 Hi, my name's Alex Bush and this presentation will cover a mini-demonstrator project on the potential benefits of eco-acoustics for measuring biodiversity net gain and was supported by the Constructing a Digital Environment Strategic Priorities Fund, as organised through NERC and UKRI, and it was co-led by Tom August at UKCH and Carlos Abraham at Baker Consultants. This project comes at a really important time. We've had a lot of changes in the UK policy framework around environmental policy, and the most important in the context of this project is the Recent Environment Act, and this makes it mandatory for all developments to begin delivering a minimum of 10% biodiversity net gain, and it will be made mandatory by November this year. That net gain is calculated through a biodiversity metric as decided by Natural England, and it's through balancing the units of that metric that a developer can gain planning approval, and that the planning authority can show their sort of due diligence under this Act, and that habitat has to be secured for a minimum of 30 years. Biodiversity net gain is quite a simple concept in principle. It's in the understanding that we want to approach land development with the aim of leaving it in a measurably better state than it was before. So under a standard development scenario, habitat gets lost, and that's why we see widespread biodiversity loss around the planet. It's the primary driver of biodiversity loss. So there's an alternative to that. A policy of no net loss was introduced and is intended for a developer to follow a mitigation hierarchy where they avoid destruction of habitat as much as possible or mitigate the impact that they're having. And finally, if that impact cannot be avoided, then they offset those losses. Through no net loss, we try and meet the losses through an equivalent standard. Biodiversity net gain acknowledges that that net loss is no longer really a viable alternative, partly because it wasn't stemming the losses at the largest scale, but also because our policies now regard it as being critical that we forge a path towards nature recovery. And this net gain can be achieved either through a larger offset or through an increase in habitat condition, as I will discuss. And it can be achieved within the footprint of that development, or it can be achieved through offsite developments in the creation of new habitats elsewhere. The biodiversity net gain metric as going through iterations with natural England has been defined by habitat classification and vegetation types. Different vegetation types have different unit values based on their distinctiveness, and you can also have a greater or a lesser number of units that measure the biodiversity value based on the condition of that habitat. And this is considered a manageable approach for non-specialists to identify the value of the habitat they're having an impact on. But it also, from an ecological point of view, is a really coarse way of describing biodiversity complexity and doesn't really incorporate any species information at all. The bigger issue also is that if this applies to all developments and has a lifespan of 30 years, it's going to be really challenging to scale this up to that kind of effort. Furthermore, there's a key point in the legislation about we must be able to measure that the biodiversity net gain has occurred. And to show that in a robust and confident way requires a design that acknowledges that there can be other sources of variation and during global change and climate change this can become even more important. So this diagram on the right is just to illustrate the number of sites that you might need, particularly number of control sites that you might need in order to show that your restoration has been successful and the kinds of designs are in different colours there. Habitat condition assessment is also problematic from the perspective that lots of surveyors disagree. It's quite a subjective way of assessing habitats. There's also a lot of variation in the way that individuals assess particular habitats. So it's not a very consistent method. It's not very quantitative. And it's quite difficult to expand because you also have to visit the site in person. You have to visit a particular time of year when you're able to observe the particular plant species that characterize those habitats. As I said, this is going to be an enormous task for people. And so there's a lot of appetite for considering what technologies we might be able to adopt that would help automate some of this assessment workload. Ecoacoustics is the branch of acoustic monitoring that focuses on environmental sounds made by wildlife. And it has exploded in its potential in recent years. And if you're interested, there are many reviews out there. Most pertinent within the UK context are records for birds and bats, which have seen a lot of academic development in particular. But it's also possible to record sounds underwater, ponds, rivers, even in the soil. And so the potential of acoustics is still growing. But it has also reached a stage where we're able to do various kinds of analysis with confidence. In the early stages, analysis focused on a very quick understanding of environments based on the variety and level of noises and sounds that were going on. And you're going to characterize those with various acoustic indices as proxies for the wider soundscape of that landscape. How are these still proxies? They kind of relate to the community that's available, but doesn't really describe in detail what biodiversity is present. And gradually we've been able to move on towards more in-depth ecological analysis where we can identify what particular sounds came from which particular types of species. And then from those, you can recreate some kind of metrics that describe biodiversity that we're quite familiar with species richness or species diversity. Abundance is potentially possible, but it requires a lot more surveying effort even from the eco-acoustic side. So for a net game perspective, we don't necessarily believe that that will be instantly scalable. And critically, the acoustic indices from soundscapes do not directly align with species diversity. And so there is a sense now that if the technology is available to identify the species, it's often better to go to that extra level if you want to understand what biodiversity changes. In July we held a workshop at Windermere, and the objective there was to identify how eco-acoustics could play its role in the development of net game policy in the future. And so we invited members of Natural England who are involved in delivering that policy, but also members of the environmental community as professionals and non-government organizations who are doing the delivery of habitat assessment and scoring based on that metric. So consultancies, BTO, Derbyshire Wildlife Trust and the Environment Bank. And in summary, the major objective of this workshop was to understand how habitat change relates to eco-acoustics. And by habitat change, we mean can we discriminate between different types of habitat, habitats in different condition, and also recognize then those changes that result from restoration. And if those changes can be identified through measures through eco-acoustics, or in fact that they are dissimilar to those metrics that we measure through eco-acoustics, then that can identify how net game policy is likely to influence biodiversity. To help us understand what that relationship is between the metric for habitat condition and eco-acoustics, we've set up a couple of pilot projects to collect data. In the first case with Eden Project in Cornwall on different types of grasslands that they're restoring. And then secondly on different types of grasslands at Forest Hills in Lancashire. And both of these sites are related to development of solar farms as it happens as well. And so there's an interest in how we can integrate that positive change with something that can also be associated with biodiversity. One of the principal outcomes of the workshop was understanding what it is that we want to demonstrate from this relationship, how this relationship will inform change for policy in the future. And the first part is to recognize how the metric relates to eco-acoustic change, but also more evidence and understanding of how habitat restoration and habitat types can reflect biodiversity in the broader sense. And whether or not birds and bats are predictable in their distribution and their occurrence and their diversity with respect to habitat change and whether that habitat is described through local means or through remote means is optional. But if those species do not respond to those metrics, then it's very difficult to understand whether BNG policy is then going to have the desired effect for biodiversity at larger landscape scales. And whether or not these two relationships are strong or whether they are weak determines whether or not eco-acoustics can provide an alternative way of assessing environmental change that effectively complements the metric and strengthens it and provides another line of evidence or whether it actually provides another different source of information about how biodiversity change is occurring. Both alternatives are potentially valuable and it remains to be seen whether or not how this relationship holds. So the next steps following from the workshop are to expand that collaboration, particularly with the professional consultancy community as our primary audience for people that are delivering assessment through the current metric and will be responsible for offering their expertise on biodiversity assessment to planning authorities. Developing the guidance for them to do eco-acoustic assessment is important but also providing a network for coordinating those actions so that we can start to combine metric and eco-acoustic assessments together to assess that relationship will be key. And in future we hope to apply for formal funding so that we can develop a digital repository that can act as that evidence base for providing a more quantitative assessment to whether or not a site has improved or simply shifted or met its targets through eco-acoustic assessment. And this will combine both the academic and governmental objectives.