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Free and open access to the Landsat archive has enabled the implementation of national and global terrestrial monitoring projects. Herein, we summarize a project characterizing the change history of Canada's forested ecosystems with a time series of data representing 1984-2012. Using the Composite2Change approach, we applied spectral trend analysis to annual best-available-pixel (BAP) surface reflectance image composites produced from Landsat TM and ETM+ imagery. A total of 73,544 images were used to produce 29 annual image composites, generating ∼400 TB of interim data products and resulting in ∼25 TB of annual gap-free reflectance composites and change products. On average, 10% of pixels in the annual BAP composites were missing data, with 86% of pixels having data gaps in two consecutive years or fewer. Change detection overall accuracy was 89%. Change attribution overall accuracy was 92%, with higher accuracy for standreplacing wildfire and harvest. Changes were assigned to the correct year with an accuracy of 89%. Outcomes of this project provide baseline information and nationally consistent data source to quantify and characterize changes in forested ecosystems. The methods applied and lessons learned build confidence in the products generated and empower others to develop or refine similar satellite-based monitoring projects. ARTICLE HISTORY

Aim Trophic cascades are a common consequence of herbivore outbreak and in the absence of hunting can cause the local extinction of native plant species and communities. We compared plant communities at 66 island and mainland sites to test the hypothesis that deer (Cervidae) determine species cover, richness and diversity and that palatable species become rare at high deer density. We validate a region-wide index of deer density and impact on plant communities in a region where culturally significant food plants maintained by aboriginal people prior to European contact helped to define baseline plant communities.Location Gulf and San Juan Island archipelagos and North American mainland.Methods We conducted surveys of 49 native, 10 exotic and 15 culturally significant plant species and deer sign at 66 sites on 35 islands and mainland to determine deer abundance and plant species cover, richness and diversity. We identified culturally significant food plants facilitated by aboriginal people using ethnobotanical knowledge, quantified plant palatability via cafeteria trials and characterized shrub architecture.Results Native and culturally significant shrub cover, richness and diversity were 52-85% lower at sites with abundant deer (0.9-2.8 ha À1 ) versus no deer. However, these values were also 38-82% lower at sites in the lowest deer density class (< 0.08 ha À1 ) versus sites with no deer present. Palatable cover was 92% lower where deer were abundant versus absent and 28% lower in low-density versus deer-free sites. Shrub architecture provided an easily applied index of native and culturally significant plant cover and deer density.Main conclusions We provide comparative examples of endangered plant communities to demonstrate that, contrary to the intermediate disturbance hypothesis, any positive effect of deer on plant diversity on islands in the Pacific north-west of North America occurs at densities < 0.08 ha À1 , if at all. This detailed example of trophic downgrading highlights the need and provides the methods to identify herbivore densities compatible with the persistence of all native species in conserved landscapes.

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