CHAPTER FOUR

ENVIRONMENTAL CONSEQUENCES

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Methodology

Introduction

In analyzing the environmental consequences of the alternatives proposed in the Draft Yosemite Fire Management Plan/Environmental Impact Statement (EIS), three factors are looked at for each resource: type of impact, duration of impact, and intensity of impact. After the environmental consequences of the alternative are examined for separate topics, the impact of implementing the alternative is considered along with the impacts of other relevant actions in the area. This is the cumulative impacts analysis, explained below. Whether or not an impact will cause impairment is included for some resources, also explained below.

The type of impact describes a relative measure of beneficial or adverse effects on biological or physical systems, cultural resources, or on the social environment. For example, adverse impacts on ecosystems might be those that would degrade the size, integrity, or connectivity of a specific habitat. Conversely, beneficial impacts would enhance ecosystem processes, native species richness, or native habitat quantity or quality.

Because impacts could have short-term adverse impacts while having long-term beneficial impacts, it is important to look at the duration of the effect of an impact. Effects from fire management activities described within this document are likely to occur within nested long- and short-term time scales. Many of the adverse impacts may occur for relatively short time periods while concurrent improvements to the ecosystem are just beginning. For example, on a small scale, after a fire some areas are likely to begin to resemble pre-fire conditions within one or two growing seasons, while, on a landscape scale, the benefits from a change in forest condition and restoration of the fire regime may take years.

Examining the type and duration of an impact is not enough because an impact could cover a large area or a large portion of a population or could be highly noticeable or even irreversible. Impacts are of varying intensities from small and imperceptible to large and substantial. Measures of intensity consider whether an impact would be negligible, minor, moderate, or major. These designations are used to describe both beneficial and adverse impacts.

A cumulative impact is described in the Council on Environmental Quality regulations (1508.7) as: “the impact on the environment which results from the incremental impact of the action when added to other past, present, and reasonably foreseeable future actions regardless of what agency (federal or non-federal) or person undertakes such other actions.” Cumulative impacts can result from individually minor but collectively significant actions taking place over a period of time.

A comprehensive list of present and reasonably foreseeable future actions is provided in Appendix 5. These actions are evaluated in cumulative impact analyses in conjunction with the impacts of each alternative to assess whether they have any additive or interactive effects on a particular environmental, cultural, or social resource. Because most of these cumulative actions are in the planning stages, the evaluation of cumulative impacts has been based on a general description of the project.

This document also evaluates whether resources might suffer impairment. Impairment is not a NEPA issue but instead relates to the National Park Service Organic Act (1916). Impairment that is prohibited by the Organic Act is an impact that, in the professional judgement of the responsible National Park Service manager, would harm the integrity of park resources or values, including the opportunities that otherwise would be present for the enjoyment of those resources or values. Nonetheless, an impact is less likely to constitute impairment if it is an unavoidable result of an action necessary to preserve or restore the integrity of park resources or values.

According to National Park Service Policy,  “An impact would be more likely to constitute an impairment to the extent that it affects a resource or a value whose conservation is: a) Necessary to fulfill specific purposes identified in the establishing legislation or proclamation of the park; b) Key to the natural or cultural integrity of the park or to opportunities for enjoyment of the park; or c) Identified as a goal in the park’s general management plan or other relevant National Park Service planning documents.” (NPS Management Policies, Part 1.4.5)

Biological Environment

Vegetation and Fire Ecology

The alternatives will be evaluated by looking at structure and composition of the vegetation, and fuels. Because of similarities in fire regimes and the mosaic of vegetation types found at any elevation, the fifteen vegetation types listed in Chapter 3 will be lumped into five clusters for this analysis. Subalpine forests, upper montane forests, lower montane forests, meadows, and foothill woodlands are the groups. The types in each group are found in Chapter 3, tables 3.1 and 3.2.

Type of Impact

Adverse:         Moves the system outside of or away from the natural range of variability for vegetation (structure, composition, and fuels).

Beneficial:       Moves the system inside of or toward the natural range of variability for vegetation (structure, composition, and fuels).

Duration of Impact

Short-term:      Can be reversed within one or two fire return intervals.

Long-term:      Requires three or more fire return intervals to reverse effects.

