Evaluating the evolution of forest restoration research in a changing world: a big literature review

In a rapidly changing world, characterized by novel ecological scenarios and fluctuating socioeconomic and ecological demands, ecological restoration practices must constantly adapt to emerging issues and circumstances. Restoration ecology, the scientific discipline that informs ecological restoration, must therefore evolve and expand its focus to address this need. To describe and evaluate the evolution of research pertaining to the ecological restoration of forests within the field of forestry, we performed a review of all 29,766 abstracts published over the last 35 years (1980-2014) in 15 leading forestry journals using automated content analysis, a machine learning-based tool for automated review of large volumes of literature (big literature). We found not only a 50-fold increase in the prominence of restoration ecology in forestry literature from 2000 to 2013, but also an evolution in the focus of forest restoration research. This evolution is likely in response to emerging topics and issues affecting forest restoration, such as exotic species, altered disturbance regimes, degraded tropical forests, and ecosystem services. Our results also revealed a pattern of cyclic development, in which research in the 1990s was focused on constructing theoretical frameworks, in the 2000s research appeared to be concentrated on restoration practices and programs, while in the 2010s research revisited established theoretical frameworks, possibly indicating a conceptual expansion. Our study highlighted gaps in research on important topics and emerging challenges, such as global climate change, genetic considerations, landscape-level factors, and restoring degraded systems, thus pointing the way for new and necessary research directions.