B08_Attachment_6_BIBE_Low_Stress_Trespass_Livestock_Mgt_Plan_and_EA.pdf

National Park Service US Department of the Interior Big Bend National Park

Trespass Livestock Management Plan Environmental Assessment

May 2018

Trespass cattle in Big Bend National Park below Punta de la Sierra

United States Department of the Interior • National Park Service • Big Bend National Park

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Trespass Livestock Management Plan and EA

TRESPASS LIVESTOCK MANAGEMENT PLAN

ENVIRONMENTAL ASSESSMENT

SUMMARY

The National Park Service (NPS) at Big Bend National Park (BIBE or park) proposes to protect park resources from the adverse impacts of domestic trespass livestock that enter the park from adjacent lands in Mexico and the US. These trespass livestock include horses, burros, and cattle.

Trespass livestock damage the park's natural resources via grazing on and trampling vegetation;

causing soil erosion from hoof disturbance, trail creation, and wallowing; and threatening cultural resources by trampling archeological and historic sites and rubbing against historic structures and rock art panels.

This environmental assessment (EA) evaluates two alternatives: the No Action Alternative and an action alternative, the Proposed Action. The No Action Alternative would continue current, individually applied management activities to control target trespass livestock. This limited approach is not preventing damage to park resources and the visitor experience over the long-term. The action alternative, the Proposed Action, would use an integrated approach to manage trespass livestock in the park. No lethal methods would be used. This EA examines the potential environmental impacts associated with the two alternatives and 1) analyzes a reasonable range of alternatives to meet objectives of the proposal; 2) evaluates potential concerns and impacts to the park's resources and values; and 3) identifies best management practices (BMPs) and other mitigation measures to avoid, reduce, or eliminate adverse effects.

Park managers conducted internal scoping with NPS staff and contractors and external scoping with agencies, organizations, and the public to identify resource concerns. The following resource topics were retained for analysis in this EA: soils, vegetation, wilderness, and archeological resources and historic structures.

PUBLIC COMMENT

If you wish to comment on this EA, you may post comments online at http://parkplanning.nps.gov/bibe, via email at bibe_planning@nps.gov, or mail comments to the name and address below. This EA will be on public review for 30 days. Before including your address, telephone number, e-mail address, or other personal identifying information in your comment, you should be aware that your entire comment – including your personal identifying information – may be made publicly available at any time. While you can ask us in your comment to withhold your personal identifying information from public review, we cannot guarantee that we will be able to do so.

Superintendent Attention: Trespass Livestock Management Plan and EA P.O. Box 129 Big Bend National Park, Texas 79834-0129 http://parkplanning.nps.gov/bibe

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TABLE OF CONTENTS

1. PURPOSE AND NEED

1.1 Purpose and Proposal

1.2 Background

Regional Setting History of Trespass Livestock

1.3 Need and Known Impacts

1.4 Impact Topics Retained For Further Analysis

1.5 Impact Topics Dismissed From Further Analysis

Air Quality Biosphere Reserves Environmental Justice Wild and Scenic River Natural Soundscapes Wildlife Special Status Species Surface Water Paleontological Resources Cultural Landscapes Ethnographic Resources Indian Trust Resources and Sacred Sites Health and Safety Visitor Experience

2. ALTERNATIVES

2.1 Alternatives Carried Forward

Alternative A – No Action, Continue Using Current Treatments Alternative B – Develop and Implement a Trespass Livestock Management Plan (NPS Preferred Alternative and Proposed Action)

2.2 Mitigation Measures

2.3 Alternatives Considered and Dismissed

Use Only Cooperative and Incentive-Driven Methods Use Lethal Means to Control Trespass Livestock Additional Border Fencing Aerial Capture and Transport

2.4 Alternative Summaries

3. AFFECTED ENVIRONMENT AND ENVIRONMENTAL

CONSEQUENCES

3.1 Cumulative Impact Scenario

Past Projects and Actions Present Projects and Actions Reasonably Foreseeable Future Projects and Actions

3.2 Soils

Affected Environment Impacts of Alternative A (No Action Alternative) Impacts of Alternative B (Proposed Action)

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3.3 Vegetation

Affected Environment Impacts of Alternative A (No Action Alternative) Impacts of Alternative B (Proposed Action)

3.4 Wilderness

Affected Environment Impacts of Alternative A (No Action Alternative) Impacts of Alternative B (Proposed Action)

3.5 Archeological Resources and Historic Structures

Affected Environment Impacts of Alternative A (No Action Alternative) Impacts of Alternative B (Proposed Action)

4. CONSULTATION AND COORDINATION

4.1 Agency Consultation

4.2 Native American Consultation

5. REFERENCES

APPENDIX A: WILDERNESS MINIMUM REQUIREMENTS DECISION GUIDE 1

APPENDIX B: EUTHANASIA GUIDELINE

APPENDIX C: ANIMAL WELFARE STANDARDS FOR TRESPASS LIVESTOCK

MANAGEMENT

APPENDIX D: STANDARD BEST MANAGEMENT PRACTICES AT BIBE

APPENDIX E: REASONABLE AND PRUDENT MEASURES, TERMS AND

CONDITIONS, AND CONSERVATION RECOMMENDATIONS ... 1

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LIST OF FIGURES

Figure 1 – Big Bend National Park and Surrounding Protected Areas Figure 2 - Trespass Livestock Captures by NPS and USDA on BIBE, 2012-2013 Figure 3 - Trespass Livestock Observations on BIBE, 2007-2013 Figure 4 - Example of Trespass Livestock Trails in a Historic Site (16 acres), 2016 Figure 5 - Example of Trespass Livestock Trails in a Prehistoric Site (82 acres), 2016 Figure 6 – Trespass Livestock Management Zones Figure 7 – Proposed and Recommended Wilderness Areas

