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Research · WP1

Mapping the cooling potential: the distribution of riparian woodland in Scotland

A spatial analysis of where riparian woodland is missing across Scotland — and where planting it would cool rivers the most, revealing the opportunities and limits for stream daylight management.

The geographical context

Scotland covers roughly 77,900 km² — about 32% of the UK — with river catchments that run from the wet, mountainous west to the drier eastern lowlands. Across this range, rising water temperatures increasingly threaten aquatic ecosystems, and the presence or absence of riparian woodland is a decisive factor.

Foundations: insights from the literature

The work builds on Jackson et al. (2018, 2021), which established three key mechanisms:

  • Riparian woodland within a 25 m buffer extending 1,000 m upstream can reduce maximum daily river temperatures by approximately 2 °C.
  • Trees provide seasonal thermal buffering — summer cooling by blocking radiation, and winter heat retention.
  • Northern, western and Cairngorm regions are the most sensitive to climate change, because of naturally sparse tree cover.
Two maps of Scotland showing predicted summer and winter river-temperature change under climate warming
Insight: Research indicates that rivers in the northwest and Cairngorm mountains regions are most sensitive to climate change. Maps show the predicted change in maximum daily river temperature for a 1 °C change in maximum daily air temperature (Source: Jackson et al., 2018).
Two maps of Scotland showing the modelled effect of riparian shading on summer and winter river temperatures
Insight: Research indicates that increasing riparian woodland from 0% to 100% creates a drastic shift in daily temperature profiles, essential for protecting cold-water species like Atlantic Salmon (Source: Jackson et al., 2018).

Our contribution: mapping and geometric analysis

Using SEPA datasets, the National Land Capability for Forestry (James Hutton Institute) and the Riparian Woodland Scotland dataset, we analysed 20 m riparian buffers across the country. Our analysis reveals that 81% (3,018 km²) of Scotland's riparian zones currently lack woodland cover, indicating a massive theoretical potential for restoration.

81%
of riparian zones lack woodland cover (3,018 km²)
923 km²
unsuitable for planting — wind throw, soil wetness, topography
380 km²
"Good"–"Excellent" for tree growth — LCF 1–3 (≈17.7%)
>70%
of unplanted riparian land suitable for forestry in the priority catchments
  • The reality check. Not all land is ready for planting. Environmental factors — including wind throw, soil wetness and topography — render 923 km² of this area unsuitable for tree crops (see map a below).
  • The spatial mismatch. A critical insight from our work is a geographical disconnect: while previous studies (Jackson et al., 2018) identify rivers in the north, west and Cairngorms as most sensitive to climate warming, our analysis shows these regions largely coincide with land that is physically difficult to plant.
  • High-priority targets. Despite these challenges, we identified 380 km² of non-wooded riparian land (≈17.7%) classified as offering "Good" to "Excellent" flexibility for tree growth — the top classes of the Land Capability for Forestry scale (LCF 1–3), which runs from Excellent (LCF 1) down to Unsuitable (LCF 7). The Eastern and Southern Lowlands, along with specific catchments on the western coast, emerge as the primary targets — where over 70% of unplanted riparian land is suitable for forestry.
Two maps of Scotland: (a) Land Capability for Forestry classification of unplanted 20 m riparian areas, and (b) proportion of unplanted riparian area suitable for forestry (LCF 1–4)
Spatial analysis of riparian restoration potential in Scotland. (a) Currently unplanted riparian areas within 20 m buffers, classified by Land Capability for Forestry (LCF). Dark green areas (LCF 1–3) represent high-priority targets for active planting. Lighter tones indicate decreasing suitability: LCF 4 offers moderate flexibility, LCF 5–6 indicate limited flexibility, and LCF 7 is unsuitable. (b) Catchment-scale prioritization. The map displays the proportion of unplanted riparian zones classified as suitable for forestry (LCF 1–4) within each catchment. Darker regions denote a higher share of suitable land, representing greater potential for active restoration.

To explore the data in depth, please visit our interactive map: Potential of Riparian Woodland Restoration in Scotland ↗

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