Atlantic forest, Brazil (credit: Felipe Nincao Begliomini)
A new study led by researchers at the University of Cambridge has produced the first large-scale, high-resolution map of how quickly tropical forests recover carbon and structure when simply left to regrow on former pastureland, using repeated airborne laser scans across Brazil's Atlantic Forest.
Why it matters for carbon markets
The Atlantic Forest is one of the world’s most degraded biodiversity hotspots, having been extensively cleared for cropland, cattle ranching, and short-rotation eucalyptus plantations. In response to this widespread degradation, Brazilian law requires landowners to restore at least 20 percent of their land to native vegetation. Carbon credit projects are helping to meet this requirement by financing restoration and expanding the area of young forest across the region. However, as lead author Felipe Begliomini and colleagues note, current carbon-accounting methods have often proven insufficient for verifying restoration outcomes at scale, a gap that "can lead to inaccurate estimates that erode investor confidence in climate mitigation efforts". The team's framework, published in the ISPRS Journal of Photogrammetry and Remote Sensing, is designed to address this challenge by giving restoration projects and carbon-credit certifiers a repeatable, high-resolution tool for tracking real forest recovery over time.
Six years of lidar reveal rapid recovery
The research team analysed two lidar surveys flown in 2012 and 2018 over 475 eucalyptus farms in Brazil's Paraíba Valley, covering 69 square kilometres of land undergoing passive restoration. The team developed a new correction method to remove sensor-related errors, such as terrain-model offsets and differences in laser pulse density. These errors can otherwise mask real forest growth in repeat lidar surveys. The study concludes that "multi-temporal airborne laser scanning delivers rapid, large-scale, and reliable data on forest structure change, enabling accurate carbon accounting and restoration forecasts", noting the findings can directly support the planning and scaling of tropical forest restoration projects.
A standout carbon accumulation rate
The study found that young secondary forests in the region accumulated carbon at 2.03 megagrams of carbon per hectare per year, among the highest rates reported in any multi-temporal lidar study and roughly double the rate typically reported for other temperate and old-growth tropical biomes. Overall, restoration across the 69 square kilometre study area generated a net carbon gain of 45,000 megagrams of CO2 per year – equivalent to offsetting the annual carbon footprint of 20,000 people. Restoring all legally required pasture in the region could sequester roughly 14.7 million megagrams of CO2 over 30 years across 770 square kilometres.
Senior author points to broader implications
David Coomes, Professor of Forest Ecology at Cambridge and senior author on the paper, emphasises that "the integrity of carbon markets for forest restoration depends on precise structural change measurements over large scales", and that robust, standardised monitoring methodologies are essential "to ensure accurate assessments, restore credibility, and support greater investment in natural climate solutions". The paper argues that simulated carbon uptake rates in the region, while below broader Neotropical and IPCC estimates, were 45 percent above the regional mean drawn from a global chronosequence dataset – underscoring, in the authors' words, "the importance of locally calibrated models for accurate carbon accounting".