LIST OF TABLES

Table 1 – Criteria Air Pollutants Estimated Maximum Likely Emissions (in tons per year) Table 2 – Listed and Protected Animal Species Known or Likely to Occur in BIBE Table 3 - Summary of major components of Alternatives A and B

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LIST OF ACRONYMS

AHPA Animal Health Protection Act APHIS Animal and Plant Health Inspection Service BMPs Best Management Practices BIBE Big Bend National Park BA Biological Assessment BO Biological Opinion CAA Clean Air Act CEs Categorical Exclusions (NEPA) CEQ Council on Environmental Quality CFR Code of Federal Regulations CONANP Comisión Nacional de Áreas Naturales Protegidas dBA decibel (A-weighted) DO Director's Order DOI Department of Interior EA Environmental Assessment EPA Environmental Protection Agency EO Executive Order ESA Endangered Species Act GMP General Management Plan IDT Inter-Disciplinary Team kg kilogram MBTA Migratory Bird Treaty Act NEPA National Environmental Policy Act of 1969 NHPA National Historic Preservation Act NPS National Park Service NRCS Natural Resources Conservation Service SHPO State Historic Preservation Office SOPs Standard Operating Procedures TPWD Texas Parks and Wildlife Department UAS Unmanned aerial system UNESCO United Nations Educational, Scientific and Cultural Organization US United States USDA United Stated Department of Agriculture USFWS United States Fish and Wildlife Service WMA Wildlife Management Area WMRDG Wilderness Minimum Requirements Decision Guide

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1. PURPOSE AND NEED

1.1 PURPOSE AND PROPOSAL

1.2 BACKGROUND

Regional Setting

Figure 1 – Big Bend National Park and Surrounding Protected Areas

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History of Trespass Livestock Since the park was established in 1935, domestic horses, burros, and cattle have entered the park from neighboring lands in Mexico and the US and have damaged park resources. US law, specifically Title 36 Code of Federal Regulations (CFR) Part 2, Section 2.60, makes it illegal for livestock to be herded, driven across, pastured on, allowed on, or to run-at-large on park lands.

There are exceptions to this requirement, but none apply to the trespass livestock in the park.

Results of fixed-wing and helicopter surveys conducted by the NPS from 2010 through 2015 indicate an average minimum of 93 head of livestock (cattle, horses, burros), graze the river zone of the park at any one time (NPS 2012, 2013, 2014, 2016c). Additionally, surveys have confirmed that a minimum of 12 horses consistently occupy the Paint Gap/Onion Flat zone of BIBE. Thus, a minimum average of 105 trespass livestock occupied the park during 2010 through 2014. The composition is 60% horses, 38% cattle, and 2% burros. The livestock are distributed almost entirely within two miles of the Rio Grande (NPS 2012, 2013, 2014, 2016c). The two-mile-wide corridor encompasses an area of 183 square miles, based on Geographic Information System (GIS) data. However, livestock within this zone are not distributed evenly due to landscape ruggedness, accessibility, and occupancy patterns in Mexico. Some areas are used more often or by greater numbers of livestock than others, resulting in resource-impact variability and patchiness throughout the corridor.

The primary sources of livestock that enter the park are ejidos, which are unfenced community lands in Mexico. Some are from larger private Mexican ranches. Trespass livestock are domestic, not wild, animals. Their owners are Mexican farmers and ranchers. Most trespass livestock that wander or are herded into the park have indicators of their domestic status, including but not limited to brands, ear-tags, collars, horseshoes, and occasionally bells. Given the economically challenged condition of ejido communities and farmers in Mexico, it has long been advantageous for livestock owners in Mexico to make use of grazing opportunities in the park when possible. Sometimes this is inadvertent, but often it is intentional (Carrera 1996). In all cases, it is illegal. The park's 118-mile-long boundary with the Rio Grande is not fenced because periodic flooding would damage or destroy fencing and create hazards to river navigation, and would block wildlife access to drinking water.

In addition to pushing horses and cattle onto the park to graze illegally, livestock owners in Mexico also bring burros into Boquillas Canyon, where workers harvest the candelilla plant, which is used to make wax. The workers use the burros in Mexico to transport heavy bundles of the plant to processing locations at river's edge in Boquillas Canyon. The harvest occurs during cooler months of the year. At the end of the production season, owners release burros to roam in the canyon, untended until the next production season. In general, the burros remain within a mile of the Rio Grande, which is their only source of water, and roam both sides of the river.

Some burros have reproduced in the canyon, and not all are recaptured at the beginning of the next wax production season.

