Wildfires during this period burned an estimated 9246 square kilometres of the Amazon rainforest in total – even affecting the central region, which is historically very wet and fire-resistant. Aline Pontes-Lopes at the National Institute for Space Research in São Paulo, Brazil, and her colleagues have measured how plants in the central Amazon fared in the three years after the wildfires.
The researchers created 18 closed-off study areas, each measuring 250 metres by 10 metres, across the central Amazon in the northern Purus-Madeira of Brazil in December 2015. Then, every subsequent November until 2018, they visited each study area and measured the impact of fire damage on each plant.
“We looked at over 2420 [individual] trees, palms and lianas [woody vines],” says Pontes-Lopes. Over the three years after the fire, 27 per cent of the plants died – representing 13 per cent of total biomass. Although this is less than in other parts of the Amazon, the results suggest that the strongest fire events are still felt in the wettest regions of the rainforest. Some areas in the southwestern Amazon reported 50 per cent vegetation loss in the same period.
The most affected plants were small to medium trees, those with a trunk diameter of less than 40 centimetres. “The large trees in the central Amazon are more resistant because they have a higher wood density and thicker tree bark,” says Pontes-Lopes.
The impacts of severe wildfires on vegetation are seen long after the main events. Some low-intensity fires even increase tree growth, as there is less competition for resources and nutrients are released into the soil, says Ted Feldpausch at the University of Exeter in the UK.
“Other studies from Amazonia have shown there can be a lag in mortality for large trees for up to eight years following fires,” says Feldpausch. Pontes-Lopes and her team are therefore planning to continue to measure these areas, ideally for the next 20 years.