Evaluating the assumptions of population projection models used for conservation

Earl, Julia E.

doi:10.1016/j.biocon.2019.06.034

Cited by 18 publications

(17 citation statements)

References 59 publications

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“…The IPM does not explicitly include immigration or emigration, and we assume that all adult females breed each year. These assumptions can be violated for amphibian populations (Earl 2019) but were necessary because we had no data to estimate these parameters. We calculated the long‐term log stochastic growth rate (log λ s ) for each population using the estimated abundance of adult females each year (Caswell 2001).…”

Section: Methodsmentioning

confidence: 99%

“…Because of complex life histories and cryptic life stages, vital rates can be challenging to quantify for a wide range of taxa that are emblematic of the current biodiversity crisis, from lepidoptera to amphibians (Dirzo et al 2014, Scheele et al 2019). The life history of a free‐living larval stage followed by a dispersing post‐metamorphic stage can complicate parameterization of models (Williams et al 2002, Oberhauser et al 2017, Earl 2019). In particular, survival of recently metamorphosed individuals can be difficult to estimate in the wild when recapture rates for marked individuals are low (Kupferberg et al 2009).…”

Section: Introductionmentioning

confidence: 99%

“…When vital rates are highly uncertain and models are parameterized using independent data sources, demographic models, such as matrix models, can produce unrealistic estimates of population growth rates (Schaub and Abadi 2011). Despite the challenges posed by high uncertainty in estimates of vital rates for early life stages, many authors have used stage‐based population models to study the demography of amphibians (Earl 2019). Integrated population models can partially resolve the aforementioned challenges by explicitly integrating different data types into a joint likelihood and can produce demographic estimates with greater precision and accuracy than independent models (Abadi et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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Estimating the survival of unobservable life stages for a declining frog with a complex life history

et al. 2021

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Demographic models enhance understanding of drivers of population growth and inform conservation efforts to prevent population declines and extinction. For species with complex life histories, however, parameterizing demographic models is challenging because some life stages can be difficult to study directly. Integrated population models (IPMs) empower researchers to estimate vital rates for organisms that have cryptic or widely dispersing early life stages by integrating multiple demographic data sources. For a stream‐inhabiting frog (Rana boylii) that is declining through much of its range in Oregon and California, USA, we collected egg‐mass counts and capture–mark–recapture data on adults from two populations in California to fit IPMs that estimate adult abundance and the survival rate of both marked and unobserved life stages. Estimates of adult abundance based on long‐term monitoring of egg‐mass counts showed that study populations fluctuated greatly inter‐annually but were stable at longer timescales (i.e., decades). Adult female survival during 5–6 yr of capture–mark–recapture study periods was nearly equal in each population. Survival rate of R. boylii eggs to the subadult stage is low on average (0.002) but highly variable among years depending on post‐oviposition stream flow. Population viability analysis showed that survival of adult and subadult life stages has the greatest proportional effect on population growth; the survival of egg and tadpole life stages, however, is more malleable by management interventions. For example, simulations showed head‐starting of tadpoles, salvaging stranded egg masses, and limiting aseasonal pulsed flows could dramatically reduce the threat of extirpation. This study demonstrates the value of integrating multiple demographic data sources to construct models of population dynamics in species with complex life histories.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimating the survival of unobservable life stages for a declining frog with a complex life history

et al. 2021

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“…Lack of species-specific data can be overcome to some extent; we found estimates for species within the same genus for a further 43 species. Population projection models are increasingly being used to identify effective management strategies for threatened species (Alemayehu 2013;Earl 2019;Hartmann et al 2017;Hegg et al 2013), and as such, the availability of demographic data is likely to continue to improve, particularly for known threatened species.…”

Section: Discussionmentioning

confidence: 99%

Disparity between ecological and political timeframes for species conservation targets

2021

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The Convention on Biological Diversity’s (CBD) Aichi Target 12 aimed to prevent species extinctions and improve the conservation status of known threatened species by 2020 but has not been met. As the post-2020 global biodiversity framework is negotiated, it is essential that we learn lessons from past failures. Here, we investigate whether a reduction in extinction risk could realistically be achieved within the ten-year timeframe of the Aichi Targets. We identified threatened bird and mammal species for which a population increase could lead to down-listing on the IUCN Red List and created population models that assumed exponential population growth to predict how long it would take to reach the population size threshold required for down-listing. We found that in the best-case scenario, 39/42 birds (93%) and 12/15 mammals (80%) could be expected to show the population increase required to achieve down-listing by one Red List category within a ten-year timeframe. In contrast, under the worst-case scenario, 67% birds and 40% mammals were predicted to take > 10 years to reach the population threshold. These results indicate a disparity between the ecological timeframes required for species to show a reduction in extinction risk, and the political timeframes over which such ecological change is expected to be achieved and detected. We suggest that quantitative analyses should be used to set realistic milestone targets in the post-2020 framework, and that global indicators should be supplemented with temporally sensitive measures of conservation progress in order to maintain political and societal motivation for species conservation.

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“…Effective conservation laws, government investment in tiger reserves and government reward programs that encourage local support, all of which brighten potential prospects (Ghosh-Harihar et al, 2019). Models of population projection, such as matrix and integral projection models, can also be used to interpret and inform conservation behavior of the possible consequences of anthropogenic stressors (Earl, 2019). Information on the vital rate and life history used to construct robust population models is often lacking or incomplete, rendering assumptions possible about parameters and population processes.…”

Section: Conservation Strategiesmentioning

confidence: 99%

Conservation Status of Bengal Tiger (Panthera tigris tigris)- A Review

Kumar¹

2021

JSR

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Bengal tiger is one of the majestic carnivores found in regions of the Indian subcontinent. It possesses immense intrinsic values contributing significantly to the cultural and ecological aspects. However, a drastic decline in the population has been perceived for the past few years. Anthropogenic activities and fall in prey density are considered to be the major threats. Several conservation actions and plans have been executed to stabilize and increase the population. This review article summarizes ecology, threats to tiger population and its conservation strategies.

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Evaluating the assumptions of population projection models used for conservation

Cited by 18 publications

References 59 publications

Estimating the survival of unobservable life stages for a declining frog with a complex life history

Estimating the survival of unobservable life stages for a declining frog with a complex life history

Disparity between ecological and political timeframes for species conservation targets

Conservation Status of Bengal Tiger (Panthera tigris tigris)- A Review

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