On the US side of the border, lands adjacent to the park are fenced, except in the Deadhorse Mountains where rugged terrain generally deters livestock from entering the park. On rare occasions, trespass livestock originate from US properties. More specifically, a small group of horses from an adjacent US ranch entered in the late 1980s or early 1990s and has remained in the park's Paint Gap/Onion Flat area. Current ranch owners in the area do not claim the animals

United States Department of the Interior • National Park Service • Big Bend National Park 4 and terrain ruggedness has thwarted NPS efforts to remove them via traditional mounted wrangler methods.

The NPS conducted trespass livestock roundups over 18 roundup-days in 2012, 19 in 2013, 9 in 2014 and 9 in 2015 (NPS 2016c). Thus, roundup days averaged 13 per year. The total number of hours NPS horses were ridden in the field by roundup staff for trespass livestock management purposes is recorded as NPS horse-hours. In 2012 there were 64 NPS horse-hours used during trespass livestock roundups, 561 hours in 2013, 324 hours in 2014, and 64 hours in 2015. Thus the average yearly horse-hours was 253 during those years. Figure 2 illustrates the locations of trespass livestock captures in 2012 and 2013, which are typical.

In August 2007, the NPS conducted an aerial survey of Boquillas Canyon. The survey identified 120 burros, 12 horses, and one cow within one mile of the Rio Grande. Between 2010 and 2015, the NPS conducted six aerial surveys of BIBE trespass livestock. Helicopter surveys for trespass livestock were conducted in 2010 and 2012 (NPS 2016c). Fixed-wing surveys occurred in 2012, 2013, 2014, and 2015. The 2014 fixed-wing survey, limited to 79 miles of the 113-mile BIBE river corridor, produced the lowest trespass livestock count, at 10 animals. The 2012 helicopter survey of the entire BIBE river corridor produced the largest result, documenting 287 trespass livestock, mostly cattle, in the BIBE river corridor. The survey data indicates the average minimum number of trespass livestock present in the park at one time is 105. NPS survey data also document that on average 60% are horses, 38% are cattle, and 2% are burros. Figure 3 depicts locations of trespass livestock observations from 2007 through 2013.

During recent decades, frequency and intensity of livestock removal efforts on the park have been highly variable due to NPS and US Department of Agriculture (USDA) funding limitations and other priorities. Without sustained, regular roundup efforts, there is little livestock owner motivation to prevent livestock from trespassing in the park. As described above, the population appears to decline after an increase in roundup-days (NPS 2016c). During periods of increased NPS vigilance and roundup efforts, owners appear to increase efforts to keep their animals in Mexico. Park and USDA staff cannot pursue trespass livestock into Mexico.

To date, only ground-based, mounted wrangler methods have been used to control trespass livestock in the park. Those methods have proven unsuccessful in removing trespass livestock from very rugged and/or remote areas, such as Boquillas Canyon and Paint Gap/Onion Flat (see Figure 1), or to maximize removal of wary and fleeing animals in remaining areas. Even in less rugged areas, the unfenced nature of the park makes livestock capture challenging. This has resulted in trespass livestock being continually present in the park despite ongoing traditional efforts to reduce their numbers. The addition of helicopter assistance to roundups, and use of temporary traps, would increase effectiveness of trespass livestock removal. Where there is no ongoing source of new trespass livestock, such as Paint Gap / Onion Flat, removal of existing animals would result in a permanent livestock-free zone. The current management of trespass livestock has sporadically reduced the number of trespass livestock in the park, but has not adequately protected natural and cultural resources, or the visitor experience.

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Figure 2 - Trespass Livestock Captures by NPS and USDA on BIBE, 2012-2013.

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Figure 3 - Trespass Livestock Observations on BIBE, 2007-2013

1.3 NEED AND KNOWN IMPACTS

Trespass livestock are known to cause soil erosion through hoof disturbance, trail creation, and wallowing, as well as damaging soil crusts. Long-term livestock use of steeply-sloping park terrain has created a spider web of trails and ridges that densely crisscross hillsides in some locations (NPS 2014). These networks of trails and ridges are known as terracettes (Trimble and Mendel 1995). Terracettes represent highly altered soil and vegetation conditions, with the livestock trample zone comprised of compacted soils and the edge of the terracettes comprised of sorted stones which create a “riser” effect on the edges. Root-zone soil disruption and heavy long-term grazing make native desert vegetation sparse in terracette areas. Photo 1 illustrates terracettes caused by trespass livestock in BIBE. Photo 2 illustrates a livestock trail through a cultural resource site.

Remote sensing was completed in 2016 using Google Earth Pro to evaluate the extent of terracette development in the park. At least

5.7 square miles of park lands exhibit severe terracette development (NPS 2016b). The most severely affected areas are

2.4 square miles near the Rio Grande between Lajitas and Santa Elena Canyon along with several slopes within Boquillas Canyon comprising an area of 3.3 square miles (NPS 2016b).

Photo 1. Terracettes caused by trespass livestock, on Mesa de Anguila.

Photo 2. Livestock trail through an archeological site featuring fire-cracked rock midden.

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Trespass livestock damage native vegetation by grazing and trampling, during which they sometimes trample rare plants. Hoof action, trailing, and wallowing by livestock erodes and compacts soils, which impedes seedling establishment and normal growth of existing vegetation.

Trespass livestock also deposit feces which transport invasive plant seeds.

One of the biggest impacts within BIBE from trespass livestock is damage to archeological and historic sites by creating trails through sites and rubbing against historic structures and rock art panels. Figures 4 and 5 illustrate damage to cultural resource sites from trespass livestock.

