How Does The Wallacea Trust Methodology Calculate Biodiversity Uplift?

2 July 2024 by Georgie Tugwell

How Does The Wallacea Trust Methodology Calculate Biodiversity Uplift?


The Wallacea Trust biodiversity quantification methodology assesses:

(1) Avoided biodiversity loss for protection projects

(2) Biodiversity uplift for restoration projects

Whilst the methodology can be used in either scenario, this blog focuses on application ‘2’.


Defining A Unit of Biodiversity:

The Wallacea Trust biodiversity crediting methodology ranked top in a recent global analysis; it quantifies project biodiversity benefits and can translate these into awardable credits. The Wallacea Trust unit of biodiversity is:

A 1% uplift in biodiversity per hectare, as measured by the median % change in a basket of biodiversity metrics that reflect the conservation objectives for a project site.

Project biodiversity is assessed by monitoring changes in a basket of at least five pre-determined, site-specific and peer-reviewed biodiversity metrics. The basket of metrics approach to quantifying nature was inspired by the Consumer Price Index (CPI) – Where a basket of goods and services in each country is priced up annually to estimate inflation rates. Inflation rates are compared across borders despite the basket of goods and services analysed within each nation varying significantly. Tailoring the CPI approach to biodiversity facilitates global comparison of project success across different ecoregions whilst also ensuring that metrics relevant to a site’s conservation objectives are monitored.


Choosing Your Biodiversity Metrics:

So, what are biodiversity metrics? Metrics are measured environmental variables that link to the underlying health of an ecosystem and inform us on its functionality. Metrics may be:

  • Non-Structural – functional taxon (e.g. large herbivores, soil invertebrates, breeding birds etc.) or zoological taxon (e.g. butterflies, bats etc.)
  • Structural – (e.g. canopy cover, kelp occupancy by volume, coral reef rugosity)

A minimum of five must be selected for a project, this typically includes one structural and four non-structural metrics. A suitable basket of biodiversity metrics can be planned through BFI Stage 1 Review prior to project initiation; selected metrics must be used consistently throughout project lifetimes.


Calculating Structural Metrics:

Structural metrics are usually quantified in relation to a reference site. The difference between the structural metric value e.g. canopy cover at the reference site (e.g. healthy forest) and at the project site (e.g. deforested area) is divided into five equal quintiles. Upon project initiation, the project site is allocated a Rank of 1 and the reference site is Ranked 5. The Biodiversity Value of the structural metric is then calculated as its rank score multiplied by 100. The project site rank score will increase as the canopy cover increases, therefore, successful restoration activities should improve the structural metric biodiversity value. Different approaches to calculating structural metrics can be adopted, e.g. if higher plants was the structural metric chosen, this could be quantified using non-structural metric calculations below.

  • Biodiversity Value of a Structural Metric = Rank Score X 100


Calculating Non-Structural Metrics:

Non-structural metrics consider large assemblages of species such as breeding birds. Species Richness is weighted by the assignment of a Conservation Value (e.g. an IUCN value where 5 – Critically Endangered and 1 – Least Concern). Relative Abundance scores are also assigned to each species on a 5-point ranking system, each rank is defined by a quintile interval approach, as with structural metric. The non-structural metric Biodiversity Values are calculated by multiplying each species’ Relative Abundance by its Conservation Value and then summing these together. This approach provides taxon scores and enables uplift to be assessed.

  • Biodiversity Value of a Non-Structural Metric = Sum of (Relative Abundance Scores of Species X Conservation Value Scores of Species)


Biodiversity Uplift Quantification Process:

To quantify biodiversity uplift on sites using the Wallacea Trust methodology a biodiversity baselines is needed. Baselines establish the flora and fauna present prior to any project activities, allowing for project impacts to be assessed. To generate a baseline, a basket of biodiversity metrics must be measured at project initiation on both the project site and a reference site. Reference sites enable the biodiversity values generated on project completion to be estimated and they should have undergone similar management practices within similar timeframes to those proposed for the project site. When baselining is complete, project site biodiversity uplift is measured every five years across the same biodiversity metrics at the same sampling locations until project completion.

Biodiversity uplift across metrics over the project lifetime will be detected by comparing new values with baseline values. The median value of the percentage change across all metrics gives the overall biodiversity gain achieved over a given timeframe. This value is multiplied by the project site area (hectares) to calculate the total number of biodiversity gain units.


The Biodiversity Uplift Calculations:

To summarise, the steps needed to quantify a project sites biodiversity uplift are:

  • Biodiversity Value of a Structural Metric (in most instances) = Rank Score X 100
  • Biodiversity Value of a (min. 4) Non-Structural Metric = Sum of (Relative Abundance Scores of Species X Conservation Value Scores of Species)
  • Project Site Biodiversity Baseline = Median of the Five Biodiversity Values
  • Biodiversity Change for a Metric (1st Verification Event) = 100 X (Biodiversity Value at 1st Verification Event Biodiversity Value Baseline Assessment / Biodiversity Value at Baseline Assessment)
  • Project Site Biodiversity Uplift (1st Verification Event) = Median Biodiversity Change Across the Five Metrics


Can We Claim All The Uplift Calculated?

Once we have calculated total biodiversity uplift for a given verification event – can we claim all units as biodiversity credits? In short, no they are not. Claimable biodiversity credits issued for projects are determined by:

(1) Overall biodiversity uplift values

(2) Project site size

(3) Area deductions due to leakage issues

(4) % Buffer retained by the registry issuing the credits for their insurance pool

The number of claimable biodiversity credits can be established once all these variables have been accounted for:

  • Number of Claimable Biodiversity Credits = % Credits Retained As a Buffer by Registry X (Median Biodiversity Uplift Across Each Metric X (Project Area Restored – Area Lost to Leakage Issues)



This is article provides an overview of how the Wallacea Trust methodology enables biodiversity uplift quantification for restoration projects. The methodology is open source, to read the latest version in full, please click here. If you have any questions regarding how biodiversity quantification works, please do not hesitate to contact the rePLANET team or the Wallacea Trust.

View All Articles

Join the conversation.

Sign up to receive the latest rePLANET news, and project updates.

© 2024 rePLANET Ltd, Wallace House, Old Bolingbroke, Spilsby, England, PE23 4EX

Website by Yello