The resource economics of chemical and structural defenses across nitrogen supply gradients

In order to better understand the role of nutrient supplies in determining the prevalence of plant defense types, we investigated the theoretical relationships between ecosystem N supply and the net C gain of shoots that were undefended or defended in one of three ways: (1) by N-free chemical compounds, (2) by N-containing chemical compounds, or (3) by structural defenses. By extending economic models of shoot resource balance to include the relative value of C and N, depreciation, and amortization, we were able to show that the relative net C gain of the three defense types were similar to changes in their generally understood abundance along an N supply gradient. At low N supply, the additional C acquired when investing C in defense is much higher than investing N in defenses. Only at high N supply is it better to invest large quantities of N in defense rather than additional photosynthesis. In a sensitivity analysis, net C gain of shoots was most sensitive to factors that affect the relative value of C and N and the rate of herbivory. Although there is support for the relative value of C and N influencing defense strategies, more research is necessary to understand why tannins are not more prevalent at high N supply and why moderate amounts of N-based defenses are not used at low N supply.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.     

Productivity and thallus toughness trade‐off relationship in marine macroalgae from the Japan Sea

Trade‐offs are considered key to understanding mechanisms supporting the coexistence of multiple plant species. Thus, understanding the mechanisms underlying trade‐offs is expected to contribute to conservation and management of macroalgal beds composed of diverse macroalgae of rocky shore ecosystems. To test the occurrence of trade‐offs between productivity and thallus toughness as well as pair‐wise thallus trait relationships that are expected to indirectly relate to any trade‐offs, traits and relationships for 13 species of macroalgae from the central area along the Japan Sea coast of Honshu, Japan were examined. In each species we examined for photosynthetic capacity per unit biomass (as A_mass) and nitrogen (i.e., photosynthetic nitrogen‐use efficiency, PNUE), nitrogen content (as N_mass), thallus mass per unit thallus area (as TMA) and force required to penetrate the thallus (as F_p, a common index of leaf toughness in land plants by punch test). A significant negative correlation indicating a trade‐off between productivity and thallus toughness was found between A_mass or PNUE and F_p. Pair‐wise relationships that were expected to indirectly relate to the trade‐off were as follows. A_mass was positively correlated with N_mass. Thalli with high N_mass extensively utilizing nitrogen in the photosynthetic parts, and consequently exhibiting elevated metabolic rates. Moreover, thalli with high N_mass tended to be associated with low TMA, and N_mass decreased with increasing TMA. A significant negative correlation was observed between TMA and A_mass or PNUE because of the linkage of high A_mass or PNUE with high N_mass and high N_mass associated with low TMA, while a significant positive correlation was observed between TMA and F_p. The two correlations indicate a physiological and structural trade‐off, which underlies the interdependency of thallus traits. Results of multivariate analyses also indicated that the thallus traits interdependently vary across a single axis based on the trade‐off.     

A micro-jet array for economic intensification of gas transfer in bioreactors

Bioreactors are of interest for gas-to-liquid conversion of stranded or waste industrial gases, such as CO, CH₄, or syngas. Process economics requires reduction of bioreactor cost and size while maintaining intense production via rapid delivery of gases to the liquid phase (i.e., high k_La). Here, we show a novel bioreactor design that outperforms all known technology in terms of gas transfer energy efficiency (k_La per power density) while operating at high k_La (i.e., near 0.8 s⁻¹). The reactor design uses a micro-jet array to break feedstock gas into a downward microbubble flow. Hydrodynamic and surfactant measurements show the reactor's advanced performance arises from its bubble breakage mechanism, which limits fluid shear to a thin plane located at an optimal location for bubble breakage. Power dissipation and k_L are shown to scale with micro-jet diameter rather than reactor diameter, and the micro-jet array achieves improved performance compared to classical impinging-jets, ejector, or U-loop reactors. The hydrodynamic mechanism by which the micro-jets break bubbles apart is shown to be shearing the bubbles into filaments then fragmentation by surface tension rather than “cutting in half” of bubbles. Guided by these hydrodynamic insights, strategies for industrial design are given. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2710, 2019     