Figure 4 - Example of Trespass Livestock Trails in a Historic Site (16 acres), 2016

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Figure 5 - Example of Trespass Livestock Trails in a Prehistoric Site (82 acres), 2016

Finally, trespass livestock detract from the visitor experience by creating trails and wallows in campsites; by littering campsites, parking areas, and roadways with feces; entering occupied campsites and disturbing visitors; and intruding on the visual scene.

1.4 IMPACT TOPICS RETAINED FOR FURTHER ANALYSIS

Impact topics for this proposal were identified based on known or potential impacts from feral hogs and aoudads or their management. Input from other conservation organizations in the region, public input, and NPS knowledge of resources at BIBE was used to determine the impacts. Impact topics that are carried forward for further analysis in this EA include:

• Soils

• Vegetation

• Wilderness

• Archeological Resources and Historic Structures

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1.5 IMPACT TOPICS DISMISSED FROM FURTHER ANALYSIS

This section provides a limited evaluation and explanation of why some impact topics are not evaluated in more detail.

Air Quality

Table 1 – Criteria Air Pollutants Estimated Maximum Likely Emissions (in tons per year)

Pollutant No Action Proposed Action (additional to No Action) Regional Benchmark

Carbon Monoxide < 8 < 0.5 1,426

Nitrogen Oxides < 1 < 0.05 1,338 Volatile Organic Compounds < 1 < 0.05 123,445

Particulate Matter < 0.1 < 0.05 28,452 Source: Calculated based on data available in EPA 2008 and US Air Force 2013. Regional benchmarks obtained for Brewster County, Texas from the EPA National Emissions Inventory for 2014 from https://www.epa.gov/air-emissions-inventories/2014-national-emissions-inventory-nei-data.

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BIBE is located in an area classified by the US Environmental Protection Agency (EPA) as being in attainment for all six criteria air pollutants. However, BIBE is also known to have some of the worst visibility-reducing haze (primarily due to sulfate releases from power plants) of any western US national park (NPS 2004). Activities associated with trespass livestock and their management that could result in criteria air pollutant emissions would be limited to vehicle use and would not contribute to sulfates. Pollutants relevant to vehicle use include carbon monoxide, nitrogen oxides, volatile organic compounds, and particulate matter. Trespass livestock do not contribute to criteria air pollutants. The limited vehicle use for the No Action is much lower than for the Proposed Action. The NPS quantified the magnitude of additional annual emissions associated with exotic ungulate management under the Proposed Action.

Those results were then used to determine if additional air quality modeling was necessary.

Under the Proposed Action, airplane use would be limited to 6 hours a day for 5 days per year;

helicopter use would be limited to 8 hours a day for up to 20 days per year; and vehicle use would be intermittent over up to 30 days per year for trespass livestock management activities.

This results in a maximum 30 additional hours airplane use, 160 hours helicopter use, and 240 additional hours vehicle use per year. The maximum likely emissions would be less than 0.5 ton per year of carbon monoxide, less than 0.05 ton of nitrogen oxides, volatile organic compounds, and particulate matter (EPA 2008; US Air Force 2013).

For comparison, existing airplane use generates less than 0.1 ton of all these except carbon monoxide which is less than 3 tons per year. Existing ground vehicle use by visitors and park operations results in estimated total annual emissions of less than 5 tons per year of carbon monoxide, less than 1 ton each per year of nitrogen oxides and volatile organic compounds, and almost no particulate matter. Table 1 summarizes the estimated maximum likely emissions under both the No Action and the Proposed Action.

https://www.epa.gov/air-emissions-inventories/2014-national-emissions-inventory-nei-data https://www.epa.gov/air-emissions-inventories/2014-national-emissions-inventory-nei-data

The Proposed Action represents an increase of approximately 5-6 percent for any particular pollutant. If unmanned aerial systems (UAS) are eventually used instead of airplanes or helicopters for some of the Proposed Action, emissions would be even lower. Given this low annual emissions level under either the No Action or Proposed Action, daily pollutant concentrations resulting from trespass livestock management are anticipated to be extremely low and there would not be a noticeable change in overall air quality. Thus, this topic was dismissed from further analysis in this EA.

Biosphere Reserves The park is a designated US biosphere reserve. Biosphere reserves are terrestrial or coastal/marine ecosystems or a combination, internationally recognized within the framework of the United Nations Educational, Scientific and Cultural Organization's (UNESCO) program on Man and the Biosphere. Biosphere reserves are established to promote and demonstrate a balanced relationship between humans and the biosphere. Neither alternative alters the ability of BIBE to serve as a biosphere reserve. BIBE would continue to serve the same functions for conservation, sustainable development, and logistic support of research functions. Thus, this topic was dismissed from further analysis in this EA.

Environmental Justice Trespass livestock in the Big Bend region are not used by minority or low income populations within the US or its territories for food or income. They are used by populations within Mexico, but those impacts are not analyzed in this EA. Under the Proposed Action, none of the management activities are expected to impact minority or low income populations in the US.

