Background
In Germany, apart from the Amflora potato licensed for cultivation since March 2010, Bt-maize MON810 is the only genetically modified organisms (GMO) licensed for commercial cultivation (about 3,000 ha in 2008). Concerns have been raised about potential adverse environmental impacts of the GMO and about potential implications on the coexistence between conventional and genetically modified production. These issues should be considered on a regional base. The objective of this article is to describe how GMO monitoring that is required after risk assessment and GMO release can be complemented by a Web-based geoinformation system (WebGIS). Secondly, it is also described how WebGIS techniques might support coexistence issues with regard to Bt-maize cultivation and conservation areas. Accordingly, on the one hand, the WebGIS should enable access to relevant geodata describing the receiving environment, including information on cultivation patterns and conservation areas containing protected species and habitats. On the other hand, metadata on already established environmental monitoring networks should be provided as well as measurement data of the intended GMO monitoring. Based on this information and based on the functionality provided by the WebGIS, the application helps in detecting possible environmental GMO impacts and in avoiding or identifying coexistence problems.

Results
The WebGIS applies Web mapping techniques to generate maps via internet requests and offers additional functionality for analysis, processing and publication of selected geodata. It is based on open source software solely. The developments rely on a combination of the University of Minnesota (UMN ) MapServer with the Apache HTTP server, the open source database management systems MySQL and PostgreSQL and the graphical user interface provided by Mapbender. Important information on the number and the location of Bt-maize fields were derived from the GMO location register of BVL. The &quot;WebGIS GMO Monitoring&quot; provides different tools allowing for the application of basic GIS techniques as, for instance, automatic or interactive zooming, distance measurements or querying attribute information from selected GIS layers. More sophisticated GIS tools were implemented additionally, e.g. a buffer function which enables generating buffers around selected geo-objects like Bt-maize fields. Finally, a function for intersection of different maps was developed. The WebGIS comprises information on the location of all Bt-maize fields in Germany according to the official GMO location register of the Federal Office of Consumer Protection and Food Safety between 2005 and 2008. It facilitates, amongst others, access to geodata of GMO fields and their surroundings and can relate them with additional environmental data on climate, soil, and agricultural patterns. Furthermore, spatial data on the location of flora-fauna-habitats and environmental monitoring sites in the federal state of Brandenburg were integrated.

The WebGIS GMO monitoring was implemented according to the concept for an &quot;Information System for Monitoring GMO&quot; (ISMO) which was designed on behalf of the German Federal Agency for Nature Conservation. ISMO includes hypotheses-based ecological effects of GMO cultivation and suggests checkpoints for GMO monitoring to test whether impacts may be observed in the receiving environment.

In contrast to the public GMO register, the WebGIS GMO monitoring enables mapping of GMO fields and provides relevant geodata describing environmental and agricultural conditions in their neighbourhood of the cultivation sites as well as information derived from monitoring sites. On this basis, spatial analyses should be enabled and supported, respectively. Further, the WebGIS GMO monitoring supplements PortalU which, in Germany, is the technical realisation of the Infrastructure for Spatial Information in Europe directive (Directive 2007/2/EC) released by the EU in 2007.

Conclusions
The article should have shown how to support and complement GMO monitoring with the help of the WebGIS application. It facilitates co-operation and data access across spatial scales for different users since it is based on internet technologies. The WebGIS improves storage, analysis, management and presentation of spatial data. Apart from the improved flow of information, it supports future long-term GMO monitoring and modelling of the dispersal of transgenic pollen, for instance. Additional information (e.g. data on wind conditions or soil observation sites) provided by the WebGIS will be helpful to determine representative monitoring sites for detecting potential GMO impacts by means of monitoring or modelling. Thus, the WebGIS can also serve as part of an early warning system. In the near future, the integration of locations of all Bt-maize fields in Germany into the WebGIS as a continuous task should be automatised. Additionally, a methodology should be developed to detect maize fields by means of remote sensing data to manage coexistence problems on the basis of actual field patterns.