Dynamics of extinction debt across five taxonomic groups

Halley, John M.; Monokrousos, Nikolaos; Mazaris, Antonios D.; Newmark, William D.; Vokou, Despoina

doi:10.1038/ncomms12283

Cited by 96 publications

(143 citation statements)

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“…individuals, (meta) populations and (meta)communities, respond hierarchically to perturbations. 1) and the time to first extinction (e, the time necessary for species to fall from S to S − 1; Halley et al 2016). Extinction debts were detected across a range of ecosystems and taxonomic groups, with estimates ranging from 9 to 90% of current species richness.…”

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Understanding extinction debts: spatio–temporal scales, mechanisms and a roadmap for future research

et al. 2019

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Extinction debt refers to delayed species extinctions expected as a consequence of ecosystem perturbation. Quantifying such extinctions and investigating long-term consequences of perturbations has proven challenging, because perturbations are not isolated and occur across various spatial and temporal scales, from local habitat losses to global warming. Additionally, the relative importance of eco-evolutionary processes varies across scales, because levels of ecological organization, i.e. individuals, (meta) populations and (meta)communities, respond hierarchically to perturbations. To summarize our current knowledge of the scales and mechanisms influencing extinction debts, we reviewed recent empirical, theoretical and methodological studies addressing either the spatio-temporal scales of extinction debts or the eco-evolutionary mechanisms delaying extinctions. Extinction debts were detected across a range of ecosystems and taxonomic groups, with estimates ranging from 9 to 90% of current species richness. The duration over which debts have been sustained varies from 5 to 570 yr, and projections of the total period required to settle a debt can extend to 1000 yr. Reported causes of delayed extinctions are 1) life-history traits that prolong individual survival, and 2) population and metapopulation dynamics that maintain populations under deteriorated conditions. Other potential factors that may extend survival time such as microevolutionary dynamics, or delayed extinctions of interaction partners, have rarely been analyzed. Therefore, we propose a roadmap for future research with three key avenues: 1) the microevolutionary dynamics of extinction processes, 2) the disjunctive loss of interacting species and 3) the impact of multiple regimes of perturbation on the payment of debts. For their ability to integrate processes occurring at different levels of ecological organization, we highlight mechanistic simulation models as tools to address these knowledge gaps and to deepen our understanding of extinction dynamics.The extinctions that comprise an extinction debt can be expected based on the assumption of a new equilibrium to be achieved. This new equilibrium is also a community state that depends on how much the perturbation changes environmental conditions and community properties. The changes in species richness will then emerge from the interactions of eco-evolutionary processes over time at multiple levels of ecological organization (Cabral et al. 2017(Cabral et al. , 2019. This reasoning emphasizes extinction debt as a community (or metacommunity) state. Therefore, we further refer to mechanisms of extinction debt as eco-evolutionary processes creating or prolonging this state, i.e. delaying extinctions and thus putting and maintaining the community into debt.Being a state, an extinction debt has to be first and foremost, detected. Once detected, it can be characterized (Fig. 1). The extinction debt itself is the number of extinctions expected to happen as consequence of a perturbation, therefore, the main m...

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“…1). 1) and the time to first extinction (e, the time necessary for species to fall from S to S − 1; Halley et al 2016). Depending on the strength of the perturbation, immediate extinctions might happen, but most extinctions are usually delayed (a and b in Fig.…”

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Understanding extinction debts: spatio–temporal scales, mechanisms and a roadmap for future research

et al. 2019

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“…Er is dus een grote spreiding in de snelheid van extincties, maar er bestaat nog onzekerheid over de factoren die invloed hebben op deze snelheid. Uit een recente meta-analyse van gepubliceerde data over de halfwaardetijd voor vijf groepen, waaronder ongewervelden, blijkt dat er voor ongewervelden een duidelijke relatie is tussen de halfwaardetijd en het habitatoppervlak (Halley, Monokrousos et al 2016). De auteurs geven echter aan dat de resultaten voor ongewervelden waarschijnlijk minder robuust zijn vanwege het geringe aantal bruikbare studies (weinig langetermijnmonitoring-studies, veel studies met incomplete sampling, vaak geen betrouwbare determinaties tot op soortniveau).…”

