The gaharu trade in Indonesia: Is it sustainable?

When subjected to fungal attack, Aquilaria spp. (Thymelaeaceae) produce a fragrant resin that is traded internationally as gaharu. Socioeconomic aspects of the gaharu trade were investigated via interviews with collectors and local and international traders. In addition, the extent of local and international trade was evaluated by reference to official government statistics. Evidence that gaharu resources are declining was obtained from the personal experience of gaharu collectors, and official statistics relating to the declining number of gaharu export companies in operation. Traders also reported that the main source of gaharu has recently switched from Sumatra and Kalimantan to sources in eastern Indonesia (Maluku and Irian Jaya), a finding supported by official statistics. Disparities recorded between official figures for the price and volume of gaharu in local and international trade, supported by comments made by export traders, indicate that a high proportion of the more valuable, high-grade gaharu is traded illegally by personal transaction. Interviews with gaharu collectors indicated that traditional approaches to harvesting are declining, as more nonlocal people become involved in collection, leading to more intensive harvesting practices. Together, these findings suggest that the current Indonesian trade in gaharu is not sustainable.     

Sustainability impact assessment of increasing resource use intensity in forest bioenergy production chains

Changing forest management practices towards more intensive biomass utilization for energy purposes will affect the sustainability of resource management. The Tool for Sustainability Impact Assessment was applied to evaluate the environmental, social, and economic sustainability impacts of the stepwise increased extraction of forest biomass of three typical Scandinavian Scots pine bioenergy production chains (BPCs). The assessed sources of the woody biomass were pellets as a by‐product of the sawmilling industry, wood chips deriving from early whole‐tree harvesting, and residues from final cuttings. Three commercially practiced BPCs were compared. By the additional extraction of biomass for heat production, the employment increased by 0.6 person‐years 1000 m^?3 solid wood chips, while there was a decrease in the costs and greenhouse gases emitted per unit of heat consumed. Furthermore this practice did not only add positive socio‐economic but also positive environmental impacts on sustainability, particularly on the greenhouse gas balance and the energy efficiency ratio (input to output ratio along the BPC), which was determined to be 1–24. Potential drawbacks, on the other hand, include decreasing nutrient returns to the soil and the associated potential reduction in future stand productivity. Fertilization might be needed to maintain sustainable forest growth on poor sites.     

Linear age-dependent population growth with seasonal harvesting

A population growth is modelled by the Von Foerster PDE with accompanying Lotka-Volterra integral equation describing the birth rate; the age specific death and fertility rates are assumed to depend only on age and not time. A harvesting policy where a fraction of the population of age greater than a given age is harvested for a fraction of a given season. This introduces a time dependence, but this difficulty is circumvented by devising approximate timeindependent models whose birthrates bracket the true birthrate-the standard renewal equation theory applies to the approximate models so quantitative results can be obtained.The author wishes to thank Professors J. J. Levin and R. K. Miller for some useful remarks. This research was partially supported by NIH Grant GMO 7661-02.     

Non-timber forest products in the community of El Terrero, Sierra de Manantlán Biosphere Reserve, Mexico: Is their use sustainable?

The importance of non-timber forest products (NTFPs) to rural income was examined in a highland community in the Sierra de Manantlán Biosphere Reserve, Jalisco-Colima, Mexico. Rapid Rural Appraisal (RRA) techniques were used to interview 70% of households in the community of El Terrero. Of the nine plant species identified as NTFP sources, the two principal species traded by the community were tila (derived from the flowers and fruits of the tree Ternstroemia lineata), and blackberry (Rubus spp.). Collecting and selling of NTFPs was almost exclusively undertaken by women, with 80% of respondents participating. NTFP sale ranked as the most important source of cash income for 30% of women interviewed, and either second- or third-most important for the remainder. The research examined harvesting impact on populations of T. lineata, an understory tree species characteristic of cloud forest, which this was assessed in the four most-frequented collecting sites. Our results suggested that current harvesting approaches appear to be sustainable, although 95% of the women interviewed reported a decline in resource availability within the last 15 years, apparently resulting from illegal cutting. Suggestions are made with respect to the sustainable development of NTFP resources to help alleviate poverty within the Reserve.     

生态系统可持续管理的原理和方法

人口、资源与环境是当前社会关注的重点 ,三者相互依存 ,互为影响 ,因此如何协调三者之间的关系显得极为重要 ,它关系到人类社会的可持续发展。生态系统作为人类生存条件-资源和环境的保育基础 ,其管理的重要性已被广泛认识和接受。本文运用生态学、管理学等原理 ,从生态系统结构、功能和过程等特征出发 ,详细论述了生态系统可持续管理的原理、手段和方法。并依据生态系统的不确定性和对管理的反馈作用 ,强调了适应性管理是实现生态系统可持续管理的基本途径 ,为进一步研究生态系统的可持续管理的案例提供理论依据     

Is There a Role for Risk Assessment within Precautionary Legislation?

