Grasslands have an important role to play as part of Chew Valley’s agriculture. They are generally on the lower grade land that is less valued for arable crop production and also in more difficult terrain. It is worth noting that the Chew Valley lies over some tortuous geology which in places is expressed at the surface in a complex and characterful form.
There are a number of different types of grassland some species-rich and other species-poor. It doesn’t make sense to replace a species-rich and biodiverse grassland with woodland and care should be taken to avoid this. Using satellite imagery or other mapping tools it is difficult to tell what type a grassland is without doing a field survey.
- Temporary grassland – this is grassland that is actually part of the arable crop rotation and is probably a mono-culture. It is possible to detect temporary grassland from satellite by observation over a period of years.
- Improved grassland – this is grassland that has been “improved” using fertilisers and has probably been ploughed
- Semi-improved grassland has been improved in the past but may have some biodiversity value and can be differentiated into good-quality and poor-quality
- Biodiverse grassland and meadows
There are no comprehensive and completely reliable data on the distribution of grassland types in England. The tools we have to differentiate different grassland types are as follows:
- Temporary grassland can be distinguished using satellite imagery by using four years of DEFRA CROME crop data
- Persistent, non-temporary, grassland can similarly be identified using the DEFRA CROME dataset
- Priority habitats can be identified using Natural England’s Priority Habitats dataset which identifies (of relevance in the Chew Valley):
- Good quality semi-improved grassland
- Lowland meadows
- Lowland calcareous grassland
- Lowland dry acid grassland
Using these different data sets it has been possible to exclude all grasslands from the opportunity woodland area that are: priority habitats, good-quality semi-improved grassland, temporary grassland, sites of special scientific interest or other gazetted protected areas. The remaining grassland is put forward as a candidate area for either opportunity woodland or silvopasture. There will be remaining biodiverse grassland that has been missed – which is why it is important to undertake an ecological survey.