What is a Site Survey (also known as a "walkover")?
A site survey is when a competent person or qualified ecologist goes to a site and records what habitats are on the site and all the other necessary information to complete the biodiversity metric.
Don't worry if you are not an ecologist, with Joe's Blooms tools you can enter in all the information you need to be fully compliant, and also comply with best practice.
This is based on a walkover of the site (i.e. literally walking over the site) and recording what habitats are there and their condition. You can get more information on what sort of things you need to measure here.
The competent person or ecologist will need to record on what date they did the site walkover. While site surveys can be undertaken at any time, you should factor in the impact of the season and time of year.
What are baseline habitats / parcels?
What does "baseline" mean when we talk about baseline assessment / baseline parcels?
The "baseline" assessment is when you work out what is currently on your site. This is the step where we will work out what the current biodiversity value of your site is before you begin development.
To work out the baseline parcels, you need to do a site survey (also known as a walkover) of your site. This is explained in ore detail below, but in short it means going to the site and looking at what habitats are there.
You should, using your judgement, split the site into different habitat parcels. When doing so, you should consider different land uses across the site and identify any areas of higher biodiversity interest.
What is a Habitat Parcel?
A habitat parcel is a single, continuous piece of land within your site which clearly is part of a single piece of habitat with the same condition.
You should inspect the site and determine what habitats are within your red line boundary. This means breaking up the area within the redline into different parts (e.g. a grassy area, a wooded area, a sealed area). For example, in this red line boundary there are very clearly two different types of parcel: grassland and woodland:
The whole red line diagram should be filled up with different habitats, there should be no empty space.
Most habitat parcels should be recorded as area, but hedgerows and linear waterways (i.e. culverts, ditches, canals and rivers) are recorded as linear features. Individual trees are also recorded according to special rules.
With hedgerows (including lines of trees) you should simply draw the hedgerow as if it was a line with no area (so imagine a hedgerow dividing a meadow and paved land, you would simply draw in the grassland and paved land touching each other, and then draw a line down the middle to show where the hedgerow is.
With waterways you will need to make sure you have the specialist knowledge to map these out. You should review the Government's User Guide for how these are mapped out.
Trees are recorded as individual trees, but you will need to set out what their diameter is at breast height (DBH)
Size Class | Diameter at breast height (cm) |
Small | Greater than 7.5cm and less than or equal to 30cm |
Medium | Greater than 30cm and less than or equal to 60cm |
Large | Greater than 60cm and less than or equal to 90cm |
Very Large | Greater than 90cm |
You should take photos of the different types of habitat that you think are within the site. It's important that you have clear photographic evidence of all the different habitats that are within your redline boundary.
If you are not sure what a species is, you may wish to use a credible tool. For example, the Seek tool is a free tool that can be used to identify plants.
How to do a Site Survey / walkover")
A site survey is when a competent person or qualified ecologist goes to a site and records what habitats are on the site and all the other necessary information to complete the biodiversity metric. This is based on a walkover of the site (i.e. literally walking over the site) and recording what habitats are there and their condition. You can get more information on what sort of things you need to measure here.
Surveys can be done at any time, but ideally should be scheduled to reflect the best times. Some parcels may require 2 or more visits to confirm their nature.
Guide to appropriate times to do site surveys
Broad habitat type | Start date | End date | Notes |
Woodland | April | May | n/a |
Scrub | April | May | n/a |
Grassland | April | May | Can also be done from July to August (before hay cut if relevant) |
Heathland | June | August | n/a |
Wetland | June | September | n/a |
Rock Exposures | February | May | n/a |
Sand Dune | April | June | n/a |
Arable | April | May | Can also be done from July to August |
Urban | May | July | n/a |
Source: Forestry Commission
The whole of each parcel should be walked over
All habitat types should be visited
typically species-rich or otherwise interesting habitat features such as flushes, arable margins, transitions, open ground or ancient fragments, should be inspected in detaik.
The competent person or ecologist will need to record on what date they did the site walkover.
BNG surveys are different to all other ecological surveys, however it is advisable to know what best practice is for those other types of survey. Below is some idea of the sorts of survey that should be done at specific times.
Source: CIEEM
More information on other types of site surveys can be found here. You may also wish to undertake UKHAB training to understand how best to identify the different habitats.
Other useful resources
Bat Conservation Trust: Good Practice Guidelines