Posing the question of whether the precautionary principle has a role in risk assessment effectively constrains any debate of the issue within a framework predicated on the assumption that application of risk assessment is inevitable in the formulation of regulatory decisions. The question can equally validly be expressed in terms of whether there is a role for risk assessment in the formulation of precautionary legislation. This allows the debate then to turn on consideration of two questions: Firstly, does the precautionary principle have a role in policy development? and secondly, is this role consistent and compatible with a risk based approach to regulation? When recast in these terms, a more holistic comparison of the aims and objectives of both approaches and of their relative power in the formulation of regulation becomes possible. This leads to the conclusion that the precautionary principle is, when defined and applied correctly, scientifically more robust than risk assessment. Precautionary approaches utilize scientific information and conform robustly to a scientific process but also explicitly incorporate indeterminacies into the decision making framework. Moreover, the precautionary principle when applied to environmental regulation, is more likely to lead to regulation consistent with global sustainability. On this premise, this paper argues that risk based approaches are essentially incompatible with approaches based on the precautionary paradigm, and that of the two, risk assessment is more likely to lead to unsustainable underprotection of the environment.     

Stochasticity and spatial coexistence of semelparity and iteroparity as life histories

We investigate conditions enabling long-term coexistence of semelparity (reproducing only once per lifetime) and iteroparity (repeated spells of reproduction in subsequent breeding seasons). Bulmer (1985, 1994) has transferred the study of the fitness merit of reproducing semelparously vs. iteroparously into a density-dependent system, using an invasion scenario with an abundant resident population of one reproductive strategy and a rare mutant invader population of another reproductive strategy. For stable population dynamics, Bulmer (1994) derived condition v + P _A < 1 (P _A is adult survival and v is the ratio of offspring number of the iteroparous type over that of the semelparous type) where a semelparous population cannot be invaded by an iteroparous strategy. In order to study the generalisation of Bulmer's results in spatial population dynamics, we generate a population system consisting of a linear string of habitable sub-units. The sub-units are semi-independent, obeying discrete-time Ricker dynamics in renewal, but they are close enough for dispersing individuals to couple them together. At each time step, a random fraction of individuals in each sub-unit disperses into neighbourhood. In this setting, we observe long-term persistence of semelparity and iteroparity when dispersal is stochastic and positively autocorrelated. Stochasticity in dispersal creates fluctuating local dynamics and thus permits long-term persisting coexistence of semelparity and iteroparity even in the parameter region where Ricker dynamics are stable and the Bulmer inequality is true. Positively autocorrelated, in contrast to negatively autocorrelated dispersal time-series, promoted coexistence between semelparity and iteroparity.     

Size-specific spawing pattern in ayu,Plecoglossus altivelis

The spawning pattern and relationship to body size at maturation of amphidromous and land-locked forms of ayu,Plecoglossus altivelis, was investigated. Ovarian eggs of prespawning females showed a multimodal size distribution, regardles of body size, indicating that all the females were potentially a batch spawners. The spawning schedules of individual fish were described under simulated spawning conditions. Most large-sized females died soon after their first spawning, whereas approximately half of the medium and small-sized females successfully completed a second spawning some two weeks after the first. Such a size-specific spawning pattern was common to both forms, but development of a third batch of ovarian eggs after the second spawning occurred only in the land-locked form. Spawning tactics in ayu were related to offspring survival and adult mortality during spawning season.     

Effects of Ration and Temperature on Reproduction of a Semelparous and an Iteroparous Triclad

Summary

This paper compares aspects of the reproduction of a semelparous triclad, Dendrocoelum lacteum, with those of an iteroparous triclad, Dugesia polychroa. Cocoon output was less sensitive to ration and possibly temperature for the former as compared with the latter species. Cocoons of D. lacteum were on average bigger and contained more hatchlings than those of D. polychroa. The sizes of hatchlings did not differ between species, but for D. lacteum only, the hatchlings emerging from late cocoons were significantly larger, and less numerous, than those emerging from earlier cocoons. Possible reasons for these differences are considered.     

Pontryagin's principle for control problems in age-dependent population dynamics

In this paper, Pontryagin's principle is proved for a fairly general problem of optimal control of populations with continuous time and age variable. As a consequence, maximum principles are developed for an optimal harvesting problem and a problem of optimal birth control.