How to establish a reference period

Because data on the number of existing (extant) and extinct populations is needed, a reference baseline time period is needed for estimating the total number of populations. The monitoring framework of the GBF recommends using “…the period from 2011–2020, where data is available, as the reference period, unless otherwise indicated, for reporting and monitoring progress” (paragraph 2 of CBD, 2022b). The framework also notes that “baselines, conditions and periods used to express desirable states or levels of ambition in goals and targets should, where relevant, take into account historical trends”. For this reason, we recommend considering a baseline period for the Populations Maintained indicator that is before the industrial era. Since the exact period representing this varies by country and may depend on the species and what data are available, we suggest using a relatively broad baseline time period of 50–200 years ago for data retrieval, and allowing for more specific baselines to be defined by countries.

Thus, the date range for which the indicators are available is dependent on data availability at the national scale. Typically Nc for the Ne 500 indicator will be obtained from the past decade e.g. post 2010. Going forward it will be reported every 2 to 5 years, typically every 4 years, making it suited to the CBD reporting schedule. As the indicator is increasingly deployed, indicator calculation can be made in temporal windows, including through the use of older biodiversity observation data, reports and consultation with knowledge holders, likely extending indicator assessment at least back to the 1990s.

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