Ecological Footprint Policy? Land Use as an Environmental Indicator

This article argues that policies aimed at sustainability need to address the spatial dimensions of environmental problems and their solutions. In particular, spatial configurations of economic activities deserve attention, which means addressing land use, infrastructure, trade, and transport. Unfortunately, good theory and indicators to support the analysis and design of spatial‐environmental policies are not fully developed. One approach that has become very popular in the last decade is the ecological footprint (EF). It is both an environmental accounting tool and aggregate indicator, which is used by scientists, environmental organizations, and popular media. Despite criticisms of the EF method in the past, its popularity has only increased. In fact, an increasing number of publications with an application of the EF appear in scientific journals. We review the EF approach from indicator‐methodology and welfare angles and assess its policy relevance. Our conclusion is that it does not offer any meaningful information for public policy.     

Stress‐tolerator leaf traits determine population dynamics in the endangered New Caledonian conifer Araucaria muelleri

Demographic and ecophysiological data for the endangered New Caledonian conifer, Araucaria muelleri (Araucariaceae), were analysed to: (i) evaluate population viability in relation to site conditions and human impacts; and (ii) advance our understanding of how stress‐tolerator plant functional traits affect the population dynamic behaviour and conservation requirements of long‐lived tree species. Growth, survivorship and recruitment in four A. muelleri populations were monitored across 9 years. Demographic rates were analysed using stage‐based transition matrices. Leaf δ¹³C, %N and photosystem II stress (Fv/Fm) were measured for seedlings, saplings and trees, and leaf mass per area (LMA) for trees, and correlations among ecophysiological and demographic variables explored. Seedling, sapling and tree stem growth were among the slowest, and annual survivorship among the highest, reported for any tree. Transition matrix analyses yielded stable estimated population growth rates, λ, not significantly different from 1.0 for all populations. Leaf δ¹³C was positively correlated with seedling and sapling height growth, while daytime photosystem II stress (Fv/Fm) was high in seedlings, but low in saplings and trees. Ecophysiological measures suggest that individuals transition from moisture‐limited growth at the seedling stage to nutrient‐limited growth as adults. High levels of environmental stress result in slow stand dynamics, characterized by low recruitment and growth rates counterbalanced by equally low mortality rates. These dynamics result in populations with limited capacity to increase in size quickly, but potentially highly vulnerable to decline should the rate of adult mortality increase. This combination of traits is likely typical of extreme stress‐tolerator woody species and suggests a conservation focus on the preservation of mature individuals.     

It is the economy,stupid! Projecting the fate of fish populations using ecological–economic modeling

Four marine fish species are among the most important on the world market: cod, salmon, tuna, and sea bass. While the supply of North American and European markets for two of these species – Atlantic salmon and European sea bass – mainly comes from fish farming, Atlantic cod and tunas are mainly caught from wild stocks. We address the question what will be the status of these wild stocks in the midterm future, in the year 2048, to be specific. Whereas the effects of climate change and ecological driving forces on fish stocks have already gained much attention, our prime interest is in studying the effects of changing economic drivers, as well as the impact of variable management effectiveness. Using a process‐based ecological–economic multispecies optimization model, we assess the future stock status under different scenarios of change. We simulate (i) technological progress in fishing, (ii) increasing demand for fish, and (iii) increasing supply of farmed fish, as well as the interplay of these driving forces under different scenarios of (limited) fishery management effectiveness. We find that economic change has a substantial effect on fish populations. Increasing aquaculture production can dampen the fishing pressure on wild stocks, but this effect is likely to be overwhelmed by increasing demand and technological progress, both increasing fishing pressure. The only solution to avoid collapse of the majority of stocks is institutional change to improve management effectiveness significantly above the current state. We conclude that full recognition of economic drivers of change will be needed to successfully develop an integrated ecosystem management and to sustain the wild fish stocks until 2048 and beyond.     

