Remote sensing of land cover change: secondary growth dynamics in Rondonia, Brazil

Land cover change in Rondonia, Brazil was estimated using Landsat and JERS-1 SAR data. Annual Landsat TM data from 1989 to 1995 were used to document rates of deforestation, abandonment and re-clearing of secondary growth for a 460000 hectare area in Rondonia. Results indicate secondary growth was a large, rapidly changing pool (varied annually between 24 to 55% of the total deforested area). Annual rates of deforestation ranged from 5800 to 18700 hectares per year, while annual rates of abandonment varied from 2100 to 36000 hectares per year. Over 90% of the secondary growth area in 1989 was re-cleared at least once by 1995. 65% of the deforested areas in use in 1989 was abandoned into secondary growth for some period of time by 1995. This rapid cycling of the secondary growth may have a minimal effect on the net biotic flux of carbon on a decadel basis. Nevertheless, variability in clearing and abandonment rates, however, may have a significant impact on the interannual variability in net fluxes of biotic CO₂. JERS-1 SAR data from 1993 were merged with the TM analysis to assess the influence pasture and secondary growth stand age on L-band radar backscatter. General trends of decreasing backscatter with pasture age and increasing backscatter with secondary growth age were observed. Significant differences in backscatter, however, existed within pasture and secondary growth stands age classes