Assessing reforestation failure at the project scale: The margin for technical improvement under harsh conditions. A case study in a Mediterranean Dryland

Abstract

[EN] Poor reforestation outcomes imply unfulfillment of program goals and might erode institutional willpower and political momentum towards reforestation efforts, affecting both public and private support. However, program improvement in real reforestation projects is challenging due to the conjunction of many different variables of distinct nature that mutually interact and feedback in an inextricable fashion. In this work, we deploy a comprehensive integral assessment of reforestation program based in a study case where technical and environmental information is gathered and related to indicators of performance both in the short and mid-term. This assessment aims to provide reliable end-results for survival and growth, unveils pitfalls on successful plantation establishment and allows for learning processes on how to improve plantation performance and the potential margin for this improvement. The selected project was carried out on harsh site conditions, with different species, cultural treatments and contractors, and was affected by the driest year on record, encompassing enough technical and ecological complexity that makes it suitable for the purpose of this study. Mortality, either in the short (53%) or in the mid-term (83%), was high, but very variable according to site and species. Anthropogenic variables (project planning and execution) gathered high relative importance on plantation performance in the first two years (11-29%) that decreased with time, whilst environmental variables (site and meteorological) showed increased importance ten years after planting (>50%). In the short-term, soil moisture and meteorology during planting season have been identified as key factors that trigger the effects of both technical decisions (planting date and planting technique) and other environmental variables on performance. In the design phase, some decisions related to zoning, species selection and cultural treatments application have been related to poor performance. The results provide practical information and guidelines for forest restoration improvement under similar setup.