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What this layer is
The Enhanced Vegetation Index — EVI — is a satellite-derived measure of how much healthy green vegetation is present in every 10-metre square of ground. Plants reflect a lot of near-infrared light and absorb a lot of red light; the ratio between the two, with some corrections for atmosphere and soil brightness, gives a very reliable signal of photosynthetic activity. High EVI values mean actively growing, healthy, leafy vegetation. Low values mean bare ground, stressed plants, dormant vegetation or water.
The European Space Agency's Sentinel-2 satellites image the whole of Europe roughly every five days at 10-metre resolution, and the data is free. The cluster's ecology platform pulls the latest cloud-free images, calculates EVI, and produces a time-series for every field and woodland block in the cluster.
EVI is particularly good for agricultural monitoring. Where the older NDVI index saturates in dense canopy (a wheat field at peak growth and a mature woodland read similarly), EVI keeps resolving detail into the higher range and handles dense canopy better. It is “enhanced” in the sense that you can see differences where simpler indices go flat.
What it reveals in this catchment
- Phenology. The season-by-season wave of green-up and senescence is clearly visible. Woodlands lag a couple of weeks behind grasslands in the spring; arable fields show a sharp harvest drop.
- Field-level variation. Within a single field, patterns of stress, compaction or drainage show up as patches of persistently lower EVI. These are usually exactly the parts of the field the farmer already suspects are underperforming.
- Drought signal. In dry summers — 2022 was the most striking recent example — the EVI of improved grasslands collapses dramatically, while rooted woodland, hedgerows and deep-rooted semi-natural grassland hold up. That resilience difference is quantifiable from space.
- Hedgerow and shaw productivity. Linear features that are easy to overlook on the ground show up clearly as narrow corridors of sustained high EVI through most of the growing season.
- Year-on-year trends. Is a grassland becoming more or less productive over time? Is a woodland showing dieback? Is a restored pond margin greening up? EVI answers all of these with actual numbers.
What land stewards can do with this
- Evidence-based management. Rather than relying on “the north field always looks a bit yellow”, the EVI time-series gives a quantified baseline. Interventions — compaction alleviation, drainage repair, cover crops — can be measured against it.
- Detect stress early. Significant EVI departures from a field's own multi-year norm often appear before anything is visible on the ground. Early detection means earlier, cheaper response.
- Compare holdings and practices. Within the cluster, different holdings can share EVI profiles and ask honest questions about why one is more drought-resilient than another. This is one of the practical outputs of the cluster's land-steward network activity.
- Demonstrate outcomes to funders. For natural-capital investment, quantified, satellite-derived evidence of sustained productivity or resilience is some of the strongest evidence possible. It doesn't rely on claims — the data is independent and archival.
Data source: European Space Agency Sentinel-2 imagery via the Copernicus Data Space Ecosystem. Cloud masking, atmospheric correction, EVI calculation and cluster-level time-series analysis by the ecology platform.