Odense Pilot River Basin: implementation of the EU Water Framework Directive in a shallow eutrophic estuary (Odense Fjord,Denmark) and its upstream catchment

Implementation of the EU Water Framework Directive (WFD) is a huge environmental management challenge for Europe, demanding an integrated sustainable approach to water management and a common objective of obtaining ‘good status’ for all water bodies before 2015. The main task is the preparation of a river basin management plan for each of the 96 European river basin districts before the end of 2009. In Odense River Basin (island of Fyn, Denmark), one of 14 appointed European Pilot River Basins, the implementation of the WFD has been developed and tested in practice. Reference conditions and ecological status classification for Odense Fjord, based on eelgrass (Zostera marina) depth limit and nutrient concentrations, have been drawn up through a combination of historical data and modelling tools. A subsequent quantitative linking of pressures and impact, in casu between land-based nitrogen (N) loading of the fjord and resulting nutrient concentrations and eelgrass appearance, provided an estimate of the needed nitrogen load reduction of the fjord. This amounted to approx. 1,200 tonnes N per year (an annual load reduction of ca. 11 kg N ha^?1 of catchment area or ca. 19.5 g N m^?2 of fjord surface)—a load reduction of ca. 60% from the present level—to obtain at least ‘good’ ecological status sensu WFD. It is presently not possible to quantify a target load for phosphorus (P) in relation to marine environmental objectives. An economically feasible programme of measures to obtain ‘good’ status in all surface water and groundwater bodies in Odense River Basin, using an integrated cost-effectiveness analysis, showed that re-establishment of wetlands, catchcrops, and reduced fertilisation norms are the most effective measures if large reductions in N loads to the aquatic environment are to be achieved. The total socio-economic cost of implementing the WFD in the river basin amounts to about 13 million €/year, which will increase the expense for water services by only 0.5–0.6% of the total income and production value in the basin (15,650 million €/year). Investments to obtain the needed nitrogen load reductions from agriculture are thus economically feasible. Further, it is not an impossible task, either economically or technically, to reach the objectives of the WFD while still retaining the possibility of keeping a high agricultural production in the catchment (maintaining livestock production but decreasing crop production in the case of Odense River Basin). The future conditions in Odense Fjord will not only depend on the success in reducing the load from the river basin area, but will also be affected by the trend in the nutrient loss from the whole Baltic catchment area. The high growth rates in the new EU Member States thus pose an important challenge to water managers, and decoupling of economic growth from pressure on water bodies will be necessary. Finally, a number of challenges facing water managers around the Baltic and within the EU, namely preconditions required to successfully implement the WFD, are presented.     

Hen harriers and red grouse: economic aspects of red grouse shooting and the implications for moorland conservation

1.  Thirgood & Redpath (2008) propose ways in which red grouse : hen harrier conflicts could be resolved. It has also been suggested that grouse management could accept lower bag sizes (number of birds shot) thus reducing the need for intensive management of predators and habitats. This would allow hen harriers to co-exist more easily on grouse moors.
2.  We compare the bags, costs and incomes from these less intensive forms of grouse shooting with the more intensive driven shooting.
3.  Allowing high density grouse moors to decline to low density ones will result in greater loss of income than the corresponding saving of costs. This can result in moor owners abandoning grouse management and thus gamekeepers losing their employment.
4.  Losing gamekeepers from the uplands would jeopardize the protection of heather moorland and Special Protection Areas for birds, large areas of which are keepered and which currently support high numbers of breeding waders.
5.   Synthesis and applications . We agree with the study by Thirgood & Redpath that consideration of social and economic factors will be needed to resolve conflict but a reduction in management effort from driven to walked-up shooting is not the answer. A more satisfactory approach to the harrier : grouse conflict could be to try to reduce harrier predation by means of diversionary feeding and to address the problem of the rapid build-up in harrier numbers by exploring the use of a ceiling on harrier densities.