Habitat Loss, Fragmentation, and Degradation

The PCC’s natural habitat (wet pine flatwoods) has been lost or degraded through residential, commercial, and industrial development and through conversion to intensive pine silviculture, ranching, and farming uses (Mansell 1994; Keppner 2001; Keppner and Keppner 2001, 2005; FWC 2006). It is likely that no unaltered natural pine flatwoods remain within the PCC’s current range (Keppner and Keppner 2001, 2005).

Most known PCC occurrence points are in human-altered habitats and are vulnerable to loss or further alteration. Although artificial habitats such as roadside ditches and rights-of-way have allowed the PCC to persist in areas from which they would otherwise likely have been extirpated, human activities can alter the hydrology and configuration of these sites, making them unsuitable for long term PCC conservation. For example, roadside ditch maintenance and construction activities have resulted in the destruction of several crayfish sites (Keppner and Keppner 2001, 2005). While ditch maintenance activities may have temporary impacts, they may provide long-term habitat improvements that support PCC presence when conducted using conservation management practices (CMPs) (see Appendix 6 in FWC 2017). The horizontal to vertical configuration of ditch slopes, i.e., the width of the ditch slope relative to the ditch’s height, helps determine whether the ditch can support PCC. Swales and ditches with herbaceous vegetation and a 3:1 or shallower slope are more likely to support PCC (FWC 2017).

Infrastructure development has impacted, or is anticipated to impact, several other sites (Keppner and Keppner 2001, 2005). These projects can result in direct loss of habitat and additional issues such as fragmentation and isolation. For example, several proposed road construction or expansion projects may impact PCC habitat in the future.

Areas in silviculture adjacent to human-altered habitats may serve as refuges for PCC, and those who follow silvicultural BMPs minimize impacts to PCC (see Appendix 5 in FWC 2017). However, silvicultural practices such as ditching and bedding, roller chopping, installing fire breaks, and constructing roads can alter the hydrology of PCC sites, create physical barriers to PCC movement, and destroy underground burrows (Hobbs 2001; Keppner and Keppner 2001, 2005; FWC 2006). Fire suppression and high tree-density on silvicultural sites can reduce herbaceous groundcover necessary for suitable crayfish habitat (Keppner and Keppner 2001, 2005; FWC 2006). Similarly, removal of tree canopy cover, changes in ground cover vegetation, and possible associated changes in water quality and surface water availability are all possible changes associated with the effects of conversion to farming and ranching practices, such as cattle grazing (e.g., Jansen and Robertson 2001). Minimal changes are expected to occur in the area due to these two land uses, although conversion from silviculture to grazing use has occurred on the periphery of the PCC range. Use of BMPs for agriculture and grazing can help minimize impacts to aquatic species (e.g., FDACS 2008).

Declines in water quality are known to present a significant threat to other species of crayfish (and presumably to PCC). These declines can range from oxygen-deficient conditions resulting from algal blooms or sewage spills to pollution originating from roadway runoff, pesticide applications, or chemical spills (Acosta and Perry 2001).

The majority of known PCC occurrence points in the western part of the range are in roadside ditches and swales that are isolated from other PCC populations by roads, development, and land use changes. Fragmentation and isolation can increase vulnerability to local extinction due to adverse genetic, demographic, and environmental events. Further, when PCC have gone extinct from an area, the lack of habitat connections among sites can prevent PCC from recolonizing the newly vacant sites (Keppner 2001; Keppner and Keppner 2001, 2005; FWC 2006). Recent genetic work indicates the isolation in the western portion of the range has resulted in inbreeding and drift (Duncan et al. 2017).

In addition to the indirect effects described above, many of the activities contributing to habitat loss and degradation can also directly harm or kill PCC. Continuous loss of individuals can eventually lead to extinction of isolated populations (Gilpin and Soulé 1986). In particular, if done without appropriate safeguards, roadside maintenance, and infrastructure development in roadside ditches, silvicultural and farming activities in areas supporting PCC have the potential to kill, harm, or displace PCC as soil is removed from sites with heavy machinery. In addition, fill placed on sites in preparation for construction activities can entomb crayfish in their burrows.