An insufficient knowledge on the state of the environment and its behavior is one of the environmental management major problems. To overcome this limitation and support environmental decision-making, monitoring systems have been established. However, the quality and quantity of the data available is often not adequate; the data usually have spatial and temporal inconsistencies and the accuracy does not always match the users' needs. Moreover, access to these data in a format understood by the different stakeholders of any environmental decision-making process is usually difficult.

Non-governmental organizations and concerned citizens have made some voluntary efforts to collect data contributing for a broad understanding of the environment. One example of such initiatives is the volunteer monitoring program from the United States Environmental Agency (EPA - http://www.epa.gov/OWOW/monitoring/). However the access to these data by decision-makers and other stakeholders is difficult since they represent isolated initiatives and the data are dispersed and usually non-structured. Recent developments in information technologies, particularly in the use of WWW may facilitate the access to environmental information at the same time that improve public participation within the environmental monitoring and management process. The WWW is being used to support information infrastructures to facilitate the access to information: the Portuguese National Geographic Information Infrastructure (SNIG - http://snig.cnig.pt) is one example of such initiatives. Moreover, the WWW has allowed to create collaborative systems where different stakeholders can express their view of the problem. This type of systems can also be developed to allow citizens to store and retrieve their data. They can provide tools to facilitate the exploration and use of the multidimensional environmental data.

This paper analyses the role of information infrastructures to facilitate access to environmental information while supporting the public participation process. Additionally, it describes a collaborative system, identifying its structure and tools allowing the public to express its knowledge while participating within the decision-making process. The institutional framework required is also referred.