Hidden collapse is driven by fire and logging in a socioecological forest ecosystem

Abstract

Increasing numbers of ecosystems globally are at risk of collapse. However, most descriptions of terrestrial ecosystem collapse are post hoc with few empirically based examples of ecosystems in the process of collapse. This limits learning about collapse and impedes development of effective early-warning indicators. Based on multidecadal and multifaceted monitoring, we present evidence that the Australian mainland Mountain Ash ecosystem is collapsing. Collapse is indicated by marked changes in ecosystem condition, particularly the rapid decline in populations of keystone ecosystem structures. There also has been significant decline in biodiversity strongly associated with these structures and disruptions of key ecosystem processes. In documenting the decline of the Mountain Ash ecosystem, we uncovered evidence of hidden collapse. This is where an ecosystem superficially appears to be relatively intact, but a prolonged period of decline coupled with long lag times for recovery of dominant ecosystem components mean that collapse is almost inevitable. In ecosystems susceptible to hidden collapse, management interventions will be required decades earlier than currently perceived by policy makers. Responding to hidden collapse is further complicated by our finding that different drivers produce different pathways to collapse, but these drivers can interact in ways that exacerbate and perpetuate collapse. Management must focus not only on reducing the number of critical stressors influencing an ecosystem but also on breaking feedbacks between stressors. We demonstrate the importance of multidecadal monitoring programs in measuring state variables that can inform quantitative predictions of collapse as well as help identify management responses that can avert system-wide collapse.

Altered ignition catchments threaten a hyperdiverse fire‐dependent ecosystem

“…can be implemented (Lindenmayer & Sato, 2018). Our approach, based on the notion of ignition catchments, allows the anticipation of landscape changes in fire regime, facilitating the development of hypotheses that can be tested and/or quantified with fire models or similar approaches.…”

“…These include altering fire regimes by changing the sources of ignition and the spread of fire, with case studies reporting localized threats to biodiversity and the state of ecosystems from both human‐caused increases (e.g. Lindenmayer & Sato, ; Syphard, Radeloff, Hawbaker, & Stewart, ) and decreases in fire occurrence (e.g. Parsons & Gosper, ; Tulloch, Pichancourt, Gosper, Sanders, & Chadès, ; Venter, Cramer, & Hawkins, ).…”

Pervasive admixture between eucalypt species has consequences for conservation and assisted migration

“…Substantial biodiversity declines are occurring in many regions of the world due to widespread land clearing, habitat degradation, introduced species and climate change (Evans et al, 2011;Pounds et al, 2006;Woinarski, Burbidge, & Harrison, 2015). Extensive and ongoing land clearing has led to major reductions in forest cover globally (Achard et al, 2014;Reside et al, 2017;Taubert et al, 2018), with synergistic interactions between stressors placing some ecosystems under high threat of rapid collapse or changes in ecosystem state (Brook, Sodhi, & Bradshaw, 2008;Lindenmayer, Hobbs, Likens, Krebs, & Banks, 2011;Lindenmayer & Sato, 2018). With such widespread changes facing ecosystems, it is critical to understand how these stressors interact with the fundamental ecological processes operating within and between foundation species, to adequately manage biodiversity across landscapes.…”

High fire disturbance in forests leads to longer recovery, but varies by forest type

“…). Many studies exploring the ecological impacts of fire are conducted at a local scale, typically focussing on specific ecosystems, such as the mountain ash (Lindenmayer and Sato ) and alpine ash (Bassett et al. ) forests of south‐east Australia.…”

“…However, communication between the ecology and remote sensing communities, on what can and should be measured from space, is lacking (Skidmore et al 2015). Many studies exploring the ecological impacts of fire are conducted at a local scale, typically focussing on specific ecosystems, such as the mountain ash (Lindenmayer and Sato 2018) and alpine ash (Bassett et al 2015) forests of south-east Australia. These studies contain highly detailed information over limited spatial extents.…”