The park would remain available for use by all people regardless of race or income, and any contract support would not be hired based on race or income. Furthermore, the park staff and planning team actively solicited public participation as part of the planning process and gave equal consideration to all input from persons regardless of age, race, income status, or other socioeconomic or demographic factors. As both alternatives would similarly affect park residents and residents of surrounding communities in the US, no disproportionate effects would occur. Neither alternative would result in any impacts to minority populations or low-income populations in the US. Thus, this topic was dismissed from further analysis in this EA.

Wild and Scenic River Of the Park’s 118-mile BIBE reach of the Rio Grande, the lower 71 miles is within the Rio Grande Wild and Scenic River, designated in 1978 under the National Wild and Scenic Rivers Act of 1968. Descriptively, the designation within BIBE begins upstream of Mariscal Canyon and extends downstream to the park boundary below Boquillas Canyon, for ¼ mile within the park boundary. The designation was made because of its "outstandingly remarkable" scenic, geologic, fish and wildlife, and recreational values. The Act itself and the outstanding remarkable values for the Rio Grande Wild and Scenic River do not preclude the presence of agriculture, livestock, and / or other traditional uses. Both the national park status of the reach and the Proposed Wilderness status of portions of the park adjacent to the river within Mariscal and Boquillas Canyons are more restrictive than the Wild and Scenic River designation.

Presence of trespass livestock does not jeopardize the outstanding remarkable values or the designation of this reach as a Wild and Scenic River nor does management of trespass livestock.

Thus, this topic was dismissed from further analysis in the EA.

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Natural Soundscapes Natural soundscapes exist in the absence of human-caused sound. The natural ambient soundscape is the aggregate of all the natural sounds that occur in an NPS unit, together with the physical capacity for transmitting natural sounds. The range of frequencies, magnitudes, and durations of human-caused sound considered acceptable varies among NPS units, as well as potentially within each NPS unit, being generally greater in developed areas and less in undeveloped areas.

Activities described in this document, in both the No Action and Proposed Action Alternatives, include use of motorized equipment. The No Action Alternative would not modify the natural soundscapes from what currently occurs. Under the No Action alternative, approximately 400 hours would continue being flown annually for various BIBE purposes. These would be in addition to overflights by Border Patrol, military, commercial tours, and private aircraft. Hours flown by other agencies are not reported to nor tracked by NPS; however, military overflights generally average 4,800 flights per year.

The Proposed Action would add 30 hours a year to the 400 hours flown annually by the BIBE airplane. Aircraft noise impacts to natural soundscapes and visitor experience would be minimized through appropriate flight planning and voluntary compliance with the minimum altitudes in FAA Advisory Circular AC 91-36D (flight typically 2000-5000 feet above ground level). The Proposed Action would also add a maximum of 160 hours helicopter use per year during daylight hours. Helicopters may fly at lower altitudes (as low as 200 feet during control operations but higher in transit), when needed, and are more likely to generate noise sufficient to impact natural soundscapes. Helicopters most likely to be used in the Proposed Action are the Bell Jet Ranger, or similar models with similar noise profiles. These helicopters generate approximately 87 A-weighted decibels (dBA) at 200 feet above ground level and 50 dBA at 4,000 feet above ground level (Newman et al. 1982). If unmanned aerial systems are eventually used instead of airplanes or helicopters for some of the activities (primarily monitoring), noise levels would be approximately 30 decibels lower at the same altitudes.

Natural soundscapes would return immediately after each aerial event and the total period with potential increase in noise impacts due to trespass livestock management across the park would be only 0.02 percent of the year (an additional 30 hours of airplane and 160 hours of helicopter use). During any given year, only a small area of the park will experience a temporary noise increase during any control activity. Flight paths for helicopter use would be at a higher elevation from the Panther Junction helibase or other designated in-park landing site, or from a starting point outside the park, to the target destination, then a zig-zag herding pattern would be flown through each control zone. The helicopter would then make a return flight to the helibase for a total 3 hours maximum per flight. Even with these temporary adverse impacts, the natural soundscape would generally remain high quality throughout the park.

Other sources of noise under the Proposed Action include ground vehicles. Noise from ground vehicle use would largely be similar to existing ground vehicle use and be restricted to existing roads. For comparison, a chainsaw is typically 100 decibels at typical range, a large jet 100 feet above ground level is 130 decibels, while quiet wilderness is approximately 10 decibels (from Acoustical Society of America website). Under typical conditions, aircraft sounds would not be heard more than 3 miles away from the source.

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In both the Paint Gap/Onion Flat area, and a portion of Boquillas Canyon, which are each roughly 1,280 acres, helicopter noise would be limited to the first year or two while the existing populations are removed. After that there would be no need for further helicopters in Paint Gap/Onion Flat as no new trespass livestock are likely to reinvade that area and only rarely (possibly 1 day per year for 8 hours) in Boquillas Canyon. The majority of helicopter use would be along the Rio Grande Corridor (approximately 105,000 acres) where trespass livestock are most common and regularly reinvade the area. Locations within this zone could experience helicopter noise up to 20 days per year (between 3 and 8 hours per day). The remainder of the park would only experience helicopter noise if trespass livestock have invaded, which is less likely with more effective control efforts along the Rio Grande. Overall, this is a relatively small portion of the entire park (more than 800,000 acres) and the number of hours a year where helicopter noise would occur is small.

