Effects of the forests-agriculture conversion on the availability and diversity of forest products in a neotropical rainforest region

Abstract

Tropical rainforests offer a diverse array of real or potential forest products (FP). However, the ongoing conversion of these forests to agriculture raises concerns about the future availability and sustainability of FP. In this study, we examined the changes in availability (tree density and above-ground biomass) and species richness of native trees, recognized by local communities as sources of FP, with the forest-to-agriculture conversion in a Mesoamerican tropical rainforest region. Specifically, we tested hypotheses on whether species with FP had a higher, equal, or lower reduction in the availability, diversity, and probability of persistence than species without FP with the forest conversion. We interviewed landowners to identify tree species with FP and documented management practices and regulations for using these species. In fourteen 1 km2 landscapes, encompassing the entire range of forest-to-agriculture conversion (from 0 % to ∼100 % old-growth forest cover), we analyzed changes in the availability and richness of species with and without FP. In each landscape, we randomly established 30 plots (each 706.8 m2, totaling 420 plots and 29.7 ha sampling area) covered by old-growth forest, secondary forest, or agricultural fields (mostly cattle pastures). Over four years, we surveyed all trees with a diameter at breast height ≥ 10 cm in these plots. With the forest conversion, assemblages of tree species with FP exhibited a higher reduction in aboveground biomass than species without FP. However, assemblages of species with FP exhibited a significantly lower reduction in abundance, species richness, and a higher probability of persistence than assemblages of species without FP. Furthermore, we found evidence of implementing forest management practices favoring the preservation of species with FP in agricultural lands. Thus, we conclude that people intentionally foster the persistence of valuable species in their agricultural fields, which could have important implications for the structure and composition of future regenerating forests on abandoned agricultural lands. In the long term, this might lead to an overabundance of locally valuable species, as observed in old-growth tropical rainforests that native people ancestrally managed.