Intensity of Impact

Negligible:       Imperceptible or undetectable effects upon vegetation.

Minor:             Slightly perceptible and localized effects.

Moderate:        Apparent change in plant community structure, composition, or fuels that would result in a change of the role of fire on a small scale.

Major:             Substantial change in plant community structure, composition, or fuels that represents a change in the role of fire, ecological function, vegetation type, or fire return interval on a landscape scale.

Wetlands

A programmatic approach has been developed to minimize wetland impacts from National Park Service activities. The protection of wetlands is facilitated through Executive Order 11990, Protection of Wetlands; National Park Service Directors Order 77-1, Wetland Protection and its accompanying Procedural Manual 77-1 (DO 77-1 and PM 77-1); Clean Water Act, Section 404; and the “no net loss” goal outlined by the White House Office on Environmental Policy in 1993. Executive Order 11990 requires that leadership be provided by involved agencies to minimize the destruction, loss, or degradation of wetlands. Directors Order 77-1 and Procedural Manual 77-1 provide the procedural structure in which Executive Order 11990 may be implemented. Section 10 of the Rivers and Harbors Act and Section 404 of the Clean Water Act authorize the U.S. Army Corps of Engineers to grant permits for construction and disposal of dredged material in waters of the United States.

Several tools were used to determine potential fire management impacts on wetlands within the park boundary. Information from the National Wetlands Inventory (USFWS 1995) and a park-wide vegetation map (NPS 1994e) were overlain with known fire management units and use areas. An assumption was made that all meadow and riparian communities on the vegetation map were likely to be classified as wetlands in future, site-specific (< 5acre) delineations of wetlands in the park. This information provided a conservative and broad estimate of potential wetlands in Yosemite.

Impacts were assessed with three criteria in mind:

¨       Federal laws, regulations, and executive orders; similar state laws (for example, the California Endangered Species Act); or National Park Service management policies.

¨       Issues and concerns expressed during public scoping.

¨        Projected impacts on the natural history of a species or the known sensitivities of a habitat.

The assessment of fire management impacts also needs to occur within the context of wetland condition and natural disturbance processes. For this analysis, several assumptions were made. The greater the size of a biotic community and the stronger its links to neighboring communities, the more valuable it is to the integrity and maintenance of biotic processes. Although specific fire management activities may result in short-term fragmentation and the disassociation of communities from each other, these same impacts may result in long-term ecological benefits.

Type of Impact

Adverse:         Degrades the size, integrity, or connectivity of wetlands.

Beneficial:       No detrimental effects. Enhances native ecosystem processes, native species richness or diversity, or native habitat quantity and quality.

Duration of Impact

Wetlands are likely to begin to resemble the pretreatment condition within one or two growing seasons following fire events or management activities (Davis et. al 1998). The benefits following changes in forest condition and upland fire regimes are likely to occur at much longer time scales.

Short-term:      Lasts less than 10 years following the implementation of an alternative.

Long-term:      Lasts or appearing 10 years after implementation of an alternative.

Intensity of Impact

Three primary measures were used to evaluate the intensity of impacts on wetlands: the size and type of the wetland, the integrity of the wetland, and the connectivity of the wetland to adjacent habitats.

Negligible:       Imperceptible or not detectable.

Minor:             Slightly detectable, localized within a small area, and would not affect the overall viability of wetlands in the park.

Moderate:        Apparent but could be reversed.

Major:             Substantial, highly noticeable, and could be permanent.

Wildlife

For many thousands of years, fire has been a strong force in the formation of the natural structure, distribution, and diversity of wildlife habitats in the Sierra Nevada. As a result, Sierra Nevada wildlife have developed behaviors and life history characteristics that are adapted to the influence of fire on their habitat. As there are successions of species and age classes of plants that occur between fires, there are successions of animal species that are favored or disfavored as habitats change. Prehistorically, the pattern of fire has fluctuated—climate and the use of fire by American Indians have varied over time.

