Detection of environmental change in jungles and forests of Mexico with remote sensing: a multi-scale time and space approach/Detección de cambio ambiental en selvas y bosques de México con percepción remota: un enfoque multiescalar de espacio y tiempo/Deteccao de mudanca ambiental nas selvas e bosques do Mexico com percepcao remota: um enfoque multiescalar de espaco e tempo

Global environmental change occurs at multiples scales, and is sometimes magnified by extreme hydro-meteorological events. However, due to the amplitude of the phenomenon, efforts for impact quantifications have often been limited to short time scales or long time studies at a single site. The current work proposes a regional characterization of impacts at three temporal scales using available remote sensing inputs, with emphasis on the structure and function of terrestrial ecosystems. At a short time scale (a) the event is described by the spatial distribution of mega-fires that occurred the same year as the event; at a medium time scale (b; until 7 years after the event), the annual variation of Net Primary Productivity (NPP) or Normalized Difference Vegetation Index (NDVI) of each ecosystem is analyzed in the region most affected by the mega-fires. Finally, at a longer time scale (c; 20 years, including the event), the pattern of degradation of an ecosystem is studied in multiple sites throughout the region. The ENSO 1997-1998 phenomenon was characterized in Mexico using AVHRR, MODIS and Landsat imagery with this approach. It is concluded that immediate impacts could be identified at regional scale using low resolution sensors. Next, sustained structural degradation could be linked to the ENSO event in the form of higher deforestation rates in periods which include the event. By contrast, functional impacts are probably not discernable with this type of inputs in Mexico.