Predicting Reforestation Trends in Tropical Post-Agricultural Landscapes

Changes in economic policies and human migrations driven by globalization have resulted in agricultural abandonment and the regeneration of forest cover in many parts of the world. Post-agricultural forests in the tropics have been traditionally undervalued because of the perception of intense human modification. As these forests becoming dominant land cover types worldwide, recent work suggests they provide opportunities for biodiversity conservation and the recovery of important forest ecosystem services, such as watershed protection and timber and food production. Post-agricultural forests can also contribute to carbon sequestration in regrowing biomass. The type and intensity of former land use can influence the successional trajectories of post-agricultural secondary forests, with unpredictable consequences for species composition and carbon storage. Environmental factors, such as climate and soil type can affect the rate of forest regrowth and fate of soil carbon pools. Here I explore challenges in measuring and predicting above and belowground responses to changes in land use and land cover, focusing on forest reestablishment. I present research from secondary forests regrowing on former pastures and sugar cane in the Caribbean. Different ecosystem compartments respond at very different time scales to reforestation, making it difficult to forecast changes in forest ecosystem processes at the regional scale. Geographic biases in our knowledge of drivers of deforestation and reforestation and in our understanding of the factors influencing rates of recovery confound our ability to predict changes in forest cover. The choice of baselines, both in terms of time since disturbance as well as of the original carbon stocks on the landscape also add large uncertainties to model predictions. Quantifying temporal and spatial heterogeneity in carbon dynamics in reforested landscapes is important for improved understanding of feedbacks between the biosphere and climate.