Balancing fuelwood and biodiversity concerns in rural Nepal

An agent-based model is developed to explore the pattern of fuelwood collection in an 1178 ha forest area in rural mountainous Nepal. The model relates fuelwood collection intensity and amount of dead wood available for collection to the diversity of polypore species, a group of strictly dead wood dependent fungi which can be used as indicators of the biodiversity associated with dead wood. By analysing scenarios of increased collection the model shows that the relative impact on polypore diversity is rising more rapidly than the time used for collection. This indicates that better market access in the future could potentially imply a major threat to biodiversity associated with dead wood.     

Understanding the functional principles of nature—Proposing another type of ecosystem services

Ecosystem services are usually interpreted as a free of charge “favour” provided to us and our society by nature. In other words, nature supplies us with a functionality that we would otherwise have to pay for. Our cost would be to provide resources either (1) to ensure the necessary inputs to drive our society, or (2) to assist in counteracting, absorbing or remediating unwanted effects that are results of our societal activities. Through ecosystem studies it has been found that a substantial part of the functionality of nature is laid out in all types of components—the compartments of the ecosystems together with the transactional interrelations (flows) and controls between them. Eventually, many so-called indicators have been proposed during the last decades. Such measures are dedicated to tell us about the quality side of ecosystem functionality, e.g. to tell us how well the system performs relatively to a theoretical maximum efficiency possible. As an additional hypothesis, such functions are thought to orient the systems and thus increase through time development, i.e. to be optimised under the given the constraints, through the evolution of the system. Recently is has been pointed out that natural and societal systems share the feature of being complex in their organisation. Meanwhile, it was remarked that societal systems in many ways evolved in opposite direction of how natural evolution would drive an ecosystem. Many philosophers of biology have stated that biological systems posses information and memory functions which improve their long-term capability to survive. This information is believed to be contained in the organisational structures of the system as much as in its gene pool. If we accept such arguments it means that studies of organisation and function of natural systems will provide us with another type of ecosystem services. This would namely give us information about in what direction to drive society in order to achieve a more sustainable system.     

A system-dynamic model on the competitive growth between Potamogeton malaianus Miq. and Spirogyra sp.

A system-dynamic model has been built to evaluate the competition between submerged macrophytes Potamogeton malaianus Miq. (PM) and filamentous green algae Spirogyra sp. (SP). The data background is based on a spring–summer and an autumn–winter experiment carried out in artificial field ponds. The experiments had the aim to acquire a knowledge base necessary to a successful restoration of submerged macrophyte vegetation in Lake Taihu, China by use of P. malaianus Miq. The model mainly focuses on variations in water volume; biomass dynamics of P. malaianus Miq., Spirogyra sp. and zoobenthos; nutrients cycling between water column, P. malaianus Miq., Spirogyra sp., zoobenthos, detritus and sediment. Sixteen state variables are included in the model: biomass of P. malaianus Miq., Spirogyra sp. and zoobenthos; nitrogen in sediments, detritus, in P. malaianus Miq., in Spirogyra sp. and zoobenthos; total dissolved nitrogen; phosphorus in sediments, detritus, in P. malaianus Miq., in Spirogyra sp. and in zoobenthos; total dissolved phosphorus, and water volume of the experiment pond. The calibration and validation of the model show a good accordance with the results of the spring–summer experiment and the autumn–winter experiment.     

Effects of increased sea water concentrations of CO2 on growth of the bivalve Mytilus edulis L

It has been proposed that emission of anthropogenic carbon dioxide to the atmosphere will lead to increased concentrations of CO(2) in sea water corresponding to a decrease of pH of several tenths of pH units. An experiment was performed to test the effects of increased sea water concentrations of CO(2) on shell growth of the blue mussel Mytilus edulis. The experiment was performed in aquaria continuously flushed with sea water spiked with CO(2) to provide five different levels of pH between 6.7 and control sea water with a pH of 8.1. The shell length of the mussels was measured at the start and end of the 44 days experimental period. No mortality was observed during the first 23 days of the experiment. The growth increment in mm was much larger for small mussels than for large mussels, but relative growth profile as function of pH was more similar in the two size groups; observed differences may be random variation between samples. The experiments showed that CO(2) induced reduction of pH affects the growth of M. edulis negatively. There was a strong and statistically significant decrease in growth at the lowest pH values, with virtually no growth at pH = 6.7 and reduced growth at pH = 7.1. The effect seems to set in between pH 7.4 and 7.1; at mean pH levels 7.4 and 7.6 the growth increments were not significantly different from growth at normal pH 8.1.     

Predicting low biota to sediment accumulation factors of PAHs by using infinite-sink and equilibrium extraction methods as well as BC-inclusive modeling

Sequestration of polycyclic aromatic hydrocarbons (PAHs) results in the slow release of PAHs from sediment to the aqueous environment, thus limiting bioavailability. Three methods to account for the limited bioavailability of native PAHs to the gastropod Hinia reticulata were therefore investigated: (i) infinite-sink extractions that measure desorption; (ii) equilibrium extractions that measure freely dissolved pore water concentrations and (iii) black carbon-inclusive modeling. The rapidly desorbing fraction was estimated based on the amount desorbed by Tenax. Relatively small amounts of PAHs (<9%) were present in F(rapid) and the observed solid-water distribution ratios (K(d,obs)) were approximately 1-2 orders of magnitude higher than literature K(oc) values. Biota to sediment accumulation factors (BSAFs) measured in the gastropod H. reticulata ranged from 0.02 to 0.07, 10-140 times lower than the theoretical value of approximately 1-2. The BSAFs calculated using the rapidly desorbing fraction or freely dissolved aqueous concentrations were also much lower than the theoretical value, and median values differed from the measured BSAFs by only a factor of 1.5-9. Furthermore, the result of using a BC-inclusive BSAF model could explain the deviation from the theoretical BSAF value and account for the low bioavailability of these native PAHs to H. reticulata. Risk assessment strategies of in situ contamination should therefore include a combination of chemical methods accounting for bioavailability, as well as bioaccumulation studies.     