While the Proposed Action does generate more noise than the No Action, neither alternative would generate sufficient adverse effects to alter the overall high quality of the natural soundscape. Thus, the topic was dismissed from further analysis in this EA. Effects of Proposed and No Action alternatives on soundscape specifically in the Wilderness context are addressed under the topic of Wilderness and in the Wilderness Minimum Decision Requirement Guide (Appendix A).

Wildlife Trespass livestock have created adverse impacts on wildlife habitat, including habitat for birds protected under the Migratory Bird Treaty Act (MBTA), by trampling, browsing, and soil disturbance. Approximately 34 square miles of desert and riparian wildlife habitat would be impacted under the No Action Alternative. While this is a sizeable area, it is a small area of wildlife habitat relative to the larger 5,150 square miles of protected area in the Big Bend region, plus additional wildlife habitat present on other types of lands. In addition, most wildlife can move on an individual basis to find undamaged habitat or to avoid interacting with trespass livestock. Therefore, the No Action alternative would have very limited to no adverse effects on wildlife, including birds protected under MBTA.

The use of horses for NPS operations in BIBE already occurs for a variety of reasons, corrals would be placed away from any occupied breeding habitat and generally away from wildlife habitat, and helicopters and aircraft land and take off from established areas. The use of helicopters for up to 8 hours during the day up to 20 days per year will generate some additional noise, primarily along the Rio Grande. There are birds protected under MBTA that use this area for foraging and breeding. Individual wildlife may notice a helicopter but a helicopter would not remain in one place for more than a few minutes (in rare occasions near a corral possibly up to 1 hour) during a particular control event. That same area (and wildlife within) is likely to not experience further noise from trespass livestock management more than a few times per year at most. Therefore, exposure and potential impact from the noise of trespass livestock management on individual wildlife is limited to a few minutes to an hour per year, primarily along the Rio Grande.

Implementing the Proposed Action would have beneficial impacts on wildlife, including birds protected under MBTA, due to recovery of wildlife habitat after removal of trespass livestock. In addition, mitigation measures and BMPs used to protect special status species (see below), particularly in the Rio Grande corridor, would benefit other wildlife who breed and forage

United States Department of the Interior • National Park Service • Big Bend National Park 14 during the same time of year and in the same habitat. When accounting for the regional conservation lands and additional wildlife habitat available throughout the Big Bend region, neither alternative is expected to have adverse effects on wildlife or their populations within BIBE or the region. Thus, this topic was dismissed from further analysis in this EA.

Special Status Species Ten federally listed species (1 mammal, 5 birds, 4 plants) identified as occurring in Brewster County by USFWS and/or TPWD were dismissed from analysis because they were determined by NPS and USFWS to not occur in BIBE, nor do they have potential habitat in BIBE. For a complete discussion of these species and why there were dismissed, refer to Table 5 in Section 6 of the Biological Assessment for Exotic Species Management Plans, Big Bend National Park (NPS 2015).

Due to location, size, connectivity with other protected lands, and high quality habitat, there are a large number of federally and state-listed animal species known to the park. Table 2 lists the federal- and state-listed special status species that are known or have potential to exist in the park. It does not include federal or state-listed species that have been documented in Brewster County but are either confirmed to not occur in the park or are highly unlikely to occur in the park. For more details on these species and their occurrence and habitat in BIBE, refer to the Biological Assessment for Exotic Species Management Plans, Big Bend National Park (NPS 2015).

Table 2 – Listed and Protected Animal Species Known or Likely to Occur in BIBE

Common Name Scientific Name Status Big Bend gambusia Gambusia gaigei Federal Endangered

Rio Grande silvery minnow Hybognathus amarus Federal Endangered (Experimental, Non-essential)

Texas hornshell Popenaias popei Federal Candidate Mexican long-nosed bat Leptonycteris nivalis Federal Endangered

Yellow-billed cuckoo Coccyzus americanus Federal Threatened and Proposed Critical Habitat (both for Western DPS only)

Southwestern willow flycatcher1 Empidonax traillii extimus Federal Endangered Mexican spotted owl1 Strix occidentalis lucida Federal Threatened Black-capped vireo Vireo atricapillus Federal Endangered Bunched cory cactus Coryphantha ramillosa Federal Threatened Chisos Mountain hedgehog cactus Echinocereus chisoensis chisoensis Federal Threatened Lloyd's Mariposa cactus Echinomastus mariposensis Federal Threatened

Guadalupe fescue Festuca ligulata Federal Candidate and Proposed Critical Habitat

Golden eagle Aquila chrysaetos Federal Bald and Golden Eagle Protection Act

Bald eagle Haliaeetus leucocephalus Federal Bald and Golden Eagle Protection Act; State Threatened

Common Name Scientific Name Status

Gray hawk Asturina nitida State Threatened White-tailed hawk Buteo albicaudatus State Threatened Zone-tailed hawk Buteo albonotatus State Threatened

United States Department of the Interior • National Park Service • Big Bend National Park 15

Common Name Scientific Name Status

Common black-hawk Buteogallus anthracinus State Threatened Swallow-tailed kite Elanoides forficatus State Threatened Reddish egret Egretta refescens State Threatened American peregrine falcon Falco peregrinus anatum State Threatened White-faced ibis Plegadis chihi State Threatened Rose-throated becard Pachyramphus aglaiae State Threatened Tropical parula Parula pitiayumi State Threatened White-nosed coati Nasua narica State Threatened American black bear Ursus americana State Threatened Spotted bat Euderma maculatum State Threatened Reticulated gecko Coleonyx reticulatus State Threatened Texas tortoise Gopherus berlandieri State Threatened Texas horned lizard Phrynosoma cornutum State Threatened Trans-Pecos black-headed snake Tantilla cucullata State Threatened Mexican stoneroller Campostoma ornatum State Threatened Blue sucker Cycleptus elongatus State Threatened Chihuahua shiner Notropis chihuahua State Threatened Salina mucket Potamilus metnecktayi State Threatened

1 Species not documented in the park but potential habitat is found in the park.

NPS, unpublished data BIBE Natural History Field Observation records; in-house survey and mapping, (verified November 2017).

