Land Unit Partitioning

From SEA.unu.edu/wiki

The construction of linear infrastructure partitions land into smaller parcels. This affects nature conservation because it fragments habitats; landscape because it reduces the scale of the landscape; and tranquillity because it reduces the size of tranquil areas.

Land use partitioning analysis uses GIS techniques to analyse the size and quality of areas of non-fragmentation before and after the strategic action. It involves, for both the before (baseline without the strategic action) and after (with the strategic action) scenario:

1. identifying areas of non-fragmentation
2. identifying areas of high nature conservation/landscape/tranquillity quality: 
   overlay of various designations and land uses, e.g. national parks, woodland
3. graphing areas of non-fragmentation in terms of their surface area (x-axis) versus their quality (y axis)
4. grading the areas of non-fragmentation according to their surface area and quality
5. representing the gradings on a map.

This is shown on the figure by BCEOM below: The top half of the figure involves analysing the environmental baseline of land use partitioning, and the bottom half involves impact prediction.

The comparison of the before-and-after gradings indicates the impact of the strategic action on land use partitioning. One can also show the impacts in a graph of the number of land units versus their cumulative area: this shows how the same cumulative area (e.g. 1,000ha) would be formed by more individual land units after the strategic action than before.

Example:

This technique has been used in analysing the effects of the Trans-European Network on nature conservation (see pp. 26-28).

Advantages:

• it deals with a topic that would otherwise be poorly (or not) considered
• it gives a good visual representation of impacts
• it makes good use of the capabilities of GIS

Disadvantages:

• it is based on GIS and needs much data: it can thus be expensive and time-consuming
• its application is limited to only a few subjects: it supports other techniques rather than being a "main" appraisal technique

Further information:

BCEOM (1994) Etude strategique d'impact sur l'environnement - essai methodologique, Ministere de l'Environnement - Direction de la Nature et du Paysage - Sous-direction de l'Amenagement et du Paysage, December.