With the arrival of Euro-Americans in the Sierra Nevada, the patterns of fire changed dramatically, mostly from intense fire suppression activities in the 20th century. Some forest habitats in Yosemite have become denser, and more prone to catastrophic, stand-replacing fires. Such changes have been detrimental to the natural diversity, abundance, and distribution of wildlife in the park. In addition, fire control activities can adversely affect wildlife through direct disturbance of animals and habitats; management actions designed to benefit habitat, such as prescribed fire, can have inadvertent adverse effects on wildlife. With these factors in mind, the following parameters were used to evaluate the effects of the various alternatives given in the Draft Yosemite Fire Management Plan/EIS.

Type of Impact

Adverse:         Likely to result in unnatural changes in the abundance, diversity, and distribution of wildlife species. Changes could occur through direct disturbance or mortality, or through destruction or alteration of habitat.

Beneficial:       Likely to protect and/or restore the natural abundance, diversity, and distribution of wildlife species. This would occur through protection and restoration of the natural structure, succession, and distribution of habitat.

Duration of Impact

Short-term:      Immediate changes in the abundance, diversity, and distribution of wildlife, but a return to the original condition within 20 years, without further impacts.

Long-term:      Changes in the abundance, diversity, and distribution of wildlife that persist for more than 20 years.

Intensity of Impact

Negligible:       Imperceptible or undetectable impacts.

Minor:             Slightly perceptible, and limited in extent. Without further impacts, adverse impacts would reverse and the resources would recover.

Moderate:        Readily apparent, but limited in extent. Without further impacts, adverse impacts would eventually reverse and the resource would recover.

Major:             Substantial, highly noticeable, and affecting a large area. Changes would not reverse without active management.

Special-Status Species - Plants

Fire plays a role in the management of many special-status plant species by maintaining open habitat, encouraging reproduction, and affecting competing species. Fire may injure or kill individual plants while the effects on the species as a whole is beneficial because competition has been reduced or openings created. Fire suppression activities can adversely affect these same species because of ground disturbance. Prescribed fires can also be detrimental, especially when timing, frequency, and intensity of fire are outside of the natural fire cycle to which the species is adapted (Hessl and Spackman 1995). Keeping these factors in mind, the following parameters have been used to evaluate the consequences on special-status plants of the various alternatives proposed in the Draft Yosemite Fire Management Plan/EIS.

Type of Impact

Adverse:         Viability of known populations and/or potential habitats of special-status species are threatened. May lead to loss of habitat, increased competition by both native and non-native species, or reduce and/or prevent reproduction.

Beneficial:       Actions that improve habitat conditions and enhance the viability of populations. May eliminate competitive species, thereby increasing available habitat, or improve reproductive output and success.

Duration of Impact

Short-term:      May immediately affect the population or species, but with no long-term effects to population trends or species viability.

Long-term:      May lead to a loss in population or species viability—exhibited by a trend suggesting decline in overall species abundance, viability, and/or survival.

Intensity of Impact

Negligible:       Imperceptible or undetectable.

Minor:             Slightly perceptible and localized, without the potential to expand if left alone.

Moderate:        Apparent and sufficient to cause a change in the resources (e.g., abundance, distribution, quantity, or quality).

Major:             Substantial, highly noticeable, and with the potential for landscape-scale effects.

Special-Status Species – Animals

Like most wildlife in the Sierra Nevada, special-status species have adapted to natural fire regimes. In many areas, including Yosemite National Park, however, a history of fire suppression has led to dense, overgrown stands, with high accumulations of forest fuels. This affects special-status species by altering habitat and placing these species and their habitats at risk of high-intensity, stand-replacement fire. In addition, stand-replacement fire could create unsuitable habitat conditions that would last for many years. Fire control activities could also adversely affect special-status species through direct disturbance of animals and habitats. Even management actions designed to benefit habitat, such as prescribed fire, can have inadvertent adverse effects on special-status species. With these factors in mind, the following parameters have been used to evaluate the effects on special-status animals of the various alternatives proposed in the Draft Yosemite Fire Management Plan/EIS.

Type of Impact

Adverse:         Likely to result in unnatural changes in the abundance or distribution of a special-status species. This could occur through direct disturbance or mortality, or through destruction or alteration of habitat.

Beneficial:       Likely to protect and/or restore the natural abundance and distribution of a special-status species. This would occur through protection and restoration of structure, succession, and distribution of habitat.

