Severe droughts can trigger Amazon dieback

Severe droughts can trigger Amazon dieback

SHARE

Brazil: A new study conducted by the a team of researchers from Brazil's Amazon Environmental Research Institute and the Woods Hole Research Center (US) found that severe droughts could trigger dieback of Amazon forests in the near-term.

The findings were based on data gathered from a long-running field experiment, described as the first of its kind. In 2004, the team established three plots in the south-east Amazon – one of which was burned annually, another was burned every three years, while the remaining one was left untouched as a control plot. The experiment zone was surveyed and studied using high-resolution image (1.85m) captured with the sensor Worldview-2 in 2011.

Aerial photo of experimental plots: annual burn (left); burned every three years (centre) and unburned/control (right). The dashed line indicates the forest edge/interior zone.

Above: Aerial photo of experimental plots: annual burn (left); burned every three years (centre) and unburned/control (right). The dashed line indicates the forest edge/interior zone.

The study revealed that climate change alone is unlikely to drive severe tropical forest degradation in the next few decades. Recent droughts caused greatly elevated fire-induced tree mortality in a fire experiment and widespread regional forest fires that burned 5–12% of southeastern Amazon forests. These results suggest that feedbacks between fires and extreme climatic conditions could increase the likelihood of an Amazon forest “dieback” in the near-term.

Burn scars in forested areas were mapped from 2000 to 2010 using MODIS images. Regional maps of dryness for 2000–2010 were obtained from the TRMM data product for the entire Upper Xingu region. Maps of land-surface temperature for the dry seasons of 2007 and 2010 (July–September) were derived from the MODIS temperature and emissivity product (MOD11A2). The metrics for landscape fragmentation (edge length, area and deforestation) were calculated for the Xingu Region for1997 and 2000–2011 based on Landsat-5 images.

Source: PNAS