Surface albedo raise in the South American Chaco: Combined effects of deforestation and agricultural changes

HOUSPANOSSIAN JAVIER; GIMÉNEZ, RAUL; JOBBÁGY ESTEBAN; NOSETTO, MARCELO

AGRICULTURAL AND FOREST METEOROLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 232 p. 118 - 127

0168-1923

Deforestation affects climate and the energy balance of theEarth not only through the release of greenhouse gases but also throughshifts in the physical properties of the surface. These physical effectscan be strongly dependent not only on the deforestation event but on theland use choices and management that follow it. Here we explored how thealbedo and radiation balance of the dry subtropical Chaco forests ofSouth America changed over the last decade in response to bothdeforestation and land use/management. For the whole region we analyzedchanges in the mean annual albedo derived from MODIS imagery and theirrelation with the dominant land use trajectories for a 12-year period(2000-2012). In two focal areas we identified how specific land uses andmanagement shifts affected the seasonality of surface albedo and greenvegetation cover, quantifying their associated radiation budget changesand radiative forcing effects. Deforestation accounted for 83% of theregional albedo increase observed in Chaco, yet, land use and landmanagement changes were also a main driver of albedo shifts, explainingthe rest of the albedo rise occurred in the region. Albedo raisesincreased the mean annual outgoing shortwave energy flux at the top ofthe atmosphere producing a biophysical cooling effect which was stronglydependent on the land use choice and agricultural management, rangingfrom -8 W m-2 in silvopastoral systems to -17 W m-2 under single annualcropping schemes. These values are equivalent to a reduction inatmospheric CO2 of 12-27 Mg C ha-1, or 15 to 55% of the typical emissionsthat accompany deforestation in this region. Land use and managementchoices in the Chaco region produce strong divergences in the resultingalbedo seasonality that should not be ignored in the assessment of theirnet climatic effects and the discussion of possible mitigation actions.