Caribbean small-island tourism styles and sustainable strategies

This article focuses on developing a sustainable tourism in small Caribbean islands, defined here as those that have populations of fewer than 500,000. Such islands share a very fragile ecology and a high dependence on tourism. They differ in their degree of tourist penetration and visitor density and the related degree of environmental degradation. To explain the link between tourism intensity and ecological vulnerability, the so-called “destination life-cycle model” is presented. This suggests that islands pass through three primary stages of tourist development low-density exploration, rapid growth and consolidation, and high-density maturation involving the substitution of man-made for natural attractions. A broad empirical test of the model is performed through a quantitative examination of the tourism characteristics and visitor densities of a cross section of 23 small Caribbean islands. The three basic stages or tourism styles are identified: low-impact emerging areas, high-density mass-market mature destinations, and rapidly growing intermediate islands in between. Some broad strategies consistent with the systems framework for a sustainable tourism with moderate densitites are briefly explored. An earlier version of this article was presented to Caribbean Conservation Association Conference on Economics and the Environment. Barbados, West Indies, 6–8 November, 1989.     

Individual protein balance strongly influences δ<Superscript>15</Superscript>N and δ<Superscript>13</Superscript>C values in Nile tilapia,<Emphasis Type="Italic"> Oreochromis niloticus</Emphasis>

Although stable isotope ratios in animals have often been used as indicators of the trophic level and for the back-calculation of diets, few experiments have been done under standardized laboratory conditions to investigate factors influencing ¹⁵N and ¹³C values. An experiment using Nile tilapia [Oreochromis niloticus (L.)] was therefore carried out to test the effect of different dietary protein contents (35.4, 42.3, and 50.9%) on ¹⁵N and ¹³C values of the whole tilapia. The fish were fed the isoenergetic and isolipidic semi-synthetic diets at a relatively low level. ¹⁵N and ¹³C values of the lipid-free body did not differ between the fish fed the diets with different protein contents, but the trophic shift for N and C isotopes decreased with increasing protein accretion in the individual fish, for N from 6.5 to 4 and for C in the lipid-free body from 4 to 2.5. This is the first study showing the strong influence of the individual protein balance to the degree to which the isotopic signature of dietary protein was modified in tissue protein of fish. The extrapolation of the trophic level or the reconstruction of the diet of an animal from stable isotope ratios without knowledge of the individual physiological condition and the feeding rate may lead to erroneous results.     

Comparison of selected aerobic and anaerobic procedures for MSW treatment

This paper considers selected efficiency rates and process data of aerobic and anaerobic procedures for the treatment of municipal solid waste and residual waste. Data are exclusively related to mechanical-biological treatment (MBT) procedures for generating waste appropriate for landfilling. The following aspects are regarded: general framework conditions for the application of MBT, efficiency of decomposition and of stabilisation, air and water emissions and energy balances. The presented data can be used for more efficient planning. In comparison to aerobic processes, anaerobic digestion can be ecologically advantageous, particularly with regard to exhaust emissions and energy balances. On the other hand, the wastewater emissions and the wastewater treatment required must be regarded as disadvantageous. Due to the relatively short period of operational history of most anaerobic processes for mechanical-biological waste treatment and thus limited experiences, operational reliability of anaerobic processes is slightly lower. Extensive biological stability of the treated waste for low-emission disposal cannot be reached by anaerobic digestion alone, but only in combination with additional aerobic post-treatment. In connection with the utilisation of renewable energies and the rising relevancy of climate protection, it can be affirmed that anaerobic digestion for the treatment of municipal solid waste has a high potential for further development.     

Vorläufige klinische Beobachtungen mit einem neuen N-Lost-Phosphamidester in der Tumortherapie

The Science of Nature -     

碳底物含量对厌氧条件下水稻土N2、N2O、NO、CO2和CH4排放的影响

理解底物碳氮对厌氧条件下水稻土排放氮素气体——氮气(N2)、氧化亚氮(N2O)和一氧化氮(NO)以及二氧化碳(CO2)和甲烷(CH4)的影响,有助于制定合理的温室气体减排措施,定量了解反硝化产物组成对碳底物水平的依赖性,也有助于氮转化过程模型研发中制定正确的关键过程参数选取方法或参数化方案.本研究采用粉砂壤质水稻土为研究对象,设置对照(CK)和加碳(C+)两个处理,前者的初始硝态氮和可溶性有机碳(DOC)含量分别为~50 mg·kg-1和~28 mg·kg-1,后者的分别为~50 mg·kg-1和~300 mg·kg-1.采用氦环境培养-气体及碳氮底物直接同步测定系统,研究了完全厌氧条件下碳底物水平对上述气体排放的影响.结果表明,CK处理无CH4排放,而C+处理可观测到CH4排放;C+处理的综合增温潜势显著高于CK处理(P<0.01);NO、N2O和N2排放量占这3种氮素气体排放总量的比重,在CK处理分别约为9%、35%和56%,在C+处理分别约为31%、50%和19%,处理间差异显著(P<0.01).由此表明,碳底物水平可显著改变所排放氮素气体的组成;对于旱地阶段硝态氮比较丰富的水稻土,避免在淹水前或淹水期间施用有机肥,有利于削减温室气体排放.