There are positive and negative parts of almost everything in life including forests, wetlands, and "the environment." There are zero-and-upward risks within the outdoors. In the forest there are noxious plants and insects; there are disease-carrying animals. Trees or tree limbs may fall. All of these must be remembered and with care, related problems or their potential magnitude can be avoided or reduced.

A tree hazard evaluation program is being developed based on the work of Dr. Lee A. Paine, USFS that began in 1971. A separate analysis is available for areas and trees. Some tree-care companies already provide such analyses. The number of injuries and deaths from limbs or trees falling has increased as use of forest land for recreation has increased. The cost per accident has also increased.

A hazard analysis usually provides excellent evidence that a land owner has done everything feasible in the unfortunate and unlikely event that an accident occurs to any visitor or client on the land.

A tree hazard is defined as the expected loss from mechanical failure of a tree during the current inspection cycle unless the probability of an accident is reduced by control efforts. The expected loss is the product of:

1. The probability of tree failure (for example, 0.10)
2. The probability of impact on a "targe" (0.80)
3. The damage potential (0.12) and
4. The target value ($4000).

For example:

0.10 x 0.80 x 0.12 x 4000 = $38.

If control costs are $100, then no control would be recommended. The procedure reduces hazards but also prevents "over-control", that is excessive expenditures and loss of beauty and desirable conditions of the site.

There are other hazards associated with the outdoors. These can be addressed by:

1. Land classification for its relative fire and other hazard severity, reducing development and periodic use of such areas.
2. Require all plans for development address the likely hazards at a site and specify how they are to be handled.
3. Require all planned developments to specify location, spacing, design, materials, and full details of how to prevent destruction by wildfires including suppression with water and other private immediate responses.
4. Reduce the density of the surrounding forest stands (within 100 ft. of buildings) whenever possible by harvest techniques.
5. Require fire retardancy of roofs.
6. Incorporate perimeter protection. Create a fuelbreak - an area around the structure from which all hazardous fuels have been removed. Closely-spaced trees and shrubs should be thinned.
7. Install electric power distribution circuits underground in wildland areas.
8. Mark roads and buildings (name or number) in fire-hazard areas so they are visible from public roads.
9. Cover all exterior attic and underfloor vents with screens that can adequately prevent the entrance of flammables and firebrands.
10. Construct exterior walls using fire-resistant material.
11. Do not install permanent roof sprinklers.
12. Provide visitors or occupants warning of fire and an escape routes.
13. Remove flammable vegetation near buildings. Mow the grass and weeds, remove clippings, and keep the ground litter minimized (within 30 ft. of buildings). Controlled burns of nearby understory, grazing, or physical removal.
14. Reduce the spacing between existing brush and trees to a minimum of 12 ft. Maintain or plant forest trees or shrub at least 10 ft from the structure. Stack any lumber or firewood away from structure.
15. Do not store uncovered flammable materials against walls of buildings.
16. Make swimming pool water readily accessible to fire fighters if needed.
17. Make outbuildings as fire-safe as the main building.
18. Provide 10 ft. of tree clearance along drives.
19. Establish fire insurance rates for structures located in or near wildfire hazardous areas to reflect the actual probability of destruction by conflagration.
20. Remove any large, old, or dead trees that appear to have any probability of falling/breaking toward the structure.
21. Provide tax incentives to people who meet or exceed fire-safe standards and apply penalties to those who do not.
22. Do not build structures on steep slopes due to higher tree failure rates, less stable soil drainage, and rapid fire spread rates.
23. Establish a fire defense system.

Hazard ratings or indices for pests have been developed (e.g., Gansner 1981; Stage and Hamiton 1981; Ferrell 1980). We plan to develop hazard ratings for each stand and to create a GIS map of the ratings. The higher the value for each stand, the greater should be the intensity of management and monetary loss reduction. The rating procedure we plan to use (after Gansner 1981) is:

1. Probability of pest being present
2. Probability of pest abruptly increasing to a high density
3. Proportion of growth of a stand in a rotation that is likely to be lost due to a pest being present.
4. Likely native or non-pest stand condition growth per acre
5. Likely average value of one unit of an acre's growth per year

For example, where

Rating = A x B x C x D x E

48.6= 0.9 x 0.6 x 0.3 x 300 x $1.00

Ferrell (1980), using regression analysis, showed how risks could be described for firs in Northern California. He was predicting the probability of a tree dying within 5 years. This procedure offers potential for future hazard estimates and the development of refined expressions of "expected loss" suggested in the above Rating. Reducing risks and increasing the Rating is the managerial challenge.

Other material is available on risk and risk aanalyses.

Literature Cited

Ferrell, G. T. 1980. Risk-rating systems for mature red fir and white fir in Northern California. U.S.D.A. For. Service Pacific S.W. For. and Range Exp. Sta., Berkeley, CA 29 pp.

Gansner, R. A. 1981. Estimating forest stand vulnerability to gypsy moth, p 159-164 in Hazard-rating systems in forest insect pest management. USDA Forest Service Gen. Tech. Rpt. WO-27, Washington, DC 169 pp.