Stochastic Demography for Conservation Biology

Nations, Chris; Boyce, Mark S.

doi:10.1007/978-1-4615-5973-3_15

Cited by 13 publications

(7 citation statements)

References 52 publications

(68 reference statements)

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“…This approximation assumes no between‐year autocorrelation in environmental conditions and therefore demography (as observed on Islay, Reid et al . 2003a), and is robust to reasonable demographic variation (CV ≈ 0·40, Tuljapurkar 1990; Nations & Boyce 1997).…”

Section: Methodsmentioning

confidence: 94%

Identifying the demographic determinants of population growth rate: a case study of red‐billed choughs Pyrrhocorax pyrrhocorax

Reid

Bignal²,

Bignal³

et al. 2004

Journal of Animal Ecology

151

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Summary 1.Identifying which age-specific demographic rates underlie variation in a population's growth rate ( λ ) is an important step towards understanding the population's dynamics. Using data from a 20-year study of marked individuals, we describe patterns of demographic variation and covariation in the Scottish red-billed chough population ( Pyrrhocorax pyrrhocorax ), and investigate which demographic rates have the greatest projected and realized influence on λ . 2. Survival, the probability of breeding and breeding success varied with age in this population. Data were sufficient to estimate year-specific probabilities of first-year, second-year and adult (all ages over 2) survival and mean breeding success. A population trajectory modelled using these parameter estimates closely matched census data, suggesting that estimates and simplifying assumptions were sufficient to accurately describe important demographic processes. 3. Elasticity analyses based on stage-classes for which year-specific survival was estimable suggested that λ was more elastic to variation in adult survival than first-or second-year survival or breeding success. These ranks were consistent across all 15 years for which λ could be estimated directly, although the elasticity of adult survival declined with population growth. 4. Survival and breeding success were positively correlated across years. λ remained most sensitive to adult survival when this demographic covariation was incorporated into elasticity analyses. 5. However, elasticities calculated from a fully age-structured model suggested that λ was more elastic to variation in first-and second-year survival than to survival at any individual older age class. These ranks were robust to realistic demographic variation, but sensitive to postulated patterns of demographic covariation. We emphasize that covariation should be measured and incorporated into elasticity analyses, and that estimated elasticities must be interpreted in the context of the way in which stage-classes are defined. 6. Of the demographic rates in which we quantified between-year variation, first-year survival varied most, followed by second-year survival, breeding success and adult survival. These rates consequently contributed more equally to variation in λ than elasticities predicted. Overall, variation in λ was caused primarily by variation in survival rather than breeding success, and variation in prebreeding survival accounted for 56% of the total variation in λ .

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Section: Methodsmentioning

confidence: 94%

Identifying the demographic determinants of population growth rate: a case study of red‐billed choughs Pyrrhocorax pyrrhocorax

Reid

Bignal²,

Bignal³

et al. 2004

Journal of Animal Ecology

151

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“…Stochastic and periodic population projections take into account some interannual variability in vital rates, such as mortality and fecundity, by including a number of different yearly matrices in the projections. Environmental variations may interact in various ways with the effects of harvest ( Nations & Boyce 1997 ), and the annual rate of harvest itself may vary from year to year. For the two species they studied, Nantel et al ( 1996 ) found that stochastic simulations predicted MSH to be much lower than those estimated under the assumption of a favorable and unchanging environment, but it remains unknown how this may apply to other NTFP.…”

Section: Introductionmentioning

confidence: 99%

Effects of Variation on Harvest Limits for Nontimber Forest Species in Mexico

Ticktin

Nantel

Ramírez³

et al. 2002

Conservation Biology

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Successful conservation of nontimber products and their rainforest habitats requires the identification of optimal harvest regimes, the accurate estimation of maximum harvest limits, and the implementation of those limits by local harvesters. We used a combination of participatory research techniques and demographic modeling to determine maximum sustainable harvest rates of the bromeliad Aechmea magdalenae in the buffer zone of the Los Tuxtlas Biosphere Reserve in Mexico. We examined the effects of three types of variation on maximum harvest rates: variation between forest types, between harvest regimes, and over time. We also tested the accuracy of estimating maximum harvest limits using matrix-model projections of unharvested populations. Maximum harvest rates of ramets from secondary forest populations were much higher than from primary-forest populations. Likewise, variation in local harvest regimes had a large effect on maximum harvest rates. Populations concurrently harvested for leaves and ramets had higher maximum sustainable levels of ramet harvest than those harvested for ramets only. Simulations using harvested and unharvested populations yielded significantly different estimates of maximum sustainable harvest limits, indicating that methods for calculating maximum harvest limits that assume linear responses to harvest may lead to erroneous conclusions. Active participation in the research process enabled local harvesters to accept as valid the harvest limits determined in this study, to switch to using a more sustainable harvest regime, and to pass a local law prohibiting the destruction of their remaining primary forest because of its potential as A. magdalenae habitat. Efectos de la Variación Sobre los Límites de Cosecha de Especies Forestales No Maderables en MéxicoResumen: La conservación exitosa de productos no maderables y sus hábitats boscosos requiere de la identificación de regímenes de cosecha óptimos, la estimación precisa de límites de cosecha máximos y la instrumentación de esos límites por los recolectores locales. Utilizamos una combinación de técnicas de investigación participativa y modelaje demográfico para determinar las tasas máximas de cosecha sostenible de la bromeliácea Aechmea magdalenae en la zona de amortiguamiento de la Reserva de la Biosfera Los Tuxtlas en México. Examinamos los efectos de tres tipos de variación en las tasas máximas de cosecha: variación entre tipos de bosque, entre regímenes de cosecha y en el tiempo. También probamos la precisión de la estimación de límites máximos de cosecha utilizando modelos de proyección matricial de poblaciones no cosechadas. Las tasas máximas de cosecha de rámulas en poblaciones de bosque secundario fueron mucha más altas que en poblaciones de bosque primario. De igual modo, la variación en los regímenes de cosecha local tuvo un efecto notable en las tasas de cosecha máxima. Las poblaciones concurrentemente cosechadas para hojas y rámulas tuvieron niveles de máxima cosecha sostenible de rámulas más altos que las cosechadas para rám...

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“…Importantly, their model neglects annual variance in agricultural productivity. When there is variance in productivity, population growth is limited by minimal productivity and better modeled using the geometric mean rather than the arithmetic mean (Renshaw, 1993;Nations and Boyce, 1997;Freckleton and Watkinson, 1998, p. 113), and populations in variable environments can stabilize at substantially lower levels than under more constant conditions. Rapa Nui has unpredictable annual rainfall and on longer-term timescales, resulting in potentially substantial variability in food productivity (Genz and Hunt, 2003;Morrison, 2012).…”

mentioning

confidence: 99%