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The extent to which conservation is feasible is constrained by budgets and the financial sacrifice stakeholders are willing to bear. Therefore a possible objective for conserving a species is to minimise the cost of achieving that stated aim. For example, if a minimum viable population (MVP) of a species is to be conserved, the size and type of habitats reserved for this could be selected to minimise cost. This requires consideration of the comparative (relative) opportunity costs of reserving different land types for conservation. A general model is developed to demonstrate this and is applied to the case of the orangutan. In the ecological literature, recommendations for reserving different types of land for conservation have been based on comparisons of either the absolute economic returns they generate if converted to commercial use or on differences in the density of a species they support. These approaches are shown to be deficient because they ignore relative trade-offs between species population and economic conversion gains at alternative sites. The proposed model is illustrated for orangutan conservation. [Copyright &y& Elsevier]

In the vegetation corridors that connect small remnants of undisturbed primary forest in the Lavras landscape (Brazil), Protium spruceanum is a representative of a mass-flowering insect-pollinated and bird-dispersed tree. Allozyme variation was quantified from five forest remnants (N = 150) from secondary vegetation corridors linking them (N = 80) to generate information for genetic conservation. The species adhered to H-W equilibrium in all fragments in most of the loci. The results indicated high gene diversity in the fragments (Hˆe = 0.381-0.507) and corridors (Hˆe = 0.336-0.470); positively correlated with the plant density (r = 0.742, R² = 0.551, d.f. = 4). We did not find evidence of inbreeding within fragments (fˆ = -0.188; P<0.05) nor overall (Fˆ = -0.101; P<0.05). The genetic differentiation among remnants was low (θp = 2.8%). Evidence of recent bottlenecks by anthropogenic disturbance was detected in fragments (P<0.05, Wilcoxon sign-rank test). The minimal viable population was estimated for conservation in situ, indicating fragments with possibilities of maintaining genetic equilibrium diversity in the short term (except F3) and in the long term (only F5). The Nˆe/N ratios was also calculated to contribute to vegetation enrichment, area recovery or creation of new vegetation corridors. We found high levels of gene diversity in the vegetation corridors, genetic identity with the fragments and absence of inbreeding. Thus, our results suggest that landscape management strategies should therefore consider both the creation of new vegetation corridors and the protection of extant ones. [ABSTRACT FROM AUTHOR]

Conservation biologists struggle to decide how many animals to save. In this article, I outline 18 approaches to setting population target levels (PTLs) for animals, with rules of thumb and analytical recommendations for each approach. Minimally viable populations, the most common target level, are necessary but not sufficient for most efforts, given the range of values that bear on conservation. Reference ecosystems, either extant or historical, are key for setting practical target levels. Setting PTLs sufficient for conserved populations to be animals in all respects (including functional, social, landscape, ethical, aesthetic, and spiritual aspects) is a critical consensus point. In many cases densities as well as overall population size will need to be specified. I suggest a four-tiered system of setting incrementally higher population target levels such that conservation provides first for demographic sustainability, then ecological integrity, then sustainable use, and finally restoration of historical numbers of wildlife, based on times when human beings had less impact on the planet than we do today. [ABSTRACT FROM AUTHOR]

In Belgium, Primula vulgaris is a rare and declining species. Its fate is bound up with the ever-changing agricultural landscape in northwestern Belgium and analysis of historical data showed a shrinking distribution area during the last decades. Contrary to the situation in England and France, most of the populations are situated in small landscape elements in the agricultural landscape and not in woodland. The population size distribution is skewed to very small populations (<10 individuals) with few younger life stages in small populations, higher proportions of older adults and unequal flower morph numbers. The changes in several population traits during a 13-year interval are correlated with initial population status, indicating that small populations tend to be more prone to extinction than larger ones. Small remnant woodland patches may be seen as ‘safe sites’: in this environment population sizes were more or less stable during the 13-year period whereas populations in ditches around arable fields were particularly susceptible to decline. Under current conditions, the long term survival of the species in small landscape elements is highly critical unless land use practices change drastically in the near future. The minimum viable populations concept and management of small landscape elements are discussed. [Copyright &y& Elsevier]

The concept of minimum populations of wildlife and plants has only recently been discussed in the literature. Population genetics has emerged as a basic underlying criterion for determining minimum population size. This paper presents a genetic framework and procedure for determining minimum viable population size and dispersion strategies in the context of multiple-use land management planning. A procedure is presented for determining minimum population size based on maintenance of genetic heterozygosity and reduction of inbreeding. A minimum effective population size ( N) of 50 breeding animals is taken from the literature as the minimum shortterm size to keep inbreeding below 1% per generation. Steps in the procedure adjust N to account for variance in progeny number, unequal sex ratios, overlapping generations, population fluctuations, and period of habitat/population constraint. The result is an approximate census number that falls within a range of effective population size of 50-500 individuals. This population range defines the time range of short- to long-term population fitness and evolutionary potential. The length of the term is a relative function of the species generation time. Two population dispersion strategies are proposed: core population and dispersed population. [ABSTRACT FROM AUTHOR]