Wireless Sensor Networks (WSN, wireless networks of miniaturized, sensor-enabled computers) are an important emerging technology for monitoring geographic environments (sometimes termed geosensor networks). WSN provide the capability for generating and processing information about spatial and spatiotemporal changes and events at very fine levels detail. This paper first introduces the technology behind WSN and then identifies the key challenges facing spatial applications of WSN, including limited accuracy and precision of sensors; limited information communication resources; efficient integration of diverse information sources; and processing of spatial information in the network. The paper uses the specific case study of a pilot WSN deployed in Victoria to illustrate these challenges. This case study concerns monitoring a range of simple environmental parameters relevant to conservation contracts (contracts issued by government to promote environmentally sustainable management on private land). The results of the study indicate that despite the challenges, WSN can complement existing spatial data sources, providing new, flexible, and low-cost spatial data sources for environmental monitoring. The conclusions identify a number of important hot topics for spatial information science research in the coming 5 years, including highlighting the importance of new methods for low-power self-localization of sensor nodes in heterogeneous environments, and algorithms for in-network filtering and analysis of real-time spatial data.