DOI: 10.5061/dryad.zs7h44jb2
title: Removing climbers more than doubles tree growth and biomass in degraded tropical forests

description: Huge areas of tropical forests are degraded, reducing their biodiversity,
 carbon, and timber value. The recovery of these degraded forests can be
 significantly inhibited by climbing plants such as lianas. Removal of
 super-abundant climbers thus represents a restoration action with huge
 potential for application across the tropics. While experimental studies
 largely report positive impacts of climber removal on tree growth and
 biomass accumulation, the efficacy of climber removal varies widely, with
 high uncertainty as to where and how to apply the technique. Using
 meta-analytic techniques, we synthesise results from 26 studies to
 quantify the efficacy of climber removal for promoting tree growth and
 biomass accumulation. We find that climber removal increases tree growth
 by 156% and biomass accumulation by 209% compared to untreated forest, and
 that efficacy remains for at least 19 years. Extrapolating from these
 results, climber removal could sequester an additional 32 Gigatons of CO2
 over 10 years, at low cost, across regrowth and production forests. Our
 analysis also revealed that climber removal studies are concentrated in
 the Neotropics (N=22), relative to Africa (N=2) and Asia (N=2), preventing
 our study from assessing the influence of region on removal efficacy.
 While we found some evidence that enhancement of tree growth and AGB
 accumulation varies across disturbance context and removal method, but not
 across climate, the number and geographical distribution of studies limits
 the strength of these conclusions. Climber removal could contribute
 significantly to reducing global carbon emissions and enhancing the timber
 and biomass stocks of degraded forests, ultimately protecting them from
 conversion. However, we urgently need to assess the efficacy of removal
 outside the Neotropics and consider the potential negative consequences of
 climber removal under drought conditions and for biodiversity.
description: Dataset collected from published articles and associated data.
 Response data (treatment and control) and variance has then been converted
 into effect size (standardised mean difference) using <em>metafor
 </em>and <em>compute.es</em> R packages (Viechtbauer,
 2010; Del Re, 2013). Missing variances were imputed using linear
 relationships between variance, mean growth and sample size. Imputation
 was run 10 times, generating 10 sets of imputed SD and SS for the tree
 growth and biomass datasets. Climate variables were calculated from the
 Climate Research Unit (CRU) (Harris <em>et al.</em>, 2020),
 and elevation was calculated from the International Centre for Tropical
 Agriculture (CIAT), using the site coordinates with a 1 km buffer (Jarvis
 <em>et al.</em>, 2008). Dataset includes calculations from
 correction to original article.
description: <strong>finlayson_climber_removal_tree_growth_effect_size: </strong>This includes the data required for running the tree growth models: mean tree growth, variance (SD), effect sizes (g and variance), and all variables included in the models in the manuscript. 10 sets of imputed SD and sample sizes are also included, with the corresponding effect sizes. <strong>finlayson_climber_removal_biomass_effect_size </strong>which includes data required to run the biomass analysis in the original article in which we calculate the SMD effect size (models for Objective 1.2 and 2.2; repeated for each set of imputed SD and SS). <strong>finlayson_climber_removal_biomass_RR </strong>which includes data required to run the biomass analyses from the correction in which we calculate the response ratio effect size. <strong>finlayson_climber_removal_study_metadata </strong>which gives a summary of the studies included in the analyses. <strong>finlayson_climber_removal_global_extrapolation </strong>which outlines the calculation, justification and references used to estimate global carbon sequestration potential of climber removal; includes both original and corrected calculations.