Mapping land use & land cover

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Rivers and roads give a map its bones. Land use and land cover give it flesh: the difference between intact forest and a cleared field, between a swamp and dry ground, between an empty stretch and a village. This context is what makes a map feel like a real place — and it's essential for studying environmental change.

The main categories

• Forest and natural vegetation. The dominant cover across the basin. Mapping the edge between intact forest and everything else creates a baseline against which clearing can be measured over time.
• Farmland and plantations. Cleared, cultivated ground — often visible in imagery as regular shapes with sharper edges than natural forest.
• Wetlands and floodplains. Seasonally or permanently waterlogged land along the rivers. Important for both ecology and flood planning, and easy to confuse with open water.
• Built-up and residential areas. Settlements, from large towns to a handful of riverside houses. Tracing building footprints and the settlement outline puts communities on the map.
• Water bodies. Lakes, ponds and reservoirs, mapped as areas (covered in detail in the rivers guide).

How to map an area cleanly

1. Trace a closed shape. Land cover is mapped as areas — closed loops of nodes — rather than lines. Make sure the shape actually closes.
2. Share edges where features meet. Where farmland borders forest, the two areas should share the boundary nodes rather than overlap or leave a gap.
3. Map what's clearly distinguishable. If you can confidently tell forest from field in the imagery, map the boundary. If it's ambiguous, map the part you're sure of.
4. Tag buildings and settlements. Trace building outlines where they're visible, and add the settlement as a named place so it appears in searches and at lower zooms.

Why land cover is worth the effort

Land-cover data is what turns OpenStreetMap from a navigation tool into an environmental record. Researchers tracking deforestation, organisations defending community land, and planners preparing for floods all need to know not just where things are but what's there. Because the data is open, a careful afternoon spent mapping forest edges and village outlines can feed into work you'll never see — which is exactly the point of contributing to a shared commons.

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