Declining old‐forest species as a legacy of large trees lost

Abstract

Aim Global declines in large old trees from selective logging have degraded old‐forest ecosystems, which could lead to delayed declines or losses of old‐forest‐associated wildlife populations (i.e., extinction debt). We applied the declining population paradigm and explored potential evidence for extinction debt in an old‐forest dependent species across landscapes with different histories of large tree logging. Location Montane forests of the Sierra Nevada, California, USA. Methods We tested hypotheses about the influence of forest structure on territory extinction dynamics of the spotted owl (Strix occidentalis) using detection/non‐detection data from 1993 to 2011 across two land tenures: national forests, which experienced extensive large tree logging over the past century, and national parks, which did not. Results Large tree/high canopy cover forest was the best predictor of extinction rates and explained 26%–77% of model deviance. Owl territories with more large tree/high canopy cover forest had lower extinction rates, and this forest type was ~4 times more prevalent within owl territories in national parks (truexfalse¯ = 19% of territory) than national forests (truexfalse¯ = 4% of territory). As such, predicted extinction probability for an average owl territory was ~2.5 times greater in national forests than national parks, where occupancy was declining (truenormalλfalse¯false^<1) and stable (truenormalλfalse¯false^=1), respectively. Large tree/high canopy cover forest remained consistently low, but did not decline, during the study period on national forests while owl declines were ongoing—an observation consistent with an extinction debt. Main conclusions In identifying a linkage between large trees and spotted owl dynamics at a regional scale, we provide evidence suggesting past logging of large old trees may have contributed to contemporary declines in an old‐forest species. Strengthening protections for remaining large old trees and promoting their recruitment in the future will be critical for biodiversity conservation in the world's forests.

Patterns and drivers of long‐term changes in breeding bird communities in a global biodiversity hotspot in Mexico

“…These patterns together with observed associations with climatic factors suggest poleward and up‐elevation distributional shifts linked to climate change, which match recent trends elsewhere on Earth (Chen, Hill, Ohlemüller, Roy, & Thomas, ; Parmesan, ). Additionally, ongoing forest recovery following extensive logging in some ranges in the early 1900s, persistent habitat degradation linked to past logging and higher extinction risks of small populations in more vulnerable habitat patches likely drove other observed changes (Clarke, Rostant, & Racey, ; Hanski & Gaggiotti, ; Jones, Keane, Gutiérrez, & Peery, ).…”

“…Importantly, nest cavities required by these species often occur only in large trees and snags (Lanning & Shiflett, ; Monterrubio‐Rico & Enkerlin‐Hoeflich, ), which are among the last legacies of old forests to recover following logging (Franklin et al, ) and were often rare. Limitations of these keystone resources due to past logging have been implicated in declines of these and other similar bird species in coniferous forests across western North America (Brawn & Balda, ; Hejl, ; Jones et al, ), including endemic Thick‐billed Parrot and Imperial Woodpecker in Mexico (Lammertink, Rojas‐Torre, Casillas‐Orona, & Otto, ; Monterrubio‐Rico et al, ). Such patterns are especially troublesome in the SMO where logging remains widespread, and for declining regional endemics of foremost conservation concern.…”

Is fire “for the birds”? How two rare species influence fire management across the US

“…The amount of forest composed of large trees (>60 cm diameter at breast height [DBH]) and high canopy cover (>70%) within an owl territory was determined to be the best predictor of territory extinction rates (Jones et al . ). The invasive barred owl is also a serious threat to the CSO (Keane et al .…”

Need for a global map of forest naturalness for a sustainable future

“…) or continuity (McMullin & Wiersma ), is crucial for preserving biodiversity and ecosystem functioning and is a challenging target for sustainable development (Jones et al. , ). Mapping, monitoring, and preserving intact forests and old‐growth stands worldwide is a priority task because of their unique function in biodiversity conservation and role in mitigating climate change (e.g., global fluxes).…”