Likely federally listed species confirmed with USFWS as part of Biological Assessment in 2015 and verified through USFWS and TPWD County List website in November 2017.

As with wildlife, both alternatives would have very limited to no impacts on special status animal species. Aquatic species (both federally and state-listed) would not be impacted by either trespass livestock or their management under either alternative. These include Big Bend gambusia, Rio Grande silvery minnow, Texas hornshell, Mexican stoneroller, blue sucker, Chihuahua shiner, and salina mucket. Big Bend gambusia are almost entirely fenced off and protected from trespass livestock and no trespass livestock management will occur in the ponds.

The remaining aquatic species all occur in the Rio Grande, and possibly a short distance up Terlingua Creek. Livestock are unlikely to step on or harm directly any individual and the sediment resulting from livestock presence under either alternative is small in relation to the overall volume of water and sediment load from upstream that flows through the Rio Grande daily and is unlikely to impact aquatic species.

A number of federally and state listed species are associated with the Chisos Mountains, where trespass livestock are not found and where it is unlikely trespass livestock management would ever be performed. These include Mexican long-nosed bat, Mexican spotted owl, black-capped vireo, American black bear, and Trans-Pecos black-headed snake.

There are also a number of federally and state listed species that occur throughout the park and would generally not likely be impacted by trespass livestock or their management. These include all raptors (i.e., eagles, hawks, falcon, and kite), tropical parula, spotted bat, reticulated gecko, and Texas horned lizard. Use of airplanes would be limited and bird strikes are not generally known with helicopters. Bird species in general would not likely be affected by trespass livestock management, with the exception of infrequent and short duration helicopter noise

United States Department of the Interior • National Park Service • Big Bend National Park 16 impact. Given the short duration of control activities in any one location and the general avoidance of occupied habitat, control activities are unlikely to have a long-term effect on any individual or population. Spotted bats are nocturnal and would not be out at BIBE during management activities. Reticulated geckos and Texas horned lizards are both cryptic species that are usually well hidden and would just freeze or hide while any trespass livestock or management activities pass through their area.

Neither eagle is known to nest in BIBE. Up to several wintering golden eagles forage broadly over BIBE each year. Wintering bald eagles are documented less than once in several years on average. Helicopter noise could temporarily disrupt eagle foraging behavior, although the likelihood of an eagle being present and impacted by a control activity in any given year is very low. Given the short duration of control activities in any one location, and eagle mobility, control activities are unlikely to have a long-term effect.

There are four federally listed plant species, with no additional state-listed species. No effects under either action would be likely on the Lloyd’s mariposa cactus, Chisos hedgehog cactus, or Guadalupe fescue as trespass livestock are either rare or do not occur in the same locations and no control activities would occur in habitat for these listed plants. Bunched cory cactus occur near trespass livestock along the Rio Grande. Livestock are known to cross through bunched cory cactus populations while moving between grazing areas; however, livestock generally just pass through and generally would avoid stepping on a cactus. During control activities, livestock may move in any direction and occasionally enter bunched cory cactus habitat; however, wranglers do not enter cactus habitat and direct livestock away from these populations. Control activities (i.e., ground-based removal activities, corrals, traps, etc.) would avoid all known cactus populations, which would reduce the likelihood of accidental trampling of bunched cory cactus to a discountable (extremely unlikely) effect.

The federally and state listed species most likely to be impacted by either trespass livestock or their management are those terrestrial species found along the Rio Grande. These include yellow-billed cuckoo, southwestern willow flycatcher, reddish egret, white-faced ibis, rose-throated becard, and white-nosed coati. The cuckoo and flycatcher are discussed below; the remaining species are uncommon in the park and can avoid any management activities while they are occurring and would not be likely to be affected by trespass livestock themselves.

For more details on survey results, population data, and known locations within BIBE, refer to the Biological Assessment for Exotic Species Management Plans, Big Bend National Park (NPS 2015). The impacts of this Plan on federally listed species were also analyzed in this Biological Assessment (BA). The BA was prepared for activities related to trespass livestock management, as well as for activities related to managing exotic animals, exotic plants, and direct management activities associated with federally listed species. The BA concluded that there would be either no effect or indirect beneficial effects of trespass livestock management (Proposed Action) on federally listed species, with the exception of two species (yellow-billed cuckoo and southwestern willow flycatcher). The BA noted that, under the Proposed Action, helicopter use during livestock roundup would have the potential to disturb western yellow-billed cuckoos and, should they exist in the area, southwestern willow flycatchers. Helicopter noise may cause temporary disruption of foraging. Helicopter use would likely be in these species’ habitat as trespass livestock routinely occur along the Rio Grande and Terlingua Creek. Helicopter use near or in potential habitat would be limited to 3-8 hours per day up to a maximum of 20 days per year. Helicopter use parkwide for trespass livestock management would be limited to 20

United States Department of the Interior • National Park Service • Big Bend National Park 17 days per year. Much of that would be along the Rio Grande. Overall, removal of trespass livestock would be beneficial to western yellow-billed cuckoos and southwestern willow flycatchers by preventing habitat damage. Helicopter noise effects would generally be either insignificant (limited duration) or discountable (unlikely).