Duration of Impact

Short-term:      Immediate changes in the abundance and distribution of a special-status species, but a return to the original condition occurs within two generations of that species, without further impacts.

Long-term:      Changes in the abundance and distribution of a special-status species that persist for greater than two generations of that species.

Intensity of Impact

Negligible:       Imperceptible or undetectable.

Minor:             Slightly perceptible and limited in extent. Without further actions, adverse impacts would reverse, and the resource would recover.

Moderate:        Readily apparent but limited in extent. Without further actions, adverse impacts would eventually reverse, and the resource would recover.

Major:             Substantial, highly noticeable, and affecting a large area. Changes would not reverse without active management.

California Wildlife Habitat Relationships was used to generate a list of suitable habitat for each species (Mayer and Laudenslayer 1988). For each habitat that occurs in Yosemite, an average suitability value was generated. This process examines the size and stage classes of vegetation that are likely to occur for each habitat type and then looks at how these vegetation classes fulfill the requirements for reproduction, cover, and feeding for each animal species. The California wildlife habitat relationships information was evaluated and adapted to the situations in Yosemite using in-house knowledge about species occurrence and habitat use specific to the park. The average suitability value and knowledge of habitat conditions, distribution, and ecology of each species in Yosemite was used to assign high, medium, and low values to each suitable habitat type. These ranked habitats were then compared to the fire return interval departure (FRID) maps and the fire unit maps to determine how habitats of different values correspond to current fire-related habitat conditions and different treatment scenarios under the various alternatives. For a more extensive description of the status, biology, and distribution of special-status species, see Appendix 11, Biological Assessment.

Physical Environment

Watersheds, Soils, and Water Quality

Water resources, watershed, and soils are interrelated in their reactions to the treatments proposed by the alternatives. Due to these relationships, the analysis has been done on them as a group. Effects upon soils and watersheds are assessed by considering the likely scale of the effect—whether fire would affect all or part of the watershed slope (ridge, mid-slope, bottom)—and as a result, the likely effect upon water yield, peak flows, sediment yield, nutrient yield, and/or stream system response.

Type of Impact

Adverse:         Moves the system outside of or away from the natural range of variability for watershed conditions (water yield, peak flows, sediment yield, nutrient yield or stream system response).

Beneficial:       Moves the system inside of or toward the natural range of variability for watershed conditions (water yield, peak flows, sediment yield, nutrient yield, or stream system response).

Duration of Impact

Short-term:      Can be reversed within two fire return intervals.

Long-term:      Requires three or more fire return intervals to reverse effects.

Intensity of Impact

Negligible:       Imperceptible or undetectable.

Minor:             Slightly perceptible and localized, without the potential to expand if left alone.

Moderate:        Apparent, but would remain localized.

Major:             Substantial, highly noticeable, with the potential for landscape (watershed)-scale effects.

Air Quality

Fire management activities could potentially affect air quality in the Yosemite area through smoke emissions from wildland and prescribed fires and exhaust from machinery used in site preparation, monitoring, and thinning activities.

Smoke Emissions

In order to quantify smoke emissions predicted to result from each alternative, the First Order Fire Effects Model 5.0 (FOFEM) was used to generate emission factors for PM₁₀, PM_2.5, volatile organic compounds (as CH₄), CO, and CO₂. FOFEM is a computer-based planning tool that is used to provide a variety of quantitative predictions for planning prescribed fires, impact assessment, and long-range planning and policy development. FOFEM provides quantitative fire effects information for tree mortality, fuel consumption, mineral soil exposure, and smoke (USDA 1997). The smoke module of FOFEM models the productions of emissions but not smoke dispersion or visibility. The smoke module requires a number of inputs related to burn characteristics, including fuel category, cover type, fuel loading, moisture content, and percent of crown burn. For this analysis, park fire management staff provided burn parameters for each burn unit (Appendix 6); burn parameters were assumed to be consistent throughout a prescribed burn unit regardless of mosaic of vegetation cover types.

