The combination of spatial data from the variety of sources on the web, being either legislative, commercially or voluntarily driven, is a major requirement for the establishment of a fully integrated geospatial web. Therefore, spatial data fusion techniques need to be linked to current web-developments, in particular on Spatial Data Infrastructures and the Semantic Web, to allow for standardized and effective use of combined spatial data for information retrieval. In this paper, crowdsourced environmental observations, representing the rapidly increasing amount of voluntarily collected data on the web, and INSPIRE, acting as the legal framework for spatial environmental information in Europe, are chosen to design and develop capabilities for spatial data fusion on the web. Possible use cases show mutual benefits for both volunteers and INSPIRE data providers, and might thus facilitate further collaboration. A prototypical implementation based on common SDI and Linked Data standards demonstrates the feasibility of the proposed approach and offers a starting point for further exploration.