Economics of biodiversity and sustainable fisheries management

Akpalu, Wisdom

doi:10.1016/j.ecolecon.2009.05.014

Cited by 16 publications

(24 citation statements)

References 14 publications

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“…For moderately non-linear fitness functions, the reliability of aggregate models has to be severely questioned and we suggest a combination with species sorting models (Tirok and Gaedke 2010) to reduce the variances of the individual trait distributions and the non-linearities of the individual fitness functions . Our results and conclusions may also apply to other fields as aggregate approaches were also used in e.g., spatial ecological (Gandhi et al 2000) and social-economical models (Wirtz and Lemmen 2003) and fishery management (Akpalu 2009).…”

mentioning

confidence: 69%

Analyzing the shape of observed trait distributions enables a data‐based moment closure of aggregate models

Gaedke

Klauschies

2017

Limnology & Ocean Methods

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The shape of trait distributions may inform about the selective forces that structure ecological communities. Here, we present a new moment‐based approach to classify the shape of observed biomass‐weighted trait distributions into normal, peaked, skewed, or bimodal that facilitates spatio‐temporal and cross‐system comparisons. Our observed phytoplankton trait distributions exhibited substantial variance and were mostly skewed or bimodal rather than normal. Additionally, mean, variance, skewness und kurtosis were strongly correlated. This is in conflict with trait‐based aggregate models that often assume normally distributed trait values and small variances. Given these discrepancies between our data and general model assumptions we used the observed trait distributions to test how well different aggregate models with first‐ or second‐order approximations and different types of moment closure predict the biomass, mean trait, and trait variance dynamics using weakly or moderately nonlinear fitness functions. For weakly non‐linear fitness functions aggregate models with a second‐order approximation and a data‐based moment closure that relied on the observed correlations between skewness and mean, and kurtosis and variance predicted biomass and often also mean trait changes fairly well and better than models with first‐order approximations or a normal‐based moment closure. In contrast, none of the models reflected the changes of the trait variances reliably. Aggregate model performance was often also poor for moderately nonlinear fitness functions. This questions a general applicability of the normal‐based approach, in particular for predicting variance dynamics determining the speed of trait changes and maintenance of biodiversity. We evaluate in detail how and why better approximations can be obtained.

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mentioning

confidence: 69%

Analyzing the shape of observed trait distributions enables a data‐based moment closure of aggregate models

Gaedke

Klauschies

2017

Limnology & Ocean Methods

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“…This may have a strong impact on the food web structure, the energy transfer from one trophic level to the next, and related ecosystem services, when implementing the aggregate model approach into global ocean or other ecosystem models tailored to specific systems. Trait variation was also incorporated into fishery management models using an aggregate approach (Akpalu 2009). However, our results lead us to the expectation that, depending on the underlying trade-offs of the system, a FTD model may deliver strongly deviating predictions concerning the sustainable yield of fish, with major economic and ecological consequences.…”

Section: Discussionmentioning

confidence: 91%

Bimodal trait distributions with large variances question the reliability of trait-based aggregate models

2016

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Functionally diverse communities can adjust their species composition to altered environmental conditions, which may influence food web dynamics. Trait-based aggregate models cope with this complexity by ignoring details about species identities and focusing on their functional characteristics (traits). They describe the temporal changes of the aggregate properties of entire communities, including their total biomasses, mean trait values, and trait variances. The applicability of aggregate models depends on the validity of their underlying assumptions that trait distributions are normal and exhibit small variances. We investigated to what extent this can be expected to work by comparing an innovative model that accounts for the full trait distributions of predator and prey communities to a Renato Mendes Coutinho and Toni Klauschies contributed equally to this work.

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“…However, the efficacy of such a policy instrument hinges on the knowledge of the biophysical dynamics of the stocks. Two recent studies have shown that a fish stock could be potentially depleted if the biodynamic is misperceived, even if catch policies exist (Sterner 2007;Akpalu 2009). Using time series data on artisanal marine fishing in Ghana (1972Ghana ( -2007, this study extends the existing surplus production function to account for the impact of changes in atmospheric temperature and its variance on the environmental carrying capacity of artisanal fish stock; estimate the biophysical parameters employing the generalized maximum entropy (GME) estimators, which addresses the classical linear regression problems of endogeneity, multi-collinearity, and limited observations; estimate the optimum tax necessary to internalize congestion externality and the climate impact on fish yield; and forecast the local atmospheric temperature as well as discuss its implication for the optimum tax.…”

Section: Introductionmentioning

confidence: 99%

Unpacking women’s health in public-private partnerships: A return to instrumentalism in development policy and practice?

Gideon¹,

Porter²

2014

WIDER Working Paper

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Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. Abstract:In most coastal developing countries, the artisanal fisheries sector is managed as a common pool resource. As a result, such fisheries are overcapitalized and overfished. In Ghana, in addition to anthropogenic factors, there is evidence of rising coastal temperature and its variance, which could impact the environmental carrying capacity of the fish stock. This study investigates the effect of climate variation on biophysical parameters and yields. Our results indicate that the rising temperature is decreasing the carrying capacity. As a result, an optimum tax on harvest must reflect climate variability, as well as the congestion externality.

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Economics of biodiversity and sustainable fisheries management

Cited by 16 publications

References 14 publications

Analyzing the shape of observed trait distributions enables a data‐based moment closure of aggregate models

Analyzing the shape of observed trait distributions enables a data‐based moment closure of aggregate models

Bimodal trait distributions with large variances question the reliability of trait-based aggregate models

Unpacking women’s health in public-private partnerships: A return to instrumentalism in development policy and practice?

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