Review of Assisted Natural Regeneration in Tropical Forest Landscapes

Assisted Natural Regeneration (ANR) is an approach to restoring degraded forest landscapes that depends on the presence of naturally established tree regeneration in-situ. The growth of spontaneously established seedlings is facilitated and accelerated by removing competition and tending to seedlings through methods such as weeding, burning, and fertilization. ANR is a relatively recent term now widely used in ecological literature to describe a practice that has been going on for at least several centuries under formal documented use in Western conventional forestry, and for likely over one thousand years on an informal basis by indigenous forest peoples. 

 This review analyzes the literature on ANR in the tropics with regards to the geographical distribution of studies, species patterns, previous land use, treatments used, and measures of success. The analysis of growth and survival rates under ANR treatments helps practitioners assess and select best performing species and treatments for their local context. By synthesizing different understandings of ANR, we aim to close significant gaps in the literature on tropical forest restoration. Additionally, we aim to provide a coherent definition and conceptual framework for ANR, its implementation context, and success factors under specific local conditions. In total, we analyzed 91 studies distributed across 30 countries most of which were conducted in Latin America (51%) and Asia (31%). Studies were conducted on land that had previously been used for logging, pasture and agriculture as well as plantations; and reported quantitative metrics such as physical attributes of seedlings and success metrics such as seedling density and species diversity.