A recent study published in Nature highlights that about 215 million hectares of land—in humid tropical areas worldwide, which is larger than Mexico—has the capacity to naturally regrow. This extensive forest area could absorb 23.4 gigatons of carbon over the next three decades and significantly address issues like biodiversity loss and decline in water quality. The research revealed that over half of the land with high regrowth potential is found in five countries: Brazil, Mexico, Indonesia, China, and Colombia.
According to Brooke Williams, the co-lead author of the study and a researcher from the Queensland University of Technology in Australia, “Tree planting in degraded lands can be pricey. Utilizing natural regrowth techniques allows countries to achieve their restoration targets in a more cost-effective manner.” She adds, “Our model can help identify where these cost savings can be optimized.”
Years of Research in One Study
Matthew Fagan, an associate professor of geography and environmental systems at the University of Maryland, Baltimore County (UMBC) and the study’s second author, relied on a detailed data set developed during “a decade’s worth of study.”
He explains, “We used satellite imagery to pinpoint small areas where tree cover has expanded over the years. We then eliminated human-planted areas using machine learning to focus solely on natural regrowth.” The study monitored regrowth patterns from 2000 to 2012 and continued to verify whether this growth was sustained through 2015. “These naturally growing patches formed the foundational data for our innovative study,” Fagan elaborates. It is the first research to forecast where future forest regrowth is likely to happen based on previously observed growth.
This study, co-led by Hawthorne Beyer, who heads geospatial science at Mombak—a startup in Brazil dedicated to generating quality carbon credits through Amazon reforestation—and also serves as director of science at the Institute for Capacity Exchange in Environmental Decisions, incorporated global data sets examining factors like soil quality, terrain slope, infrastructure and population density, local wealth, and proximity to urban areas and healthy forests, among others. Fagan notes, “When conducting such global studies, it builds upon years of efforts from numerous other scientists.” Each contributing study represents a significant investment of time and resources.
Key factors associated with higher regrowth potential identified in the research include the proximity of patches to existing forests, the density of adjacent forests, and the carbon content in the soil. These variables effectively explain global regrowth patterns, according to Fagan. Being close to existing forests is crucial as it allows for a variety of seeds to disperse into the area, promoting diverse regrowth.
Promoting Local Solutions through a Global Map
The study produced a digital map detailing potential regrowth areas across the global tropics. Each pixel in the map, covering an area of 30 x 30 square meters, represents the estimated potential for natural regrowth. This map, resulting from international research collaboration, serves as a valuable resource for environmental advocates worldwide who aim to localize their conservation efforts.
“Our aspiration is for this map to be utilized openly by local individuals, organizations, and regional authorities, from county levels up to national scales, to determine where restoration efforts should be directed,” Fagan states. “Local residents should have the authority to make decisions about their environment—restoration efforts should reflect local needs and conditions.”
Fagan also highlights that while some identified potential regrowth areas may not be feasible for restoration due to ongoing agricultural use or their proximity to developed regions, a considerable portion of the 215 million hectares includes abandoned cattle pastures or overexploited forests. Encouraging natural regrowth in these areas could lead to minimal economic costs while offering extensive ecological benefits.
“Restoring these areas back to rainforest could significantly enhance water quality, local biodiversity, and soil health,” Fagan notes. “It would also greatly aid in carbon sequestration, prompting the essential question: ‘Where can we achieve this effectively?’ This study aims to address that very question.”
