Abstract
The Convention on Biological Diversity’s (CBD) Aichi Target 12 aimed to prevent species extinctions and improve the conservation status of known threatened species by 2020 but has not been met. As the post-2020 global biodiversity framework is negotiated, it is essential that we learn lessons from past failures. Here, we investigate whether a reduction in extinction risk could realistically be achieved within the ten-year timeframe of the Aichi Targets. We identified threatened bird and mammal species for which a population increase could lead to down-listing on the IUCN Red List and created population models that assumed exponential population growth to predict how long it would take to reach the population size threshold required for down-listing. We found that in the best-case scenario, 39/42 birds (93%) and 12/15 mammals (80%) could be expected to show the population increase required to achieve down-listing by one Red List category within a ten-year timeframe. In contrast, under the worst-case scenario, 67% birds and 40% mammals were predicted to take > 10 years to reach the population threshold. These results indicate a disparity between the ecological timeframes required for species to show a reduction in extinction risk, and the political timeframes over which such ecological change is expected to be achieved and detected. We suggest that quantitative analyses should be used to set realistic milestone targets in the post-2020 framework, and that global indicators should be supplemented with temporally sensitive measures of conservation progress in order to maintain political and societal motivation for species conservation.
Highlights
The rapid decline in biodiversity driven by human activities over recent decades (Chase 2014; Pimm et al 2014) has resulted in losses similar to those last seen during massextinction events recorded over geological time periods (Ceballos et al 2017; Drira et al 2019)
Our study used simple population models to test whether the ten-year timeframe of Aichi Target 12 was long enough for a selection of threatened species to achieve down-listing on the IUCN Red List
We found that in the best-case scenario, 39/42 birds (93%) and 12/15 mammals (80%) could be expected to show the population increase required to achieve down-listing by one Red List category within a ten-year timeframe
Summary
The rapid decline in biodiversity driven by human activities over recent decades (Chase 2014; Pimm et al 2014) has resulted in losses similar to those last seen during massextinction events recorded over geological time periods (Ceballos et al 2017; Drira et al 2019). Despite increasing policy and management responses, at the conclusion of the Aichi Targets, the evidence shows that we have failed to halt biodiversity loss, and species extinction risk continues to increase (IPBES 2019; CBD Secretariat 2020). As Parties to the CBD negotiate a new post-2020 global biodiversity framework (CBD 2020) it is essential that we learn lessons from the Aichi Targets, in order that new targets will promote greater progress in conserving biodiversity over the coming decades. While Target 12 may have been ambitious, a recent study found that progress towards achieving global conservation targets was not related to the ambitiousness of the target (Green et al 2019). One of the most fundamental questions regarding the appropriateness of a target, is whether the target can realistically be met within the timeframe set; in other words, is the target achievable?
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