Evolução do desmatamento de um mosaico de unidades de conservação do município de Sena Madureira – Acre e suas implicações para gestão

Abstract

This study analyzed deforestation from 1988 to 2014 in a mosaic and buffer area of conservation units in theSena Madureira Municipality, Acre, Brazil to support management of these units. This mosaic is composed of the Cazumbá Iracema Extractive Reserve, Macauã National Forest and San Francisco National Forest for a total of 968.438 ha. Data from "the Amazon Deforestation Program - PRODES" and from Hansen et al (2013) method, both using Landsat imagery, provided the basis for analysis of deforestation in the Mosaic and 10 km from its boundaries. The calculations were made in ArcGIS 9.3 and Excel. The area was divided into internal and external buffers to identify critical areas for management. In a second stratification process the area was divided into two geographical regions (northeast and southwest), followed by a third stratification into six subregions, subdivided into inside and outside buffers of 10 km width, producing 12 strata. During the period 1988-2014 6,385 ha were deforested within the Mosiac, corresponding to 0.7% of its total area. About 1.1% of the internal buffer of the Mosaic was deforested and 8.6% of the external buffer. The Northeast macro-region, which has 23% of the area contains about 97% of the deforested area. We conclude that the majority of deforestation is concentrated in an area of less than a quarter of the total area. In temporal analysis using PRODES data, there is a general decrease in the annual rates of deforestation for the period 2000-2014, with alternating peaks from year to year. PRODES and Hansen databases produced similar cumulative values when grouped by strata; nine of the twelve strata were differences within a range of ± 20% But when analyzed separately by year values for strata differed by up to 182%, which cannot be explained by the minimum criteria of registered polygons or the difference in the beginning months of the year (August versus January). During the period 2000 to 2003, for example, PRODES recorded a dramatic increase in deforestation rates in the strata when Hansen data indicated a reduction in the deforestation rates. For management purposes it is suggested to use the two databases to identify trends in the deforestation rates. When the two trends are consistent, decisions on location and landscape transformation rates are more robust. When trends are divergent, the recommendation is to use additional information to determine which of the two is more representative of reality.