Among the options listed, the best use of satellite imagery is:
4. Detecting a change in regional forest cover.
This application leverages satellite imagery effectively because it allows for the monitoring of large areas over time, enabling the assessment of deforestation, reforestation, and changes in land use. Satellite imagery can provide critical information for conservation efforts, land management, and understanding ecological changes on a regional and global scale.
While the other options have their merits, they are generally more individualized or localized and may not utilize the full capabilities of satellite imagery to monitor large-scale environmental changes.