of time to think about risks and our environment in Southern California, risks that we all face. After we reached home and discovered that the winds had died in time and our house was standing, we talked with friends and acquaintances who had lost their houses in the fire, a tragedy that has affected everyone in Santa Barbara. One of the most poignant aspects was how many people seemed surprised and shocked that they lived in a high-risk area.

People who come to Southern California seem to assume that society--the government or some institution--has determined that the house they buy is in a safe location. People who have moved here from the urban East have told me that it never occurred to them that their house would be in danger. But those of us who study the environment can read the terrain and see that there are plenty of homes in Southern California in high-risk locations.

We live in a Mediterranean climate where the native vegetation--the scrubby, dense bush called chaparral--has evolved to endure in a fire-prone habitat. If it does not burn, chaparral vegetation eventually becomes old, its growth slows or ceases and the plants die back. Only a fire rejuvenates an area, promoting new root-sprouting and allowing seed germination, so chaparral plants produce an abundance of fuel that tends to promote fires on an average of every several decades.

So we know that we live in an area where fire is natural and where its natural rate of occurrence in any one spot is about every 30 to 50 years. A house high up the hillside, surrounded by chaparral, is a higher fire risk.

Mel Manalis, a physicist at UC Santa Barbara and a specialist on wind energy, says that the landscape also determines where the windiest spots are likely to be. Air, like water, flows downslope, following low-lying canyons. The Painted Cave fire spread this way, moving rapidly downslope, more or less along lower channels in the topography. A house in one of these airsheds is also at higher risk for fire.

Most of us don’t have the expertise or the time to learn how to read the landscape when we shop for a house. But house-buying in California requires a complete disclosure of defects by the seller. We could add to the list of disclosure items the relative environmental fire risk, on a scale from one (almost none) to five (very high). The fire department or another government agency with expertise would determine the rating.

People have asked me whether there should be zoning or regulations to prevent house construction in high-fire zones. My answer is: We need to divide the risks we face into two categories--risks that affect only us, and risks that, if we accept them, also impose additional risks on others. For example, if we choose to build a house well up in the mountains, far from other houses, then the risk is pretty much ours alone. As long as homeowners understand it, and can obtain insurance, then we can justify allowing people to take such risks.

In contrast, suppose you build a house in a high-fire neighborhood and insist on cedar shingles. This imposes additional fire hazards on your neighbors as well as yourself. It would seem fairest to use zoning regulations to prevent that non-voluntary sharing of risks.

Of course, fires are not the only environmental risks we face in southern California. Three other important ones are flooding, mudslides and earthquakes. When I first came to California I was amazed to see houses built on small flood plains in tight canyons where, if an infrequent flood occurs, houses would be rapidly inundated and residents would have little chance of escape because of the steep sides of the flood plain. I was also amazed to see houses cantilevered out on on unstable slopes. Disclosure during house buying should also rate the risk of flooding and mudslides.

Some may ask why we can’t eliminate the risk of chaparral fires. I suppose we could, if we were willing to pave the hillsides, but then why live here? Didn’t most of us choose this part of the world in part because of its beauty?

We can’t realistically eliminate the risk of chaparral fires. But we can increase awareness and develop policies so that each citizen knows the risks.

Let us hope that it is a long time until the next fire, and that during that time we improve the ways in which we approach the risks that are part of the environment in Southern California.