The new biodiversity net gain proposals are the perfect storm of ecological and governmental jargon. Full of unnecessary acronyms and Shakespeare-esque compound adjectives (‘future-fit‘), mixed in with the familiar buzzwords like ‘Stakeholder Engagement’ and ‘Ecosystem Services’.
When biodiversity net gain eventually becomes mandatory for new developments, some of these key words may well be blowing around in your inbox. But, let’s leave behind this new frontier of eco-jargon, for a moment, and take a step back to look at the key principals which underpin all wildlife conservation.
There are a few universal principles which developers could keep in mind when incorporating biodiversity in their developments at the design stage; principles which have always been fundamental to wildlife conservation, these are: size, connectivity and complexity. Your ecologist will thank you for thinking about these key principals at the design stage of your project; the details – which as Oscar Wilde stated ‘…are always vulgar’ can always be ironed out a later stage, after any ecological surveys.
Principle 1: Size
It goes without saying that size is an important factor; habitat area being one of the most important metrics measured in the new biodiversity calculator. Using the points-based biodiversity metric which will be used, it becomes increasingly difficult to achieve a net gain when replacing an existing habitat, which is to be lost, with a smaller habitat. This can result in ever more complicated and convoluted habitat schemes – which often require specific management regimes for each habitat.
This may be less of an issue if the existing habitat to be developed is, for example, an area of shortly cut amenity grassland field, in which case a new smaller portion of woodland or species rich grassland could be considered an offset, and increase the biodiversity net gain of the site.
It becomes an uphill battle, however, when for example, a large area of woodland is to be lost on site. As a rule, it is best to avoid developments which require large scale habitat loss on site.
This principal will likely have implications on whether or not a developer would purchase a certain site. Developers may be put off purchasing land with areas of trees or large expanses of grasslands, if the development requires most of the onsite habitats to be lost. This is probably the most difficult principal to incorporate into a new development, as the nature of developments usually reduce natural habitat, which is why the next two principals are particularly important.
Principle 2: Connectivity
There is a principal on wildlife conservation called ‘several small or single large’. It is referred to as the ‘SLOSS’ debate (I told you ecologist like acronyms!). The debate compares habitat conservation value of many different small sites across a land mass, VS the value of fewer, but much lager areas.
However, when it comes to urban developments, it is almost always better to have one large contiguous area of wild space for your site. At a local, urban level, small areas of wildlife would be disproportionately impacted by human disturbance. Whereas, one large area would be less impacted by such things as light spill and road-traffic accidents etc.
Connectivity of habitats such as hedgerows and trees are also an important consideration, can your development connect to areas of woodlands? Or wildflower fields with a tree line or hedgerow? These ‘connections’ will go toward the biodiveristy net gain of your site, and help animals to commute, shelter and forage between habitats.
Principle 3: Complexity
Having a mosaic of habitats on a site will increase the site’s biodiversity, especially for protected species. Consider bats , reptile and great crested newts, these animals thrive in landscapes with multiple habitats like woodland, grassland and water. Animal populations and biodiversity is typically higher in the zone where two natural habitats overlap.
As a rule, rarer habitats (i.e. NERC Act habitats, formerly ‘BAP habitats’) are more ‘valuable’ for biodiversity.
Consider rare ‘transitionary’ habitats for big net gains
I spent 6 months cutting reeds on the Norfolk Broads – you may think that this is a bizarre thing to do, why maintain a habitat in this laborious manor? It is because reedbeds are just one example of a rare transitionary habitat in the UK. Which means, that many reedbeds, if left unmanaged would eventually turn into their ‘climax habitat’ – a woodland. Traditionally, reedbeds would have been managed for thatch and other uses, or they would have naturally arisen as new areas were seasonally flooded.
After changes in land uses and drainage of many wetlands, hundreds of years ago, this habitat is now relatively rare in the UK. If many reedbeds in the UK were not artificially maintained, there would be a lot less reedbeds. Considering a small reedbed for a new development, would be a great way of improving the site’s biodiversity, as would other transitionary habitats such as a wildflower meadows.
Figure 3.2 below is from 2019 document by CIRIA: Biodiversity net gain: Good practice principles for development. This is a great example of the above principals, you can clearly see that the natural space is large, well connected and complex (consider the surrounding farmland, and contrast this with the several ponds, wooded areas (including orchards), grasslands and more of the newly created habitats).
Categories: Developers Resources