Accounting for the biodiversity benefits of woody plantings in agricultural landscapes: A global meta-analysis

Woody plantings are widely promoted to ameliorate biodiversity loss in agricultural landscapes. New market mechanisms are rapidly emerging to expedite such efforts, but limited tools and data to account for benefits achieved hamper their implementation. Using data from 204 primary studies and 1206 paired comparisons, we present a global meta-analysis of the biodiversity benefits of woody plantings in agricultural landscapes, in a biodiversity and ecosystem accounting framework. Consistent with emerging biodiversity and ecosystem accounting methods, we express results as agricultural field:natural reference and planting:natural reference ratios to estimate the biodiversity values of agricultural fields and plantings, respectively. Mean biodiversity abundance and species richness for agricultural fields were 0.40 of those for natural reference sites, compared with 0.62 for plantings averaging 20 years old, indicating a mean biodiversity benefit of 0.22. These values varied significantly among taxonomic groups, with unexpectedly high values for agricultural fields driven by high means for invertebrates. Variation among studies was substantial, and biodiversity values for plantings increased with higher diversity and native dominance of plantings and lower management intensity. Critically, estimates of biodiversity benefits based on abundance versus richness were comparable, but estimates using compositional measures typically implied substantially lower benefits, likely owing to effects of species identity. Our study operationalises approaches for quantifying the benefit of plantings for biodiversity and ecosystem accounting, and emphasises the need to use compositional measures for realistic estimates of biodiversity benefits.