Julien Barde

Eating up the world’s food web and the human trophic level

Significance Here we combine ecological theory, demography, and socio-economics to calculate the human trophic level (HTL) and position humans in the context of the food web. Trophic levels are a measure of diet composition and are a basic metric in ecology, but have never been calculated for humans. In the global food web, we discover that humans are similar to anchovy or pigs and cannot be considered apex predators. In addition, we show that, although countries have diverse diets, there are just five major groups of countries with similar dietary trends. We find significant links between HTL and important World Bank development indicators, giving insights into the relationship between socio-economic, environmental, and health conditions and changing dietary patterns. Trophic levels are critical for synthesizing species’ diets, depicting energy pathways, understanding food web dynamics and ecosystem functioning, and monitoring ecosystem health. Specifically, trophic levels describe the position of species in a food web, from primary producers to apex predators (range, 1–5). Small differences in trophic level can reflect large differences in diet. Although trophic levels are among the most basic information collected for animals in ecosystems, a human trophic level (HTL) has never been defined. Here, we find a global HTL of 2.21, i.e., the trophic level of anchoveta. This value has increased with time, consistent with the global trend toward diets higher in meat. National HTLs ranging between 2.04 and 2.57 reflect a broad diversity of diet, although cluster analysis of countries with similar dietary trends reveals only five major groups. We find significant links between socio-economic and environmental indicators and global dietary trends. We demonstrate that the HTL is a synthetic index to monitor human diets and provides a baseline to compare diets between countries.

A Metadata Service for Integrated Management of Knowledges Related to Coastal Areas

The research outlined in this paper is part of a wider research program named SYSCOLAG (Coastal and LAGoonal SYStems in Languedoc-Roussillon area, France) dedicated to sustainable coastal management. The main objective of this program is to build up a communication infrastructure to improve the exchange of information and knowledge between the various scientific disciplines involved in the research. In order to ensure the sharing of resources without affecting the autonomy and independance of the partners, we propose a three-level infrastructure (resources, federation and knowledge access) based on a metadata service (using ISO 19115 standard for geographic information metadata) completed by a common vocabulary (ontology).

Reply to Roopnarine: What is an apex predator?

Roopnarine (1) suggests that the significance of the human trophic level (HTL) (2) is reduced because it defines the position of humans in the food web by diet and is not representative of our functional role in the ecosystem. He is concerned that humans are compared with low trophic level omnivores and asserts that we are apex predators because in marine systems, our extraction of wild fish is linked to high trophic level species.

Reply to Feeley and Machovina: Trophic ecology complements estimates of land use change due to food production

Feeley and Machovina assert that even though humans occupy a low trophic level, we have larger ecosystem impacts than any other species because of the sheer volume of food consumed (linked to population size) and the inefficiency of its production (1). The authors argue that large differences in the impact on resource use exist between dietary preferences (e.g., differing proportions of beef, pork, or poultry in a diet), even if human diets are represented by the same trophic level.

A Metadata Service for Managing Spatial Resources of Coastal Areas

Within the framework of the SYSCOLAG pluridisciplinary research programme on ICZM in the Languedoc-Roussillon region of France, we propose an ISO-19115-compliant metadata service to share informational resources. Each resource is described using a metadata form. Each form consists of textually and spatially controlled terms which are stored in a single DBMS (Postgres and Postgis). The graphical user-interfaces contain the expert knowledge (thematic and spatial ontologies) and include a mapping service (SVG and OGC-compliant WMS-WFS) that allows spatial and thematic queries to be addressed to the metadata service.