# Aiming Higher to Test a Bend in the Curve of Biodiversity Loss: The Challenge of Halt‐The‐Loss Targets

## TL;DR

This paper introduces a method to test if biodiversity loss has been halted, using simulations and data analysis to improve target assessments.

## Contribution

The novel contribution is a case-specific simulation-based approach to evaluate and refine biodiversity loss halting targets.

## Key findings

- Smoothing had minimal impact on test outcomes, but variability and species count in datasets significantly influenced results.
- Thresholds for accepting targets should be set on a case-by-case basis using simulations.
- Assessments before including post-target data should be considered interim.

## Abstract

Efforts to ‘bend the curve’ of biodiversity loss involve setting targets to halt declines. Here, we propose an empirical test of such targets. This test states the probability that the rate of change in a biodiversity indicator is greater than or equal to zero. We used a combination of real and simulated data to explore factors affecting test performance. We found that while smoothing had a minimal effect, the outcome depends heavily on the variability and number of species in a dataset. This suggests that thresholds for target acceptance should be set on a case‐by‐case basis. Adding data for subsequent years could retrospectively change the outcome in a target year. Assessments made with data only up until the target year should therefore be regarded as interim, with the assessment of the target only finalised once subsequent data are also included. We recommend that simulations are used a priori to choose smoothing levels and to set thresholds for accepting a target has been met.

We present a test to evaluate targets to ‘halt the loss’ of biodiversity. We use simulations to explore the accuracy of this test with different datasets. We recommend that thresholds for target assessments are set on a case‐by‐case basis using simulations, and that assessments are regarded as interim until data following the target year can be included.