Tracking forest degradation in the Dry Chaco region using high-resolutio UAV-SfM techniques

GOBBI, BRATRIZ; ANTON VAN ROMPAEY; GAERTNER PHILIPP; FERNANDEZ PEDRO; LOTO DANTE; GASPARRI IGNACIO; VEERLE VANACKER

Bern

Workshop; 4th Open Science Meeting of the Global Land Programme; 2019

Global Land Programme

Gradual changes in forest structure, biomass and functioning that are the results of forest degradation are challenging to quantify usingtraditional, classification-based change detection methods. In contrast to forest conversion or natural disturbances, forest degradation is a gradualprocess through which the forest?s biomass declines, its species composition and vertical complexity change and the soil physico-chemicalproperties degrade.Using the woodlands of the Argentinean Dry Chaco ecosystem as an example, this study aims to explore the potential of UAV-derived opticalimages to monitor forest degradation as a function of change in forest structure. Selective logging, charcoal production, firewood collection andheavy cattle ranching are abundant in the Dry Chaco, and have a different imprint on the forest structure. Along a gradient of forest disturbancefrequency and intensity, we collected UAV-imagery in 50 different forest plots (of 4 ha each) in the Argentinean Dry Chaco. Forest degradationindicators were developed to track observable differences in the horizontal and vertical structure of vegetative elements between forest plots, and allow site-level comparison with well-preserved forests.Our preliminary data show that structural indicators are able to describe efficiently forest degradation from the forest structure. Areas degraded byselective logging are easily distinguishable with the lowering of the vegetation and the densification of the lower strata. More intense degradation related to charcoal production or heavy cattle ranching are also distinguishable and show a structure characterized by many large vegetation openings in encroached forested areas