This methodology is based on the one for identifying opportunity woodland in the Chew Valley and the Finding the Land to Double Tree Cover report by Friends of the Earth, 2019.
Doubling woodland cover can be achieved in various ways including agro-forestry, sylvo-pasture, trees in hedgerows, shelter belts and land use conversion to woodland. The methodology is fundamentally simple and is based on the following criteria:
- Primary arable production should not be encroached upon
- Grasslands that are encroached up should not have high biodiversity value
- Sites should not be designated as protected
- Peat bogs should be preserved
Further the methodology should only use data that is freely available under the Open Government Licence, or other similar open data that are free to use.
To undertake this analysis it is necessary to know the Grade of agricultural land according to the Agricultural Land Classification, the land cover/use and whether the land is protected. At the scale of England and Wales the follow data sets are available to approach the problem.
- Agricultural Land Classification of England and Wales
- CROME Crop Maps
- Protected Areas
- Administrative Units
Assumptions
- Grade 1 to 3 (inclusive) are excluded because they are suitable for arable agriculture
- Grade 5 land is “a good proxy for upland peat bogs”
- Grade 4 poor-quality land is “mostly used for pasture”
- Agroforestry will be adopted on 10% of land of Grades 1 to 3
Are these assumptions correct?
“Grades 1 – 3 are mainly arable”
Grades 1, 2 and 3 are dominated by arable crops with a total of 45% cover, followed by Grass (21%), Non-vegetated (15%) and Trees (13%). A portion of the Grass will be temporary and part of the arable rotation.
| Category | Class | Area (Ha) | % | Cumulative % |
| 74 | Grass | 1,774,416 | 21 | 21 |
| 41 | Winter Wheat | 1,291,808 | 15 | 36 |
| 75 | Non-vegetated | 1,280,943 | 15 | 51 |
| 79 | Trees | 1,132,991 | 13 | 65 |
| Other arable crops | 2,512,584 | 30 | 90 | |
| Other | 495,797 | 6 | 100 |
“Grade 5 is a good proxy for upland peat bogs”
In England Grade 5 land occupies 1,100,761 ha.
In England Blanket Bog occupies 234,585 ha of land, of which 232,366 ha are within Grade 5 land.
So, 99% of Blanket Bog occurs within Grade 5 land.
Grade 5 land is predominantly covered by priority habitats (67%) and is mainly (54%) comprised of Blanket Bog (21%), Upland Heathland (20%) and Grass Moorland (13%). The rest is made up of small amounts of other categories.
Perhaps better to say that Grade 5 is a good proxy for Blanket Bog, Upland Heathland and Grass Moorland.
| Category | Habitat | Area (Ha) | % | Cumulative % |
| 0 | No Data | 42818031.75 | ||
| 1 | Blanket Bog | 232366.25 | 21.11 | 21.11 |
| 23 | Upland Heathland | 220794.00 | 20.06 | 41.17 |
| 32 | Grass Moorland | 143143.25 | 13.00 | 54.17 |
| 29 | Deciduous Woodland | 27434.00 | 2.49 | 56.66 |
| 11 | Lowland Heathland | 24623.25 | 2.24 | 58.90 |
| 36 | No main habitat | 21093.50 | 1.92 | 60.82 |
| 22 | Upland flushes, fens & swamps | 9517.25 | 0.86 | 61.68 |
| 21 | Upland calcareous grassland | 8827.00 | 0.80 | 62.48 |
| 30 | Fragmented Heath | 8710.50 | 0.79 | 63.28 |
| 9 | Lowland calcareous grassland | 8596.75 | 0.78 | 64.06 |
| 31 | 5951.50 | 0.54 | 64.60 | |
| 13 | 5181.75 | 0.47 | 65.07 | |
| 4 | 3781.75 | 0.34 | 65.41 | |
| 10 | 3613.00 | 0.33 | 65.74 | |
| 27 | 3609.25 | 0.33 | 66.07 | |
| 33 | 3479.50 | 0.32 | 66.38 | |
| 19 | 2415.25 | 0.22 | 66.60 | |
| 5 | 1656.75 | 0.15 | 66.75 | |
| 34 | 1406.00 | 0.13 | 66.88 | |
| 14 | 1402.75 | 0.13 | 67.01 | |
| 12 | 1197.25 | 0.11 | 67.12 | |
| 8 | 1133.25 | 0.10 | 67.22 | |
| 35 | 962.50 | 0.09 | 67.31 | |
| 39 | 588.00 | 0.05 | 67.36 | |
| 37 | 245.50 | 0.02 | 67.38 | |
| 3 | 162.50 | 0.01 | 67.40 | |
| 20 | 37.25 | 0.00 | 67.40 | |
| 38 | 27.50 | 0.00 | 67.40 | |
| 28 | 11.25 | 0.00 | 67.41 | |
| 741968.25 | 67.41 |
“Grade 4 is mostly used for pasture”
Total Grade 4 land in England = 1,840,335 Ha
Using 2018 CROME data as an example Grade 4 land is comprised of the following cover types:
| Category | Class | Hectares | % | Cumulative % |
| 74 | Grass | 646,160.50 | 35 | 35 |
| 79 | Trees | 467,451.25 | 25 | 61 |
| 75 | Non-vegetated | 308,137.00 | 17 | 77 |
| 72 | Fallow | 308,137.00 | 3 | 80 |
| 73 | Heathland | 57,161.00 | 3 | 84 |
| 1-70 | Arable Crops | 299,746 | 16 | 100 |
In order: Grass (35%), Trees (25%), Non-vegetated (17%), Arable Crops (16%), Fallow (3%), Heathland (3%)
Perhaps it is better to say that Grade 4 is mostly used for pasture and trees and is 1/3 pasture and 1/4 trees.
“Agroforestry can be adopted on 10% of Grade 1 to 3 land”
Planting densities for agroforestry and sylvopasture could be applied using the CROME cropland / pasture classification.
Inclusions
Certain areas are expressly included, namely:
- Agricultural Land Classification Grade 3b, Grade 4 and Grade 5
Exclusions
Certain areas are expressly excluded from the areas of inclusion, namely:
- Priority Habitats
- NFI Woodlands
- Special Areas of Conservation (Habitats and Species)
- Special Protection Areas (Birds)
- Ramsar Sites (Wetlands)
- Sites of Special Scientific Interest
- National Nature Reserves
- Local Nature Reserves
- Moor Line
- Persistent Non-Vegetation (according to CROME)
- Persistent Water (according to CROME)
- In Wales – CORINE artificial surfaces
- In Wales – CORINE open water
Spatial Models
| Model Name | Comment |
| make_arable_grass_fallow_heathland_powers_addition | Make inputs for next model. |
| calculate_woodland_opportunity_england_mark02 | |
| calculate_woodland_opportunity_wales | |
| make_ag_land_slope_categories_England | Does Wales too. |
| prep_protection_areas | |
| agro_forestry_england |
References
Chew Valley report…
Friends of the Earth, 2019, Finding the land to double tree cover