Restoration plantings in the Atlantic Forest use a small, biased, and homogeneous set of tree species

Abstract

Investigating which species are planted in active restoration initiatives is useful for identifying underrepresented species and functional groups, which in turn can inform and improve the practice and policies of forest restoration. The Atlantic Forest is one of the global hotspots for biodiversity conservation and a region where many forest restoration initiatives have been carried out in recent decades. We conducted a taxonomic and functional analysis of a database with 1073 forest restoration plantings implemented from 2002 to 2018 in the Brazilian Atlantic Forest. We assessed how well restoration plantings represent the dispersal syndromes, successional groups, and the ratio of nitrogen-fixing, and threatened species, based on a comparison with 268 Atlantic Forest remnants. Comparisons were made for the entire biome as well as three subtypes: Atlantic Rainforest, Araucaria Forest and Seasonal Forest. We found 423 tree species planted in the restoration efforts, which represent less than 8 % of the Atlantic Forest tree flora. In comparison with the forest remnants, restoration plantings have a greater proportion of nitrogen-fixing tree species (17 % in plantings vs. 9 % in remnants) but underrepresent non-pioneer (67 % vs. 85 %), animal-dispersed (56 % vs. 74 %), and threatened species (18 species found in plantings vs. 83 in remnants). Our results indicate a bias towards N-fixing, non-animal-dispersed, and pioneer species in restoration plantings and towards using the same set of species across different regions of the Atlantic Forest. We recommend actions to increase the representation of the native tree flora in Atlantic Forest restoration plantings, especially concerning inclusion of animal-dispersed and threatened species and groups of species that are less likely to colonize restoration sites, such as large-seeded animal-dispersed species.