The pan-tropical expansion of tree plantations (2000-2012)
Abstract
Numerous studies have reported regional expansions in agricultural tree crop monocultures (e.g., banana, oil palm, rubber) and timber plantations (e.g., pine, eucalyptus monocultures) across the tropics. However, consistent, spatially-explicit estimates of global increases in tree plantation area are lacking, complicating assessments of their impacts on conservation efforts. In this study, we use remote sensing data to distinguish tree plantations from natural regrowth at a global scale, examine challenges to accuracy and consistency, and evaluate the expansion of tree plantations across biomes, biodiversity hotpots, and selected protected areas. Potential plantation expansion locations were isolated from the Hansen et al. Global Forest Change (HGFC) dataset, which identified patches of tree cover gain between the years 2000 and 2012. To reclassify gain patches into one of four classes (natural regrowth, oil palm, other tree plantations, and non-forest), we integrated data from three types of satellite imagery (Landsat, Alos PalSAR, and Sentinel 1) across a large, pan-tropical training dataset (n>600,000) with labeled land uses in 2015. We then used an ensemble machine learning approach to predict the land cover of all HGFC gain footprints between 25° N and 25° S (n>6,900,000). We assessed model predictive accuracy by random sampling of 2000 points within gain patches across the tropics (>85% overall accuracy), and examined spatial patterns in the resulting map of plantation expansion. Although natural regrowth was more abundant in biomes with high remnant natural forest cover, expansion of plantations was common in biodiversity hotspots and humid tropical ecosystems. We further quantify the recent expansion of plantation species into selected protected areas in southeast Asia (palm oil and rubber), west Africa (oil palm), and South America (eucalyptus). The observed increase in tropical tree plantation area has significant implications for global estimates of carbon sequestration, available agricultural area, and pressure on natural forests.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB071...07F
- Keywords:
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- 0410 Biodiversity;
- BIOGEOSCIENCES;
- 0466 Modeling;
- BIOGEOSCIENCES;
- 0480 Remote sensing;
- BIOGEOSCIENCES;
- 1922 Forecasting;
- INFORMATICS