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Federal Register / Vol. 86, No. 243 / Wednesday, December 22, 2021 / Proposed Rules and charcoal makers utilize large, mature mesquite and ironwood trees growing in riparian areas Taylor 2006, p. 12, which is the tree class that is of most value as pygmy-owl habitat. Loss of leguminous trees results in long-term effects to the soil as they add organic matter, fix nitrogen, and add sulfur and soluble salts, affecting overall habitat quality and quantity Rodriguez Franco and Aguirre 1996, p. 647. Ironwood and mesquite trees are important nurse species for saguaros, the primary nesting substrate for pygmy-owls in the northern portion of their range Burquez and Quintana 1994, p. 11. Declining tree populations in the Sonoran Desert as a result of commercial uses and land conversion threatens other plant species and may alter the structure and composition of the vertebrate and invertebrate communities as well Bestelmeyer and Schooley 1999, p.
644. This has implications for pygmyowl prey availability because pygmyowls rely on a seasonal diversity of vertebrate and invertebrate prey species;
loss of tree structure and diversity reduces prey diversity and availability.
Once common in areas of the Rio Grande delta, significant habitat loss and fragmentation due to woodcutting have now caused the pygmy-owl to be a rare occurrence in this area of Texas.
Oberholser 1974, p. 452 concluded that agricultural expansion and subsequent loss of native woodland and thornscrub habitat, begun in the 1920s, preceded the rapid demise of pygmyowl populations in the Lower Rio Grande Valley of southern Texas.
Because much of the suitable pygmyowl habitat in Texas occurs on private ranches, habitat areas are subject to potential impacts that are associated with ongoing ranch activities such as grazing, herd management, fencing, pasture improvements, construction of cattle pens and waters, road construction, and development of hunting facilities. Brush clearing, in particular, has been identified as a potential factor in present and future declines in the pygmy-owl population in Texas Oberholser 1974, p. 452.
However, relatively speaking, the current loss of habitat is much reduced in comparison to the historical loss of habitat in Texas. Conversely, ranch practices that enhance or increase pygmy-owl habitat to support ecotourism can contribute to conservation of the pygmy-owl in Texas Wauer et al. 1993, p. 1076. The best available information does not indicate that current ranching practices are significantly affecting pygmy-owl habitat in Texas.

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Habitat fragmentation in northeastern Mexico is extensive, with only about two percent of the ecoregion remaining intact, and no habitat blocks larger than 250 square km 96.5 square mi, and no significant protected areas Cook et al.
2000, p. 4. Fire is often used to clear woodlands for agriculture in this area of Mexico, and many of these fires are not adequately controlled. There may be fire-extensive related effects to native plant communities Cook et al. 2000, p.
4; however, there is no available information of how much area may be affected by this activity.
Areas of dry subtropical forests, important habitat for pygmy-owls in southwestern Mexico, have been used by humans through time for settlement and various other activities Trejo and Dirzo 2000, p. 133. The long-term impact of this settlement has converted these dry subtropical forests into shrublands and savannas lacking large trees, columnar cacti, and cover and prey diversity that are important pygmyowl habitat elements. In Mexico, dry tropical forest is the major type of tropical vegetation in the country, covering over 60 percent of the total area of tropical vegetation. About 8
percent approximately 160,000 square km 61,776 square mi of this forest remained intact by the late 1970s, and an assessment made at the beginning of the present decade suggested that 30
percent of these tropical forests have been altered and converted to agricultural lands and cattle grasslands Trejo and Drizo 2000, p. 134. However, the best available information indicates that there are still expanses of dry tropical forest along the Pacific coast in Mexico, including some areas below 1,200 m 4,000 ft where pygmy-owls are found.
Summary of Habitat Loss and Fragmentation In summary, pygmy-owls require habitat elements such as mature woodlands that include appropriate cavities for nest sites, adequate structural diversity and cover, and a diverse prey base. These habitat elements need to be available across the geographic range of the pygmy-owl and spatially arranged to allow connectivity between habitat patches. Pygmy-owl habitat loss and fragmentation are affecting pygmy-owl viability throughout its range. These threats vary in scope and intensity throughout the pygmy-owls geographic range and specific threats are a more significant issue in certain parts of the range than in others. For example, in Arizona and Northern Sonoran, pygmy-owl habitat loss and fragmentation resulting from
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urbanization, changing fire regimes due to the invasion of buffelgrass, and agricultural development and woodcutting are significant threats that have negatively affected pygmy-owl habitat. In Texas, historical loss of habitat has reduced the pygmy-owl range, but current impacts are reduced from historical levels in their magnitude and severity. However, in Texas and other areas of the pygmy-owls range, these past impacts continue to affect the current extent of available pygmy-owl habitat, because of the extended time it takes for these lands to recover.
Therefore, even if habitat destruction ceases, the negative effects of past land use are expected to continue in many of these areas into the future.
For the remainder of the pygmy-owls range and habitat in Mexico northeastern Mexico and south of Sonora, data available for our analysis were limited. The rate of growth in these southern Mexican States appears to be lower than in Sonora and the Arizona border region. Historical loss of pygmy-owl habitat in northeastern Mexico has occurred, but the extent to which significant habitat destruction is currently taking place is not available.
In addition, pygmy-owls are still considered common in the southern part of their range Enriquez-Rocha et al.
1993, p. 154; Cartron et al. 2000, p. 5;
GBIF 2020.
This information indicates that the impacts to pygmy-owl habitat discussed herein may be having different levels of effects on the populations of pygmyowls throughout their range, and habitat effects may not have the impacts to pygmy-owl population groups in the southern portion of the pygmy-owls range due to increased pygmy-owl numbers. Nonetheless, Enrquez and Vazquez-Perez 2017, p. 546 indicate that during the last 50 years, Mexico has seen drastic changes in land uses due to rapid urbanization and industrialization, which has been poorly planned. The result has been impacts to the natural environment, including the degradation and loss of biological diversity in Mexico. There has been limited work in Mexico, however, to understand what the direct impacts of these threats are on owl population losses and changes in distribution and abundance of subspecies in long term Enrquez and Vazquez-Perez 2017, p.
546.
Climate Change and Climate Conditions Climate change projections within the geographic range of the pygmy-owl show that increasing temperatures, decreasing precipitation, and increase intensity of weather events are likely
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