美国生物工程食品信息披露制度的新变化及启示 *

In December 2018, the United States Department of Agriculture published the national bioengineered food information disclosure standard (detailed implementation rules), which detailed and improved the specific content of the bioengineered food information disclosure system in the United States, marking the basic establishment of the bioengineered food information disclosure system in the United States. The text mainly includes the following aspects: add the conditions of detectability, unify the exemption conditions of bioengineering food information disclosure, improve the form of bioengineering food information disclosure, set up voluntary labels, and the obligations of the subjects of bioengineering food information disclosure. Through analysis, it is found that under the premise of mandatory labeling, the United States still adheres to the principle of substantive equivalence to ensure the smooth transition of labeling system while protecting consumers’ right to know. In view of the chaos of GM food labeling in China, this paper draws lessons from the experience of the United States and puts forward Suggestions on how to improve GM food labeling system in China in terms of concept, labeling object, management institution and exemption.     

Food webs in space: On the interplay of dynamic instability and spatial processes

Ecologists increasingly recognize that a consideration of spatial dynamics is essential for resolving many classical problems in community ecology. In the present paper, I argue that understanding how trophic interactions influence population stability can have important implications for the expression of spatial processes. I use two examples to illustrate this point. The first example has to do with spatial determinants of food chain length. Prior theoretical and empirical work has suggested that colonization–extinction dynamics can influence food chain length, at least for specialist consumers. I briefly review evidence and prior theory that food chain length is sensitive to area. A metacommunity scenario, in which each of various patches can have a food chain varying in length (but in which a consumer is not present on a patch unless its required resource is also present), shows that alternative landscape states are possible. This possibility arises if top predators moderate unstable interactions between intermediate predators and basal resources. The second example has to do with the impact of recurrent immigration on the stability of persistent populations. Immigration can either stabilize or destabilize local population dynamics. Moreover, an increase in immigration can decrease average population size for unstable populations with direct density-dependence, or in predator–prey systems with saturating functional responses. These theoretical models suggest that the interplay of temporal variation and spatial fluxes can lead to novel qualitative phenomena.     

Climate variability and vulnerability to climate change: a review

The focus of the great majority of climate change impact studies is on changes in mean climate. In terms of climate model output, these changes are more robust than changes in climate variability. By concentrating on changes in climate means, the full impacts of climate change on biological and human systems are probably being seriously underestimated. Here, we briefly review the possible impacts of changes in climate variability and the frequency of extreme events on biological and food systems, with a focus on the developing world. We present new analysis that tentatively links increases in climate variability with increasing food insecurity in the future. We consider the ways in which people deal with climate variability and extremes and how they may adapt in the future. Key knowledge and data gaps are highlighted. These include the timing and interactions of different climatic stresses on plant growth and development, particularly at higher temperatures, and the impacts on crops, livestock and farming systems of changes in climate variability and extreme events on pest‐weed‐disease complexes. We highlight the need to reframe research questions in such a way that they can provide decision makers throughout the food system with actionable answers, and the need for investment in climate and environmental monitoring. Improved understanding of the full range of impacts of climate change on biological and food systems is a critical step in being able to address effectively the effects of climate variability and extreme events on human vulnerability and food security, particularly in agriculturally based developing countries facing the challenge of having to feed rapidly growing populations in the coming decades.     

Relationship between the chemical composition of aquatic macrophytes and their consumption by grass carp, Ctenopharyngodon idella

The rate at which triploid grass carp, Ctenopharyngodon idella , consumed two plant species from different locations was measured and compared to the chemical composition of the plants. Grass carp fed on Elodea canadensis from three lakes at significantly different rates ( P > 0.001), but did not eat Elodea densa from two of the sites at different rates. Feeding rate of the grass carp was positively correlated to the concentration of calcium ( r = 0.976) and lignin ( r = 0.946), but negatively correlated to the content of iron ( r =−0.808), silica (r=-0.934) and cellulose ( r =−0.922). Multiple regression analysis revealed that calcium and cellulose content were the most important predictors of consumption rate. These experiments demonstrate that water chemistry may affect palatability and could in part be responsible for some of the discrepancies in grass carp consumption rate and preference studies.     

The effect of Daphnia on filament length of blue-green algae

Water from a hypertrophic lake rich in filamentous blue-green algae was passed through a continuous-flow system of aquaria containing Daphnia magna, and a control system without Daphnia. Daphnia caused a significant decrease in the blue-green algal density, and a two-fold reduction in filament length. It is suggested that feeding activity of Daphnia may result in an increase in the availability of blue-green filaments to filter-feeding cladocerans.