The area of each cover type in a given prescribed burn unit was determined using GIS data. This was done by intersecting two GIS datasets: the prescribed burn unit area and the vegetative cover type. The burn unit cover types were then correlated with the Society for American Foresters (SAF)/Society for Range Management (SRM) cover types available in FOFEM. In some cases, direct correlation between cover types was not possible, and a surrogate SAF/SRM cover type was selected. Table 4.1 provides a cross-reference for cover types. Not all cover types exist within all burn units. Several burn units include areas of bare rock or water for which no smoke emissions are expected.

For a given prescribed burn unit and pollutant, the emissions were quantified by the following equation:

Average emission factors for all prescribed burns were calculated from the FOFEM predictions to facilitate comparison of alternatives. The average emission factors were used to quantify emissions from prescribed fire and managed wildland fire since both are expected to have similar burn characteristics. However, separate FOFEM runs were used to develop emission factors for unwanted wildland fires which typically burn under drier conditions and consume more fuel, particularly crown and branch fuels, and therefore, produce higher emissions. In order to develop average wildland fire emission factors, representative burn parameters for unwanted wildland fire were provided by park staff for three of the predominant cover types: Pacific ponderosa pine, Sierra Nevada mixed conifer, and white fir. These are the types representative of the vegetation in the park where fire has been suppressed and which are targeted for treatment.

Both the prescribed and wildland fire emission factors predicted by FOFEM are considerably higher than similar emission factors in the Environmental Protection Agency’s Compilation of Air Pollution Emission Factors (AP-42) for the same region. However, the AP-42 derived emission factors are generalized for large regions and “can vary by as much as 50 percent with fuel and fire conditions” (EPA 1996). Since fuel loadings in many areas of the park may be heavier than normal due to decades of fire suppression, the average emission factors used here can be considered more representative of park conditions. Finally, the FOFEM model does not provide emission factors for NO_X. According to EPA AP-42, the emission factors for NO_X from wildland and prescribed fires are approximately 35 times less than those for CO emissions. Therefore, the CO emission factors produced by the FOFEM model were scaled down proportionately to estimate NO_X emission factors. Table 4.2 provides the emission factors used for each fire type.

The median number of years to achieve ecosystem restoration or a natural background for Alternatives B, C, and D are 12.5, 25, and 17.5 years, respectively. For prescribed fire, comparison of the alternatives is based on a listing of tentative prescribed fire projects and associated number of acres to be treated by prescribed burning for the years 2003-2009. This list of tentative prescribed fire projects includes areas that are part of the ecosystem restoration goals, wildland/urban interface goals, and maintenance burning to keep previously treated areas within their range of variability.

Table 4.1   Vegetative Cover Types Used in Air Quality Emissions Analysis

Table 4.2   Smoke Emission Factors by Fire Type

Each alternative is compared using the decade average number of acres of wildland fire (wildfire) per year of 5,760 acres (average from 1991 to 2000, including both lightning and human-caused fires). However, as the park is returned to an ecologically natural state and heavy fuel loadings are reduced, it is expected that unwanted wildland fires would occur less frequently and burn less intensely in the future. Air emissions from fire will diminish when fire regimes are restored to forest ecosystems since fuel loads and fuel consumption will decline—thus, the park will be under a regime of maintenance burning. To illustrate this effect a proposed burn unit, the PW-17 Elevenmile project on the west park boundary, was analyzed. Pre-burn characteristics were assumed to be heavy fuel loading with a concentration of heavy fuels (larger size branches, logs, etc.), and post-burn characteristics were assumed to be approximately one-third of the pre-burn fuel loading and size. The FOFEM model was run and the results are noted in table 4.3. As anticipated, the air emissions are reduced in proportion to the fuel loading reduction.

Table 4.3   Modeled Pre-Burn and Post-Burn Emissions using Prescribed Fire Unit PW-17, the Elevenmile project on the west park boundary

Mechanical Treatments Emissions

Depending on the alternative, air pollutants would be generated by various mechanical thinning and site preparation methods. Motorized equipment used in thinning and site preparation activities include chainsaws, chippers, feller-bunchers, skidders, haul trucks, and all terrain vehicles (ATVs) used for low-impact skidding. These six types of equipment are a representative sample of the types of equipment used in Yosemite. Table 4.4 shows the emission factors used to figure emissions under each alternative.

Table 4.4   Emissions Factors for Equipment Used in Fire Management Activities