Monitoring trends in migratory species provides a unique window into the state of our environment. Migratory bird species serve as indicators for the flyway region, the different biomes and habitats and pressures they face along the migration route. This paper highlights the significance and the difficulty of interpreting trends in migratory birds, with a focus on the African-Eurasian Flyway. Changes in coastal management, agricultural and forestry practices, habitats, climate and global warming are all reflected to varying degrees in population trends. Indeed global and climate change, often mirrored in the varying trends of long-distance migrants, makes them excellent sentinel species. Trends are also influenced by inter and intra-specific interactions which increase the complexity of data interpretation. Impacts in one trophic level can cascade into another and also interfere with parallel food chain patterns. For instance, eutrophication promotes an increase in vegetative biomass, including bushes and trees in some parts of the Arctic, reducing the area of open space available for ground nesting water birds.

The potential for web-based GIS analyses of monitoring data is discussed. Once tested for the Arctic region the same can be applied to other major flyways systems and regions, such as the African-Eurasian region, identified for waterbirds. The most obvious challenge lies in the analysis of biodiversity trend data, both in itself and in relation to factors such as climate change. The Arctic region and its biota seem certain to experience pronounced changes in climate in the coming years and the proposed GIS based portal could provide the integration of essential data sets and allow analysis of the relative
importance of different parameters.

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