Biodiversity Net Gain calculator
The Biodiversity Net Gain (BNG) metric, which applies primarily to the United Kingdom, requires the natural environment of a development site to be left in a better state than it was before any development activities, replacing lost habitat, and creating or enhancing remaining habitat to achieve a 10% net gain in biodiversity. The gain must be sustainable for at least 30 years. There are two versions of the metric: full and Small Site Metric (SSM); smaller sites can use the SSM for calculations, which are the the calculations performed by the Sustainability Dashboard. The full metric must be evaluated by an ecologist; the Sustainability Dashboard does not implement the full framework at this time.
Local planning authorities review submitted calculations and may reject them if not completed by a professional, such as an ecologist. While an ecologist or other expert may still need to review the final plan, implementing the BNG SSM as you design in Vectorworks will help you as you prepare the design for submittal.
To use the BNG calculator:
Create the boundary of the project by adding a site model, or by drawing a simple polygon. The calculation uses a projected area, so a site model can be used but it is not required. Once the project boundary is established, it cannot change.
Attach the BNG Project Boundary record format to the boundary object, so that the Sustainability Dashboard can properly identify the object as the project boundary. The sustainability record formats are located in the Libraries\Defaults folder in the Record Formats\Sustainability file. See Attaching record formats to a symbol instance or object for information on how to attach records to objects.
Evaluate the existing environment within the boundary, before any development. This is the baseline. Create the appropriate habitats, hedgerows, and watercourses that make up the project; hedgerows and watercourses are reported linearly, while other habitats' area is reported. For a preliminary design, use geometry such as circles, polygons, and rectangles, and attach the BNG Sheet record format. For a more advanced design, use tools like the Hedgerow, Landscape Area, Hardscape, Plant, Existing Tree, and more.
To open the Vectorworks Biodiversity Net Gain Editor dialog box, do one of the following:
For parametric objects created by Vectorworks tools, click Settings from the Object Info palette, and open the Sustainability pane. Click New Framework. For the Framework, select BNG Sheet, and then click Edit Framework.
For a hedgerow object, click Sustainability Framework from the Object Info palette. In the Hedgerow Sustainability Data dialog box, click New Framework. For the Framework, select BNG Sheet, and then click Edit Framework.
For geometry, click Edit Sustainability Data from the Data tab of the Object Info palette.
Use the Eyedropper tool to pick up data from one object with an attached record and drop it onto other, similar ones. For larger projects, save the sustainability settings of parametric objects as a style. You can also use the Data Manager to attach the record as a criteria-based object.
Plants do not normally participate in BNG calculations, with the exception of trees. From the Data tab of the Object Info palette, attach the BNG Plant record format. On the Data tab, specify the predicted Diameter at Breast Height (DBH) of the tree at maturity. For existing trees, this value is taken from the existing tree parameters.
From the Vectorworks Biodiversity Net Gain Editor dialog box, specify the parameters related to habitat, hedgerow, or watercourse. Based on the selections, a Distinctiveness and Condition index is assigned, which factors into the BNG calculation.
Click to show/hide the parameters.Click to show/hide the parameters.
|
Parameter |
Description |
|
Type |
Select whether the object is in one of the allowed categories: Habitat, Hedgerow, or Watercourse |
|
|
Select whether this is a baseline, new, or improved object; this determines whether the object already exists or is new, or is an improvement to an existing object and therefore, how it affects the calculation and the project. Improved objects must be placed over a baseline object. |
|
Included in an Identified Local Strategy |
This multiplier affects the value of the habitats |
|
Broad Habitat Group |
For the habitat Type, select a broad category; enter text in the search box to filter the list |
|
Habitat Type |
Select a more specific category for the habitat |
|
Distinctiveness/Condition |
Displays an index for the selected habitat's characteristics |
Begin by specifying the baseline values for objects, and then add the new (created) and improved (enhanced) habitat types. Improved objects must be placed on top of a baseline object, and the baseline habitat must allow for improvement; otherwise, a new habitat is required.
Retaining existing habitats is better than replacing them with new ones, and improving an existing habitat is better than building a completely new one.
In the Sustainability Dashboard, specify the Goal percentage, or (suggested) leave the default of 10%. Select participating layers. As you add more habitat types to the design, click Recalculate; the dashboard indicates the results. See The Sustainability Dashboard.
As you modify the site and refresh the data, you'll see the changes to the BNG values in the Sustainability Dashboard. The results will go up or down, calculated from the baseline, depending on the total value of the parameter. Any created or enhanced habitats deduct the area from the underlying baseline habitats; the result is always calculated on the project's total area.
Once you have achieved a design with required results, click Export to create a report that can be submitted or shared with an expert for review. If you are submitting a SSM, you can input data to the official spreadsheet. You can also export the file as a shapefile.