Reducing nitrogen loading of inland and marine waters--evaluation of Danish policy measures to reduce nitrogen loss from farmland

An evaluation in December 2003 of the Danish National Action Plan for the Aquatic Environment II showed that nitrogen leaching from farmland had declined to almost half the amount of that in 1989. This can be ascribed to successful implementation of several measures, the most efficient of which were related to the use of fertilizers: lowered nitrogen standards for crops, increased nitrogen utilization in manure and catch crops. Although the objectives of the plan were almost met and measurements have shown a similar, but not percentually as high a decrease in nitrogen concentrations in both inland and coastal waters, the ecological impact in estuaries and coastal areas is not yet satisfactorily significant. As a consequence, a new National Action Plan for the Aquatic Environment III, including both nitrogen and phosphorus reduction from farming, was agreed to in April 2004. To ensure that good ecological status can be achieved in water bodies according to the requirements of the European Union Water Framework Directive, the national measures will be combined with additional measures for individual river basins.     

Juvenile life stages of the brown alga Fucus serratus L. are more sensitive to combined stress from high copper concentration and temperature than adults

The combined effects of exposure to copper and temperature were investigated in adult specimens and germlings of the canopy-forming brown alga Fucus serratus. A matrix of four temperatures, 6, 12, 17 and 22 °C, and three concentrations of copper, 0, 100 and 1,000 nM total copper were used. Measured endpoints were growth rate, chlorophyll fluorescence parameters and for germlings also survival. The growth rate of adult specimens of F. serratus changed with increasing temperature. Growth tended to be negatively affected by high concentrations of copper when exposed to heat (22 °C) though not significantly so. The photosynthetic performance (i.e., chlorophyll fluorescence parameters: F _v/F _m, maximum electron transport rate (ETR_max) and maximum non-photosynthetic quenching (NPQ_max) of adults was largely unaffected by both copper and temperature. Germling survival, growth rate and chlorophyll fluorescence parameters were affected by the combination of copper concentration and temperature. Increasing temperature led to reduced survival, increased rhizoid growth and higher F _v/F _m and ETR_max, whereas high copper concentration had a negative effect on the latter three endpoints. The negative effect of high copper concentration was amplified by high temperature. We conclude that juveniles of F. serratus are more susceptible to environmental stressors than adult specimens and recommend therefore including early life stages when assessing the risk of exposure to toxic compounds. Considering the response of adult specimens only may lead to false conclusions regarding the ecological impact of environmental stress.     

Feeding opportunities of larval and juvenile cod (Gadus morhua) in a Greenlandic fjord: temporal and spatial linkages between cod and their preferred prey

Feeding of fish depends on a spatial and temporal match with prey, and since larval and juvenile feeding can be highly selective, their preferences for given prey sizes and taxa should be considered when quantifying the actual availability of potential prey. We investigated the diet and prey preferences of the early-life stages of Atlantic cod (Gadus morhua) to quantify the availability of prey during a spring-summer season in a West Greenlandic fjord. We hypothesized that abundances of larval and juvenile cod at size were synchronized to optimal availability of preferred prey in space and time. The present analysis is based on nine cruises each covering 5 stations visited between 24 May and 5 August 2010 comparing zooplankton abundance, cod gut content and distribution patterns. Cod 4–25 mm in length preferred prey of about 5 % of their own length. During ontogeny, their preferences changed from calanoid nauplii towards Pseudocalanus spp. and Calanus spp. copepodites. The larvae/juvenile had an exceptionally high dietary contribution from cladocerans, which were highly preferred by cod larger than 9 mm, while the abundant Metridia longa and the non-calanoid copepods contributed less. These findings stress the importance of focusing on abundance of preferred prey when assessing the actual prey availability to young fish. We found a spatio-temporal overlap between cod and their preferred prey, and observations suggest that advection of both zooplankton and cod contributed to this overlap. Hence, the larval feeding opportunities might be sensitive to climate-related changes affecting the circulation patterns in this fjord.     

The effect of grazing on biodiversity in coastal dune heathlands

The effect of sheep grazing on species richness, higher order diversity measures, inequality, species composition, functional diversity and allometric relationships at a coastal dune heathland site was investigated. After a prescribed fire in 2002, the site was divided into two parts, where one of the parts was unmanaged and the other part was fenced and grazed by sheep. Sheep grazing had a positive effect on species richness as well as a significant positive effect on the functional diversity at the coastal dune heathland site. Generally, the cover of dwarf shrubs was negatively affected by grazing, whereas the cover of sedges and grasses was positively affected by grazing. There is a need for comparative investigations of the effect of different management methods not only on floristic biodiversity, but on all relevant kinds of biodiversity as well as on soil structure, soil chemistry and habitat micro- and macrostructure. Consequently, we advocate the initiation of an international systematic investigation of the effect of different management methods.