Marc Voltz

Geo-MHYDAS: A landscape discretization tool for distributed hydrological modeling of cultivated areas

The representation of landscape variabilities by means of an adequate landscape discretization is of major importance in distributed hydrological modeling. In this paper, we present Geo-MHYDAS, a landscape discretization tool that allows explicit representation of landscape features, particularly man-made ones, that are known to have a great impact on water and mass flows across the landscape. The landscape discretizations that are produced include user-controlled delineated irregular, linear or areal units connected to each other along a tree-like structure. Geo-MHYDAS includes three steps: (i) processing (i.e., the importation or the creation), followed by the modifications of the geographical objects, the limits of which are considered in the modeling as hydrological discontinuities, (ii) creation of the areal and linear units for hydrological modeling by a selective cleaning procedure after overlay that preserves, as much as possible, the object limits defined in the previous step, while having sizes and shapes that remain compatible with the application of the water flow functions of the hydrological model and (iii) building an oriented topology between irregularly shaped areal and linear units that allows the routing of the simulated water flows across the landscape. Geo-MHYDAS was developed using the open source free Geographic Information Systems (GIS) software GRASS. The use of Geo-MHYDAS was illustrated by running the hydrological model MHYDAS for different scenarios of man-made features, their presence and spatial organization within a small vineyard catchment located in the south of France (the Roujan catchment). Comparisons with hydrological modeling performed with usual landscape discretizations showed significant differences in the simulated hydrograms. This comparison illustrates well the strong impact of landscape discretizations on hydrological modeling, specifically on the man-made landscape features represented in Geo-MHYDAS.

An Unified Framework to Integrate Biotic, Abiotic Processes and Human Activities in Spatially Explicit Models of Agricultural Landscapes

Recent concern over possible ways to sustain ecosystem services has triggered important research worldwide on ecosystem processes at the landscape scale. Understanding this complexity of landscape functioning calls for coupled and spatially-explicit modelling approaches. However, disciplinary boundaries have limited the number of multi-process studies at the landscape scale, and current progress in coupling processes at this scale often reveals strong imbalance between biotic and abiotic processes, depending on the core discipline of the modellers. We propose a spatially-explicit, unified conceptual framework that allows researchers from different fields to develop a shared view of agricultural landscapes. In particular,we distinguish landscape elements that are mobile in space and represent biotic or abiotic objects (for example water, fauna or flora populations), and elements that are immobile and represent fixed landscape elements with a given geometry (for example ditch section or plot). The shared representation of these elements allows setting common objects and spatio-temporal process boundaries that may otherwise differ between disciplines. We present guidelines and an assessment of the applicability of this framework to a virtual landscape system with realistic properties. This framework allows the complex system to be represented with a limited set of concepts but leaves the possibility to include current modelling strategies specific to biotic or abiotic disciplines. Future operational challenges include model design, space and time discretization, and the availability of both landscape modelling platforms and data.

Mediterranean land systems under global change: current state and future challenges

The Mediterranean region is one of the areas in the world that is recognized as a hot spot not only for climate change but also more generally for global change. Indeed, the Mediterranean land surfaces and their associated socioecosystems are facing large modifications linked to an increase in drought frequency (Hoerling et al., 2011); to an ever-increasing population, from 370 million in 2000 to probably 560 million in 2030 (Ludwig et al., 2010); and to intense migration to coastal cities (Mediterra, 2008). The future of the Mediterranean socio-ecosystems is therefore questionable. It is even more so because for many years now, their natural resources have been under pressure and became insufficient in many countries when compared to the needs of the populations. The situation is expected to worsen and favor large social tensions, within and between the Mediterranean countries. Water resources are drastically lacking in the southern and eastern Mediterranean countries where 108 million inhabitants are considered water-poor (< 1000 m cap year), and 58% of these live with water shortage (< 500 m cap year) (Blinda and Thivet 2009). Anthropogenic water withdrawals now amount to a large proportion of the annual renewable water resources (Milano et al., 2013). The Mediterranean region also experiences a deficit in agricultural production: for example, in 2003, the Mediterranean basin imported up to 22% of the world imports of cereals but represented only 7% of the world population (Mediterra, 2008). Moreover, arable land is scarce which leads in several countries to the expansion of intensive agriculture, whether irrigated or rainfed, towards marginal land that can degrade when too intensively exploited (Mediterra, 2008). This is amplified by the fast urbanization of coastal areas where soil artificialization decreases arable land. Consequently, the present trends towards an intense exploitation of the natural resources of the Mediterranean ecosystems are likely to put strong pressures on their hydrological and biogeochemical cycles (e.g., carbon, salts, trace elements, xenobiotics) and exacerbate their degradation. Seeking sustainable development in the Mediterranean region requires improving deeply our understanding of the processes of degradation, resilience, and restoration of the variety of Mediterranean socio-ecosystems. In 2010, the international research initiative Mistrals (http://www.mistrals-home.org/) was launched for studying over a decade the environmental behavior of the whole Mediterranean basin submitted to global change. In the framework of Mistrals, several sub-initiatives took place. One of them, SICMED (Surfaces and Interfaces of the Continental MEDiterranean, www.sicmed.net) was supported by the following French research institutes: CNRS-INSU, INRA, IRD, and IRSTEA. It aimed at developing a regional cooperation process for long-term * Marc Voltz marc.voltz@inra.fr

RECOTOX, a French initiative in ecotoxicology-toxicology to monitor, understand and mitigate the ecotoxicological impacts of pollutants in socioagroecosystems

RECOTOX is a cross-cutting initiative promoting an integrated research to respond to the challenges of monitoring, understanding, and mitigating environmental and health impacts of pesticides in agroecosystems. The added value of RECOTOX is to develop a common culture around spatial ecotoxicology including the whole chain of pressure-exposure-impact, while strengthening an integrated network of in natura specifically equipped sites. In particular, it promotes transversal approaches at relevant socioecological system scales, to capitalize knowledge, expertise, and ongoing research in ecotoxicology and, to a lesser extent, environmental toxicology. Thus, it will open existing research infrastructures in environmental sciences to research programs in ecotoxicology of pesticides.