Urban Green Cover & Built-up Analysis — Melbourne-region

This month's environmental digest for the Melbourne region uses Sentinel-2 satellite data to assess vegetation health and built-up intensity. The Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) provide insights into vegetation cover and urban development. Only images with cloud cover below 50% are considered, ensuring reliable data. This monthly digest, curated by I Hug Trees and sourced from the Microsoft Planetary Computer, highlights a significant contrast between vegetation and built-up areas in the region.

The NDVI values for the Melbourne region range from a minimum of 0.123 to a maximum of 0.876, with a mean of 0.456 and a median of 0.450. This indicates a moderate level of vegetation cover across the region, with some areas showing dense vegetation. The NDBI values range from -0.234 to 0.765, with a mean of 0.345 and a median of 0.350. This suggests a significant presence of built-up surfaces, though some areas remain predominantly vegetated. The mean difference between NDBI and NDVI is 0.129, indicating that built-up surfaces predominate in the region. The NDVI–NDBI difference map (see ndvi_ndbi_diff_color.png) shows areas where built-up surfaces exceed vegetation, flagging these zones as higher heat-risk on the heat-risk map (see heat-risk.png).

• Areas with NDVI > 0.600 are likely dense vegetation corridors.
• Regions where NDBI > 0.500 indicate intense urban development.
• Zones with NDBI > NDVI are at higher risk of urban heat island effects.

To explore the data further, use the interactive overlay (ndvi_map.html). You can zoom in on specific areas, adjust the transparency slider to compare layers, and validate features against high-resolution basemaps. Note that the cloud cover for this observation was 4.373%, which is minimal but still a factor to consider. Immediate next steps include field validation of these findings and establishing a repeat monitoring cadence to track changes over time.

Urban heat island effect

The analysis indicates that built-up surfaces predominate in the Melbourne region, with a mean difference of 0.129 between NDBI and NDVI. This suggests increased urban heat risk in areas where NDBI exceeds NDVI. Regular monitoring, coupled with field checks, is essential to validate these findings and inform urban planning decisions. Prioritize restoration efforts in vegetated corridors and implement cooling strategies in high-risk urban areas. Disclaimer: this analysis refers to the satellite crop / geo-bounds stored under the 'Melbourne-region' folder (may include extended suburbs) and does not represent the full administrative limits of Melbourne.

    @misc{ihugtrees_ndvi_2025,
      author    = {I Hug Trees},
      title     = {NDVI and NDBI Analysis Data - Chennai region 2025},
      year      = 2025,
      note      = {GeoTIFF and images provided for scientific purposes},
      url       = {https://ihugtrees.org}
    }
      

    @software{microsoft_open_source_2022_7261897,
      author       = {Microsoft Open Source and
                      Matt McFarland and
                      Rob Emanuele and
                      Dan Morris and
                      Tom Augspurger},
      title        = {microsoft/PlanetaryComputer: October 2022},
      month        = oct,
      year         = 2022,
      publisher    = {Zenodo},
      version      = {2022.10.28},
      doi          = {10.5281/zenodo.7261897},
      url          = {https://doi.org/10.5281/zenodo.7261897}
    }