The USFWS concurred with the above determinations in a Biological Opinion dated December 15, 2015 (USFWS 2015), and confirmed by the USFWS in January 2017. USFWS consultation is summarized in Section 4.1.

In addition, the BMPs (Appendix D) and mitigation measures (Section 2.2) would ensure that management actions would not adversely impact listed animal species. Impacts to listed animal species from trespass livestock are unlikely or of small magnitude and only occur in a portion of the park, primarily along the Rio Grande. These impacts are most likely under the No Action Alternative as there would be more intensive control efforts in the Proposed Action, so trespass livestock numbers would be lower. In summary, because the potential effects on state and federally listed species or proposed critical habitat would be either non-existent, highly unlikely, or temporary as described above, this topic was dismissed from further analysis in this EA.

Surface Water Surface water in BIBE includes the Rio Grande, streams, wetlands, and natural springs. There are 118 miles of the Rio Grande within park boundaries. Tornillo Creek and Terlingua Creek are large, named tributaries of the Rio Grande within the park. Additionally, there are dozens of additional small, unnamed tributaries (based on National Atlas geographic data). In addition to the Rio Grande and its tributaries, the park features more than 350 discrete sources of surface water, including springs (NPS, unpublished data, 2008), and other natural catchment that hold water for extended periods. There are 69 springs within the 2-mile-wide zone along the Rio Grande, including Boquillas Canyon. There are 10 springs in the Paint Gap/Onion Flat area (NPS springs database, unpublished data, 2017).

Intermittent streams and wetlands have not been mapped in BIBE. Wetlands generally occur as small fringes along springs, seeps, and streams. Wetlands within the 2-mile-wide river zone include springs/wetlands near Rio Grande Village and wetlands associated with Tornillo Creek and Terlingua Creek. Before establishment of the park, agricultural development degraded the extensive wetlands and springs near Rio Grande Village. Pre-park agricultural development resulted in containment of springs, diversion into irrigation systems, and removal of beaver populations. When Rio Grande Village campground, roads, and maintenance facilities were established, they were placed in areas cleared by decades of agricultural use. Five decades of protection and removal of former infrastructure have allowed some natural re-establishment of wetlands in the area. Warm springs supply two artificial ponds and a beaver pond with water to support the only habitat of endangered Big Bend mosquitofish. These wetland areas have high NPS and visitor presence and almost no trespass livestock.

NPS staff noted trespass livestock disturbance during a 2010-2012 inventory of springs and during a 2014-2016 pilot monitoring study (NPS 2016f). Based on these inventories, the springs in the Paint Gap/Onion Flat area did not show impacts from trespass livestock, but 5 of 24 surveyed springs in the Rio Grande corridor had signs of trespass livestock disturbance such as browsing, hoof impact, and scat (NPS 2016f). The signs generally were mild with browsed

United States Department of the Interior • National Park Service • Big Bend National Park 18 vegetation and a few hoof impacts and feces. Only one spring had disturbance with clear vegetation trampling and damage to banks of the spring.

Under the No Action Alternative, trespass livestock would continue to show signs of visiting a small number of springs and occasionally trampling vegetation near a spring. These are relatively small impacts (e.g., hoofprints visible on the water’s edge, a few plants pushed over/stepped on but not killed) in a very small number of locations (20%) and all within 2 miles of the Rio Grande.

Trespass livestock walking in the Rio Grande or crossing the Rio Grande would contribute a negligible amount of additional sediment above that already present in the Rio Grande.

Livestock are not creating or eroding crossing points on the Rio Grande. Under the Proposed Action, mitigations and BMPs would avoid and protect surface waters during trespass livestock management by ensuring activities avoid them. Removal of trespass livestock would eliminate or reduce the few impacts that are occurring at or near surface waters. Neither alternative is expected to alter the surface waters present on BIBE. Thus, this topic was dismissed from further analysis in this EA.

Paleontological Resources The park is known to contain an abundance and diversity of paleontological resources representing an uninterrupted 35 million-year fossil record, which includes fossil remains of dinosaurs, crocodiles, turtles, plants, fish, amphibians, and early mammals. Mitigation measures and BMPs have been established (Section 2.2 and Appendix D) to protect paleontological resources. Under both the No Action and Proposed Action, if previously unidentified paleontological resources should be found during ground-disturbing activities associated with the proposal, work would stop in the area of discovery and an NPS paleontologist would determine the appropriate treatment of those resources in accordance with NPS Management Policies 2006, NPS Reference Manual 77, and the Paleontological Resources Protection Act of 2009. Because known paleontological resources would be avoided and mitigation measures implemented to manage any potential discovery of paleontological resources, it is anticipated that neither alternative would have impacts on paleontological resources.