Case study 2: freshwater

Hypothetical Case Study: Riverine Retreat

At the end of this case study, you should be able to:

Apply the SGBA to a development project impacting terrestrial and freshwater ecosystems primarily and secondarily, respectively.
Use the SGBA to calculate Habitat Biodiversity Units (HBUs) for baseline and post-development habitats as functions of habitat area, distinctiveness, condition, creation and enhancement multipliers.
Identify habitat trading rules for enhancement across habitats and habitat biodiversity compensation between terrestrial and freshwater ecosystems.
Describe how overall biodiversity net gain may be achieved from biodiversity net loss and gain from terrestrial and freshwater ecosystems, respectively.
Suggest mitigation strategies to enhance, maintain biodiversity or minimise its loss.

Below is a hypothetical case study demonstrating how the SGBA can be applied to a new tourism development project within terrestrial and freshwater ecosystems in Singapore. This case study highlights the metric's utility in quantifying biodiversity impacts and demonstrating how strategic design and habitat management can achieve Biodiversity Net Gain (BNG).

1. Location and Current Area Use: The proposed project site, Riverine Retreat, is a 5-hectare (ha) relatively undeveloped parcel located along the western bank of a river in Singapore. Historically, the area was a mix of secondary vegetation and a naturalised stream, with some minor existing infrastructure and paths. The current land use is predominantly green space with limited human intervention, making it a valuable, albeit undermanaged, ecological corridor.

2. Project Overview: A new tourism development is planned for the Riverine Retreat, aiming to integrate recreational and commercial structures with nature-based experiences. The development will include eco-lodges, a visitor center, nature trails, and a waterfront dining area. This project necessitates some habitat modification and loss but also presents opportunities for significant habitat enhancement and creation.

SGBA Application: Baseline Assessment

Before any development, a comprehensive baseline assessment using the SGBA was conducted to quantify the existing biodiversity value of the 5-hectare site in Habitat Biodiversity Units (HBUs). The site comprised a mix of terrestrial and freshwater habitats, with no marine component.

Detailed SGBA calculations for what follows may be found herein:

Case study 2 XL vs GS- Copy of Camphora Master - SG Biodiversity Accounting Metric 1.1 DevV01b

Table 1: Baseline Habitat Biodiversity Units (HBUs) - Pre-Development of Terrestrial and Freshwater Ecosystems.

This baseline assessment provides the fundamental value against which all post-development changes will be measured.

SGBA Application: Post-Development Assessment

The development plan for Riverine Retreat involved strategic design choices to minimize ecological impact and maximize biodiversity gains. Certain areas were designated for retention and enhancement, while new habitats and urban green infrastructure were created. The development resulted in the following changes across the 5-hectare site:

Habitat Loss:
- 0.8 ha of exotic-dominated secondary forest was cleared for eco-lodge construction.
- 0.5 ha of scrubland/ grassland was converted to new recreational areas.
- 0.2 ha of naturalised stream was impacted by the waterfront dining area construction.
- The existing 1.0 ha of Developed Land was re-purposed for new commercial structures and hardscaping.
Mitigation Measures (Retention, Enhancement, and Creation):
- Retention: 1.2 ha of the original exotic-dominated secondary forest was retained untouched.
- Enhancement:
  - The remaining 0.5 ha of scrubland/ grassland was enhanced to a more biodiverse exotic-dominated secondary forest with improved condition.
  - The remaining 0.3 ha of naturalised stream underwent rehabilitation to improve its ecological condition.
- Creation:
  - 0.5 ha of outdoor rooftop greenery was created on the eco-lodges and visitor center.
  - 1.5 ha of urban park/ garden was established, incorporating native plants and diverse flora.
  - 0.2 ha of managed soft bank pond was created as a new freshwater feature.
  - 1.3 ha was developed as new Developed Land for tourism facilities and hardscaping.

The SGBA calculation for post-development HBUs includes values for retained habitats, enhanced habitats, and newly created habitats, incorporating risk multipliers for creation and enhancement to account for the inherent challenges and time required for these initiatives to reach their target conditions. For this case study, "Time-to-target condition" is recorded for planning purposes but does not directly impact HBU calculations in the SGBA.

Table 2: Post-Development Habitat Biodiversity Units (HBUs) - Including Retention, Enhancement, and Creation of Terrestrial and Freshwater Ecosystems.

a: Retained from baseline.

b: Enhanced from 0.5 ha of scrubland/ grassland (low to moderate distinctiveness trading, permissible). Time to Target Condition: 20 years.

c: Enhanced from baseline condition (poor to good), keeping the same distinctiveness. Time to Target Condition: 4 years.

d: Created on new building structures. Time to Target Condition: 10 years.

e: Created green space. Time to Target Condition: 15 years.

f: Created freshwater feature. Time to Target Condition: 3 years.

g: New facilities/ hardscaping.

Note: While Time to Target Condition (i.e., b - f) does not count towards HBU calculation, it provides a guardrail for developmental planning and monitoring.

SGBA Application: Net Biodiversity Change Summary

By comparing the total HBUs before and after development, we can determine the net change in biodiversity for the Riverine Retreat project:

Total Baseline HBUs (Pre-Development): 19.00 + 1.00 = 20.00 HBUs
Total Post-Development HBUs: 17.85 3.00 = 20.85 HBUs

Combined Net Change in HBUs = Post-Development HBUs - Baseline HBUs

Combined Net Change in HBUs = 20.85 - 20.00 = +0.85 HBUs

Combined Net Percentage Change = (Net Change in HBUs / Total Baseline HBUs) × 100% Combined Net Percentage Change = (+0.85 / 20.00) × 100% = +4.25%

The SGBA analysis for the Riverine Retreat project indicates a Biodiversity Net Gain of +4.25%. This positive outcome demonstrates that by strategically planning and implementing habitat retention, enhancement, and creation, particularly through urban green infrastructure and freshwater features, a development project can contribute positively to local biodiversity, even in a tropical city-state experiencing rapid urbanization.

This result highlights that while some habitat loss is inevitable with development, thoughtful integration of ecological considerations can lead to a significant "nature-positive" outcome. The project successfully leveraged less distinctive habitats for enhancement and created new, valuable green spaces, fulfilling the objective of improving biodiversity value within the development footprint.

Disclaimer: All calculations in this case study are based on the provided SGBA parameters and a hypothetical scenario. In a real-world application, detailed ecological surveys and expert judgment would inform the precise area, distinctiveness, and condition scores, as well as the feasibility and success rates of habitat creation and enhancement initiatives. The area assigned to linear features like "Naturalised stream" has been treated as an area-based habitat (in hectares) for the purpose of this calculation, consistent with how the SGBA inputs habitat area.

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