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The Singapore Biodiversity Accounting Metric (SGBA) is a local adaptation of the England’s Statutory Biodiversity Metric, which is briefly presented here.
At the core of biodiversity accounting is the realisation of threats to biodiversity posed by habitat loss, degradation and fragmentation brought about by climate change and increasing urbanisation-induced land-use 1. One example of governmental policy formulated in the face of these challenges is England’s Biodiversity Net Gain (BNG) policy which mandates nature recovery via habitat creation, enhancement, off-setting or compensation for any biodiversity loss. The BNG is part of a legislative act, namely, Schedule 14 of the Environment Act 2021, which stipulates that a minimum 10% biodiversity net unit gain must be achieved for any development project 2, 3, 4.
The BNG policy has given rise to the design of an accounting tool in the form of the Statutory Biodiversity Metric by the United Kingdom’s Department of Food and Rural Affairs 5. Local councils in England and Scotland have been utilising earlier iterations of the Statutory Biodiversity Metric several years ahead of time 6, 4.
The Statutory Biodiversity Metric is a tool that provides a proxy evaluation of extant habitats (e.g., terrestrial and riparian) in England, by assigning a numerical figure thereon before and after impact which typically accompanies development and construction projects. The term ‘proxy’ is applied as the metric is largely a semi-quantitative distillation of composite measures based on ecological and other surveys of the British isles, which might be deemed too technical for the uninitiated. The estimations employed include assigning a plethora of weights to indicate the relative importance of various categories pertaining to habitat and biodiversity worth, and the impacts on them following development. While in its fourth iteration, this tool best serves the British isles and surrounding European habitats, for which the Biodiversity Metric 4.0 was developed.
The positive utility, practicality, cross-border applicability and interoperable versatility of the Statutory Biodiversity Metric can be seen from several peer-reviewed international scientific journal publications on its predecessors, offering analytical insights and providing recommendations for future action. In a study of BNG assessment reports from 6 English local councils which used the Biodiversity Metric version 2.0 (an earlier iteration of the Statutory Biodiversity Metric), quantifiable units were reported for area reduction due to development, matching proxy measurements for compensatory remediation and the proportion of such compensation by location relative to the development sites 4. This quantification method provided a more useful means to assess and compare reports across different council projects as opposed to subjective measures of the past. Herein lies the usefulness of the Statutory Biodiversity Metric: a recorded reduction in biodiversity units, even though a proxy value, is potentially reflective of real-world biodiversity loss.
While initially planned for use in England only, another report from a study in Scotland indicated how the Biodiversity Metric (version 1.0) was applicable beyond borders 6. The aforesaid study indicated that BNG was achievable via the internal calculation rules-based mechanism of the metric for which it was designed, that is, ‘trading upwards’ or compensating for any loss via an improvement of predetermined conditions or habitat quality. Once again, the method of quantification provided a means for interchangeable standards across habitat subtypes.
While the use of the Biodiversity Metric centred on Scotland in the cited study above was understandably applicable to due it still being used within the British Isles 6, another study demonstrated its international applicability to riparian systems 7. The Biodiversity Metric (version 2.0) was used alongside another tool which was designed as a river habitat survey, in an attempt to report the assessment of both condition and physical parameters of riverine habitats collectively. The Biodiversity Metric circumvented the use of sampling transects which the latter required and which was limited in area coverage. This complementary use of both types of tools was also adopted after evaluating approximately 55 other pre-existing tools for riparian assessments which were found unsuitable for the purposes of the study, as they were largely limited in spatial coverage and were mostly semi-quantitative with many being qualitative in nature. Thus, the Biodiversity Metric was adopted as it accommodates spatially detailed monitoring of both small and large areas, is habitat-based, takes into account habitat condition, supports forecasting apart from assessing current parameters and is inherently flexible across geographical regions.
In summary, the Statutory Biodiversity Metric is a tool which has been formulated in light of the Biodiversity Net Gain legislation in England in response to address impacts on biodiversity via habitat loss and degradation in the face of continued development and climate change. It has been successfully implemented and endorsed by local government bodies. It provides a more objective means of assessment via quantification in contrast to pre-existing measures, allowing for comparison across different projects. Its unique features include its flexibility in covering a wide range of habitats regardless of size, interchangeable compensatory measurement metrics among habitat subtypes and traceable habitat history from planning to post-project development. Perhaps one of the biggest attractions of the Statutory Biodiversity Metric is its ease of use and cross-applicability across geographical regions as demonstrated in the section which follows.
The Singapore Biodiversity Accounting Metric (SGBA) was developed to suit the geographical region and tropical climate of Southeast Asia, wherein Singapore is located. Since the Statutory Biodiversity Metric has undergone several rounds of refining, improvement, endorsement and adoption by local governmental organisations, the SGBA inherits these positive attributes while tailoring it to suit a tropical environment.
See the section on "Further reading" for a comparison of both the SGBA and England’s Statutory Biodiversity Metric.
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