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December 28, 2015

El Nino Induced Dry Weather impacting Amazon Rainforest

This year's strong El Nino continues to have a major impact on the weather in Brazil. While southern Brazil continues to be deluged by very heavy rains, for many months the weather in central and northern Brazil has been much hotter and dryer than normal.

Not only are these adverse conditions impacting the soybean production in central and northeastern Brazil, it is also having a major impact on the Amazon Rainforest in northern Brazil. According to a recent report in the newspaper Jornal O Globo, the rainfall in the eastern Amazon region is significantly below normal and it is resulting in an increase in the number of fires in the region. Brazilian environmental scientist Erika Berenguer, along with colleagues from Oxford and Lancaster in England, reported that for many days over the last three months, much of the Amazon region has been covered with smoke.

The Brazilian National Space Research Institute (Inpe) reported a 26% increase in fires in 2015. The state of Para, which encompasses much of the eastern Amazon Rainforest, has recorded the greatest number of fires. Berenguer indicates that during years with a strong El Nino, the dry season (May to September) is generally hotter and longer than normal. That has certainly been the case this year with much below normal rainfall being recorded during the spring and early summer months. Unfortunately, the forecast is calling for continued below normal rainfall in the region until at least February.

Many of the forest fires are the result of fires escaping from farmers and ranchers burning pastures and brush. When the fire gets into the tinder dry forest it is no longer controllable. The forest floor is covered by leaf litter and dead branches, which is prime fuel for the fires.

In its normal state, the Amazon Forest has a complete canopy with the sun rarely hitting the soil surface. This results in a very humid environment on the forest floor. But under extreme drought, the escaped fires clear out many of the smaller tress and the underbrush, opening up the forest to more sunlight and air circulation, which dries it out even more. The smaller trees die immediately from the fire, but the trunks of the giant canopy trees may burn for days and they may not die for 2-3 years. So the total impact on the forest from these fires is not immediately evident.

The last major drought in the Amazon Region was in 2005 and scientists say that we have to wait until April of 2016 when the rainy season starts to ebb to see if water levels in the rivers will fall to the historic lows of 2005.