Madeira Basin Case Study

How has deforestation changed trends in Amazon deforestation since 2009?

Rates decreased after 2009, reached a low in 2012, then increased again in recent years, with highest rates during the dry season (August)

When and where did the 2014 devastating floods occur in the Amazon basin?

April 2014 on the Madeira River, the largest tributary of the Amazon River, especially affecting the Upper Madeira basin

What evidence shows the severity of the 2014 Madeira River floods?

At Porto Velho, river levels reached a record 19.68 m above normal

What deforestation occurred in Bolivia and Peru within the Upper Madeira basin?

Around 30,000 km² of rainforest cleared between 2000 and 2012, mainly for subsistence farming and cattle ranching

How did deforestation increase rapid water flows in the Upper Madeira basin?

Loss of interception and soil erosion on steep Andes slopes reduced soil storage and increased saturation-excess overland flow

How does deforestation reduce water recycling and increase flood risk regionally?

Reduced transpiration and interception mean more rainfall becomes river discharge instead of being recycled into the atmosphere, increasing downstream flooding

When is the deforestation rate highest each year?

During dry season, particularly August, because Slash and burn forest clearance is easiest during this weather.

How is deforestation expected to affect regional climate? What is the special extent of its influence?

Deforestation is expected to reduce regional rainfall by about 20% because less water is recycled back into the atmosphere through transpiration and interception loss from the forest canopy. Instead, more precipitation becomes river discharge and is lost to the Atlantic Ocean, rather than being returned to the atmosphere.

The spatial extent of its influence is large: the reduction in rainfall does not only affect deforested areas, but can impact regions hundreds of kilometres downwind of degraded forests.