Network gaps and stepping stones — Task

Implementation: Network gaps and stepping stones (Recipe - QGIS).

Network gaps and stepping stones is the Task of finding where new habitat would connect isolated clusters to the main network, and how much land it would take. It turns the habitat network from a diagnosis into a proposal: the narrowest gaps, on land where new habitat is possible.

Used in examples: Habitat network at Ledreborg (Example).

Task Schema (tool-agnostic)

1. Start from the habitat network — clusters at the chosen connection distance, with the main network identified.
2. Choose which clusters to connect (decision point) — e.g. all clusters of at least 1 ha of habitat outside the main network.
3. Find the narrowest gap (Operator: shortest line) — from each cluster’s habitat to the nearest habitat in the main network.
4. Give the connection a width (decision point; Operator: dilation) — the strip that would become new habitat, e.g. 30 m.
5. Keep it on land where new habitat is possible (Operator: clip) — e.g. farmland (a positive constraint).
6. Leave out what is already habitat (Operator: difference) — and anything excluded, such as roads or buildings (negative constraints).
7. Measure — the length of each gap and the area of new habitat needed.

Output: the shortest connecting lines, the proposed new habitat as polygons, and the total length and area.

Epistemic Choices to record

• Which clusters: connecting every isolated patch is rarely realistic; a minimum size focuses on the clusters that matter.
• Measure gaps between habitat, not between buffers: shortest lines between the buffered clusters are shorter than the real gaps by the buffer distance.
• Straight lines: the shortest line ignores ownership, field boundaries and existing hedges that could be extended; a planner would adjust the route.
• Width and land: a 30 m strip on farmland is one design; a hedge along a field boundary is another, much narrower one. Say what kind of habitat the new strip is.
• Constraints as positive and negative: list them, and combine them as positive minus negative.