Section: Een Uitsterfschuld Door Uitgesteld Uitstervenunclassified

Achteruitgang insectenpopulaties in Nederland: trends, oorzaken en kennislacunes

Kleijn¹,

Bink

Braak³

et al. 2018

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“…Relaxation of invertebrate fauna should still be relatively advanced in regions cleared since the 1950s/1960s given that invertebrates have short generation times (Gonzalez & Chaneton 2002;Kuussaari et al 2009;Krauss et al 2010;Halley et al 2016). Instead, landscapes with longer clearing histories may exhibit a different degree of habitat degradation to those with shorter clearing histories, either due to differing land-use legacies (Lunt & Spooner 2005;Perring et al 2016) or perhaps because they have been exposed to deleterious agricultural practices for longer.…”

Section: Insectivorous Birds and Their Preymentioning

confidence: 99%

“…Although obtaining condition measures is often more time consuming and costly than assessing occupancy and distribution Casner et al 2014), incorporating condition measures into monitoring programs could allow conservation managers to intervene in at-risk populations sooner. The likely improvement in the effectiveness of conservation outcomes derives not from a lower monetary cost in detecting the decline, but the greater cost-effectiveness of preventing extirpations rather than trying to reverse extinctions after the fact Halley et al 2016). …”

Section: Conservation Physiologymentioning

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Why are woodland-dependent avian insectivore populations vulnerable to declines in highly-modified landscapes?

Cosgrove¹

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Habitat loss, fragmentation, and degradation are the leading causes of faunal population declines.Substantial effort has been invested in identifying how these landscape changes are related to population parameters. However, to effectively mitigate declines, we must understand the underlying mechanisms impacted by landscape change. Woodland-dependent avian insectivores seem particularly vulnerable, and decline at rates disproportionately greater than other foraging guilds. This pattern suggests that reduced food availability in less-wooded landscapes may be a contributing factor. However, the evidence supporting this hypothesis is sparse. I adopted a multidisciplinary approach to investigate the mechanisms driving population changes of an avian insectivore in highly-modified landscapes by integrating physiological indices with measures of prey availability and landscape structure. First, I presented a framework for conceptualising how the spatiotemporal scale of fragmentation influences the mechanisms impacting populations. I then used the eastern yellow robin (Eopsaltria australis) in the Brigalow Belt South bioregion of southern Queensland to test the importance of local and landscape factors on robin site occupancy, prey density, and robin condition. I also investigated whether an index of chronic stress could be used to predict changes to robin occurrence and identify potential threats to the population. I concluded this work by conducting a supplementary feeding experiment to determine whether food availability was causing the variation in robin condition. A pilot study conducted in the study region four years earlier found that robins were more physiologically stressed (had higher heterophil:lymphocyte ratios) in sites with less woodland in the surrounding landscape, but site occupancy was unrelated to woodland cover. Re-examining the same study system, I established that woodland cover was now the strongest predictor of iii occupancy. While woodland cover at a local scale (within 500 m) was important for robin persistence, woodland cover at a broader scale relevant to dispersal movements (within 5 km) was not. While my stress index could not accurately predict the precise locations of future extirpations, patterns of stress indices (birds were more stressed where woodland cover was lower) did foreshadow a change to the pattern of occurrence. Extirpations from sites with low levels of woodland cover were balanced by colonisations of more-wooded sites. Surprisingly, I found that arthropod prey density was greater at sites that had less surrounding woodland. This result was primarily driven by a large number of Formicidae (ants). However, Formicidae have low nutritional value and once they were excluded from the results, soil moisture, not woodland cover, became the primary determinant of arthropod density. I predicted that robin condition would be strongly associated with arthropod density, but this was not the case. Instead, robins had elevated stress levels at sites with apparently more-favourable...

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Dynamics of extinction debt across five taxonomic groups

Cited by 96 publications

References 42 publications

Understanding extinction debts: spatio–temporal scales, mechanisms and a roadmap for future research

Understanding extinction debts: spatio–temporal scales, mechanisms and a roadmap for future research

Achteruitgang insectenpopulaties in Nederland: trends, oorzaken en kennislacunes

Why are woodland-dependent avian insectivore populations vulnerable to declines in highly-modified landscapes?

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